Author name code: giampapa ADS astronomy entries on 2022-09-14 author:"Giampapa, Mark" ------------------------------------------------------------------------ Title: Final Report for SAG 21: The Effect of Stellar Contamination on Space-based Transmission Spectroscopy Authors: Rackham, Benjamin V.; Espinoza, Néstor; Berdyugina, Svetlana V.; Korhonen, Heidi; MacDonald, Ryan J.; Montet, Benjamin T.; Morris, Brett M.; Oshagh, Mahmoudreza; Shapiro, Alexander I.; Unruh, Yvonne C.; Quintana, Elisa V.; Zellem, Robert T.; Apai, Dániel; Barclay, Thomas; Barstow, Joanna K.; Bruno, Giovanni; Carone, Ludmila; Casewell, Sarah L.; Cegla, Heather M.; Criscuoli, Serena; Fischer, Catherine; Fournier, Damien; Giampapa, Mark S.; Giles, Helen; Iyer, Aishwarya; Kopp, Greg; Kostogryz, Nadiia M.; Krivova, Natalie; Mallonn, Matthias; McGruder, Chima; Molaverdikhani, Karan; Newton, Elisabeth R.; Panja, Mayukh; Peacock, Sarah; Reardon, Kevin; Roettenbacher, Rachael M.; Scandariato, Gaetano; Solanki, Sami; Stassun, Keivan G.; Steiner, Oskar; Stevenson, Kevin B.; Tregloan-Reed, Jeremy; Valio, Adriana; Wedemeyer, Sven; Welbanks, Luis; Yu, Jie; Alam, Munazza K.; Davenport, James R. A.; Deming, Drake; Dong, Chuanfei; Ducrot, Elsa; Fisher, Chloe; Gilbert, Emily; Kostov, Veselin; López-Morales, Mercedes; Line, Mike; Močnik, Teo; Mullally, Susan; Paudel, Rishi R.; Ribas, Ignasi; Valenti, Jeff A. Bibcode: 2022arXiv220109905R Altcode: Study Analysis Group 21 (SAG21) of the Exoplanet Exploration Program Analysis Group (ExoPAG) was organized to study the effect of stellar contamination on space-based transmission spectroscopy, a method for studying exoplanetary atmospheres by measuring the wavelength-dependent radius of a planet as it transits its star. Transmission spectroscopy relies on a precise understanding of the spectrum of the star being occulted. However, stars are not homogeneous, constant light sources but have temporally evolving photospheres and chromospheres with inhomogeneities like spots, faculae, and plages. This SAG has brought together an interdisciplinary team of more than 100 scientists, with observers and theorists from the heliophysics, stellar astrophysics, planetary science, and exoplanetary atmosphere research communities, to study the current needs that can be addressed in this context to make the most of transit studies from current NASA facilities like HST and JWST. The analysis produced 14 findings, which fall into three Science Themes encompassing (1) how the Sun is used as our best laboratory to calibrate our understanding of stellar heterogeneities ("The Sun as the Stellar Benchmark"), (2) how stars other than the Sun extend our knowledge of heterogeneities ("Surface Heterogeneities of Other Stars") and (3) how to incorporate information gathered for the Sun and other stars into transit studies ("Mapping Stellar Knowledge to Transit Studies"). Title: The GAPS programme at TNG. XXII. The GIARPS view of the extended helium atmosphere of HD 189733 b accounting for stellar activity Authors: Guilluy, G.; Andretta, V.; Borsa, F.; Giacobbe, P.; Sozzetti, A.; Covino, E.; Bourrier, V.; Fossati, L.; Bonomo, A. S.; Esposito, M.; Giampapa, M. S.; Harutyunyan, A.; Rainer, M.; Brogi, M.; Bruno, G.; Claudi, R.; Frustagli, G.; Lanza, A. F.; Mancini, L.; Pino, L.; Poretti, E.; Scandariato, G.; Affer, L.; Baffa, C.; Baruffolo, A.; Benatti, S.; Biazzo, K.; Bignamini, A.; Boschin, W.; Carleo, I.; Cecconi, M.; Cosentino, R.; Damasso, M.; Desidera, S.; Falcini, G.; Martinez Fiorenzano, A. F.; Ghedina, A.; González-Álvarez, E.; Guerra, J.; Hernandez, N.; Leto, G.; Maggio, A.; Malavolta, L.; Maldonado, J.; Micela, G.; Molinari, E.; Nascimbeni, V.; Pagano, I.; Pedani, M.; Piotto, G.; Reiners, A. Bibcode: 2020A&A...639A..49G Altcode: 2020arXiv200505676G Context. Exoplanets orbiting very close to their parent star are strongly irradiated. This can lead the upper atmospheric layers to expand and evaporate into space. The metastable helium (He I) triplet at 1083.3 nm has recently been shown to be a powerful diagnostic to probe extended and escaping exoplanetary atmospheres.
Aims: We perform high-resolution transmission spectroscopy of the transiting hot Jupiter HD 189733 b with the GIARPS (GIANO-B + HARPS-N) observing mode of the Telescopio Nazionale Galileo, taking advantage of the simultaneous optical+near infrared spectral coverage to detect He I in the planet's extended atmosphere and to gauge the impact of stellar magnetic activity on the planetary absorption signal.
Methods: Observations were performed during five transit events of HD 189733 b. By comparison of the in-transit and out-of-transit GIANO-B observations, we computed high-resolution transmission spectra. We then used them to perform equivalent width measurements and carry out light-curves analyses in order to consistently gauge the excess in-transit absorption in correspondence with the He I triplet.
Results: We spectrally resolve the He I triplet and detect an absorption signal during all five transits. The mean in-transit absorption depth amounts to 0.75 ± 0.03% (25σ) in the core of the strongest helium triplet component. We detect night-to-night variations in the He I absorption signal likely due to the transit events occurring in the presence of stellar surface inhomogeneities. We evaluate the impact of stellar-activity pseudo-signals on the true planetary absorption using a comparative analysis of the He I 1083.3 nm (in the near-infrared) and the Hα (in the visible) lines. Using a 3D atmospheric code, we interpret the time series of the He I absorption lines in the three nights not affected by stellar contamination, which exhibit a mean in-transit absorption depth of 0.77 ± 0.04% (19σ) in full agreement with the one derived from the full dataset. In agreement with previous results, our simulations suggest that the helium layers only fill part of the Roche lobe. Observations can be explained with a thermosphere heated to ~12 000 K, expanding up to ~1.2 planetary radii, and losing ~1 g s-1 of metastable helium.
Conclusions: Our results reinforce the importance of simultaneous optical plus near infrared monitoring when performing high-resolution transmission spectroscopy of the extended and escaping atmospheres of hot planets in the presence of stellar activity.

Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated by the Fundación Galileo Galilei (FGG) of the Istituto Nazionale di Astrofisica (INAF) at the Observatorio del Roque de los Muchachos (La Palma, Canary Islands, Spain). Title: Towards Mitigating the Impact of Stellar Photospheric Heterogeneity on Precise Exoplanet Transmission Spectra Authors: Rackham, Benjamin; Apai, Dániel; Giampapa, Mark; Espinoza, Néstor; Madhusudhan, Nikku; Zhou, Yifan Bibcode: 2019EPSC...13..971R Altcode: Exoplanet transmission spectroscopy, the study of spectroscopic transit depths, provides our best opportunity to characterize the atmospheres of temperate, Earth-sized exoplanets in the next two decades. However, this technique is subject to spurious signals introduced by the photospheric heterogeneity of exoplanet host stars, which may mimic or mask real exoplanetary signals. As the late-type hosts that provide the most favorable planet-to-star radius ratios for studying small exoplanets also tend to be more photospherically heterogeneous, our ability to disentangle stellar and planetary signals represents a possible limitation for precise transmission spectroscopy. Here we present our recent work to understand the scale of TLS signals with forward models and to characterize the photospheres of important exoplanet host stars through (1) transit crossings of magnetic active regions, (2) joint retrievals of stellar and exoplanetary properties from transmission spectra, and (3) stellar photospheric decomposition with moderate-resolution visual and near-infrared spectra. Constraining the photospheric heterogeneity of exciting exoplanet host stars with these approaches will be key to realizing the opportunity to characterize Earth-sized exoplanets via transits. Title: Constraining Stellar Photospheres as an Essential Step for Transmission Spectroscopy of Small Exoplanets Authors: Rackham, Benjamin; Pinhas, Arazi; Apai, Dániel; Haywood, Raphaëlle; Cegla, Heather; Espinoza, Néstor; Teske, Johanna; Gully-Santiago, Michael; Rau, Gioia; Morris, Brett M.; Angerhausen, Daniel; Barclay, Thomas; Carone, Ludmila; Cauley, P. Wilson; de Wit, Julien; Domagal-Goldman, Shawn; Dong, Chuanfei; Dragomir, Diana; Giampapa, Mark S.; Hasegawa, Yasuhiro; Hinkel, Natalie R.; Hu, Renyu; Jordán, Andrés; Kitiashvili, Irina; Kreidberg, Laura; Lisse, Carey; Llama, Joe; López-Morales, Mercedes; Mennesson, Bertrand; Molaverdikhani, Karan; Osip, David J.; Quintana, Elisa V. Bibcode: 2019BAAS...51c.328R Altcode: 2019astro2020T.328R; 2019arXiv190306152R Transmission spectra probe the atmospheres of transiting exoplanets, but these observations are also subject to signals introduced by magnetic active regions on host stars. We outline scientific opportunities in the next decade for providing useful constraints on stellar photospheres for the purposes of exoplanet transmission spectroscopy. Title: The Transit Light Source Effect. II. The Impact of Stellar Heterogeneity on Transmission Spectra of Planets Orbiting Broadly Sun-like Stars Authors: Rackham, Benjamin V.; Apai, Dániel; Giampapa, Mark S. Bibcode: 2019AJ....157...96R Altcode: 2018arXiv181206184R Transmission spectra probe exoplanetary atmospheres, but they can also be strongly affected by heterogeneities in host star photospheres through the transit light source effect. Here we build upon our recent study of the effects of unocculted spots and faculae on M-dwarf transmission spectra, extending the analysis to FGK dwarfs. Using a suite of rotating model photospheres, we explore spot and facula covering fractions for varying activity levels and the associated stellar contamination spectra. Relative to M dwarfs, we find that the typical variabilities of FGK dwarfs imply lower spot covering fractions, though they generally increase with later spectral types, from ∼0.1% for F dwarfs to 2%-4% for late-K dwarfs. While the stellar contamination spectra are considerably weaker than those for typical M dwarfs, we find that typically active G and K dwarfs produce visual slopes that are detectable in high-precision transmission spectra. We examine line offsets at Hα and the Na and K doublets and find that unocculted faculae in K dwarfs can appreciably alter transit depths around the Na D doublet. We find that band-averaged transit depth offsets at molecular bands for CH4, CO, CO2, H2O, N2O, O2, and O3 are not detectable for typically active FGK dwarfs, though stellar TiO/VO features are potentially detectable for typically active late-K dwarfs. Generally, this analysis shows that inactive FGK dwarfs do not produce detectable stellar contamination features in transmission spectra, though active FGK host stars can produce such features, and care is warranted in interpreting transmission spectra from these systems. Title: The Transit Light Source Effect in F to M Dwarf Systems Authors: Rackham, Benjamin V.; Apai, Dániel; Giampapa, Mark S.; Zhang, Zhanbo; Zhou, Yifan Bibcode: 2019AAS...23310302R Altcode: Transmission spectra are powerful probes of exoplanet atmospheres, but they are also subject to spectral features introduced by the transit light source (TLS) effect. This phenomenon imprints on transit depths the contrast between the emergent spectrum of the transit chord—the true light source for the transmission measurement—and the out-of-transit disk-averaged stellar spectrum—the necessarily assumed light source. Here we summarize a series of studies exploring the TLS effect in F to M dwarfs. We use a suite of model rotating photospheres to determine spot and faculae covering fractions for typical stellar activity levels, with which we calculate the corresponding TLS signals in transmission spectra. We find that transit depth changes due to the TLS effect can be comparable to or even an order of magnitude larger than those expected for transiting exoplanets. TLS signals are more pronounced in smaller and cooler main sequence stars—the same stars that have been the focus of many transit studies, given their favorable planet-to-star radius ratios. The TLS effect can mimic or mute H2O features from planetary atmospheres in M-dwarf systems and TiO/VO features in active late-G- and K-dwarf systems. We will discuss the spectral characteristics and scales of TLS signals for F to M spectral types and present transmission spectra from two M-dwarf systems that show evidence for TLS contamination: the GJ 1214 system (M4.5V) and the TRAPPIST-1 system (M8V). Robust methods of disentangling stellar and planetary features in transits will be crucial to interpretations of high-precision transmission spectra from JWST and future missions. Title: Enhanced Stellar Activity for Slow Antisolar Differential Rotation? Authors: Brandenburg, Axel; Giampapa, Mark S. Bibcode: 2018ApJ...855L..22B Altcode: 2018arXiv180208689B High-precision photometry of solar-like members of the open cluster M67 with Kepler/K2 data has recently revealed enhanced activity for stars with a large Rossby number, which is the ratio of rotation period to the convective turnover time. Contrary to the well established behavior for shorter rotation periods and smaller Rossby numbers, the chromospheric activity of the more slowly rotating stars of M67 was found to increase with increasing Rossby number. Such behavior has never been reported before, although it was theoretically predicted to emerge as a consequence of antisolar differential rotation (DR) for stars with Rossby numbers larger than that of the Sun, because in those models the absolute value of the DR was found to exceed that for solar-like DR. Using gyrochronological relations and an approximate age of 4 Gyr for the members of M67, we compare with computed rotation rates using just the B - V color. The resulting rotation-activity relation is found to be compatible with that obtained by employing the measured rotation rate. This provides additional support for the unconventional enhancement of activity at comparatively low rotation rates and the possible presence of antisolar differential rotation. Title: Understanding Stellar Contamination in Exoplanet Transmission Spectra as an Essential Step in Small Planet Characterization Authors: Apai, Dániel; Rackham, Benjamin V.; Giampapa, Mark S.; Angerhausen, Daniel; Teske, Johanna; Barstow, Joanna; Carone, Ludmila; Cegla, Heather; Domagal-Goldman, Shawn D.; Espinoza, Néstor; Giles, Helen; Gully-Santiago, Michael; Haywood, Raphaelle; Hu, Renyu; Jordan, Andres; Kreidberg, Laura; Line, Michael; Llama, Joe; López-Morales, Mercedes; Marley, Mark S.; de Wit, Julien Bibcode: 2018arXiv180308708A Altcode: Transmission spectroscopy during planetary transits is expected to be a major source of information on the atmospheres of small (approximately Earth-sized) exoplanets in the next two decades. This technique, however, is intrinsically affected by stellar spectral contamination caused by the fact that stellar photo- and chromospheres are not perfectly homogeneous. Such stellar contamination will often reach or exceed the signal introduced by the planetary spectral features. Finding effective methods to correct stellar contamination -- or at least to quantify its possible range -- for the most important exoplanets is a necessary step for our understanding of exoplanet atmospheres. This will require significantly deepening our understanding of stellar heterogeneity, which is currently limited by the available data. Title: The Transit Light Source Effect: False Spectral Features and Incorrect Densities for M-dwarf Transiting Planets Authors: Rackham, Benjamin V.; Apai, Dániel; Giampapa, Mark S. Bibcode: 2018ApJ...853..122R Altcode: 2017arXiv171105691R Transmission spectra are differential measurements that utilize stellar illumination to probe transiting exoplanet atmospheres. Any spectral difference between the illuminating light source and the disk-integrated stellar spectrum due to starspots and faculae will be imprinted in the observed transmission spectrum. However, few constraints exist for the extent of photospheric heterogeneities in M dwarfs. Here we model spot and faculae covering fractions consistent with observed photometric variabilities for M dwarfs and the associated 0.3-5.5 μm stellar contamination spectra. We find that large ranges of spot and faculae covering fractions are consistent with observations and corrections assuming a linear relation between variability amplitude, and covering fractions generally underestimate the stellar contamination. Using realistic estimates for spot and faculae covering fractions, we find that stellar contamination can be more than 10× larger than the transit depth changes expected for atmospheric features in rocky exoplanets. We also find that stellar spectral contamination can lead to systematic errors in radius and therefore the derived density of small planets. In the case of the TRAPPIST-1 system, we show that TRAPPIST-1's rotational variability is consistent with spot covering fractions {f}{spot}={8}-7+18 % and faculae covering fractions {f}{fac}={54}-46+16 % . The associated stellar contamination signals alter the transit depths of the TRAPPIST-1 planets at wavelengths of interest for planetary atmospheric species by roughly 1-15× the strength of planetary features, significantly complicating JWST follow-up observations of this system. Similarly, we find that stellar contamination can lead to underestimates of the bulk densities of the TRAPPIST-1 planets of {{Δ }}(ρ )=-{8}-20+7 % , thus leading to overestimates of their volatile contents. Title: Exoplanet Transits of Stellar Active Regions Authors: Giampapa, Mark S.; Andretta, Vincenzo; Covino, Elvira; Reiners, Ansgar; Esposito, Massimiliano Bibcode: 2018AAS...23123402G Altcode: We report preliminary results of a program to obtain high spectral- and temporal-resolution observations of the neutral helium triplet line at 1083.0 nm in transiting exoplanet systems. The principal objective of our program is to gain insight on the properties of active regions, analogous to solar plages, on late-type dwarfs by essentially using exoplanet transits as high spatial resolution probes of the stellar surface within the transit chord. The 1083 nm helium line is a particularly appropriate diagnostic of magnetized areas since it is weak in the quiet photosphere of solar-type stars but appears strongly in absorption in active regions. Therefore, during an exoplanet transit over the stellar surface, variations in its absorption equivalent width can arise that are functions of the intrinsic strength of the feature in the active region and the known relative size of the exoplanet. We utilized the Galileo Telescope and the GIANO-B near-IR echelle spectrograph to obtain 1083 nm spectra during transits in bright, well-known systems that include HD 189733, HD 209458, and HD 147506 (HAT-P-2). We also obtained simultaneous auxiliary data on the same telescope with the HARPS-N UV-Visible echelle spectrograph. We will present preliminary results from our analysis of the observed variability of the strength of the He I 1083 nm line during transits.Acknowledgements: Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. The NSO is operated by AURA under a cooperative agreement with the NSF. Title: The Light Source Problem: The Effect of Heterogeneous Stellar Photospheres on Searches for Transiting Exoplanet Biosignatures Authors: Rackham, B. V.; Apai, D.; Giampapa, M. S. Bibcode: 2017LPICo2042.4032R Altcode: TESS will soon enable the study of terrestrial exoplanet atmospheres. However, spots and faculae in stellar photospheres can complicate these measurements by mimicking or masking atmospheric features. We detail our work to constrain this effect. Title: VizieR Online Data Catalog: HeI 5876 & 10830Å EWs of solar-type stars (Andretta+, 2017) Authors: Andretta, V.; Giampapa, M. S.; Covino, E.; Reiners, A.; Beeck, B. Bibcode: 2017yCat..18390097A Altcode: A total of 134 FEROS spectra (R=48000) of our targets (including telluric standards) were acquired on the night of UT 2011 December 6-7; spectral coverage from 3500 to 9200Å. The Fiber Extended-range Optical Spectrograph (FEROS) was mounted at the 2.2m Max-Planck Gesellschaft/European Southern Observatory (MPG/ESO) telescope at La Silla (Chile).

The HeIλ10830 spectroscopic observations were carried out on the same night as the FEROS D3 observations, using the CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES), mounted at Unit Telescope 1 (Antu) of the VLT array at Cerro Paranal.

The details of the observations is given in table 1.

(3 data files). Title: The Effect of Stellar Contamination on Transmission Spectra of Low-mass Exoplanets Authors: Rackham, Benjamin V.; Apai, Daniel; Giampapa, Mark S. Bibcode: 2017DPS....4941620R Altcode: Transmission spectroscopy offers the exciting possibility of studying terrestrial exoplanet atmospheres in the near-term future. The Transiting Exoplanet Survey Satellite (TESS), scheduled for launch next year, is expected to discover thousands of transiting exoplanets around bright host stars, including an estimated twenty habitable zone super-Earths. The brightness of the TESS host stars, combined with refined observational strategies and near-future facilities, will enable searches for atmospheric signatures from smaller and cooler exoplanets. These observations, however, will be increasingly subject to noise introduced by heterogeneities in the host star photospheres, such as star spots and faculae. In short, the transmission spectroscopy method relies on the assumption that the spectrum of the transit chord does not differ from that of the integrated stellar disk or, if it does, the contribution of photospheric heterogeneities to the transmission spectrum can be constrained by variability monitoring. However, any axisymmetric populations of spots and faculae will strongly affect transmission spectra, and their presence cannot be deduced from monitoring efforts. A clear need exists for a more robust understanding of stellar contamination on transmission spectra. Here we summarize our work on the impact of heterogeneous stellar photospheres on transmission spectra and detail implications for atmospheric characterization efforts. By modeling spot and faculae distributions in stellar photospheres, we find that spot-covering fractions extrapolated from observed variability amplitudes are significantly underestimated. Likewise, corrections based on variability monitoring likely fall short of the actual stellar spectral contamination. We provide examples of contamination spectra for typical levels of stellar activity across a range of spectral types. For M dwarfs, molecular absorption features in spots and faculae can imprint apparent features in transmission spectra of small exoplanets, including those of the TRAPPIST-1 system. Constraining stellar contamination will likely be a limiting factor for detecting atmospheric features in transmission spectra of low-mass exoplanets around late-type stars from TESS. Title: Science-Driven Optimization of the LSST Observing Strategy Authors: LSST Science Collaboration; Marshall, Phil; Anguita, Timo; Bianco, Federica B.; Bellm, Eric C.; Brandt, Niel; Clarkson, Will; Connolly, Andy; Gawiser, Eric; Ivezic, Zeljko; Jones, Lynne; Lochner, Michelle; Lund, Michael B.; Mahabal, Ashish; Nidever, David; Olsen, Knut; Ridgway, Stephen; Rhodes, Jason; Shemmer, Ohad; Trilling, David; Vivas, Kathy; Walkowicz, Lucianne; Willman, Beth; Yoachim, Peter; Anderson, Scott; Antilogus, Pierre; Angus, Ruth; Arcavi, Iair; Awan, Humna; Biswas, Rahul; Bell, Keaton J.; Bennett, David; Britt, Chris; Buzasi, Derek; Casetti-Dinescu, Dana I.; Chomiuk, Laura; Claver, Chuck; Cook, Kem; Davenport, James; Debattista, Victor; Digel, Seth; Doctor, Zoheyr; Firth, R. E.; Foley, Ryan; Fong, Wen-fai; Galbany, Lluis; Giampapa, Mark; Gizis, John E.; Graham, Melissa L.; Grillmair, Carl; Gris, Phillipe; Haiman, Zoltan; Hartigan, Patrick; Hawley, Suzanne; Hlozek, Renee; Jha, Saurabh W.; Johns-Krull, C.; Kanbur, Shashi; Kalogera, Vassiliki; Kashyap, Vinay; Kasliwal, Vishal; Kessler, Richard; Kim, Alex; Kurczynski, Peter; Lahav, Ofer; Liu, Michael C.; Malz, Alex; Margutti, Raffaella; Matheson, Tom; McEwen, Jason D.; McGehee, Peregrine; Meibom, Soren; Meyers, Josh; Monet, Dave; Neilsen, Eric; Newman, Jeffrey; O'Dowd, Matt; Peiris, Hiranya V.; Penny, Matthew T.; Peters, Christina; Poleski, Radoslaw; Ponder, Kara; Richards, Gordon; Rho, Jeonghee; Rubin, David; Schmidt, Samuel; Schuhmann, Robert L.; Shporer, Avi; Slater, Colin; Smith, Nathan; Soares-Santos, Marcelles; Stassun, Keivan; Strader, Jay; Strauss, Michael; Street, Rachel; Stubbs, Christopher; Sullivan, Mark; Szkody, Paula; Trimble, Virginia; Tyson, Tony; de Val-Borro, Miguel; Valenti, Stefano; Wagoner, Robert; Wood-Vasey, W. Michael; Zauderer, Bevin Ashley Bibcode: 2017arXiv170804058L Altcode: The Large Synoptic Survey Telescope is designed to provide an unprecedented optical imaging dataset that will support investigations of our Solar System, Galaxy and Universe, across half the sky and over ten years of repeated observation. However, exactly how the LSST observations will be taken (the observing strategy or "cadence") is not yet finalized. In this dynamically-evolving community white paper, we explore how the detailed performance of the anticipated science investigations is expected to depend on small changes to the LSST observing strategy. Using realistic simulations of the LSST schedule and observation properties, we design and compute diagnostic metrics and Figures of Merit that provide quantitative evaluations of different observing strategies, analyzing their impact on a wide range of proposed science projects. This is work in progress: we are using this white paper to communicate to each other the relative merits of the observing strategy choices that could be made, in an effort to maximize the scientific value of the survey. The investigation of some science cases leads to suggestions for new strategies that could be simulated and potentially adopted. Notably, we find motivation for exploring departures from a spatially uniform annual tiling of the sky: focusing instead on different parts of the survey area in different years in a "rolling cadence" is likely to have significant benefits for a number of time domain and moving object astronomy projects. The communal assembly of a suite of quantified and homogeneously coded metrics is the vital first step towards an automated, systematic, science-based assessment of any given cadence simulation, that will enable the scheduling of the LSST to be as well-informed as possible. Title: Estimates of Active Region Area Coverage through Simultaneous Measurements of the He I λλ 5876 and 10830 Lines Authors: Andretta, Vincenzo; Giampapa, Mark S.; Covino, Elvira; Reiners, Ansgar; Beeck, Benjamin Bibcode: 2017ApJ...839...97A Altcode: 2017arXiv170310060A Simultaneous, high-quality measurements of the neutral helium triplet features at 5876 Å and 10830 Å in a sample of solar-type stars are presented. The observations were made with ESO telescopes at the La Silla Paranal Observatory under program ID 088.D-0028(A) and MPG Utility Run for Fiber Extended-range Optical Spectrograph 088.A-9029(A). The equivalent widths of these features combined with chromospheric models are utilized to infer the fractional area coverage, or filling factor, of magnetic regions outside of spots. We find that the majority of the sample is characterized by filling factors less than unity. However, discrepancies occur among the coolest K-type and the warmest and most rapidly rotating F-type dwarf stars. We discuss these apparently anomalous results and find that in the case of K-type stars, they are an artifact of the application of chromospheric models best suited to the Sun than to stars with significantly lower T eff. The case of the F-type rapid rotators can be explained by the measurement uncertainties of the equivalent widths, but they may also be due to a non-magnetic heating component in their atmospheres. With the exceptions noted above, preliminary results suggest that the average heating rates in the active regions are the same from one star to the other, differing in the spatially integrated, observed level of activity due to the area coverage. Hence, differences in activity in this sample are mainly due to the filling factor of active regions. Title: The Photometric Variability of Solar-Type Stars Authors: Giampapa, Mark S. Bibcode: 2016IAUFM..29A.365G Altcode: The joint variability of chromospheric emission with the integrated flux in the Kepler visible band for the Sun as a star is examined. No correlation between our Ca II K line parameter and the Kepler passband is seen, suggesting that visible-band variability in solar-like stars is mostly independent of solar-like chromospheric activity. However, the K-line parameter time series and the total solar flux in the infrared K band appear weakly correlated, reflecting the wavelength dependence of the relationship between magnetic activity and broadband variability. We then apply a schematic, three-component model as a framework for the discussion of stellar photometric variability as observed by Kepler. The model confirms that spots tend to dominate stellar photometric variability in the visible though interesting cases do emerge where the facular disk coverage may become important in determining the amplitude of broadband variability. Title: Maximizing Science in the Era of LSST: A Community-Based Study of Needed US Capabilities Authors: Najita, Joan; Willman, Beth; Finkbeiner, Douglas P.; Foley, Ryan J.; Hawley, Suzanne; Newman, Jeffrey A.; Rudnick, Gregory; Simon, Joshua D.; Trilling, David; Street, Rachel; Bolton, Adam; Angus, Ruth; Bell, Eric F.; Buzasi, Derek; Ciardi, David; Davenport, James R. A.; Dawson, Will; Dickinson, Mark; Drlica-Wagner, Alex; Elias, Jay; Erb, Dawn; Feaga, Lori; Fong, Wen-fai; Gawiser, Eric; Giampapa, Mark; Guhathakurta, Puragra; Hoffman, Jennifer L.; Hsieh, Henry; Jennings, Elise; Johnston, Kathryn V.; Kashyap, Vinay; Li, Ting S.; Linder, Eric; Mandelbaum, Rachel; Marshall, Phil; Matheson, Thomas; Meibom, Soren; Miller, Bryan W.; O'Meara, John; Reddy, Vishnu; Ridgway, Steve; Rockosi, Constance M.; Sand, David J.; Schafer, Chad; Schmidt, Sam; Sesar, Branimir; Sheppard, Scott S.; Thomas, Cristina A.; Tollerud, Erik J.; Trump, Jon; von der Linden, Anja Bibcode: 2016arXiv161001661N Altcode: The Large Synoptic Survey Telescope (LSST) will be a discovery machine for the astronomy and physics communities, revealing astrophysical phenomena from the Solar System to the outer reaches of the observable Universe. While many discoveries will be made using LSST data alone, taking full scientific advantage of LSST will require ground-based optical-infrared (OIR) supporting capabilities, e.g., observing time on telescopes, instrumentation, computing resources, and other infrastructure. This community-based study identifies, from a science-driven perspective, capabilities that are needed to maximize LSST science. Expanding on the initial steps taken in the 2015 OIR System Report, the study takes a detailed, quantitative look at the capabilities needed to accomplish six representative LSST-enabled science programs that connect closely with scientific priorities from the 2010 decadal surveys. The study prioritizes the resources needed to accomplish the science programs and highlights ways that existing, planned, and future resources could be positioned to accomplish the science goals. Title: Maximizing Science in the Era of LSST, Stars Study Group Report: Rotation and Magnetic Activity in the Galactic Field Population and in Open Star Clusters Authors: Hawley, Suzanne L.; Angus, Ruth; Buzasi, Derek; Davenport, James R. A.; Giampapa, Mark; Kashyap, Vinay; Meibom, Soren Bibcode: 2016arXiv160704302H Altcode: This is the stars chapter of the Kavli workshop report, which resulted from the community-based study of needed US OIR capabilities in the LSST era. The full report, which will include this chapter, is anticipated to be available in Fall 2016. See NOAO website (http://www.noao.edu/meetings/lsst-oir-study/) for more details. Title: The solar-stellar connection Authors: Giampapa, Mark S. Bibcode: 2016AsJPh..25..411G Altcode: A review of some principal results achieved in the area of stellar astrophysics with its origins in solar physics - the Solar-Stellar Connection - is presented from the perspective of an observational astronomer. The historical origins of the Solar-Stellar Connection are discussed followed by a review of key results from observations of stellar cycles analogous to the solar cycle in terms of parameters relevant to dynamo theory. A review of facets of angular momentum evolution and irradiance variations, each of which is determined by emergent, dynamo-generated magnetic fields, is given. Recent considerations of the impacts of stellar magnetic activity on the ambient radiative and energetic particle environment of the habitable zone of exoplanet systems are summarized. Some anticipated directions of the Solar-Stellar Connection in the new era of astronomy as defined by the advent of transformative facilities are presented. Title: Variability of Kepler Solar-like Stars Harboring Small Exoplanets Authors: Howell, Steve B.; Ciardi, David R.; Giampapa, Mark S.; Everett, Mark E.; Silva, David R.; Szkody, Paula Bibcode: 2016AJ....151...43H Altcode: 2015arXiv151203108H We examine Kepler light-curve variability on habitable zone transit timescales for a large uniform sample of spectroscopically studied Kepler exoplanet host stars. The stars, taken from Everett et al., are solar-like in their properties and each harbors at least one exoplanet (or candidate) of radius ≤2.5 {R}{{e}}. The variability timescale examined is typical for habitable zone planets orbiting solar-like stars and we note that the discovery of the smallest exoplanets (≤1.2 {R}{{e}}) with corresponding transit depths of less than ∼0.18 mmag occur for the brightest and photometrically quietest stars. Thus, these detections are quite rare in Kepler observations. Some brighter and more evolved stars (subgiants), the latter of which often show large radial velocity jitter, are found to be among the photometrically quietest solar-like stars in our sample and the most likely small planet transit hunting grounds. The Sun is discussed as a solar-like star proxy to provide insight into the nature and cause of photometric variability. It is shown that Kepler’s broad, visible light observations are insensitive to variability caused by chromospheric activity that may be present in the observed stars. Title: Photometric Variations In The Sun And Solar-Type Stars Authors: Giampapa, Mark Bibcode: 2016csss.confE...1G Altcode: The rich array of solar magnetic field-related phenomena we see occurs not only on stellar counterparts of our Sun but in stars that represent significant departures in their fundamental parameters from those of the
Sun. Though these phenomena appear energetically negligible when compared to the total luminosity of stars, they nevertheless govern the angular momentum evolution and modulate the radiative and particle output of the Sun and late-type stars. The term "The Solar-Stellar Connection" has been coined to describe the solar-stellar synergisms in the investigation of the generation, emergence and coupling of magnetic fields with the outer solar-stellar atmosphere to produce what we broadly refer to as magnetic activity. With the discovery of literally thousands of planets beyond our solar system, the Solar-Stellar-Planet Connection is quickly emerging as a new area of investigation of the impacts of magnetic activity on exoplanet atmospheres. In parallel with this rapid evolution in our perspectives is the advent of transformative facilities for the study of the Sun and the dynamic Universe. The primary focus of this invited talk will be on photometric variations in solar-type stars and the Sun. These brightness variations are associated with thermal homogeneities typically defined by magnetic structures that are also spatially coincident with key radiative proxies. Photometric variability in solar-type stars and the Sun includes transient brightening, rotational modulation by cool spots and cycle-related variability, each with a characteristic signature in time and wavelength. The emphasis
of this presentation will be on the relationship between broadband photometric variations and magnetic field-related activity in solar-type stars and the Sun. Facets of this topic will be discussed both retrospectively and prospectively as we enter a revolutionary, new era for astronomy. Title: Seeing SPOTS with SOFIA: Starspot Photometric Observations of Transiting Systems Authors: Giampapa, Mark Bibcode: 2015sofi.prop...24G Altcode: We propose to utilize the unique capabilities provided by HIPO/FLITECAM (FLIPO) and the FPI to obtain simultaneous, time-resolved multi-color photometry extending from the visible to the near infrared of magnetically active dwarf stars that are also the hosts of transiting exoplanets. In this way, we can measure the fundamental properties of starspots that are eclipsed by the transiting planet and thereby provide much improved constraints for starspot models than has been possible with the single-band data from Kepler and CoRoT. Since starspots are the strongest concentrations of magnetic flux on the Sun and stars, an understanding of their properties can yield critical constraints for stellar dynamo models and influence our views of the role of stellar magnetic activity in star-planet interactions. Title: A Method for Measuring Active Region Filling Factors on Solar-Type Stars Authors: Giampapa, Mark Steven; Andretta, Vincenzo; Beeck, Benjamin; Reiners, Ansgar; Schussler, Manfred Bibcode: 2015TESS....120101G Altcode: Radiative diagnostics of “activity” in the Sun and solar-type stars are spatially associated with sites of emergent magnetic flux. The magnetic fields themselves are widely regarded as the surface manifestations of a dynamo mechanism. The further development of both dynamo theory and models of the non-radiative heating of outer stellar atmospheres requires a knowledge of stellar magnetic field properties. In this context, it becomes important to determine the surface distribution, or at least the fractional coverage of, magnetic active regions as one critical constraint for dynamo models. But, while information on the spatial distribution of activity on stellar surfaces can be gathered in some special cases (mostly rapid rotators), such measurements have always been elusive in more solar-like stars. We discuss the challenges and results obtained from a method that relies on the non-linear response of the two principal He I triplet lines (at 1083 nm and 587.6 nm) to infer useful constraints on the fractional area coverage of magnetic active regions on solar-type stars. Title: SOLIS: Reconciling Disk-integrated and Disk-resolved Spectra from the Sun Authors: Pevtsov, Alexei A.; Bertello, Luca; Harker, Brian; Giampapa, Mark; Marble, Andrew R. Bibcode: 2015csss...18..887P Altcode: 2014arXiv1411.7266P Unlike other stars, the surface of the Sun can be spatially resolved to a high degree of detail . But the Sun can also be observed as if it was a distant star. The availability of solar disk-resolved and disk-integrated spectra offers an opportunity to devise methods to derive information about the spatial distribution of solar features from Sun-as-a-star measurements. Here, we present an update on work done at the National Solar Observatory to reconcile disk-integrated and disk-resolved solar spectra from the Synoptic Optical Long-term Investigation of the Sun (SOLIS) station. The results of this work will lead to a new approach to infer the information about the spatial distribution of features on other stars, from the overall filling factor of active regions to, possibly, the latitude/longitude distribution of features. Title: Line Bisector Variability in the Sun as a Star Authors: Giampapa, Mark; Bertello, Luca Bibcode: 2015csss...18..495G Altcode: We utilize spectra obtained with the Integrated Sunlight Spectrometer (ISS) instrument of the NSO SOLIS facility on Kitt Peak, AZ to perform a preliminary study of the variability of line asymmetries in the Mn I line at 539.5 nm and the nearby Fe I line at 539.3 nm, respectively. We derive the line bisector for these photospheric features from daily spectra of the Sun as a star acquired since January 2007, and characterize the variability of a measure of bisector amplitude with the solar cycle. A simple two-component model of the solar magnetic field is investigated as a possible origin for the variation in line depth with time of the magnetically sensitive Mn I feature. Title: Solar Cycle Dependency of Sun-as-a-Star Photospheric Spectral Line Profiles Authors: Bertello, Luca; Pevtsov, Alexei A.; Giampapa, Mark S.; Marble, Andrew R. Bibcode: 2015csss...18..693B Altcode: We investigate solar-cycle related changes in the profile of several photospheric spectral lines taken with the Integrated Sunlight Spectrometer (ISS) operating at the National Solar Observatory at Kitt Peak (Arizona). ISS, which is one of three instruments comprising the Synoptic Optical Long-term Investigations of the Sun (SOLIS) facility, is designed to obtain high spectral resolution (R = 300,000) observations of the Sun-as-a-star in a broad range of wavelengths (350 nm - 1100 nm). Daily measurements were obtained since December 2006, covering the decline of solar cycle 23 and the rising phase of cycle 24. We present time series of line parameters and discuss their correlation to indices of solar magnetic activity. Because of their different response to variations in the thermodynamic and magnetic structures of the solar atmosphere, the measured line shape parameters provide an excellent tool for disentangling thermal and magnetic effects occurring during different phases of the solar cycle. The results of this analysis may also help with developing a better understanding of magnetic cycles of activity in other solar-like stars. Title: Stellar Activity and Variability: Our Sun in a Stellar Context Authors: Giampapa, M. Bibcode: 2013ASPC..478..365G Altcode: The variability of the Sun in its chromospheric emission and associated irradiance changes is compared with that of other solar-type stars. A review of the results thus far obtained indicates that the Sun is not atypical in its magnetic field-related variations when compared to relatively homogeneous samples of stars that are also solar-like in key parameters such as effective temperature, gravity, rotation rate, and mean level of activity. In a comparison with more heterogeneous samples of ostensibly solar-type stars, the Sun appears to reside at a boundary between “active” and “quiet” chromosphere stars, suggesting that the structure of the outer solar atmosphere as delineated by emergent magnetic fields includes attributes of each of these broad stellar categories. Title: Stellar cycles: general properties and future directions Authors: Giampapa, Mark S. Bibcode: 2012IAUS..286..257G Altcode: We discuss the general properties of stellar cycles with emphasis on their amplitudes as a function of stellar parameters, particularly those stellar characteristics relevant to dynamo-driven magnetic activity. We deduce an empirical scaling relation between cycle frequency and differential rotation based on previously established empirical relations. We also compare the recent Cycle 23 to cycles in solar-type stars. We find that the extended minimum of Cycle 23 resembled in its Ca II H & K emission at minimum the mean levels of activity seen in stars with no cycles. Title: Joint Response of the Helium Lines to Chromospheric Heating in Solar-type Stars Authors: Giampapa, Mark S.; Andretta, V.; Beeck, B.; Reiners, A.; Schussler, M. Bibcode: 2012AAS...22020314G Altcode: We present a preliminary report on simultaneous observations of the He I 5876 and 10830 triplet lines, respectively, in a sample of solar-type stars. The near-IR spectra were obtained with the VLT and CRIRES instrument while the visible spectra were acquired with the MPG/ESO 2.2-m telescope in conjunction with the FEROS spectrograph. The correlation of the observed strengths of these lines will be examined and their potential as diagnostics of active region area coverage in solar-type stars will be discussed.

The NSO is operated by AURA under a cooperative agreement with the National Science Foundation. Title: Estimating the Fractional Area Coverage of Active Regions in Dwarf Stars Authors: Andretta, V.; Giampapa, M. Bibcode: 2011ASPC..448.1111A Altcode: 2011csss...16.1111A It has been shown (Andretta & Giampapa 1995) that the two He I triplet lines at 1.083 μm and 587.6 nm, respectively, can be utilized to infer the area coverage of active (plage-like) regions on stellar surfaces by exploiting their different responses to chromospheric heating. This kind of information, which is very difficult to obtain through other methods, can serve as a fundamental constraint for the development of stellar dynamo theory. We discuss the application and limitations of this approach to the interpretation of spatially resolved solar data along with some preliminary stellar observations. Title: Splinter Session "Solar and Stellar Flares" Authors: Fletcher, L.; Hudson, H.; Cauzzi, G.; Getman, K. V.; Giampapa, M.; Hawley, S. L.; Heinzel, P.; Johnstone, C.; Kowalski, A. F.; Osten, R. A.; Pye, J. Bibcode: 2011ASPC..448..441F Altcode: 2011csss...16..441F; 2012arXiv1206.3997F This summary reports on papers presented at the Cool Stars-16 meeting in the splinter session "Solar and Stellar flares." Although many topics were discussed, the main themes were the commonality of interests, and of physics, between the solar and stellar flare communities, and the opportunities for important new observations in the near future. Title: The evolution of stellar surface activity and possible effects on exoplanets Authors: Giampapa, Mark S. Bibcode: 2011IAUS..273...68G Altcode: The evolution of stellar activity involves a complex interplay between the interior dynamo mechanism, the emergent magnetic field configurations and their coupling with stellar winds, the subsequent angular momentum evolution, and fundamental stellar parameters. The discussion of the evolution of surface activity will emphasize the main sequence phase, from the ZAMS to stars of solar-age. We will focus particularly on the evolution of the fractional area coverages of spots on the surfaces of solar-type stars. We fit an empirical relation to the fractional mean spot area coverage as a function of age for ages greater than the Pleiades of the form log(MeanSpotCoverage) = 0.90(+/-0.26) - 1.03(+/-0.10)log(Age), where Age is in Myr. In addition, we summarize the relative evolution of radiative emissions in various short wavelength bands that are associated with stellar magnetic field-related activity. Possible effects on young planetary atmospheres also are appropriate to consider given that stellar surface activity is the origin of the high-energy component of the ambient radiation and particle fields in which planetary atmosphere evolution occurs. Title: Stellar Imager (SI): developing and testing a predictive dynamo model for the Sun by imaging other stars Authors: Carpenter, Kenneth G.; Schrijver, Carolus J.; Karovska, Margarita; Kraemer, Steve; Lyon, Richard; Mozurkewich, David; Airapetian, Vladimir; Adams, John C.; Allen, Ronald J.; Brown, Alex; Bruhweiler, Fred; Conti, Alberto; Christensen-Dalsgaard, Joergen; Cranmer, Steve; Cuntz, Manfred; Danchi, William; Dupree, Andrea; Elvis, Martin; Evans, Nancy; Giampapa, Mark; Harper, Graham; Hartman, Kathy; Labeyrie, Antoine; Leitner, Jesse; Lillie, Chuck; Linsky, Jeffrey L.; Lo, Amy; Mighell, Ken; Miller, David; Noecker, Charlie; Parrish, Joe; Phillips, Jim; Rimmele, Thomas; Saar, Steve; Sasselov, Dimitar; Stahl, H. Philip; Stoneking, Eric; Strassmeier, Klaus; Walter, Frederick; Windhorst, Rogier; Woodgate, Bruce; Woodruff, Robert Bibcode: 2010arXiv1011.5214C Altcode: The Stellar Imager mission concept is a space-based UV/Optical interferometer designed to resolve surface magnetic activity and subsurface structure and flows of a population of Sun-like stars, in order to accelerate the development and validation of a predictive dynamo model for the Sun and enable accurate long-term forecasting of solar/stellar magnetic activity. Title: Photometric Variability of Solar-Type Stars in the Young Pleiades Open Cluster Authors: Giampapa, Mark S.; Sherry, W. H.; Craine, E. R. Bibcode: 2010AAS...21640014G Altcode: 2010BAAS...41..856G We present some preliminary results from a program of intensive photometric monitoring of four solar-type stars in the young Pleiades cluster at an age of approximately 100 Myr utilizing a small-aperture robotic telescope. The Pleiades targets and their spectral types include hz 212 (K7), hz 253 (G1 V), hz 345 (G8 V) and hz 489 (G0 V). Photometry of the comparison stars and selected field stars included in the CCD frame is also given. The monitoring program over 43 nights of observations and 1500 frames yields information on the nature of both long-term variability and any short-term, transient activity such as flare outbursts.

This investigation is part of a broad effort to delineate the joint evolution of activity and irradiance variability in solar-type stars that may be the hosts of planetary systems. Understanding the nature of the joint variability of irradiance and magnetic activity on sun-like stars spanning a range of ages will provide crucial insight on how frequently earth-like atmospheres are likely to form and survive, and how frequently exo-earths encounter benign climatic variations.

We acknowledge support by a grant from the NASA Astrobiology Institute. The NSO and the NOAO are each operated by AURA under separate cooperative agreements with the National Science Foundation.

This research was partially supported by a grant from the American Astronomical Association. Title: The Asteroseismic Potential of Kepler: First Results for Solar-Type Stars Authors: Chaplin, W. J.; Appourchaux, T.; Elsworth, Y.; García, R. A.; Houdek, G.; Karoff, C.; Metcalfe, T. S.; Molenda-Żakowicz, J.; Monteiro, M. J. P. F. G.; Thompson, M. J.; Brown, T. M.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Kjeldsen, H.; Borucki, W. J.; Koch, D.; Jenkins, J. M.; Ballot, J.; Basu, S.; Bazot, M.; Bedding, T. R.; Benomar, O.; Bonanno, A.; Brandão, I. M.; Bruntt, H.; Campante, T. L.; Creevey, O. L.; Di Mauro, M. P.; Doǧan, G.; Dreizler, S.; Eggenberger, P.; Esch, L.; Fletcher, S. T.; Frandsen, S.; Gai, N.; Gaulme, P.; Handberg, R.; Hekker, S.; Howe, R.; Huber, D.; Korzennik, S. G.; Lebrun, J. C.; Leccia, S.; Martic, M.; Mathur, S.; Mosser, B.; New, R.; Quirion, P. -O.; Régulo, C.; Roxburgh, I. W.; Salabert, D.; Schou, J.; Sousa, S. G.; Stello, D.; Verner, G. A.; Arentoft, T.; Barban, C.; Belkacem, K.; Benatti, S.; Biazzo, K.; Boumier, P.; Bradley, P. A.; Broomhall, A. -M.; Buzasi, D. L.; Claudi, R. U.; Cunha, M. S.; D'Antona, F.; Deheuvels, S.; Derekas, A.; García Hernández, A.; Giampapa, M. S.; Goupil, M. J.; Gruberbauer, M.; Guzik, J. A.; Hale, S. J.; Ireland, M. J.; Kiss, L. L.; Kitiashvili, I. N.; Kolenberg, K.; Korhonen, H.; Kosovichev, A. G.; Kupka, F.; Lebreton, Y.; Leroy, B.; Ludwig, H. -G.; Mathis, S.; Michel, E.; Miglio, A.; Montalbán, J.; Moya, A.; Noels, A.; Noyes, R. W.; Pallé, P. L.; Piau, L.; Preston, H. L.; Roca Cortés, T.; Roth, M.; Sato, K. H.; Schmitt, J.; Serenelli, A. M.; Silva Aguirre, V.; Stevens, I. R.; Suárez, J. C.; Suran, M. D.; Trampedach, R.; Turck-Chièze, S.; Uytterhoeven, K.; Ventura, R.; Wilson, P. A. Bibcode: 2010ApJ...713L.169C Altcode: 2010arXiv1001.0506C We present preliminary asteroseismic results from Kepler on three G-type stars. The observations, made at one-minute cadence during the first 33.5 days of science operations, reveal high signal-to-noise solar-like oscillation spectra in all three stars: about 20 modes of oscillation may be clearly distinguished in each star. We discuss the appearance of the oscillation spectra, use the frequencies and frequency separations to provide first results on the radii, masses, and ages of the stars, and comment in the light of these results on prospects for inference on other solar-type stars that Kepler will observe. Title: Simultaneous Multi-Wavelength Observations of Magnetic Activity in Ultracool Dwarfs. III. X-ray, Radio, and Hα Activity Trends in M and L dwarfs Authors: Berger, E.; Basri, G.; Fleming, T. A.; Giampapa, M. S.; Gizis, J. E.; Liebert, J.; Martín, E.; Phan-Bao, N.; Rutledge, R. E. Bibcode: 2010ApJ...709..332B Altcode: 2009arXiv0909.4783B As part of our on-going investigation into the magnetic field properties of ultracool dwarfs, we present simultaneous radio, X-ray, and Hα observations of three M9.5-L2.5 dwarfs (BRI 0021-0214, LSR 060230.4+391059, and 2MASS J052338.2-140302). We do not detect X-ray or radio emission from any of the three sources, despite previous detections of radio emission from BRI 0021 and 2M0523-14. Steady and variable Hα emission are detected from 2M0523-14 and BRI 0021, respectively, while no Hα emission is detected from LSR 0602+39. Overall, our survey of nine M8-L5 dwarfs doubles the number of ultracool dwarfs observed in X-rays, and triples the number of L dwarfs, providing in addition the deepest limits to date, log(L X/L bol) lsim -5. With this larger sample we find the first clear evidence for a substantial reduction in X-ray activity, by about two orders of magnitude, from mid-M to mid-L dwarfs. We find that the decline in Hα roughly follows L /L bol vprop 10-0.4×(SP-6) for SP >= 6, where SP = 0 for spectral type M0. In the radio band, however, the luminosity remains relatively unchanged from M0 to L4, leading to a substantial increase in L rad/L bol. Our survey also provides the first comprehensive set of simultaneous radio/X-ray/Hα observations of ultracool dwarfs, and reveals a clear breakdown of the radio/X-ray correlation beyond spectral type M7, evolving smoothly from L ν,rad/L X ≈ 10-15.5 to ~10-11.5 Hz-1 over the narrow spectral-type range M7-M9. This breakdown reflects the substantial reduction in X-ray activity beyond M7, but its physical origin remains unclear since, as evidenced by the uniform radio emission, there is no drop in the field dissipation and particle acceleration efficiency. Based on the results of our survey, we conclude that a further investigation of magnetic activity in ultracool dwarfs will benefit from a two-pronged approach: multi-rotation observations of nearby known active sources and a snapshot survey of a large sample within ~50 pc to uncover rare flaring objects. Title: The Origin of Enhanced Activity in the Suns of M67 Authors: Reiners, A.; Giampapa, M. S. Bibcode: 2009ApJ...707..852R Altcode: 2009arXiv0911.0424R We report the results of the analysis of high-resolution photospheric line spectra obtained with the UVES instrument on the VLT for a sample of 15 solar-type stars selected from a recent survey of the distribution of H and K chromospheric line strengths in the solar-age open cluster M67. We find upper limits to the projected rotation velocities that are consistent with solar-like rotation (i.e., v sin ilsim 2-3 km s-1) for objects with Ca II chromospheric activity within the range of the contemporary solar cycle. Two solar-type stars in our sample exhibit chromospheric emission well in excess of even solar maximum values. In one case, Sanders 1452, we measure a minimum rotational velocity of v sin i = 4 ± 0.5 km s-1, or over twice the solar equatorial rotational velocity. The other star with enhanced activity, Sanders 747, is a spectroscopic binary. We conclude that high activity in solar-type stars in M67 that exceeds solar levels is likely due to more rapid rotation rather than an excursion in solar-like activity cycles to unusually high levels. We estimate an upper limit of 0.2% for the range of brightness changes occurring as a result of chromospheric activity in solar-type stars and, by inference, in the Sun itself. We discuss possible implications for our understanding of angular momentum evolution in solar-type stars, and we tentatively attribute the rapid rotation in Sanders 1452 to a reduced braking efficiency. Title: Periodic Radio and Hα Emission from the L Dwarf Binary 2MASSW J0746425+200032: Exploring the Magnetic Field Topology and Radius Of An L Dwarf Authors: Berger, E.; Rutledge, R. E.; Phan-Bao, N.; Basri, G.; Giampapa, M. S.; Gizis, J. E.; Liebert, J.; Martín, E.; Fleming, T. A. Bibcode: 2009ApJ...695..310B Altcode: 2008arXiv0809.0001B We present an 8.5 hr simultaneous radio, X-ray, UV, and optical observation of the L dwarf binary 2MASSW J0746425+200032. We detect strong radio emission, dominated by short-duration periodic pulses at 4.86 GHz with P = 124.32 ± 0.11 min. The stability of the pulse profiles and arrival times demonstrates that they are due to the rotational modulation of a B ≈ 1.7 kG magnetic field. A quiescent nonvariable component is also detected, likely due to emission from a uniform large-scale field. The Hα emission exhibits identical periodicity, but unlike the radio pulses it varies sinusoidally and is offset by exactly 1/4 of a phase. The sinusoidal variations require chromospheric emission from a large-scale field structure, with the radio pulses likely emanating from the magnetic poles. While both light curves can be explained by a rotating misaligned magnetic field, the 1/4 phase lag rules out a symmetric dipole topology since it would result in a phase lag of 1/2 (poloidal field) or zero (toroidal field). We therefore conclude that either (1) the field is dominated by a quadrupole configuration, which can naturally explain the 1/4 phase lag; or (2) the Hα and/or radio emission regions are not trivially aligned with the field. Regardless of the field topology, we use the measured period along with the known rotation velocity (v sin i ≈ 27 km s-1), and the binary orbital inclination (i ≈ 142°), to derive a radius for the primary star of 0.078 ± 0.010 R sun. This is the first measurement of the radius of an L dwarf, and along with a mass of 0.085 ± 0.010 M sun it provides a constraint on the mass-radius relation below 0.1 M sun. We find that the radius is about 30% smaller than expected from theoretical models, even for an age of a few Gyr. The origin of this discrepancy is either a breakdown of the models at the bottom of the main sequence, or a significant misalignment between the rotational and orbital axes. Title: Photometric variability of solar-type members of the Pleiades open cluster Authors: Giampapa, Mark; Sherry, William; Craine, Eric; Tucker, Roy Bibcode: 2009AIPC.1094..648G Altcode: 2009csss...15..648G We present some preliminary results from a program utilizing a small-aperture transit telescope for the photometric monitoring of a set of solar-type stars in the young Pleiades cluster at an age of approximately 100 Myr. The photometry sample includes 12 stars in the (B-V)0 color range of 0.58-0.76, corresponding to a range in spectral type of approximately F9 V-G9 V. Title: The Lifetime of Magnetic Fields in Fully Convective Brown Dwarfs Authors: Berger, Edo; Giampapa, Mark; Sherry, William Bibcode: 2009noao.prop...84B Altcode: Until recently theoretical expectation was that magnetic activity would disappear in fully convective ultracool dwarfs (very low mass stars and brown dwarfs). We now know that magnetic activity in fact exists, but the origin, configuration, and lifetime of the field and dynamo remain largely unconstrained. Numerical simulations cannot presently accommodate the relevant conditions in the lowest mass objects, and progress mainly relies on observational clues. Recently, we uncovered the first examples of periodic and sinusoidal H(alpha) emission from two ultracool dwarfs (with a period of 2 hours). The H(alpha) emission is due to a large-scale magnetic hot spot that rigidly rotates with the stars. Here we propose observations separated by 1 and 2 years from the original discovery in order to assess the stability timescale of the magnetic field, a crucial constraint on the nature of the dynamo mechanism. Title: The Stars as a Sun: Secular Variations of Cycling and Non-Cycling Stars Authors: Hall, Jeffrey C.; Giampapa, Mark S.; Henry, Gregory W.; Lean, Judith L.; Saar, Steven H.; Soderblom, David R. Bibcode: 2009astro2010S.111H Altcode: No abstract at ADS Title: Causes of Solar Activity Authors: Giampapa, Mark S.; Gibson, Sarah; Harvey, J. W.; Hill, Frank; Norton, Aimee A.; Pevtsov, A. Bibcode: 2009astro2010S..92G Altcode: No abstract at ADS Title: Asteroseismology: The Next Frontier in Stellar Astrophysics Authors: Giampapa, Mark S.; Aerts, Conny; Bedding, Tim; Bonanno, Alfio; Brown, Timothy M.; Christensen-Dalsgaard, Jorgen; Dominik, Martin; Ge, Jian; Gilliland, Ronald L.; Harvey, J. W.; Hill, Frank; Kawaler, Steven D.; Kjeldsen, Hans; Kurtz, D. W.; Marcy, Geoffrey W.; Matthews, Jaymie M.; Monteiro, Mario Joao P. F. G.; Schou, Jesper Bibcode: 2009astro2010S..91G Altcode: No abstract at ADS Title: A global SOLIS vector spectromagnetograph (VSM) network Authors: Streander, K. V.; Giampapa, M. S.; Harvey, J. W.; Henney, C. J.; Norton, A. A. Bibcode: 2008SPIE.7014E..7PS Altcode: 2008SPIE.7014E.251S Understanding the Sun's magnetic field related activity is far from complete as reflected in the limited ability to make accurate predictions of solar variability. To advance our understanding of solar magnetism, the National Solar Observatory (NSO) constructed the Synoptic Optical Long-term Investigations of the Sun (SOLIS) suite of instruments to conduct high precision optical measurements of processes on the Sun whose study requires sustained observations over long time periods. The Vector Spectromagnetograph (VSM), the principal SOLIS instrument, has been in operation since 2003 and obtains photospheric vector data, as well as photospheric and chromospheric longitudinal magnetic field measurements. Instrument performance is being enhanced by employing new, high-speed cameras that virtually freeze seeing, thus improving sensitivity to measure the solar magnetic field configuration. A major operational goal is to provide real-time and near-real-time data for forecasting space weather and increase scientific yield from shorter duration solar space missions and ground-based research projects. The National Solar Observatory proposes to build two near-duplicates of the VSM instrument and place them at international sites to form a three-site global VSM network. Current electronic industry practice of short lifetime cycles leads to improved performance and reduced acquisition costs but also to redesign costs and engineering impacts that must be minimized. The current VSM instrument status and experience gained from working on the original instrument is presented herein and used to demonstrate that one can dramatically reduce the estimated cost and fabrication time required to duplicate and commission two additional instruments. Title: Ca II H & K Spectra From The National Solar Observatory Authors: Livingston, W. C.; Giampapa, M. S.; Harvey, J. W.; Keil, S. L.; Toussaint, R. M. Bibcode: 2008AGUSMSP53B..04L Altcode: When the Sun is observed as a star (i.e., spatially integrated full disk) the cores of the chronospheric H and K resonance lines of singly ionized calcium show the greatest cycle variability (up to 40% peak-to-peak) accessible from the ground. Synoptic archives are available at monthly intervals from 1974 (Kitt Peak) and for K only at almost a daily cadence from 1984 (Sacramento Peak). We discuss these time series and compare them with, for example, sunspot numbers and magnetic fields. Less frequent are center disk observations in which the activity cycle is found to be absent, implying the quiet basal atmosphere is constant and not, say, heated by cycle magnetic activity. New, near daily, spatially integrated full disk solar data from the SOLIS Integrated Sunlight Spectrometer (ISS)agree well with the older work. We now propose to produce calibrated (Houtgast 1970; Solar Phys 15, 273, high points: 387.5, 395.3, and 402.0 nm), low dispersion full disk spectra that may be directly compared with that from solar-type stars. Title: Simultaneous Multiwavelength Observations of Magnetic Activity in Ultracool Dwarfs. II. Mixed Trends in VB 10 and LSR 1835+32 and the Possible Role of Rotation Authors: Berger, E.; Basri, G.; Gizis, J. E.; Giampapa, M. S.; Rutledge, R. E.; Liebert, J.; Martín, E.; Fleming, T. A.; Johns-Krull, C. M.; Phan-Bao, N.; Sherry, W. H. Bibcode: 2008ApJ...676.1307B Altcode: 2007arXiv0710.3383B As part of our ongoing investigation of magnetic activity in ultracool dwarfs we present simultaneous radio, X-ray, UV, and optical observations of LSR1835+32 (M8.5), and simultaneous X-ray and UV observations of VB10 (M8), both with a duration of about 9 hr. LSR1835+32 exhibits persistent radio emission, and Hα variability on timescales of 0.5-2 hr. The detected UV flux is consistent with photospheric emission, and no X-ray emission is detected to a deep limit of LX/Lbollesssim 10-5.7. The Hα and radio emission are temporally uncorrelated, and the ratio of radio to X-ray luminosity exceeds the correlation seen in F-M6 stars by >2 × 104. The lack of radio variability during four rotations of LSR1835+32 requires a uniform stellar-scale field of ~10 G, and indicates that the Hα variability is dominated by much smaller scales, <10% of the chromospheric volume. VB10, on the other hand, shows correlated flaring and quiescent X-ray and UV emission, similar to the behavior of early M dwarfs. Delayed and densely sampled optical spectra exhibit a similar range of variability amplitudes and timescales. Along with our previous observations of the M8.5 dwarf TVLM513-46546 we conclude that late M dwarfs exhibit a mix of activity patterns, which points to a transition in the structure and heating of the outer atmosphere by large-scale magnetic fields. We find that rotation may play a role in generating the fields as evidenced by a tentative correlation between radio activity and rotation velocity. The X-ray emission, however, shows evidence for supersaturation at vsin i > 25 km s-1, which could be the result of secondary effects such as inefficient heating or centrifugal stripping of extended coronal loops. These effects may underlie the severe violation of the radio/X-ray correlation in ultracool dwarfs. Title: Externally Induced or Internally Produced: What is the Source of the Extreme Magnetic Activity Observed in Very Low Mass Stars? Authors: Howell, Steve B.; Giampapa, Mark; Harrison, Thomas; Hawley, Suzanne; Hill, Frank; Honeycutt, Kent; Kafka, Stella; Silvestri, Nicole; Szkody, Paula; Walter, Fred; West, Andrew Bibcode: 2008noao.prop...95H Altcode: Recent observations of the very low mass donor stars in short period interacting binaries have revealed the presence of active chromospheres. Our group has obtained initial spectra for five such systems to date and found evidence of stellar activity in all of them, including a brown dwarf mass (0.055 M-sun) donor star. The Washington group has obtained a SDSS sample of a number of close, but non-interacting white dwarf + red dwarf binaries and find H(alpha) emission related to activity. We plan to perform the first detailed phase-resolved spectroscopic study of the active chromospheres in this set of rapidly rotating (<0.3 day), low mass (<0.25 M-sun), fully convective late-type stars and brown dwarfs. Our observational goals are to study the extent, nature and short-term changes of these active chromospheres on the low mass stars of close binaries. Is the extreme activity caused by the low mass star itself or externally driven by tidal or magnetic forces? The long term goals are to complete a large enough sample (~10 systems) to provide statistically useful measurements and to use the extended time allocation to obtain long term ``coverage" spectra of each system to monitor, measure, and understand the solar-type cycles likely to be present. Title: Simultaneous Multiwavelength Observations of Magnetic Activity in Ultracool Dwarfs. I. The Complex Behavior of the M8.5 Dwarf TVLM 513-46546 Authors: Berger, E.; Gizis, J. E.; Giampapa, M. S.; Rutledge, R. E.; Liebert, J.; Martín, E.; Basri, G.; Fleming, T. A.; Johns-Krull, C. M.; Phan-Bao, N.; Sherry, W. H. Bibcode: 2008ApJ...673.1080B Altcode: 2007arXiv0708.1511B We present the first simultaneous radio, X-ray, ultraviolet, and optical spectroscopic observations of the M8.5 dwarf TVLM 513-46546, with a duration of 9 hr. These observations are part of a program to study the origin of magnetic activity in ultracool dwarfs, and its impact on chromospheric and coronal emission. Here we detect steady quiescent radio emission superposed with multiple short-duration, highly polarized flares; there is no evidence for periodic bursts previously reported for this object, indicating their transient nature. We also detect soft X-ray emission, with LX/Lbol ≈ 10-5.1, the faintest to date for any object later than M5, and a possible X-ray flare. TVLM 513-46546 continues the trend of severe violation of the radio/X-ray correlation in ultracool dwarfs, by nearly 4 orders of magnitude. From the optical spectroscopy we find that the Balmer line luminosity exceeds the X-ray luminosity by a factor of a few, ruling out chromospheric heating by coronal X-ray emission. More importantly, we detect sinusoidal Hα and Hβ equivalent width light curves with a period of 2 hr, matching the rotation period of TVLM 513-46546. This behavior points to a corotating chromospheric hot spot or an extended magnetic structure, with a covering fraction of about 50%. This feature may be transitory based on the apparent decline in light-curve peak during the four observed maxima. From the radio data we infer a large-scale and steady magnetic field of ~102 G. A large-scale field is also required by the sinusoidal Balmer line emission. The radio flares, on the other hand, are produced in a component of the field with a strength of ~3 kG and a likely multipolar configuration. The overall lack of correlation between the various activity indicators suggests that the short-duration radio flares do not have a strong influence on the chromosphere and corona, and that the chromospheric emission is not the result of coronal heating. Title: The First MOTESS-GNAT Variable-Star Survey Authors: Kraus, Adam L.; Craine, Eric R.; Giampapa, Mark S.; Scharlach, Werner W. G.; Tucker, Roy A. Bibcode: 2007AJ....134.1488K Altcode: We present the results of the first MOTESS-GNAT variable-star survey, a deep, wide-field variability survey conducted over 2 yr with a total sky coverage of 300 deg2. In this survey, we identified 26,042 variable-star candidates with magnitudes R = 13-19, including 5271 that are periodic at the 99% confidence level. We recovered 59 out of 68 members of the General Catalogue of Variable Stars (GCVS) that are in this brightness range. We discuss the implications for completeness and accuracy for both this survey and the GCVS; the implied completeness for distinctly classifiable variable stars in our survey is ~85%-90%. We also discuss some of the caveats of our survey results. We conclude that this instrument design is ideal for an inexpensive, longitudinally distributed telescope network that could be used to study faint or rare transient phenomena in a previously unexplored regime of parameter space. Title: Variability of Young Solar-Type Stars in the Pleiades Open Cluster Authors: Giampapa, Mark S.; Sherry, W. S.; Craine, E. R.; Tucker, R. Bibcode: 2007AAS...210.2301G Altcode: 2007BAAS...39..128G We present a preliminary report on a program of photometric monitoring of the solar-type stars in the young Pleiades open cluster. Specifically, we report on the results for 37 nights of observation in our survey region that includes 12 solar-type Pleiades members. The goal of the program is to characterize the short- and long-term brightness variability of young solar-type stars during the epoch of the formation and early evolution of young planetary atmospheres.

This work is supported in part by a joint grant from the NASA Astrobiology Institute to the University of Arizona and the NOAO/NSO. The NSO is operated by AURA under a cooperative agreement with the NSF. Title: Sun-as-a-Star Spectrum Variations 1974-2006 Authors: Livingston, W.; Wallace, L.; White, O. R.; Giampapa, M. S. Bibcode: 2007ApJ...657.1137L Altcode: 2006astro.ph.12554L We have observed selected Fraunhofer lines, both integrated over the full disk and for a small circular region near the center of the solar disk, on 1215 days over the past 30 years. Our full disk results for the chromosphere show that Ca II K 3933 Å nicely tracks the 11 yr magnetic cycle based on sunspot number, with a peak amplitude in central intensity of ~37%. The wavelength of the midline core absorption feature, called K3, referenced to nearby photospheric Fe, displays an activity cycle variation with an amplitude of 3 mÅ (6 mÅ center disk). Other chromospheric lines, such as He I 10830 Å, Ca II 8542 Å, Hα, and the CN 3883 Å bandhead, track Ca II K intensity with lower relative amplitudes. In the low photosphere, temperature-sensitive C I 5380 Å appears constant in intensity to 0.2%. In the high photosphere, the cores of strong Fe I lines, Na D1 and D2, and the Mg I b lines, present a puzzling signal, perhaps indicating a role for the 22 yr Hale cycle. Solar minimum around 1985 was clearly seen, but the following minimum in 1996 was missing. Our center disk results show that both Ca II K and C I 5380 Å intensities are constant, indicating that the basal quiet atmosphere is unaffected by cycle magnetism within our observational error. A lower limit to the Ca II K central intensity atmosphere is 0.040. This possibly represents conditions as they were during the Maunder minimum. Converted to the Mount Wilson S-index (H+K index), the Sun center disk is at the lower activity limit for solar-type stars. An appendix provides instructions for URL access to both the raw and reduced data. Title: A Survey of Chromospheric Activity in the Solar-Type Stars in the Open Cluster M67 Authors: Giampapa, Mark S.; Hall, Jeffrey C.; Radick, Richard R.; Baliunas, Sallie L. Bibcode: 2006ApJ...651..444G Altcode: 2006astro.ph..7313G We present the results of a spectroscopic survey of the Ca II H and K core strengths in a sample of 60 solar-type stars that are members of the solar-age and solar-metallicity open cluster M67. We adopt the HK index, defined as the summed H+K core strengths in 1 Å bandpasses centered on the H and K lines, respectively, as a measure of the chromospheric activity that is present. We compare the distribution of mean HK index values for the M67 solar-type stars with the variation of this index as measured for the Sun during the contemporary solar cycle. We find that the stellar distribution in our HK index is broader than that for the solar cycle. Approximately 17% of the M67 Sun-like stars exhibit average HK indices that are less than solar minimum. About 7%-12% are characterized by relatively high activity in excess of solar maximum values, while 72%-80% of the solar analogs exhibit Ca II H+K strengths within the range of the modern solar cycle. The ranges given reflect uncertainties in the most representative value of the maximum in the HK index to adopt for the solar cycle variations observed during the period AD 1976-2004. Thus, ~20%-30% of our homogeneous sample of Sun-like stars have mean chromospheric H+K strengths that are outside the range of the contemporary solar cycle. Any cycle-like variability that is present in the M67 solar-type stars appears to be characterized by periods greater than ~6 yr. Finally, we estimate a mean chromospheric age for M67 in the range of 3.8-4.3 Gyr.

The results presented herein are based on data obtained at the WIYN telescope and at the McMath-Pierce Solar Telescope. The WIYN Observatory is a joint facility of the University of Wisconsin-Madison, Indiana University, Yale University, and the National Optical Astronomy Observatory. The McMath-Pierce Solar Telescope Facility is operated by the National Solar Observatory for the National Science Foundation. This paper is WIYN Open Cluster Study XXVIII in the series. Title: Age-Activity Correlation at Young Stellar Ages Authors: Giampapa, Mark; Sherry, William Bibcode: 2006noao.prop..321G Altcode: We propose to utilize WIYN/Hydra to conduct a survey of the Ca II H & K resonance line profiles in the solar-type stars in the young (~ 100 Myr) Pleiades cluster. The results of this program will represent the first comprehensive survey of chromospheric Ca II strengths and line shapes in the young solar-type members of the Pleiades. We will use the measured chromospheric Ca II H& K line strengths to establish the empirical calibration between Ca II chromospheric emission and stellar age at young ages ~ 100 Myr. We will also directly compare the range of Ca II emission encountered in the young Pleiades sun-like stars to the range in variation of Ca II core emission seen in the contemporary Sun during the course of the modern solar cycle as well as to the results of our prior WIYN/Hydra survey of the solar-type stars in the solar-age cluster, M67. Finally, the results of the Pleiades survey will be compared to that obtained in our proposed Ca II survey of the solar-type stars in the intermediate- age cluster NGC 752 (1.8 Gyr). The combined results of these programs will yield an accurate calibration of the age-activity correlation, including the dispersion in this correlation due to the range of activity in sun-like stars at a given age, extending from cluster ages ~ 0.1 Gyr to ~ 4.5 Gyr. Finally, the intercomparison of the survey results for the Pleiades, NGC 752, M67, and the Sun, will yield quantitative insight on the evolution of the ranges in cycle-related chromospheric activity from ~ 100 Myr to solar age. Title: Collaborative Research Opportunities with the Global Network of Astronomical Telescopes (GNAT): Variable Star Research Authors: Craine, E. R.; Tucker, R. A.; Kraus, A. L.; Culver, R. B.; Giampapa, M. S. Bibcode: 2006SASS...25..111C Altcode: The Global Network of Astronomical Telescopes (GNAT) is modeling its observing system on a network of scan-mode telescopes following the designs of the Moving Object and Transient Event Search System (MOTESS), implemented at Goodricke-Pigott Observatory in Tucson, Arizona. GNAT has developed a comprehensive data pipeline for extracting photometric measurements of all of the stars observed in each of the discrete declination bands observed with the scan-mode system. This enormous volume of observations is leading to an aggressive program of discovery of objects that are in many cases of great interest in terms of follow-up observations. GNAT is reaching out to both the professional and amateur astronomy communities to identify potential collaborators who are interested in participating in a wide variety of follow-up research programs. Title: Structure and Availability of the MOTESS-GNAT Variable Star Surveys Authors: Craine, E. R.; Kraus, A. L.; Giampapa, M. S.; Scharlach, W. W. G.; Tucker, R. A. Bibcode: 2005AAS...20712212C Altcode: 2005BAAS...37.1365C The Moving Object Transient Event Search System (MOTESS) has resulted in hardware and data streams that are being used as prototypes for the Global Network of Astronomical Telescopes (GNAT) photometric monitoring systems. Multiple telescopes are operated in scan mode to collect CCD imagery of the sky, which is subsequently processed through a prototype GNAT data reduction pipeline. This process leads to large arrays of differential time series photometry for all of the detectable stars in the survey band. The first of several planned surveys is now complete, resulting in the MOTESS-GNAT MG1 variable star catalog. The MG1 survey is at a declination of 03d18m with a width of 48-arcmin. The survey has been reduced to observations of approximately 1.6 million stars with a detection limit of R=19; the MG1 variable star catalog contains 26,042 variable star candidates with R = 13-19, including 5,271 which are periodic at the 99% confidence level. In this presentation we describe the structure of the catalog and its components and provide details on accessing these data. We conclude with a status report on subsequent MOTESS GNAT variable star survey programs. Title: Chromospheric Activity at Intermediate Ages Authors: Giampapa, Mark; Stauffer, John; Deliyannis, Constantine; Sherry, William Bibcode: 2005noao.prop...84G Altcode: The calibration of the empirical relation between Ca II chromospheric strength and stellar age between 0.6 Gyr (Hyades) and 4.0 - 5 Gyr (M67 and the Sun) relies on the uncertain determination of ages for individual field stars in the solar neighborhood. We therefore propose to obtain WIYN/Hydra spectra of ~ 100 solar-type dwarf stars in the 1.8 Gyr old open cluster, NGC 752. This cluster contains a sample of solar-type dwarfs that is homogeneous in age and chemical composition. Furthermore, NGC 752 is the nearest-and hence brightest- cluster at an age ~ 2 Gyr. The results will yield an improved calibration of the age-activity relation at intermediate ages. In addition, we will determine if the chromospheric Ca II strengths for the solar-type stars in NGC 752 lie in the so-called "Vaughan-Preston Gap''- an apparent discontinuity in the Ca II H& K strength-(B-V) diagram found for field stars in the solar neighborhood. Our data will yield insight on the two proposed origins for the gap, namely, that it is a result of two different modes of dynamo action or that it is actually an artifact of a discontinuity in the local star formation rate. This is a resubmission of a previously approved proposal that was allocated two nights in 2004 November. The time was lost to instrument problems (Hydra gripper malfunctions) and weather. No usable data were obtained. Title: The Magnetic Properties of an L Dwarf Derived from Simultaneous Radio, X-Ray, and Hα Observations Authors: Berger, E.; Rutledge, R. E.; Reid, I. N.; Bildsten, L.; Gizis, J. E.; Liebert, J.; Martín, E.; Basri, G.; Jayawardhana, R.; Brandeker, A.; Fleming, T. A.; Johns-Krull, C. M.; Giampapa, M. S.; Hawley, S. L.; Schmitt, J. H. M. M. Bibcode: 2005ApJ...627..960B Altcode: 2005astro.ph..2384B We present the first simultaneous, multiwavelength observations of an L dwarf, the L3.5 candidate brown dwarf 2MASS J00361617+1821104, conducted with the Very Large Array, the Chandra X-Ray Observatory, and the Kitt Peak 4 m telescope. We detect strongly variable and periodic radio emission (P=3 hr) with a fraction of about 60% circular polarization. No X-ray emission is detected to a limit of LX/Lbol<~2×10-5, several hundred times below the saturation level observed in early M dwarfs. Similarly, we do not detect Hα emission to a limit of L/Lbol<~2×10-7, the deepest for any L dwarf observed to date. The ratio of radio to X-ray luminosity is at least 4 orders of magnitude in excess of that observed in a wide range of active stars (including M dwarfs), providing the first direct confirmation that late-M and L dwarfs violate the radio/X-ray correlation. The radio emission is due to gyrosynchrotron radiation in a large-scale magnetic field of about 175 G, which is maintained on timescales longer than 3 yr. The detected 3 hr period may be due to (1) the orbital motion of a companion at a separation of about 5 stellar radii, similar to the configuration of RS CVn systems, (2) an equatorial rotation velocity of about 37 km s-1 and an anchored, long-lived magnetic field, or (3) periodic release of magnetic stresses in the form of weak flares. In the case of orbital motion, the magnetic activity may be induced by the companion, possibly explaining the unusual pattern of activity and the long-lived signal. We conclude that fully convective stars can maintain a large-scale and stable magnetic field, but the lack of X-ray and Hα emission indicates that the atmospheric conditions are markedly different than in early-type stars and even M dwarfs. Similar observations are therefore invaluable for probing both the internal and external structure of low-mass stars and substellar objects, and for providing constraints on dynamo models. Title: The Sun, Solar Analogs and the Climate Authors: Haigh, Joanna D.; Lockwood, Michael; Giampapa, Mark S.; Rüedi, Isabelle; Güdel, Manuel; Schmutz, Werner Bibcode: 2005ssac.conf.....H Altcode: 2005SAAS...34.....H This book presents the lecture notes of the 34th Saas-Fee Advanced Course "The Sun, Solar Analogs and the Climate" given by leading scientists in the field. Emphasis is on the observed variability of the Sun and the present understanding of the variability's origin as well as its impact on the Earth's climate. The solar variability is then studied in the broader context of solar-type stars, allowing for better understanding of the solar-activity cycle and the magnetic activity in general. This book provides an accessible and up-to-date introduction to the field for graduate students and serves as a modern source of reference for active researchers in this field. Title: Stellar analogs of solar activity: the Sun in a stellar context Authors: Giampapa, Mark S. Bibcode: 2005ssac.conf..307G Altcode: 2005SAAS...34..307G Contents: 1. Introduction. 2. Stellar cycles. 3. Brightness changes in solar-type stars. 4. Activity in solar analogs. 5. Stellar surface inhomogeneities. 6. The coronae of solar analogs, low mass stars, and brown dwarfs. 7. The early Sun. 8. Stellar activity and extrasolar planets. Title: Photometric Precisions in the Prototype MOTESS-GNAT Surveys Authors: Giampapa, M. S.; Kraus, A. L.; Craine, E. R.; Sherry, W. H.; Tucker, R. A. Bibcode: 2004AAS...205.1403G Altcode: 2004BAAS...36.1360G The MG1 and MG2 MOTESS-GNAT surveys were conducted as 48-arcmin wide scan-mode CCD imaging surveys of selected areas of the sky in an efficient and highly successful asteroid search program. The images were reduced photometrically as a test of a prototype of a longitudinally distributed network of photometric scan-mode telescopes for the Global Network of Astronomical Telescopes, Inc. (GNAT). The MG1 and MG2 surveys, which are unfiltered, are centered at declinations +03o 18 m 20 s (MG1) and +02o 05 m 00 s (MG2), respectively. Although the source data were originally intended for astrometric use, they nonetheless have yielded a great deal of useful stellar brightness data. As such, they serve as excellent test-beds for both future GNAT photometry surveys and as valuable sources of new scientific discovery and analysis. To assist in defining some of the possible serendipitous programs using the MG1 and MG2 Surveys, we present in this poster an analysis of the photometric precisions that are attained in these data sets.

This effort is supported in part by the National Aeronautics and Space Administration through the NASA Astrobiology Institute under Cooperative Agreement No. CAN-02-OSS-02 issued through the Office of Space Science. The NSO and the NOAO are operated by AURA for the NSF. Title: A Summary of Known Variable Stars in the MOTESS-GNAT MG1 Survey and the Status of Future Surveys Authors: Craine, E. R.; Scharlach, W. G. G.; Kraus, A. L.; Giampapa, M. S.; Tucker, R. A. Bibcode: 2004AAS...205.1402C Altcode: 2004BAAS...36Q1360C The MG1 Survey is a two year unfiltered, scan-mode CCD imaging survey of a 48-arcmin wide band centered at declination +03° 18m 20s. The MG1 survey has yielded open channel photometry of about 2.1 million stars, of which some 35,000 were identified as likely variable star candidates. Of those 35,000 only about 200 are cataloged in the GCVS. In this poster we summarize the statistics of the detections of known variable stars which were made using the MG1 data. The results will be used to improve the methods and techniques that will be employed in future GNAT scan-mode surveys. We also indicate how these data can be used to develop useful student projects. Six new scan-mode telescopes are under construction for the Global Network of Astronomical Telescopes, Inc. (GNAT), effective October 2004. Three of these telescopes are expected to become operational during the winter of 2004-05 and will be sited in Southern Arizona as a coordinated triplet of photometric CCD imaging instruments. Another existing telescope will be operational before December 2004. All four of these telescopes will be used primarily to gather low amplitude variability data on Solar-type stars in the Pleiades and M67, respectively, in a study of parameters that control the ambient radiative and particle environments of the habitable zones around such stars. Because the telescopes will operate nightly for several years there will be a huge collateral accumulation of photometric data from 24-hour long strips of the sky approximately 48 arcmin wide. Nightly bandpass photometry will be obtained for an estimated 4-6 million stars, hence yielding a large archive of data for a wide variety of interesting research projects. We would like to attract collaborators comprised of students, professional and amateur astronomers. The next two surveys to be run are the G1 Survey, at a declination of approximately +24° (one telescope and a single filter), and the G2 survey, at a declination of approximately +12° (three telescopes and two filters). The exact declinations will be chosen to maximize the number of solar-type stars in the respective fields. We outline in this poster several of the possible research projects that offer opportunities for collaboration.

This material is based upon work supported in part by the National Aeronautics and Space Administration through the NASA Astrobiology Institute under Cooperative Agreement No. CAN-02-OSS-02 issued through the Office of Space Science. Title: High Amplitude Variable Stars in the MOTESS-GNAT MG1 Survey Authors: Culver, R. B.; Craine, E. R.; Kraus, A. L.; Giampapa, M. S.; Tucker, R. A. Bibcode: 2004AAS...205.1404C Altcode: 2004BAAS...36R1360C The Moving Object and Transient Event Search System (MOTESS) is a triplet of scan-mode telescopes located in Tucson, Arizona, and devised originally for high efficiency, unfiltered astrometric asteroid searches. Recently, the hardware system has been adopted by the Global Network of Astronomical Telescopes, Inc. (GNAT), as a prototype for a much expanded network of longitudinally distributed telescopes operating primarily as a high efficiency, high time frequency photometric survey system. The original MOTESS asteroid survey was operated for just over two years at a declination of +03° 18m 20s. We developed a photometric data reduction pipeline to process the extensive archive of deep, unfiltered digital images. As a result, we now have two years of open channel photometry for about 2.1 million stars, of which some 35,000 are identified as likely variable star candidates. Of those 35,000, only ∼ 200 are cataloged in the General Catalogue of Variable Stars (GCVS). Our primary purpose has been to use this survey, which we call the MG1 Survey, as a proof-of-principle test-bed of our data reduction system. In the process, our work has serendipitously yielded an enormous amount of useful data, including tens of thousands of new variable star discoveries. In this presentation, we discuss specifically our efforts to characterize the highest amplitude variables in the MG1 Variable Star Catalog.

This work has been supported in part by Walker & Company. Title: Extragalactic Variable Objects in GNAT Image Archives Authors: Craine, E. R.; Culver, R. B.; Giampapa, M. S.; Kraus, A. L.; Tucker, R. A. Bibcode: 2004AAS...204.4018C Altcode: 2004BAAS...36..719C The Global Network of Astronomical Telescopes (GNAT) has used the image output of its prototype, the Moving Object and Transient Event Search System (MOTESS), to create a photometric database of two years observations of over 2.5 million celestial point sources. These observations have been made through the full 24-hr range of Right Ascension at a fixed declination of +3d18m, with a field of view of 48 arcmin. The integration time in each field is 191 sec allowing detection of objects as faint as 20 mag. This catalog has been searched for variable objects at the 6-sigma level, resulting in a list of about 36,000 newly discovered variables. The majority of these objects are stars of a wide range of types, however, some of the variables are expected to be extragalactic objects. We report progress on a program to identify known extragalactic sources in the observed region of the sky and to develop light curves for these objects using the archived GNAT images.

We appreciate the support of Walker & Company for this research program. Title: Early Results from SOLIS Authors: Harvey, J.; Giampapa, M.; Henney, C.; Keller, C.; Jones, H. Bibcode: 2004AAS...204.3701H Altcode: 2004BAAS...36..708H SOLIS (Synoptic Optical Long-Term Investigations of the Sun) is a project that is replacing antiquated synoptic observing equipment at the National Solar Observatory. SOLIS consists of a suite of three instruments on an equatorial mount that will be installed on Kitt Peak in April 2004. The major SOLIS instrument is a vector spectromagnetograph (VSM) that maps magnetic fields across the full solar disk using a slit spectrograph and one arc sec pixels. Limited daily observations started at a temporary site in August, 2003 and include line-of-sight component magnetograms in the photosphere and chromosphere and, for the first time, full-disk vector magnetograms. At a medium scan speed ( ∼ 10 minutes for the full disk) noise is less than 1 Mx/cm2. This low noise, combined with negligible instrumental polarization and well resolved spectral line profiles, yields moderate resolution magnetograms of unprecedented quality. Observations show magnetic flux nearly everywhere in the photosphere from the disk center to the solar limb. Weak, intranetwork fields are now routinely observed and show a tendency to be of opposite polarity to the stronger surrounding fields. Diffuse fields surround decaying active regions and appear to be distinct from canopy fields. Vector magnetograms easily show the radial orientation of network fields, and the diffuse component surrounding decaying active regions. Near the disk center, the transverse magnetic fields of network elements change on a time scale of minutes. Detailed quantitative calibration of the observations is in progress. Good results have been obtained from the other SOLIS instruments: a full-disk filter imager at several narrow wavelengths and a double-pass grating spectrograph that provides high-accuracy line spectra of integrated sunlight. SOLIS data are freely available via the Internet and users are invited to submit observing time requests for special observations. The National Solar Observatory is operated by AURA, Inc. under a cooperative agreement with the National Science Foundation. Additional support for the development of SOLIS from NASA and ONR is gratefully acknowledged. Title: GNAT/MOTESS Data Pipeline and Variable Star Catalog Authors: Kraus, A. L.; Craine, E. R.; Giampapa, M. S.; Tucker, R. A. Bibcode: 2003AAS...203.0903K Altcode: 2003BAAS...35.1218K The Global Network of Astronomical Telescopes (GNAT) is testing a prototype system of multiple scan-mode telescopes, the Moving Object and Transient Event Search System (MOTESS), at the Goodricke-Pigott Observatory in Tucson, Arizona. A primary goal of GNAT has been to develop a data pipeline for reduction of sky survey CCD images to extract photometric data for all of the stars detected in the images. This effort is now complete and we describe here the structure of the data reduction system as it has been applied to the first two years of observations. The system relies on IRAF at its core, augmented by several custom routines for handling of the raw photometry. To date, the system has been applied to a single declination of scanning, +3d18m20s, and has resulted in systematic photometric observations of about 1.5-2.5 million stars. Processing of these data has yielded a list of about 35,000 stars which are convincingly variable. All but about 200 of these stars are new variable discoveries. Funding for this project was provided by an NSF REU grant and an anonymous donor. Title: Known Variable Stars in GNAT/MOTESS Data Authors: Craine, E. R.; Kraus, A. L.; Giampapa, M. S.; Tucker, R. A.; Scharlach, W. Bibcode: 2003AAS...203.0904C Altcode: 2003BAAS...35.1218C The Global Network of Astronomical Telescopes (GNAT) is using as a hardware prototype a system of multiple scan mode telescopes of the Moving Object and Transient Event Search System (MOTESS) of the Goodricke-Pigott Observatory in Tucson, Arizona. During the first two years of operation of the system, approximately 35,000 variable stars were observed of which approximately 200 were previously known. In this paper we provide details of the GNAT observations of the previously known variable stars, compare these results with previously published data, and use the observational results to help characterize the observational system. Funding for this project was provided by an anonymous donor. Title: First Results from SOLIS Authors: Harvey, J.; Giampapa, M.; Henney, C.; Jones, H.; Keller, C. Bibcode: 2003AGUFMSH42B0545H Altcode: SOLIS (Synoptic Optical Long-term Investigations of the Sun) is a project to replace antiquated synoptic observing equipment at the National Solar Observatory. SOLIS includes a suite of three instruments on an equatorial mount originally installed at a site in Tucson and will be moved to Kitt Peak before the end of 2003. The major SOLIS instrument is a vector spectromagnetograph that maps magnetic fields across the full solar disk using a slit spectrograph and one arc sec pixels. Daily observations include several line-of-sight component magnetograms in the photosphere and chromosphere and, for the first time, full-disk vector magnetograms. At a medium scan speed ( ∼10 minutes for the full disk) noise is less than 1 Mx/cm2. This low noise, combined with negligible instrumental polarization and well resolved spectral line profiles, yields moderate resolution magnetograms of unprecedented quality. Sample observations show magnetic flux nearly everywhere in the photosphere from the disk center to the solar limb. The flux is organized in large scale patterns that heretofore had been visible only in strong flux elements or after substantial spatial smearing. Good results have been obtained from the other SOLIS instruments: a full-disk filter imager at several narrow wavelengths and a grating spectrograph that provides high-accuracy line spectra of integrated sunlight. SOLIS data are freely available via the Internet and users may submit observing time requests for special observations. The National Solar Observatory is operated by AURA, Inc. under a cooperative agreement with the National Science Foundation. Additional support for the development of SOLIS from NASA and ONR is gratefully acknowledged. Title: The Suns of M67 Authors: Giampapa, M. Bibcode: 2003csss...12...91G Altcode: We discuss the methodology and some preliminary results of a survey of the chromspheric Ca II H & K line strengths in a sample of solar-type stars in the galactic open cluster M67. We compare the distribution of H&K line strength among the solar counterparts in this cluster with that seen in the contemporary Sun during the course of its 11-year cycle. Title: The Quiescent Corona of VB 10 Authors: Fleming, Thomas A.; Giampapa, Mark S.; Garza, David Bibcode: 2003ApJ...594..982F Altcode: We present results from a Chandra ACIS observation of the M8 dwarf star VB 10, a star near the hydrogen-burning mass limit. Until now, VB 10 has only been detected to flare at X-ray wavelengths. We can now report that nonflare, ``quiescent,'' X-ray emission has been detected with a luminosity, LX=(2.4+/-0.05)×1025 ergs s-1 and log(LX/Lbol)=-4.9. This is consistent with the previous ROSAT nondetections of quiescent emission from VB 10. We discuss the implications of this discovery for the nature of coronae in ultracool dwarfs. Title: Chromospheric Activity in Solar-Type Stars Authors: Giampapa, M. S.; Hall, J. C.; Radick, R. R.; Baliunas, S. L. Bibcode: 2003SPD....34.0710G Altcode: 2003BAAS...35..821G We present an update on the results of a survey of chromospheric activity in the solar-age and solar-metallicity open cluster, M67. The objective of the survey is to gain insight on the potential range of amplitudes of the solar cycle through observations of solar analogs that are presumably at random phases in their cycles of magnetic activity. We find that there is a significant overlap of the levels of Ca II H and K emission in the sun-like stars in M67 with the range of activity seen in the contemporary solar cycle. However, there are also stars that exhibit levels of activity outside of this range, including stars that are "super-solar" in their Ca II H and K emission. The implications of these results will be discussed.

The data presented in this investigation were obtained with the WIYN 3.5-m telescope on Kitt Peak. The WIYN Observatory is a joint facility of the University of Wisconsin-Madison, Indiana University, Yale University, and the NOAO. The NSO and the NOAO are operated by AURA for the National Science Foundation. Title: SOLIS: an innovative suite of synoptic instruments Authors: Keller, Christoph U.; Harvey, John W.; Giampapa, Mark S. Bibcode: 2003SPIE.4853..194K Altcode: SOLIS (Synoptic Optical Long-term Investigations of the Sun) is a suite of three innovative instruments under construction that will greatly improve ground-based synoptic solar observations. The Vector Spectromagnetograph (VSM) is a compact, high-throughput vector-polarimeter with an active secondary mirror, an actively controlled grating spectrograph, and two high-speed cameras with silicon-on-CMOS-multiplexer hybrid focal plane arrays. It will measure the magnetic field strength and direction over the full solar disk within 15 minutes. The Full-Disk Patrol (FDP) takes full-disk solar intensity and Doppler images in various spectral lines and in the continuum at a high cadence through liquid-crystal tuned birefringent filters. The Integrated Sunlight Spectrometer (ISS) uses a fiber-fed spectrograph to measure minute changes of the Sun-as-a-star in many spectral lines. A high degree of automation and remote control provides fast user access to data and flexible interaction with the data-collection process. SOLIS is currently in the final assembly phase and will become operational early in 2003. Title: Emission line variability in a newly discovered 2MASS star Authors: Giampapa, Mark; Liebert, James; Reid, Neil; Cruz, Kelle Bibcode: 2003noao.prop..234G Altcode: We propose to utilize the HET/HRS to obtain spectra of the newly discovered, low-mass star 2M075223.9+161215. The primary objectives are to search for (1) variability in the strength and position of the H(alpha) emission line profile and (2) determine if the Li I (lambda)6707 feature is present to confirm whether this enigmatic object is a field brown dwarf. Previous HET/HRS spectra of this object were obtained on the night of UT 01 April 2002. However, the S/N in the Li region was insufficient to arrive at a definitive conclusion concerning the presence of lithium in 2M075223.9. The additional spectra will be co-added to the previous spectra in order to examine the complex (lambda)6707 region in more detail. Of equal importance, the detection of either short- or long- term variability will yield insight on the origin of the emission line mechanism. The two competing models for the origin of the strong emission line spectrum involve either strongly enhanced chromospheric activity driven by magnetic dynamo action or accretion in a low mass binary system. Title: Implementation of the GNAT Network Design and System Configurations Authors: Culver, R. B.; Craine, E. R.; Giampapa, M. S.; Tucker, R. A.; Kraus, A. L. Bibcode: 2002AAS...20112202C Altcode: 2002BAAS...34.1304C Following the successful deployment of the three-telescope Moving Object Transient Event Search System (MOTESS), which is a model prototype of the Global Network of Astronomical Telescopes (GNAT) system, we have begun design of a geographically distributed network of 48 automated, scan-mode telescopes. During the course of the design effort it has become apparent that such a network offers great versatility by virtue of a large number of possible telescope and network configurations. This versatility allows us to modify such parameters as system limiting magnitude, image signal-to-noise ratios, time and frequency of field observation, and field of view, among others. In this paper we consider some of the most interesting system configurations discussed to date, provide a summary of the resultant system parameters and outline the nature of the science which can be most efficiently done with each configuration. We also discuss practical experience gained to date which scales the nature of the effort involved in reconfiguring the network to accommodate various types of observations. Title: A Prototype Data Reduction Pipeline for the GNAT System Authors: Kraus, A. L.; Giampapa, M. S.; Tucker, R. A.; Craine, E. R. Bibcode: 2002AAS...20112203K Altcode: 2002BAAS...34Q1304K The Moving Object and Transient Event Search System (MOTESS) has been operating for the past year as a prototype for the Global Network of Astronomical Telescopes (GNAT). During this time, it has produced approximately 200 nights of observations on a 48-arcminute band of declination near the celestial equator. We have developed an automated data reduction pipeline that performs aperture photometry and differential photometry on the nightly data and then matches the results to a standard catalog based on the United States Naval Observatory catalog. Objects that match the catalog are added to the data library, while unmatched objects are placed into a separate catalog for analysis. One data analysis technique we have been exploring is to search the new object catalog for transient events such as supernovae and cataclysmic variables. We have also been optimizing the pipeline so that it can be scaled as additional instruments are added to the GNAT network. Title: The Coronae of Low Mass Stars and Brown Dwarfs Authors: Giampapa, M. S.; Fleming, T. A. Bibcode: 2002ASPC..277..247G Altcode: 2002sccx.conf..247G No abstract at ADS Title: Stellar Variability Observations with MOTESS, a GNAT System Prototype Authors: Craine, E. R.; Giampapa, M. S.; Kraus, A. L.; Tucker, R. A.; Scharlach, W. Bibcode: 2002AAS...20112201C Altcode: 2002BAAS...34.1303C The Moving Object Transient Event Search System (MOTESS) is a three telescope, scan-mode system developed initially for near-Earth asteroid detection, and since adopted as a prototype for a Global Network of Astronomical Telescopes (GNAT) system. In this paper we summarize photometric characteristics of the prototype telescope network and discuss initial results of measurements of stellar variability using data obtained during the first full year of operation of the system. In the initial data set, 173 known variable stars were observed, of which 19 exceeded the useful upper brightness limits of the images. The remaining stars ranged down to about 17.5 mag with the brightness distribution peak at about 14.5 mag. The most frequently occurring types are Mira variables (52), eclipsing systems (33), and semi-regulars (25); with the remainder distributed over a wide range of variable types. We give examples of data for known variables, discuss the likely discovery of new variables and outline a strategy for using these data in screening stellar observations suggestive of possible planetary transits. Title: Stellar Chromospheres and the Sun Authors: Giampapa, M. Bibcode: 2002AAS...200.5301G Altcode: 2002BAAS...34..729G Observations combined with the development of semi-empirical models show that stellar chromospheres and the solar chromosphere share many of the same features. Nevertheless, are homogeneous, single-component models of stellar chromospheres adequate representations of their atmospheres in the light of observations that clearly indicate the multi-component natures of both the solar and stellar chromospheres? Is the distinction between "active" and "quiet" chromosphere stars mainly due to the fractional area coverage of otherwise identical magnetic active regions on their surfaces, or can the distinction be attributed primarily to differing heating rates in a relatively homogeneous atmosphere? Can single-component, static models successfully account for the levels of emission in the dominant radiative coolants in stellar chromospheres? How does the radiative energy balance between the chromosphere and corona change with effective temperature and gravity in the cool half of the H-R diagram? Is there evidence for "cool chromospheres" in main sequence stars? These issues will be addressed in an effort to compare and contrast stellar chromospheres with that of the Sun. The National Solar Observatory is operated for the National Science Foundation by the Association of Universities for Research in Astronomy. Title: Moving Object and Transient Event Search System (MOTESS): An Evaluation of Photometric Properties/Low Amplitude Stellar Variation Measurements Authors: Craine, E. R.; Tucker, R. A.; Giampapa, M. S.; Scharlach, W. W. G. Bibcode: 2002AAS...200.6412C Altcode: 2002BAAS...34R.750C The Moving Object and Transient Event Search System (MOTESS) is being expanded from its original task as an automated, moving object search system (astrometric application) to add the transient event detection capability (photometric application). In anticipation of this activity, photometric reductions of MOTESS images have been systematically undertaken to characterize the system in terms of photometric precision during a night, light curve stability from night to night and long term time series photometry. We discuss the data pipeline, characteristics of the system images, and photometric precision as a function of brightness of the object observed. We also present example light curves of known variable objects as a demonstration of the capabilities of the system. In this context we summarize key science programs of the Global Network of Automatic Telescopes (GNAT) which are being undertaken with the MOTESS facility, including extrasolar planetary transit searches, supernovae monitoring and other stellar variability programs. Title: Solar-stellar connections Authors: Giampapa, M. Bibcode: 2002cosp...34E.638G Altcode: 2002cosp.meetE.638G The observation of the solar cycle with the telescope extends over a few centuries while its study at high precisions with modern instrumentation is only a few decades old. In fact, the measurement of solar luminosity variability at the level of 0.1%, and the correlation of brightness changes with the solar cycle of magnetic activity, is less than two decades old. Thus, our knowledge of the full range of solar variability that may occur is extremely limited. We believe that a substantially larger brightness variation occurred during the Maunder minimum from AD 1645 to 1715. But, because individual solar cycles are different in form, amplitude and length, and because accurate solar data have been available only for the most recent cycles, there is no direct way of understanding long-term solar variability. The observation of solar-type stars, however, can overcome the temporal confines of the solar data-base, thereby revealing the potential range and nature of solar variability over time scales that are simply not accessible to the modern data-base of only a few decades. I will discuss the empirical properties of magnetic field-related activity variations in solar-type stars and the associated luminosity variability, and compare these properties to that of the Sun. In this way, we can gain insight on the full range of variability that the Sun can potentially exhibit over long time scales. The National Solar Observatory is operated for the National Science Foundation by the Association of Universities for Research in Astronomy. Title: Limits on Line Bisector Variability for Stars with Extrasolar Planets Authors: Povich, M. S.; Giampapa, M. S.; Valenti, J. A.; Tilleman, T.; Barden, S.; Deming, D.; Livingston, W. C.; Pilachowski, C. Bibcode: 2001AJ....121.1136P Altcode: We present an analysis of high-resolution synoptic spectra of ten F- and G-type stars, seven of which exhibit periodic radial velocity variations due to the presence of one or more substellar companions. We searched for subtle periodic variations in photospheric line asymmetry, as characterized by line bisectors. In principle, periodic variations in line asymmetry observed at lower spectral resolution could mimic the radial velocity signature of a companion, but we find no significant evidence of such behavior in our data. Observations were obtained from 1998 March to 1999 February using the National Solar Observatory (NSO) 1.52 m McMath-Pierce Solar Telescope Facility on Kitt Peak in conjunction with the solar-stellar spectrograph, achieving a resolving power of 1.2×105. To characterize line asymmetry, we first measured line bisectors for the unblended Fe I photospheric line at 625.26 nm. To improve sensitivity to small fluctuations, we then combined points in each bisector to form a velocity displacement with respect to the line core. We searched for periodic variations in this displacement, finding no substantial difference between stars with substellar companions and those without reported companions. We find no correlation between bisector velocity displacement and the known orbital phase of substellar companions around our target stars. Simulations of a periodic signal with noise levels that mimic our measurement errors suggest that we can exclude bisector variations with amplitudes greater than about 20 m s-1. These results support the conclusion that extrasolar planets best explain the observed periodic variations in radial velocity. Title: Photometric Monitoring of M67 with the GNAT 0.5-m Telescope Authors: Roberts, J. H.; Craine, E. R.; Giampapa, M. S. Bibcode: 2000AAS...197.4004R Altcode: 2000BAAS...32.1459R A long-term program of nightly observations of the solar-age and solar-metallicity, galactic open cluster, M67, was initiated with the prototype GNAT 0.5-m automated telescope in conjunction with a SITe 512 x 512 thermoelectrically cooled CCD. The broad objective of this program is to investigate the utilization of the GNAT 0.5-m telescope for long-term projects requiring high-precision photometry. The specific, dual applications include (1) the monitoring of low-amplitude luminosity variations in solar-type stars and (2) the detection of extrasolar planets via photometric transits. These science goals require that precisions of at least a few millimags be consistently achieved and maintained. As a prelude to these kinds of programs, we obtained a nightly time-series of automated photometric observations of M67 on 24 nights during a two month period from abbreviated JD51604-JD51679. Unfiltered photometry with an integration time of 180 sec per CCD frame was performed. A total of 1,260 frames were obtained. For those frames characterized by high signal-to-noise ratios, precisions of 4-5 mmag were attained on both an intranight and internight basis. No variations that could be attributed to a photometric transit event were detected. Further preliminary results from this program will be discussed. JR gratefully acknowledges the support of the NSF through the NSO/REU program. The NSO is operated by AURA under cooperative agreement with the NSF. Title: Red Dwarfs/Flare Stars Authors: Giampapa, M. Bibcode: 2000eaa..bookE1866G Altcode: The red dwarf stars are main-sequence stars characterized by masses in the approximate range from 0.51M⊙ to 0.08M⊙. The upper mass limit corresponds to a spectral type of M0 V and the lower limit is the critical mass for the onset of nuclear burning in the central cores of stars with chemical abundances similar to the Sun. Below the range of approximately (0.074-0.08)M⊙ is the realm of substellar... Title: The Coronae of Inactive Low-Mass Dwarfs Authors: Kashyap, V. L.; Giampapa, M.; Drake, J. J. Bibcode: 2000HEAD....5.4217K Altcode: 2000BAAS...32.1257K We analyze deep EUVE/SW data of two inactive low-mass dM stars GJ 205 and GJ 411. The spectra do not show any spectral lines that can be used for temperature or density diagnostics. We therefore model these spectra with different types of Differential Emission Measure (DEM) distributions and show that the peak temperature in the corona is akin to the Quiet Sun. We also derive constraints on the metallicity of the corona of GJ 205, and suggest that compared to its photosphere the corona appears to be metal deficient. Title: A Survey of Activity in the Solar-Type Stars in M67 Authors: Giampapa, M. S.; Radick, R. R.; Hall, J. C.; Baliunas, S. L. Bibcode: 2000SPD....3102120G Altcode: 2000BAAS...32..832G We present an update on a long-term study of the solar-type stars in the solar-age and solar-metallicity open cluster, M67. The primary objective of this program is to gain insight on the possible range of solar chromospheric activity and the associated, potential long-term variability of the Sun through the observation of stellar analogs of the Sun. Spectra in the Ca II H & K line region of over 100 stars in M67, including 76 `solar-type' stars (with unreddened colors in the range +0.60 <= B-V <= +0.76) and 21 `solar-twins' (+0.63 <= B-V <= +0.67), were obtained with the 3.5-m WIYN telescope on Kitt Peak in conjunction with the Hydra multi-fiber positioner to perform multi-object spectroscopy over a 1 degree field. We find that the distribution of chromospheric H&K line strengths in the solar-type stars is broader than the distribution of H&K line emission recorded in modern observations of the Sun, suggesting that the potential excursion in the amplitude of the solar cycle is greater than what we have seen so far in the contemporary record. Approximately 30% of the solar-type stars in M67 exhibit levels of activity that are outside the present envelope of solar activity. We interpret this to mean that the Sun can be in a state of magnetic activity---either exceptional quiescence similar to the Maunder-minimum episode or enhanced activity---about 30% of the time. The authors gratefully acknowledge both the NOAO Telescope Allocation Committee and the WIYN Queue Program for their support of this investigation. The WIYN Observatory is a joint facility of the University of Wisconsin-Madison, Indiana University, Yale University, and the NOAO. The NSO and NOAO are operated by AURA, Inc., under cooperative agreement with the National Science Foundation. Title: An X-Ray Flare Detected on the M8 Dwarf VB 10 Authors: Fleming, Thomas A.; Giampapa, Mark S.; Schmitt, Jürgen H. M. M. Bibcode: 2000ApJ...533..372F Altcode: 2000astro.ph..2065F We have detected an X-ray flare on the very low mass star VB 10 (GL 752 B; M8V) using the ROSAT High Resolution Imager. VB 10 is the latest type (lowest mass) main-sequence star known to exhibit coronal activity. X-rays were detected from the star during a single 1.1 ks segment of an observation that lasted 22 ks in total. The energy released by this flare is on the order of 1027 ergs s-1. This is at least 2 orders of magnitude greater than the quiescent X-ray luminosity of VB 10, which has yet to be measured. This X-ray flare is very similar in nature to the far-ultraviolet flare that was observed by Linsky et al. using the Goddard High Resolution Spectrograph onboard the Hubble Space Telescope. We discuss reasons for the extreme difference between the flare and quiescent X-ray luminosities, including the possibility that VB 10 has no quiescent (106 K) coronal plasma at all. Title: Line Bisector Variations in Stars with Extrasolar Planets Authors: Povich, M. S.; Giampapa, M. S.; Valenti, J. A.; Tilleman, T. Bibcode: 1999AAS...19510901P Altcode: 1999BAAS...31.1533P We present the results from a high-resolution, synoptic spectroscopic program of observation of ten F- and G-type stars, seven of which exhibit periodic radial velocity variations attributed to the presence of one or more substellar companions. The observations were obtained from 1998 March to 1999 February using the 1.52-m NSO McMath-Pierce Solar Telescope Facility on Kitt Peak in conjunction with the solar-stellar spectrograph. The spectra were acquired with a resolving power of approximately 1.2 x 105. The line bisector was then derived from unblended photospheric features. In particular, we define the velocity displacement of the spectral line bisector and determine the bisector amplitude for the Fe I absorption line at 625.26 nm in order to search for variations in the line asymmetry over time. Such variations could mimic Doppler shifts in observations with lower spectral resolution. Examination of the bisector velocity displacement over the time span of our observations reveals no substantial difference between stars with planetary companions and those without reported companions. We find no correlation between the bisector variations and the orbital phase of a substellar companion in any of our target stars. Simulations of a periodic signal with noise levels based on our measurement errors suggest that we can exclude bisector variations with amplitudes greater than about 20 m s-1. These results support the conclusion that extrasolar planets best explain the observed periodic variations in radial velocity. This work was supported by a NASA grant to the NOAO under the auspices of the Origins of Solar Systems Program. MP gratefully acknowledges support from the NSF-sponsored Research Experience for Undergraduates (REU) program at the NOAO. The NOAO is operated by AURA, Inc., under a cooperative agreement with the NSF. Title: The Suns of M67 Authors: Giampapa, M. S.; Radick, R. R.; Baliunas, S. L. Bibcode: 1999AAS...194.9212G Altcode: 1999BAAS...31..988G The results of our program to survey the level of chromospheric Ca II H&K emission in ~ 100 solar analogs in the galactic cluster M67 are discussed. This cluster is an appropriate target of observation for the study of solar-type stars since it is approximately the same age and has the same chemical composition as the Sun. The key objective of our program is to investigate the nature of solar variability. In particular, we interpret the range of Ca II H&K emission observed in the sun-like stars in M67 as indicative of the possible amplitudes of cycle-related variability that can occur in the Sun itself. In this way, we can efficiently gain insights on the potential long-term variability of the Sun that would not otherwise be possible with the modern solar Ca II synoptic database of just a few decades. This is especially important given that the amplitude of long-term solar (and stellar) variations in brightness are correlated with cycle variations in chromospheric emission. In view of the fact that the Sun is the engine that drives climate on the Earth, any variation in the solar ``constant" must be taken into account in the study of the long-term behavior of the global climate. The NOAO is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation. Title: Cycles and Long-Term Variability in Solar-Type Stars Authors: Giampapa, Mark S.; Radick, Richard R.; Hall, Jeffrey C.; Baliunas, Sallie L. Bibcode: 1999noao.prop..226G Altcode: We propose a long-term extension of our current WIYN/Hydra program to study chromospheric activity cycles in the `Suns of M67.' Our results thus far have revealed that the distribution of activity among the solar- type stars in M67 is broader than what would be expected from a comparison with the solar cycle. The next step is to determine whether our results arise from the cyclic modulation of activity alone or if the relative amplitudes of cycles in solar-type stars and the Sun are actually similar and the spread in M67 is due to differences in the mean level of activity. Only a long-term monitoring program of regular observations can address these questions. The results of this program are expected to reveal all the potential modes and amplitudes of magnetic cycles in sun-like stars and, by inference, in the Sun itself, with important implications for dynamo models and models of global climate change. Title: Differential Photometry Using the GNAT 0. 5 m Prototype Authors: Taylor, J. M.; Craine, E. R.; Giampapa, M. S. Bibcode: 1999ASPC..189..238T Altcode: 1999pcp..conf..238T No abstract at ADS Title: X-Ray Activity in the Open Cluster IC 4665 Authors: Giampapa, Mark S.; Prosser, Charles F.; Fleming, Thomas A. Bibcode: 1998ApJ...501..624G Altcode: We present the results of a joint ROSAT High Resolution Imager (HRI) and optical investigation of the open cluster IC 4665. The ROSAT data contains detections for 28 stellar sources in the field, including 22 cluster members and candidate members spanning the color range -0.18 <= (B-V)0 <= 1.63 (~B3-M3). Upper limits are given for the remaining members (or candidate members) in the HRI field. Keck HIRES spectra have been obtained that yield radial and rotational velocity measures, respectively, for faint, low-mass candidate members located within the field of the ROSAT HRI observation. In addition, photometry of possible optical counterparts to previously uncataloged X-ray sources in the HRI field is presented.

The trends in X-ray properties with B-V color in IC 4665 are found to be quite similar to that for other, more nearby young clusters such as the Pleiades and α Persei. In particular a maximum in normalized X-ray luminosity of log (LX/Lbol) ~= -3 is observed, beginning in the color range of (B-V)0 = 0.7-0.8. This is similar to the corresponding color range among Pleiades members, in agreement with the earlier estimate by Prosser & Giampapa that the age of IC 4665 is similar to the age of the Pleiades. The correlation of rotation and X-ray emission levels is consistent with that in other young clusters.

Among the high-mass stars in IC 4665, five B stars are detected as X-ray sources. Of these, one is a spectroscopic binary while the remaining objects are apparently single stars. The level of intrinsic X-ray emission observed in the rapidly rotating (v sin i > 200 km s-1), single B stars is consistent with an origin due to shock heating of the ambient medium by radiatively driven, rotationally enhanced winds. On the basis of these observations and the results for other clusters, we argue that observed levels of X-ray emission in high-mass stars of log (LX/Lbol) > -6.0 are likely due to intrinsic emission associated with the B star itself rather than emission from a late-type secondary. Finally, our results suggest that the initial angular momentum distributions and the subsequent evolution of rotation, LX, and (LX/Lbol) occur in practically identical fashions in clusters with ages <~100 Myr. Title: A Joint X-ray and Optical Investigation of the Young Open Cluster IC 4665 Authors: Giampapa, M. S.; Prosser, C. F.; Fleming, T. A. Bibcode: 1998ASPC..154.2106G Altcode: 1998csss...10.2106G We summarize the results of a joint ROSAT High Resolution Imager (HRI) and optical investigation of the open cluster IC 4665. The ROSAT data-set contains detections for 28 stellar sources in the field, including 22 cluster members and candidate members spanning the color range -0.18 <= (B-V)_o \<= +1.63 (~B3 - M3). Keck HIRES spectra have been obtained that yield radial and rotational velocity measures, respectively, for faint, low mass candidate members located within the field of the ROSAT HRI observation. Title: A Survey of Chromospheric Activity in the Solar-Type Stars in M67 Authors: Giampapa, Mark S. Bibcode: 1998saco.conf...65G Altcode: No abstract at ADS Title: The Procyon campaign: Observations from Kitt Peak Authors: Pilachowski, C. A.; Barden, S.; Hill, F.; Harvey, J. W.; Keller, C. U.; Giampapa, M. S. Bibcode: 1998IAUS..185..319P Altcode: Time series spectra of the F5IV star Procyon (alpha CMi) were obtained at the Kitt Peak National Observatory during a 35-night observing run in January-February 1997. The observations were obtained as part of an international collaboration to detect and study acoustic oscillations in solar-type stars. Spectra covered the wavelength range from 4000 to 5300 AA , with a resolving power of approximately 3500 (1.3 AA resolution). The sampling rate was one observation per minute, and the typical S/N ratio per observation is in excess of 1000. At the time of writing, we have obtained over 10,000 spectra. The spectra will be analyzed to identify any periodic signals due to acoustic oscillations in Procyon. In addition to measuring the equivalent widths of the three Balmer lines (Kjeldsen et al. 1995) covered by our spectra (Hβ, Hγ, and Hdelta) we will also examine the spectra for variations in the average metal line strength. Preliminary power spectra will be presented. Title: Asteroseismology from equivalent widths: a test of the sun Authors: Keller, C. U.; Harvey, J. W.; Barden, S. C.; Giampapa, M. S.; Hill, F.; Pilachowski, C. A. Bibcode: 1998IAUS..185..375K Altcode: Kjeldsen et al. (1995) reported a probable detection of solar-like, low-amplitude, p-mode oscillations of eta Bootes using equivalent width measurements from low-resolution spectra of the hydrogen Balmer lines. We tested the usefulness of this technique using observations of the Sun in integrated light. Despite the very high signal-to-noise ratio of the data stretching over six continuous days, no solar oscillation signal was found so far in the equivalent width of Hβ. Spatially resolved observations of the Hβ equivalent width at solar disk center reveal that the oscillation signal is suppressed in the wings of Hβ as compared to the continuum. Extrapolation of the oscillation signal seen in the spatially resolved data suggests an amplitude of about 1ppm for integrated light measurements, which is about a factor of 5 lower than expected from simple theoretical arguments. We explore other methods to deduce an oscillation signal from all spectral lines simultaneously. cont has: Deng, L. et al.; auths fixed below Title: Rotational Velocities and Chromospheric/Coronal Activity of Low-Mass Stars in the Young Open Clusters IC 2391 and IC 2602 Authors: Stauffer, John R.; Hartmann, Lee W.; Prosser, Charles F.; Randich, Sofia; Balachandran, Suchitra; Patten, Brian M.; Simon, Theodore; Giampapa, Mark Bibcode: 1997ApJ...479..776S Altcode: We have obtained high-resolution, moderate signal-to-noise ratio spectra for approximately 80 candidate low-mass members of the nearby, very young open clusters IC 2391 and IC 2602. Most of the stars observed are confirmed as cluster members based on a combination of photometric and spectroscopic criteria. We provide radial velocities, rotational velocities, and Hα equivalent widths for these stars. From comparison to theoretical pre-main-sequence (PMS) evolutionary isochrones from D'Antona and Mazzitelli, we derive an estimated age of the two clusters of ~25 Myr. By contrast, the usually quoted upper main-sequence turnoff age for the clusters is ~35 Myr. We do not believe that this provides evidence for noncoeval star formation within these clusters, but rather that the best age estimate for them given the uncertainties is ~30 +/- 5 Myr. In principle, the scatter of stars about the PMS isochrone provides a measure of the age spread among the low-mass stars in these clusters; however, with the data presently available, we are able to derive only a relatively uninteresting upper limit for an age spread of order 20 Myr.

We compare the rotational velocity distribution for IC 2391/2602 to that observed for the Pleiades. For the G dwarfs in the IC clusters, we resolve rotation in all but one of the probable cluster members, and thus except for inclination effects, our data provide the complete distribution of rotational velocities for solar mass stars on their arrival on the ZAMS. The projected rotational velocities (v sin i) of the G dwarfs in the two IC clusters span the range from ~8 to ~200 km s-1. Comparison of the distribution of rotational velocities for the G dwarfs of the Pleiades and the IC clusters indicates that both the slow and the rapid rotators lose of order half their angular momentum during the first ~35 Myr on the main sequence if they rotate as solid bodies.

The low-mass stars in these two clusters exhibit a similar correlation between rotation and coronal activity as is found in several other young open clusters. That is, there is a large spread in coronal activity for stars with v sin i < 25 km s-1, where we assume there is an intrinsic link between increasing rotation and increasing activity superimposed upon which are a variety of observational and physical mechanisms that act to smear out this relation; above v sin i ~ 25 km s-1, all of the low-mass stars have log (LX/Lbol) ~ -3.0, the canonical ``saturation'' limit. Our measurements of the Hα equivalent widths are consistent with a similar relationship holding for chromospheric activity. One and possibly two of our spectra for M dwarf members of the IC clusters show broad wings for the Hα profile, which we attribute to a flare event or to microflares. Since spectra of a small sample of late-type M dwarfs in the Pleiades also showed similarly broad Hα wings, this suggests that flare frequencies for very young M dwarfs may be quite high. Title: Preface Authors: Jokipii, J. R.; Sonett, C. P.; Giampapa, M. S. Bibcode: 1997cwh..confD..11J Altcode: 2006mslp.confD..11J No abstract at ADS Title: Cosmic Winds and the Heliosphere Authors: Jokipii, Jack R.; Sonett, Charles P.; Giampapa, Mark S. Bibcode: 1997cwh..book.....J Altcode: No abstract at ADS Title: Cosmic winds and the heliosphere. Authors: Jokipii, J. R.; Sonett, C. P.; Giampapa, M. S. Bibcode: 1997cwh..conf.....J Altcode: No abstract at ADS Title: The Coronae of Low-Mass Dwarf Stars Authors: Giampapa, M. S.; Rosner, R.; Kashyap, V.; Fleming, T. A.; Schmitt, J. H. M. M.; Bookbinder, J. A. Bibcode: 1996ApJ...463..707G Altcode: We report the results of our analysis of pointed X-ray observations of nearby dMe and dM stars using the position sensitive proportional counter (PSPC) on board the ROSA T satellite (Roentgensatellit). In the cases of those M dwarf stars where PSPC pulse-height distributions of sufficient quality for spectral fitting were obtained, we derive key coronal plasma parameters in order to investigate stellar coronal structure in more detail. In particular, we utilize temperatures and emission measures inferred for one or more distinct components as constraints for the development of semiempirical magnetic loop models as representations of the coronae of low-mass stars. The consistency of these static models as adequate descriptions of the coronae of M dwarfs is then examined.

We find that the coronae of low-mass dwarfs consist of two distinct thermal components: a "soft" component with T ∼ 2-4 x 106 K and a "hard" component with T ∼ 107 K. We find that the pulse- height spectra are systematically fitted better with "depleted" abundances compared to solar; the high- temperature emission component on dMe stars appears to contribute a systematically larger fraction of the total flux than the corresponding component in dM stars; and the high-temperature emission component on dMe stars is responsible for most of the observed variation in the count rate.

We have modeled the observed temperature components with hydrostatic coronal loop models, and find that: the low-temperature components can be modeled with loops of small size (l ≪ R*) and high pressure (Po ); and the high-temperature components require solutions with either small filling factors ( 0.1), large loops (1 > R*), and high base pressure (P0 &#8819 P0sun), or very small filling factors (∼0.1), small loops (1 &#8819 R*), and very high pressure (P0 ≫ P0sun)). Based on these observational and model results, we conclude that coronal emission in dMe stars can be interpreted as arising from quiescent active regions (a quiescent, low-temperature component) and compact flaring structures (variable, high- temperature component).

Our conclusion that the coronal geometry for low-mass dwarf stars is dominated by a combination of relatively compact, quiescent loop configurations and an unstable flaring component has implications for both stellar dynamo theory and for our understanding of stellar angular momentum evolution. With regard to rotation in late-type stars, which has a direct bearing on dynamo action, we know from observations that the lowest mass stars spin down (via magnetic braking) more slowly than the more nearly solar-type stars. The compact loops we find for the low-temperature component suggests a natural explanation for the observed mass dependence of angular momentum evolution in late-type, main-sequence stars. Title: Asteroseismology via equivalent widths - tests on Procyon, Eta Bootis, and Alpha Trianguli. Authors: Harvey, J. W.; Pilachowski, C.; Barden, S.; Giampapa, M.; Keller, C. U.; Hill, F. Bibcode: 1996BAAS...28..917H Altcode: No abstract at ADS Title: Asteroseismology via Equivalent Widths -- Tests on Procyon, Eta Bootes, and Alpha Triangulum Authors: Harvey, J.; Pilachowski, C.; Barden, S.; Giampapa, M.; Keller, C.; Hill, F. Bibcode: 1996AAS...188.5903H Altcode: 1996BAAS...28S.917H Recently, Kjeldsen et al. reported a probable detection of solar-like low-amplitude p-mode oscillations of Eta Bootes using equivalent width measurements from low-resolution spectra of the H Balmer lines. This technique has the potential to provide stellar oscillation measurements good enough to allow the asteroseismic inference of stellar structure. Here we report on the preliminary analysis of data from three observing runs with the Kitt Peak Coude Feed and 2.1-m telescope in November 1995 (Alpha Triangulum), February 1996 (Procyon), and March 1996 (Eta Bootes). These runs are being used to develop observing and data reduction techniques, such as a synchronized timing system to maintain evenly spaced temporal samples, a continuous unshuttered CCD readout to increase the duty cycle of the observations, and a simulation of the probability of a detection as a function of observing run length. We observed the region around the H beta, gamma, and delta lines with a spectral dispersion of about 0.4 Angstroms per pixel, extracted equivalent widths, and performed time series analysis. The temporal spectrum of Alpha Triangulum contains a significant peak near the theoretical prediction, however, we do not yet know the origin of this peak. Title: The Future of High Resolution Spectroscopy at Kitt Peak National Observatory Authors: Barden, S.; Pilachowski, C.; Giampapa, M. Bibcode: 1996AAS...188.3902B Altcode: 1996BAAS...28..882B Many astronomical studies benefit from observations of celestial objects at high spectral resolving power. Some of the facilities and instrumentation for high dispersion spectroscopy, however, are coming under the threat of closure or are reaching their limit of usefulness due to the small aperture of the telescopes that feed them. Many of the new facilities either don't have sufficient spectral resolution or are located at observatories with very restricted access or scheduling. KPNO has convened a committee to 1) examine the scientific needs of high resolution spectroscopy, 2) evaluate the facilities which are available to the general astronomical community, and 3) develop and prioritize instrumentation goals for future KPNO facilities. The Committee will also consider policies for scheduling KPNO telescopes to maximize scientific return from high resolution spectrographs, including possible changes to the TAC process and visitor and queue observing modes. We desire community input and will formulate our report and recommendations over the next seven months. Title: Advances in solar-stellar physics: optical and infrared studies Authors: Giampapa, M. S. Bibcode: 1996ASPC..109...11G Altcode: 1996csss....9...11G No abstract at ADS Title: Coronal Structwre in M Dwarf Stars Authors: Giampapa, M. S.; Rosner, R.; Kashyap, V.; Fleming, T. A.; Schmitt, J. H. M. M.; Bookbinder, J. A. Bibcode: 1996mpsa.conf...81G Altcode: 1996IAUCo.153...81G No abstract at ADS Title: The chromospheric activity of the many "suns" in M67. Authors: Giampapa, M. S.; Baliunas, S. L.; Radick, R. R. Bibcode: 1996BAAS...28.1197G Altcode: No abstract at ADS Title: Stellar Activity at the End of the Main Sequence: GHRS Observations of the M8 Ve Star VB 10 Authors: Linsky, Jeffrey L.; Wood, Brian E.; Brown, Alexander; Giampapa, Mark S.; Ambruster, Carol Bibcode: 1995ApJ...455..670L Altcode: We present Goddard High Resolution Spectrograph observations of the M8 Ve star VB 10 (= Gl 752B), located very near the end of the stellar main sequence, and its dM3.5 binary companion Gl 752A. These coeval stars provide a test bed for studying whether the outer atmospheres of stars respond to changes in internal structure as stars become fully convective near mass 0.3 Msun (about spectral type MS), where the nature of the stellar magnetic dynamo presumably changes, and near the transition from red to brown dwarfs near mass 0.08 Msun (about spectral type M9), when hydrogen burning ceases at the end of the main sequence. We obtain upper limits for the quiescent emission of VB 10 but observe a transition region spectrum during a large flare, which indicates that some type of magnetic dynamo must be present. Two indirect lines of evidence scaling from the observed X-ray emission and scaling from a time-resolved flare on AD Le suggest that the fraction of the stellar bolometric luminosity that heats the transition region of VB 10 outside of obvious flares is comparable to, or larger than, that for Gl 752A. This suggests an increase in the magnetic heating rates, as measured by Lline/Lbol ratios, across the radiative/convective core boundary and as stars approach the red/brown dwarf boundary. These results provide new constraints for dynamo models and models of coronal and transition-region heating in late-type stars. Title: The Photometric Method for the Detection of Extrasolar Planets Authors: Giampapa, M. S.; Craine, E. R.; Hott, D. A. Bibcode: 1995AAS...187.7017G Altcode: 1995BAAS...27.1382G We offer further perspectives on the application of the photometric technique to the search for extrasolar planets. The principal obstacles to this approach include (1) the ambiguous interpretation of the photometric signature of a possible transit event arising from the potential for confusion with stellar activity, and (2) the observational intensity of the search technique. We emphasize that the former issue can be addressed through multiband observations combined with considerations of the characteristic time scales of forms of stellar activity compared to that of a transit event. In the case of the latter concern, the advent of modern, automated telescope technologies offers the realistic prospect of meeting the demanding observational requirements of this approach. We find that joint visual and near infrared observations are necessary to immediately distinguish between, for example, a planetary transit and a cool spot on the stellar surface. However, these observations by themselves do not appear sufficient to distinguish between a brown dwarf and a Jovian-size planetary companion of a dwarf M star. In such cases, other complementary observations will be necessary. We develop a computer simulation to estimate the average number of transits per year that would be presented for a stellar sample characterized by realistic properties in terms of spectral type distribution, effective temperatures, masses, and radii. A simple thermal model is adopted to estimate star-planet separations. The simulation suggests that the frequency of transit events will be dominated by M dwarf systems. This is due to the large number of these objects combined with the relative proximity to these cool stars within which planetary formation can occur according to current models. Title: Comments on the photometric method for the detection of extrasolar planets. Authors: Giampapa, Mark S.; Craine, Eric R.; Hott, Douglas A. Bibcode: 1995Icar..118..199G Altcode: We offer further perspectives on the application of the photometric technique to the search for extrasolar planets. The principal obstacles to this approach include (1) the ambiguous interpretation of the photometric signature of a possible transit event arising from the potential for confusion with stellar activity and (2) the observational intensity of the search technique. We emphasize that the former issue can be addressed through multiband observations combined with consideration of the characteristic time scales of forms of stellar activity compared to the time scale of a transit event. In the case of the latter concern, the advent of modern, automated telescope technologies offers the realistic prospect of meeting the demanding observational requirements of this approach.

We find that joint visual and near infrared observations are necessary to immediately distinguish between, for example, a planetary transit and a cool spot on the stellar surface. However, these observations by themselves do not appear sufficient to distinguish between a brown dwarf and a jovian-size planetary companion of a dwarf M star. In such cases, other complementary observations will be necessary. We developed a computer simulation to estimate the average number of transits per year that would be presented for a stellar sample characterized by realistic properties in terms of spectral type distribution, effective temperatures, masses, and radii. A simple thermal model is adopted to estimate star-planet separations. The simulation suggests that the frequency of transit events will be dominated by M dwarf systems. This is due to the large number of these objects combined with the relative proximity to these cool stars within which planetary formation can occur according to current models. Title: The X-Ray View of the Low-Mass Stars in the Solar Neighborhood Authors: Schmitt, Juergen H. M. M.; Fleming, Thomas A.; Giampapa, Mark S. Bibcode: 1995ApJ...450..392S Altcode: We present the results of a complete and sensitive X-ray survey of all known stars of spectral type K and M in the immediate solar vicinity with distances less than 7 pc. The X-ray data were obtained primarily from the ROSA T all-sky survey (RASS); those program stars not detected in the RASS data were subsequently studied with the ROSAT pointed observation program. These new X-ray observations resulted in a detection rate of almost 94% for all K and M stars within 6 pc around the Sun, and 87% for K and M dwarfs within 7 pc around the Sun. The resulting X-ray luminosity distribution function can be well described by a log-normal distribution; the largest and smallest X-ray luminosities from our sample stars differ by almost four orders of magnitude. We show the existence of a correlation between total emitted X-ray luminosity and spectral hardness, such that more luminous objects tend to have larger spectral hardness, thus implying higher coronal temperatures. A comparison with Einstein data shows the lack of significant variability in excess of a factor of 2 in our sample stars. Title: Correlations of Coronal X-Ray Emission with Activity, Mass, and Age of the Nearby K and M Dwarfs Authors: Fleming, Thomas A.; Schmitt, Juergen H. M. M.; Giampapa, Mark S. Bibcode: 1995ApJ...450..401F Altcode: Using the ROSAT telescope, we have detected X-ray emission from 87% of all known K and M dwarfs within 7 pc of the Sun. Analysis of this volume-limited sample of K and M dwarfs reveals no evidence for a decrease in coronal heating efficiency (as measured by Lx/L bol) among the lowest mass, presumably fully convective, late-M dwarfs. Furthermore, our results indicate that those stars which exhibit little chromospheric activity (i.e., dM and dK stars) do indeed have cooler and weaker coronae than the more active dMe stars. While we also see a correlation between coronal temperature/strength and metallicity (and presumably age), no such correlation is seen with kinematic class. The latter result leads us to suggest that kinematic class is a poor age indicator for the nearby stars. Title: Helium in the Spectrum of the Sun and of Solar-Type Stars Authors: Andretta, V.; Giampapa, M. S.; Jones, H. P. Bibcode: 1995IrAJ...22..177A Altcode: We present results from detailed non-LTE radiative transfer calculations of the He I spectrum in the Sun. Using an extended grid of model chromospheres, we explore the relative importance of, respectively, the coronal XUV illumination and the thermal structure of the lower transition region. With reference to the He I lambda 587.6 and lambda 1083.0 triplet lines, we point out some implications for the study of activity in solar-type stars. Title: The Coronae of Quiescent M Dwarf Stars Authors: Giampapa, Mark S. Bibcode: 1995euve.prop....6G Altcode: We propose to obtain SW and MW EUVE spectrometer observations of the quiescent M dwarf GL 205 (dM1). This non-dMe star in the solar neighborhood is an X-ray source as seen with the ROSAT PSPC. The infrared colors of GL 205 suggest that its photospheric abundances are solar-like. Our proposed EUVE data will be used to determine if the coronal structure is characterized by only two dominant components, as suggested by our analysis of X-ray data for dM stars, or if dwarf M coronae actually consist of multiple components with a distribution of maximum loop temperatures. This will yield valuable inputs for models of coronal heating and angular momentum evolution. A comparison between the results for a quiet non-dMe star with those for active dMe stars (available in the EUVE archives) will reveal if the difference in their emission levels arises from a fundamental difference in coronal structure or if it is merely a difference in scale (e.g., filling factors of active regions). In summary, the EUVE data for a dM star will be an important comparison for active dMe stars. Title: A Method for Estimating the Fractional Area Coverage of Active Regions on Dwarf F and G Stars Authors: Andretta, Vincenzo; Giampapa, Mark S. Bibcode: 1995ApJ...439..405A Altcode: The D3 (lambda 5876) and lambda 10830 lines arising from triplet levels in neutral helium appear in absorption in active (plage) regions on the Sun and, by implication, in the active regions on Sun-like (F-early K) stars. These features either do not occur, or appear only very weakly, in the quite solar (or stellar) photosphere. Hence, these diagnostics are ideal tracers of magnetic regions outside of cool spots. The appearance of D3 and lambda 10830 in absorption immediately suggests that these lines can be utilized to infer the fractional area coverage, or filling factor, of active region on stellar surfaces if their intrinsic absorption strengths in these regions are known. In particular, a meaningful lower limit to the active filling factor can be deduced if the maximum absorption equivalent width (Wmax) in D3 or lambda 10830 as either appears in stellar analogs of solar plages can be estimated. We develop this approach by constructing a grid of model chromospheres based on the VAL C model of the quiet solar chromosphere. This thermal structure is superposed on published models for F and G dwarf photospheres. We solve for the non-LTE ionization of hydrogen to infer chromospheric electron densities. We then perform a multilevel, non-LTE computation of the helium triplet lines in the sequence of model chromospheres, taking into account the potential effects of coronal XUV back radiation on the line formation. We conservatively estimate that Wmax approximately = 100-150 mA for D3 in both F and G dwarfs. The implied lower limits to the filling factor of plagelike regions can be approximately 20% among active solar-type stars. We extend this approach by investigating a method by which the actual filling factor can be deduced through a study of the joint response of D3 and lambda 10830 to chromospheric nonradiative heating. We emphasize that our filling factor estimates indicate the area coverage at the height of formation of the helium triplet lines in the active chromosphere. Because of field line spreading with height, filling factors based on chromospheric lines are expected to exceed estimates based on purely photospheric lines. Finally, we discuss the relative importance of collisional and photoionization processes in the formation of these important diagnostics. Title: Radial Velocities of Very Low Mass Stars and Candidate Brown Dwarf Members of the Hyades and Pleiades. II. Authors: Stauffer, John R.; Liebert, James; Giampapa, Mark Bibcode: 1995AJ....109..298S Altcode: We have determined H alpha equivalent widths and radial velocities with 1 sigma accuracies of approximately 5 km/s for approximately 20 candidate very low mass members of the Pleiades cluster and for a few proposed very low mass members of the Hyades. Most of the Pleiades targets were selected from the recent Hambly, Hawkins, and Jameson proper motion survey, where they were identified as probable Pleiades brown dwarfs with an age spread from 3 to 70 Myr. Our spectroscopic data and a reinterpretation of the photometric data confirm that these objects are indeed likely Pleiades members; however, we believe that they more likely have masses slightly above the hydrogen burning mass limit and that there is no firm evidence for an age spread amongst these stars. All of the very low mass Pleiades and Hyades members show H alpha in emission. However, the ratio of H alpha flux to biometric flux in the Pleiades shows a maximum near MBol approximately equal to 9.5 (M approximately equal to 0.3 solar mass) and a sharp decrease to lower masses. This break occurs at the approximate mass where low mass stars are expected to become fully convective, and it is tempting to assume that the decrease in H alpha flux is caused by some change in the behavior of stellar dynamos at this mass. We do not see a similar break in activity at this mass in the Hyades. We discuss possible evolutionary explanations for this difference in the H alpha activity between the two clusters. Title: The β Pictoris phenomenon among young stars. I. The case of the Herbig AE star UX Orionis. Authors: Grinin, V. P.; The, P. S.; de Winter, D.; Giampapa, M.; Rostopchina, A. N.; Tambovtseva, L. V.; van den Ancker, M. E. Bibcode: 1994A&A...292..165G Altcode: In this paper we present the first results of the study of very young stars having non-periodic Algol type brightness minima. It is based on cooperative observations between the Crimean Astrophysical Observatory (CAO), the European Southern Observatory (ESO) and the National Solar Observatory (NSO). In August-September, 1992, a very deep ({DELTA}V=2.5mag), long lasting minimum of the light of the isolated Herbig Ae star UX Ori occurred. At this event the star was observed photometrically (UBVRI) and polarimetrically at the CAO, and spectroscopically (high resolution: Hα and NaiD) at the ESO. The spectroscopic observations were continued at the NSO with the McMath solar/stellar telescope in October-December, 1992, when the star returned to maximum brightness and again at the ESO in July and October, 1993, when the star was bright. The main results of our observations can be briefly summarized as follows: 1) The photometric and polarimetric results are in agreement with the model according to which UX Ori is surrounded by an edge-on circumstellar disk-like envelope, and its variability is caused by variable obscuration of the star by opaque circumstellar dust clouds. 2) The double-peaked Hα profile observed at maximum light changed to single-peaked at deep minimum; obscuration of a part of the circumstellar gas by an optically thick dust cloud is causing this variation, 3) The inverse P Cygni profiles and variable redshifted absorption components have been observed in the NaiD lines indicating the infall of cool gas onto the star. We believe that, such as in the case of the star β Pictoris, violent comet-like activity takes place in the young protoplanetary disk of UX Ori which causes the observed variability. Title: Coronal Loop Model Atmospheres for Low Mass Stars Authors: Giampapa, M.; Rosner, R.; Kashyap, V.; Fleming, T.; Schmitt, J.; Bookbinder, J. Bibcode: 1994AAS...185.9807G Altcode: 1994BAAS...26Q1480G We have constructed semi-empirical loop models that best fit key coronal parameters derived from ROSAT PSPC observations of selected low mass stars. The X-ray pulse-height distributions are represented by two dominant components. These include a soft component that is characterized by compact loop configurations with loop lengths that are one or more orders of magnitude smaller than the stellar radius. By contrast, two types of stable solutions can be found for the hard component, namely very long loops (much larger than a pressure scale height) with large filling factors, and very compact loops with very small filling factors. The ``long" solutions are physically excluded since they violate stability criteria. We identify the ``small" solutions with compact loop flares. The implications of these results for coronal structure and angular momentum evolution in low mass dwarfs will be discussed. Title: A Radial Velocity Survey of the Open Cluster IC 4665 Authors: Prosser, Charles F.; Giampapa, Mark S. Bibcode: 1994AJ....108..964P Altcode: A radial velocity survey of the open cluster IC 4665 is reported for a group of candidate members previously identified on the basis of proper motion and photometry. Of those candidates observed, 20 out of 42 have radial velocities consistent with membership; these cluster members populate the F5-K0 dwarf region and represent the first relatively conclusive membership determinations for such solar-type stars in IC 4665. Three new spectroscopic binary members of the cluster have been identified. Rotational velocities have also been derived; the v sin i distribution among IC 4665 members reveals that most apparent G dwarf members of IC 4665 are seen to exhibit substantial rotation (v sin i greater than 10 km/s). When compared to evolutionary isochrones, the current list of intermediate-mass members appears to support earlier suggestions that IC 4665 has an age comparable to the Pleiades. Title: Radial Velocities of Very Low mass Stars and Candidate Brown Dwarf Members of the Hyades and Pleiades Authors: Stauffer, John R.; Liebert, James; Giampapa, Mark; Macintosh, Bruce; Reid, Neill; Hamilton, Donald Bibcode: 1994AJ....108..160S Altcode: We have determined H alpha equivalent widths and radial velocities with 1 sigma accuracies of approximately 5 km s-1 for approximately 20 candidate very low mass members of the Hyades and Pleiades clusters. The radial velocities for the Hyades sample suggest that nearly all of these stars are indeed highly probable members of the Hyades. The faintest stars in the Hyades sample have masses of order 0.1 solar mass. We also obtained radial velocities for four candidate very low mass members of the Pleiades and two objects that are candidate BD Pleiads. All of these stars have apparent V magnitudes fainter than the Hyades stars we observed, and the resultant radial velocity accuracy is worse. We believe that the three brighter stars are indeed likely very low mass stellar members of the Pleiades, whereas the status of the two brown dwarf candidates is uncertain. The Hyades stars we have observed and the three Pleiades very low mass stars are the lowest mass members of any open cluster whose membership has been confirmed by radial velocities and whose chromospheric activity has been measured. We see no change in chromospheric activity at the boundary where stars are expected to become fully convective (M approximately equals 0.3 solar mass) in either cluster. In the Pleiades, however, there may be a decrease in chromospheric activity for stars with (V-I)K greater than 3.5 (M less than or equal to 0.1 solar mass). Title: Upgrade of the McMath-Pierce stellar spectrograph Authors: Giampapa, Mark S.; Simmons, Jorge E.; Jaksha, David B.; Perkins, E. L. Bibcode: 1994SPIE.2198..302G Altcode: We discuss a design for an echelle spectrograph based on three prisms as the cross-dispersing optical elements. Since high throughput in our particular system is achieved using an image slicer, obtaining adequate order separation is a challenge. We find that the design described herein yields good efficiencies throughout the visible wavelength range while also providing adequate order separation in the red. Title: Extrasolar planetary search using a network of automated telescopes Authors: Craine, Eric R.; Giampapa, Mark S.; Hott, Douglas A. Bibcode: 1994SPIE.2198.1398C Altcode: Conventional search techniques for extrasolar planets have not yielded indisputable evidence of such planets. The small sample sizes of previously employed searches ensure that a null result provides little or no information on the numbers or distributions of such planets. The photometric technique, wherein monitoring is performed to detect light curves distinctively characteristic of a planetary transit, has been a tantalizing prospect, but has always been rejected because of its observational intensity. Moderate aperture (0.5-1.0 m) automated telescopes and multi- color CCD imaging arrays with image recognition software form the instrumental foundation for a global network to conduct such a search. Catalogs of cool dwarf stars provide a program star list with the advantages of orbital geometries and photometric properties enabling detection of planetary transits with a network of modes proportions. We reaffirm the viability of the photometric approach and outline the methodology of the search. Computer modelling of various strategies of conducting such a planetary search has been undertaken and we outline the resulting network configurations and observing strategies suggested by this effort. Title: Lithium in RS Canum Venaticorum binaries and related chromospherically active stars. III. Northern RS CVn systems. Authors: Randich, S.; Giampapa, M. S.; Pallavicini, R. Bibcode: 1994A&A...283..893R Altcode: High-resolution spectra of Northern RS CVn binaries obtained at the NSO-Kitt Peak are analyzed with a spectrum synthesis code to derive Li abundances, metallicities and rotation rates. The data are then combined with previous observations of Southern RS CVn binaries obtained at ESO, yielding a total sample of 67 individual components in 54 catalogued RS CVn binaries. We confirm the presence of substantial amounts of Li in many chromospherically active stars in the sample, with no significant difference between the Northern and Southern samples. We specifically address the question of whether these relatively high Li abundances are due to enhanced chromospheric activity or rather are a consequence of evolutionary history in stars of sufficiently high mass. We investigate the dependence of Li abundance on mass by using mass determinations in binary systems as well as comparison with theoretical evolutionary tracks. We show that while Li abundances in subgiants and in the warmer stars of the sample may be consistent with a dependence on mass, there is no clear indication in the data that the cooler giants with larger Li abundances are also the more massive ones. Uncertainties in the comparison with evolutionary tracks may partially be responsible for this negative result. Alternatively, Li depletion and dilution in evolved stars may be more complex than predicted by standard evolutionary models. Title: The Beta Pictoris phenomenon among young stars. I. The case of Herbig AC star UX ORI Authors: Grinin, V. P.; Rostopchina, A. N.; de Winter, D.; The, P. S.; van den Ancker, V.; Giampapa, M.; Tambovtseva, L. V. Bibcode: 1994ASPC...62..130G Altcode: 1994nesh.conf..130G No abstract at ADS Title: Perspectives on the Relationship between Activity and Fundamental Stellar Parameters (Invited Review) Authors: Giampapa, M. S. Bibcode: 1994ASPC...64..509G Altcode: 1994csss....8..509G No abstract at ADS Title: The X-Ray Luminosity Function of the Nearby K and M Dwarfs: Results from ROSAT Authors: Fleming, Thomas A.; Schmitt, J. H. M. M.; Giampapa, Mark S. Bibcode: 1994ASPC...64...77F Altcode: 1994csss....8...77F No abstract at ADS Title: The Coronae of Low Mass Dwarf Stars Authors: Giampapa, Mark S. Bibcode: 1994euve.prop...63G Altcode: We propose to obtain SW and MW EUVE spectrometer observations of selected M dwarfs for which we have ROSAT PSPC X-ray pulse-height distributions. The EUVE data will be used to determine if the coronal structure is characterized by only two dominant components, as suggested by our analysis of the X-ray data, or if dwarf M coronae actually consist of multiple components with a distribution of maximum loop temperatures. We will use the potential constraints available with the density diagnostics in the EUV spectra to improve the determination of loop morphologies that thus far have been based solely on X-ray photometric data. This will yield valuable inputs for models of coronal heating (through the determination of heat dissipation scales) and models of angular momentum evolution (via magnetic braking) in low mass stars. A comparison of the results for the quiet dM star and the active dMe stars will reveal if the difference in their emission levels arises from a fundamental difference in coronal structure or if it is merely a difference in scale (e.g., filling factors of active regions). Finally, an inter-comparison of the results for the dMe stars in our program may reveal whether dynamo-related properties change across the boundary between partial and full interior convection. Title: The Relationship Between Radiative and Magnetic Fluxes on Three Active Solar-type Dwarfs Authors: Linsky, J. L.; Andrulis, C.; Saar, S. H.; Ayres, T. R.; Giampapa, M. S. Bibcode: 1994ASPC...64..438L Altcode: 1994csss....8..438L We present some preliminary results from our coordinated campaign of IUE and McMath Telescope magnetic field measurements of three active solar-type dwarf stars: 59 Vir, xi Boo A, and HD 131511. We observed the three stars nearly every day from May 9 to May 25, 1993, covering between 1 and 3 rotations. We explore the functional and spatial relationship between magnetic and radiative fluxes. Title: A Synoptic Study of H alpha Line Profile Variability in the T Tauri Star SU Aurigae Authors: Giampapa, Mark S.; Basri, Gibor S.; Johns, Christopher M.; Imhoff, Catherine Bibcode: 1993ApJS...89..321G Altcode: We present a catalog of 106 high spectral resolution observations of the H-alpha line profile in the T Tauri star SU Aurigae, obtained during the period from 1986 October through 1990 November. The spectra were acquired during joint synoptic programs to observe selected T Tauri stars using the Hamilton Echelle Spectrometer of the Lick Observatory and the solar-stellar spectrograph at the McMath telescope of the National Solar Observatory on Kitt Peak. A restricted set of Mg II h and k line profiles was also obtained in a coordinated program involving the International Ultraviolet Explorer (IUE) satellite observatory and the McMath solar-stellar facility. Striking variability is evident on a nightly basis. A key result is that the relative intensity in the blue wing of H-alpha spanning a range of velocities bear -150 km/s is modulated at a period of 2.98 +/- 0.4 days. We identify the 2.98 day period with the rotation period of the star. We also find that the occurrence of the periodic modulation of the mass outflow is episodic and most evident during a 2 week sequence of nightly observations. We find two other intervals where the periodic spectroscopic variability is likely present, although at a lower level of significance at a lower level of significance. The variability is otherwise stochastic in nature. The Mg II resonance lines exhibit clear variability that is most pronounced in the blue wing of the k line. A comparison of the Mg II k line profile with H-alpha profiles obtained nearly simultaneous yields no apparent correlation between the variable features in each line. The profile shapes of the Mg II h and k lines are generally indicative of formation in a wind. An analysis of the principal features that appear in the H-alpha profile set suggests that the line is composed of contributions from an enhanced chromosphere; a relatively slow moving, dense, optically thick component of a stellar wind formed relatively close to the star; and an optically thin, high-velocity, expanding stellar wind located further away from the star. An investigation of possible correlations among the principal features in the series of H-alpha profiles suggests that as the density in the wind increases, the wind may become more unstable to large turbulence. This may lead to a reduction in the wind bulk velocity, thus regulating the mass-loss rate. We also find that the position of the main absorption feature which is always present in the H-alpha profiles is not correlated with its depth, indicating that optical depth and wind velocity are not correlated in the denser portions of the wind. Title: The Structure of the Coronae of dMe and dM Stars Authors: Giampapa, M. S.; Schmitt, J. H. M. M.; Fleming, T. A. Bibcode: 1993AAS...183.1507G Altcode: 1993BAAS...25.1314G We discuss results obtained from preliminary coronal loop model atmospheres developed on the basis of x-ray pulse-height spectra obtained with the ROSAT PSPC. The limited sample is comprised of both active dMe stars and quiescent dM stars. An intercomparison of the inferred coronal loop parameters for the active and the relatively quiet objects will be presented. As reported earlier (Giampapa et al. 1993; BAAS, 25, 824), two-temperature fits are required to adequately represent the x-ray properties of the dMe stars. In the case of the non-dMe stars, the coronal emission measure is dominated by a single, relatively soft component. Preliminary estimates of densities, filling factors and loop lengths that characterize these separate components which define the coronae of low mass dwarf stars will be discussed. Title: Lithium and chromospheric activity in the Alpha Persei cluster. Authors: Stauffer, John R.; Prosser, Charles F.; Giampapa, Mark S.; Soderblom, Mark S.; Simon, Theodore Bibcode: 1993AJ....106..229S Altcode: We have obtained high resolution spectra of a set of proposed members of the Alpha Persei open cluster which had previously been shown to have anomalously low lithium abundances. We have used the new spectra to derive Ca II emission strengths, radial velocities, and reddening estimates in order to assess whether these stars truly are members of the Alpha Per cluster. We conclude that most of the weak lithium stars are indeed bonafide cluster members, and thus the problem of explaining their anomalous lithium abundances remains. We have also obtained spectra for another sample of stars for which the previous membership data were relatively limited. Most of these stars do not appear to be members of the cluster. Title: Active Region Area Coverages on Solar-Type Stars Authors: Giampapa, M. S.; Andretta, V. Bibcode: 1993BAAS...25.1216G Altcode: No abstract at ADS Title: Stellar Coronae at the End of the Main Sequence: A ROSAT Survey of the Late M Dwarfs Authors: Fleming, Thomas A.; Giampapa, Mark S.; Schmitt, J. H. M. M.; Bookbinder, Jay A. Bibcode: 1993ApJ...410..387F Altcode: We present X-ray data, both detections and upper limits, from the ROSAT all-sky survey for most known M dwarfs later than type M5, as well as from selected ROSAT pointed observations of some of these stars. We compare these data with similar data for early M dwarfs in an attempt to probe the nature of the magnetic dynamo and coronal heating mechanism for the very late M dwarfs, which are presumably totally convective. Our results indicate that late M dwarfs can have coronae which are just as active as those for the early M dwarfs and that coronal heating efficiency for 'saturated' stars does not drop at spectral type M6. Title: Coronal Structure of Late M Dwarf Stars Authors: Giampapa, M. S.; Fleming, T. A.; Schmitt, J. H. M. M. Bibcode: 1993AAS...182.2205G Altcode: 1993BAAS...25R.824G We present preliminary results of the analysis of x-ray pulse-height spectra of very late dwarf M stars as obtained with the ROSAT PSPC. The majority of the data are derived from a program of pointed observations. The limited sample is comprised of both active dMe stars and quiescent dM stars. The basic cornal properties are derived and compared among the dMe and dM stars in the sample. We find that two-temperature fits are required to account for the x-ray emission of dMe stars while single-temperature fits appear to adequately represent the x-ray properties of the non-dMe objects. In addition, we estimate emission measures and coronal loop parameters. The implications for coronal structure will be discussed. In particular, we suggest on the basis of these preliminary results that the coronae of low mass dwarfs are highly geometrically extended relative to the stellar radius. This may account for both the high absolute values of L_x and the high relative values, i.e., L_x /Lbol , that characterize the x-ray emission levels of the dMe stars as compared to that of more nearly solar-type stars. Title: Astronomy with the Deep UV Explorer observatory. Authors: Ferguson, D. H.; Giampapa, M. S. Bibcode: 1993uxrs.conf..309F Altcode: 1993uxsa.conf..309F Recent advances in control systems and sensors allow construction of an inexpensive yet high-performance orbiting observatory to collect data at ultraviolet wavelengths between 1150 Å and 3000 Å. The Deep Ultraviolet Explorer satellite (DUVE) will obtain all-sky imagery at various broad band wavelengths, high-resolution images, and spectra across the UV region. The DUVE program offers substantial performance advantages over current space-based observatories. Title: Stellar coronae at the end of the main sequence: A ROSAT survey of the late M dwarfs Authors: Fleming, T. A.; Giampapa, M. S.; Schmitt, J. H. M. M.; Bookbinder, J. A. Bibcode: 1993STIN...9419794F Altcode: X-ray data, both detections and upper limits, from the Rosat all sky survey for most known M dwarfs later than type M5 are presented. Selected Rosat pointed observations of some of these stars are included. These data are compared to similar data for early M dwarfs in an attempt to probe the nature of the magnetic dynamo and coronal heating mechanism for the very late M dwarfs, which are presumably totally convective. The results indicate that late M dwarfs can have coronae which are just as active as those for the early M dwarfs and that coronal heating efficiency for 'saturated' stars does not drop at spectral type M6. Title: Next generation ultraviolet astronomy with the Deep Ultraviolet Explorer observatory Authors: Ferguson, Donald H.; Giampapa, Mark S. Bibcode: 1992SPIE.1697..274F Altcode: The Deep Ultraviolet Explorer (DUVE) satellite, which is a space-based observatory providing all-sky imagery and high-resolution spectroscopy at wavelengths between 1150 and 3000 A, is discussed. Sky coverage, resolution, and sensitivity of DUVE are each equal to or better than available on existing spacecraft. Recent advances in controls, sensors, and telescope lightweighting coupled with space-qualified designs combine to make the DUVE project affordable within the guidelines of the Medium Explorer-class mission scenario. Title: Science with GNAT: An Extra-Solar System Planetary Search Authors: Craine, E. R.; Giampapa, M. S. Bibcode: 1992AAS...181.5702C Altcode: 1992BAAS...24R1214C No abstract at ADS Title: Spectroscopic and Photometric Observations of a Five-Magnitude Flare Event on UV CETI Authors: Eason, Erik L. E.; Giampapa, M. S.; Radick, R. R.; Worden, S. P.; Hege, E. K. Bibcode: 1992AJ....104.1161E Altcode: Optical observations of a 5-mag flare in the U band on UV Ceti (dM5.6e) at both spectral and temporal resolutions are presented. A strong violet continuum which cannot be reproduced solely with a thermal bremsstrahlung spectrum is seen. The energy emitted by the flare in the U band is about 5.0 x 10 exp 31 ergs. The corresponding total flare energy in white light is estimated to be 1.2 x 10 exp 32 ergs. This estimate, combined with the 700-s duration of the U-band event, yields an average white-light flare luminosity which is about 3 percent of the quiescent stellar bolometric luminosity. Strong H-alpha wings appeared after the impulsive phase. A discernible central reversal is present in both the quiescent H-alpha profile and, significantly, in the flare profile following the impulsive phase. It is suggested that the site of H-alpha flare emission is not necessarily associated with a compact, high pressure region. The flare-enhanced line emission arises from large flare volumes that are, in turn, a distinguishing feature of stellar flares of this magnitude. Title: Book-Review - the Sun in Time Authors: Sonett, C. P.; Giampapa, M. S.; Matthews, M. S. Bibcode: 1992SciAm.266f.130S Altcode: 1992SciAm.266..130S No abstract at ADS Title: Mg II Line Profiles in the T Tauri Stars Authors: Imhoff, C. L.; Giampapa, M. S.; Basri, G. Bibcode: 1992AAS...180.4310I Altcode: 1992BAAS...24..798I No abstract at ADS Title: Using Helium Lines as a Probe for Estimating Surface Filling Factors on Sun-Like Stars Authors: Andretta, V.; Giampapa, M. S. Bibcode: 1992ASPC...26..552A Altcode: 1992csss....7..552A No abstract at ADS Title: Chromospheric Activity; Kinematics of Very Low Mass M Dwarfs Authors: Liebert, J.; Saffer, R. A.; Norsworthy, J.; Giampapa, M. S.; Stauffer, J. R. Bibcode: 1992ASPC...26..282L Altcode: 1992csss....7..282L No abstract at ADS Title: Synoptic Studies of the T Tauri Star SU AUR Authors: Johns, C. M.; Basri, G. S.; Giampapa, M. S.; Defonso, E. Bibcode: 1992ASPC...26..441J Altcode: 1992csss....7..441J No abstract at ADS Title: Cool stars, stellar systems, and the sun : seventh Cambridge workshop Authors: Giampapa, Mark S.; Bookbinder, Jay A. Bibcode: 1992ASPC...26.....G Altcode: 1992csss....7.....G Bibliographic codes for individual papers begin with "1992csss....7". Title: Lithium in RS CVn binaries and related chromospherically active stars. I.Observational results. Authors: Pallavicini, R.; Randich, S.; Giampapa, M. S. Bibcode: 1992A&A...253..185P Altcode: The present survey of the Li I 6708 A line in a sample of spectral type G and K stars with luminosity classes III, IV, and V shows that many K-type stars in the sample, including a large number of RS CVn binaries, show an anomalously high Li abundance relative to typical inactive stars of the same spectral type. Only a few stars in the sample are likely to be premain sequence objects of stars which have recently arrived on the main sequence. Mechanisms that could lead to the enhanced Li absorption in chromospherically active stars are discussed; these encompass large cool spots on the stellar surface, the production of Li in stellar flares by spallation reactions, and the evolution from main-sequence progenitors without, or with very shallow, outer convective zones. Title: Proposed Upgrade of the McMath Solar/Stellar Telescope to a 4 m Aperture Authors: Giampapa, M. S.; Livingston, W. C.; Rabin, D. R. Bibcode: 1992LNP...397..279G Altcode: 1992sils.conf..279G No abstract at ADS Title: Spectroscopic Signatures of Active Regions on Main Sequence Stars Authors: Giampapa, Mark S. Bibcode: 1992LNP...397...90G Altcode: 1992sils.conf...90G The observed characteristics of Ha in M dwarf stars combined with a consideration of chromospheric line formation in cool dwarfs suggests that it is radial structure, rather than lateral inhomogeneities, which is the predominant factor in controlling chromospheric activity in low mass stars. This conclusion implies, in turn, that chromospheres determined by a single heating rate are relatively widespread on the stellar surface. The implications for magnetic field structures depend upon whether there is a unique association between chromospheric heating rate and specific kinds of magnetic field configurations. Synoptic observations of the marginal BY Draconis stars revealed irregular variability in the total strength and the positions of features in the their unique chromospheric Ha line. Further work must be done in order to ascertain the kind of chromospheric structures that yield the range of observed profiles. The special, and apparently rare, conditions that give rise to this subset of the low mass dwarfs remaim elusive. Title: Lithium Abundances in Northern RS CVn Binaries Authors: Randich, S.; Giampapa, M. S.; Pallavicini, R. Bibcode: 1992ASPC...26..576R Altcode: 1992csss....7..576R No abstract at ADS Title: Lithium in RS CVn Binaries and Related Chromospherically Active Stars Authors: Pallavicini, R.; Randich, S.; Giampapa, M. S. Bibcode: 1992LNP...397..108P Altcode: 1992sils.conf..108P No abstract at ADS Title: The Nature of the Dynamo at the End of the Main Sequence: A ROSAT Survey of the Late M Dwarfs Authors: Fleming, T. A.; Giampapa, M. S.; Schmitt, J. H. M. M.; Bookbinder, J. A. Bibcode: 1992ASPC...26...93F Altcode: 1992csss....7...93F No abstract at ADS Title: Next Generation Ultraviolet Astronomy with the Deep Ultraviolet Explorer Observatory Authors: Ferguson, D. H.; Giampapa, M. S. Bibcode: 1992ASPC...26..629F Altcode: 1992csss....7..629F No abstract at ADS Title: The Chromospheric Activity of Low-Mass Stars in the Hyades Authors: Stauffer, John R.; Giampapa, Mark S.; Herbst, William; Vincent, James M.; Hartmann, Lee W.; Stern, Robert A. Bibcode: 1991ApJ...374..142S Altcode: High-resolution spectra or narrow-band H-alpha photometry of 106 dwarf K and M stars in the Hyades cluster have been used to determine H-alpha equivalent widths. These data reveal a sequence of Hyades members with H-alpha in absorption for photospheric temperatures hotter than about 3500 K. Within this sequence, the dispersion about the mean equivalent width-color relation is only slightly larger than the measurement errors. A second sequence of Hyades members, characterized by H-alpha emission and significant scatter at a given color, appears at effective temperatures cooler than about 4000 K. This bifurcation in H-alpha properties at 4000 K coincides with a bifurcation in the rotational characteristics of Hyades stars: the dispersion in the rotational velocities of the hotter Hyades members at a given effective temperature is small while the cooler stars exhibit significant scatter in their rotational velocities. On the basis of these data, it is suggested that low-mass stars spin down to rotational velocities dependent upon mass and age, but independent of premain-sequence angular momentum. Title: Magnetic Activity in Pre-Main Stars Authors: Feigelson, Eric D.; Giampapa, Mark S.; Vrba, Frederick J. Bibcode: 1991suti.conf..658F Altcode: The extensive new evidence for extremely high levels of magnetic activity on the surface of premain-sequence stars is reviewed and analyzed in the context of solar evolution. Most of these observations concern 'weak' T Tauri stars, in which the surface properties of the young stars are not dominated by circumstellar matter as in 'classical' T Tauri stars. Optical photometry shows that weak T Tauria stars are moderately rapid rotaters with cool starspots covering 5 to 40 percent of the surface. Optical and ultraviolet spectroscopy indicates that their chromospheres are enhanced about 50 times over contemporary solar levels. X-ray and radio intensities are of order 1000 to 100,000 times greater than peak solar levels, and they vary on time scales of days and (in a few cases) hours or minutes. The variability can only be explained in terms of some extremely powerful magnetic-flare model. The large numbers of weak T Tauri stars, probably larger than the population of classical T Tauri stars, strongly suggests that the sun was a weak T Tauri star for at least part of its premain-sequence evolutionary phase. These findings are summarized in a suggested portrait of the sun as a 1 Myr old weak T Tauri star. Title: The sun in time Authors: Sonett, Charles P.; Giampapa, Mark S.; Matthews, Mildred S. Bibcode: 1991suti.conf.....S Altcode: Various papers on solar science are presented. The optics considered include: variability of solar irradiance, sunspot number, solar diameter, and solar wind properties; theory of luminosity and radius variations; standard solar models; the sun and the IMF; variations of cosmic-ray flux with time; accelerated particles in solar flares; solar cosmic ray fluxes during the last 10 million yrs; solar neutrinos and solar history; time variations of Be-10 and solar activity; solar and terrestrial components of the atmospheric C-14 variation spectrum; solar flare heavy-ion tracks in extraterrestrial objects. Also addressed are: the faint young sun problem; atmospheric responses to solar irradiation; quaternary glaciations; solar-terrestrial relationships in recent sea sediments; magnetic history of the sun; pre- and main-sequence evolution of solar activity; magnetic activity in pre-main-sequence stars; classical T Tauri stars; relict magnetism of meteorites; luminosity variability of solar-type stars; evolution of angular momentum in solar-mass stars; time evolution of magnetic fields on solarlike stars. Title: The Sun in Time Authors: Sonett, Charles P.; Giampapa, Mark S.; Matthews, Mildred Shapley Bibcode: 1991suti.book.....S Altcode: No abstract at ADS Title: The solar-stellar connection Authors: Giampapa, Mark S. Bibcode: 1990Natur.348..488G Altcode: No abstract at ADS Title: Chromospheric H alpha and CA II Lines in Late-Type Stars Authors: Robinson, Richard D.; Cram, Lawrence E.; Giampapa, Mark S. Bibcode: 1990ApJS...74..891R Altcode: Observations of H-alpha and Ca II H and K in the chromospheres of 50 main-sequence K and M stars are reported. The photospheric contribution to the integrated core flux in these lines is found to be more important than previously thought, and earlier estimates of the basal flux of cool dwarf stars are revised. The H-alpha data confirm the presence of both an upper and a lower limit to the H-alpha equivalent width attained at any given spectral type. The maximum H-alpha absorption strength decreases gradually toward cooler stars while the maximum 'saturated' quiescent emission strength increases. The Ca II emission strength is related to the strength of the emission or absorption feature at H-alpha, but there is not a one-to-one correlation. The main results may be explained in terms of photoionization and collisional control of the non-LTE H-alpha source function. Several aspects of the structure and heating of the outer atmospheres of dwarf K and M stars are discussed. Title: Lithium in chromospherically active stars. Authors: Pallavicini, R.; Randich, S.; Giampapa, M.; Cutispoto, G. Bibcode: 1990Msngr..62...51P Altcode: No abstract at ADS Title: Rotational modulation and flares on RS Canum Venaticorum and BY Draconis-type stars. XV. Observations of Proxima Centauri and solar calibration data. Authors: Haisch, B. M.; Butler, C. J.; Foing, B.; Rodono, M.; Giampapa, M. S. Bibcode: 1990A&A...232..387H Altcode: Results are reported from simultaneous Exosat and IUE observations of flaring in Proxima Cen on March 2, 1985. The data are presented in extensive tables and sample spectra and discussed in detail. The peak emission of the soft-X-ray flare is found to be about 3 x 10 to the 27th erg/sec, with energy about 3 x 10 to the 30th erg and an associated increase in Mg II flux to 17,000-67,000 erg/sq cm sec, or about an order of magnitude lower than the solar value. The presence of flare- and microflare-related processes heating the corona is inferred. Title: Introduction - Sun in Time - Conference - Tucson - 1989MAR6-10 Authors: Sonett, Charles P.; Giampapa, Mark S. Bibcode: 1990SoPh..127..295S Altcode: No abstract at ADS Title: Book Review: The restless sun / Smithsonian Institution Press, 1989 Authors: Giampapa, M. S. Bibcode: 1989S&T....78..602G Altcode: 1989S&T....78..602W No abstract at ADS Title: A Search for Chromospheres at Faint Magnitudes Authors: Fleming, Thomas A.; Giampapa, Mark S. Bibcode: 1989ApJ...346..299F Altcode: The preliminary results of a program to detect chromospheric Ca II K line emission in the faintest dwarf stars yet observed at this wavelength using high spectral resolution are reported. The star LHS 429 (VB 8; dM7e) exhibits K line emission in addition to H-alpha emission while LHS 2 (dM5-5.5) shows K line emission although no apparent H-alpha feature was seen in a spectrum obtained during the course of an earlier study by Giampapa and Liebert. A further seven stars observed did not exhibit any apparent feature at the position of the K line. The upper limits estimated for the K line surface flux in the case of the nondetections are still consistent with these stars having chromospheres characterized by a level of K line emission similar to that of LHS 2. The trend of the measured K line widths with absolute visual magnitude is qualitatively in accord with that expected from the Wilson-Bappu effect. Title: The CA II resonance lines in M dwarf stars without H-alpha emission. Authors: Giampapa, Mark S.; Cram, Lawrence E.; Wild, Walter J. Bibcode: 1989ApJ...345..536G Altcode: Spectra of the Ca II H and K lines in a sample of 31 M dwarf stars without H-alpha emission are used to calculate chromospheric K line radiative losses, F(k), and to study the joint response of Ca II K and H-alpha to chromospheric heating in dwarf M stars. It is suggested that the poor correlation found in the equivalent width - log F(K) diagram may be due either to radial segregation of the H-alpha and K line forming regions or to lateral inhomogeneities in the chromospheres. The results confirm the existence of dM stars with weak H-alpha absorption and K line emission only slightly weaker than that of the dMe stars, and show that dM stars with weak H-alpha but kinematics and metallicities representative of the young disk population belong to a class characterized by a comparatively high degree of chromospheric activity. Title: Analysis of the Chromospheric Spectrum of "Marginal" BY Draconis Stars Authors: Giampapa, M. S. Bibcode: 1989BAAS...21.1116G Altcode: No abstract at ADS Title: Variability of Chromospheric Lines in Late-Type Dwarf Stars Authors: Cutispoto, Giuseppe; Giampapa, Mark S. Bibcode: 1988PASP..100.1452C Altcode: The results of a high-resolution spectroscopic synoptic program of observations of key chromospheric diagnostics in a sample of dwarf stars are reported. Low-level variability in the strength of the chromospheric H-alpha absorption line is found. The nature of the variability implies that the operative chromospheric heating mechanism is partially characterized by a transient component. This fact, combined with the detectability of the low-level variability, suggests that magnetic field-related, nonradiative atmospheric heating is widespread in the dM stars. High-amplitude variability in the H-alpha emission strength of the active dMe star BY Dra was also observed. Synoptic observations of the He I 5876 A absorption line in three solar-type stars revealed low-level variability in the strength of this feature. Title: The High Resolution Spectroscopic Synoptic Program at the McMath Telescope Authors: Jaksha, D.; Giampapa, M. S. Bibcode: 1988BAAS...20..998J Altcode: No abstract at ADS Title: Multiwavelength observations of magnetic fields and related activity on Xi Bootis A. Authors: Saar, S. H.; Huovelin, J.; Giampapa, M. S.; Linsky, J. L.; Jordan, C. Bibcode: 1988ASSL..143...45S Altcode: 1988acse.conf...45S The authors present preliminary results of coordinated observations of magnetic fields and related activity on the active dwarf, ξ Boo A. Combining the magnetic fluxes with the linear polarization data, a simple map of the stellar active regions has been constructed. Title: Evolutionary Changes in the UV and EUV Flux of the Sun Authors: Giampapa, M. Bibcode: 1988srov.proc..241G Altcode: No abstract at ADS Title: Formation of Chromospheric Lines in Cool Dwarf Stars Authors: Cram, L. E.; Giampapa, M. S. Bibcode: 1987ApJ...323..316C Altcode: A simple theory of the formation of H-alpha and Ca II K in dwarf M stars has been developed which relates the observed variations in the emission strengths of Ca II K and the equivalent widths of H-alpha to physical differences in the underlying chromospheric structure of the stars. The theory implies that Ca II K line emission fluxes increase monotonically with increasing chromospheric temperature or mass loading. However, H-alpha equivalent widths may increase or decrease with increasing chromospheric temperature or mass loading, depending on the actual values of the chromospheric parameters and the effective temperature. The theory is used to elucidate aspects of the available observational data on H-alpha and Ca II K lines in late-type dwarfs. Title: Simultaneous Observations of the Hα and Mg II Resonance Line Profiles in the T Tauri Star SU Aurigae Authors: Giampapa, M. S.; Imhoff, C. L. Bibcode: 1987BAAS...19.1026G Altcode: No abstract at ADS Title: The Solar-Stellar Connection Authors: Giampapa, Mark S. Bibcode: 1987S&T....74..142G Altcode: The role of magnetic fields in the relation between solar and stellar theories is studied. The strength of a magnetic fields is related to the structure of a star's outer convection zone and stellar parameter such as rotation rate and surface gravity. The analyses of H and K emission lines of calcium for the sun and stars reveal the presence of plages and spots in both the sun and stars. The correlation between stellar winds, and coronal and chromospheric activity is investigated. It is determined that the magnetic field causes an interaction between a star's rotation and violent convective motions in its atmosphere. The magnetoacoustic hypothesis for heating the coronae is described. Research planned for the study of the solar-stellar relationship is discussed. Title: A Catalog of Mg II Emission Line Fluxes for T Tauri Stars Authors: Imhoff, C. L.; Basri, G.; Giampapa, M. S. Bibcode: 1987BAAS...19..728I Altcode: No abstract at ADS Title: Status Report on the SYNOP Project to Monitor Stars with High-Resolution Spectroscopy Authors: Linsky, J. L.; Giampapa, M. S. Bibcode: 1987BAAS...19..701L Altcode: No abstract at ADS Title: The Spatial Distribution of Magnetic Fields on Xi Bootis A Authors: Saar, S. H.; Huovelin, J.; Giampapa, M. S. Bibcode: 1987BAAS...19..703S Altcode: No abstract at ADS Title: Atmospheres of Stars in the Limit of Thin and Thick Convection Zones: The M Dwarf Stars (Invited review) Authors: Giampapa, Mark S. Bibcode: 1987LNP...291..236G Altcode: 1987csss....5..236G; 1987LNP87.291..236G This review summarizes our present understanding of the properties of M dwarf chromospheres and coronae determined from x-ray emission and ultraviolet and optical emission lines. These data permit estimates of the energy balance and heating rates for both dM and dMe stars and the presence of active regions. Two important questions are whether the dynamo is qualitatively different for the fully convective stars and whether the outer layers of dM stars are heated acoustically. Title: Magnetic Field Measurements on the Sun and Implications for Stellar Magnetic Field Observations Authors: Sun, Wei-Hsin; Giampapa, Mark S.; Worden, Simon P. Bibcode: 1987ApJ...312..930S Altcode: Results of solar magnetic field measurements in plages, sunspot umbrae, and sunspot penumbrae using high spectral resolution, unpolarized infrared H band spectral data are presented. A Fourier deconvolution analysis scheme similar to that utilized for stellar magnetic field measurements is adopted. As an example, a field strength of 3240 + or - 450 G is determined in a sunspot umbra combined with a value of 2000 + or - 180 G in the associated penumbra. These values are compared with a direct measurement of the spot umbra and penumbra field strengths based on the observed separation of the Zeeman components of the magnetically sensitive lines. Possible origins for the discrepancy between the results inferred by these two different techniques are discussed. The Fourier analysis results confirm the widespread occurrence of kilogauss level fields in the solar photosphere. The implications of the solar results for stellar magnetic field measurements are considered. Title: 4 meter FTS observations of photospheric magnetic fields on M dwarfs. Authors: Saar, Steven H.; Linsky, Jeffrey L.; Giampapa, Mark S. Bibcode: 1987LIACo..27..103S Altcode: 1987oahp.proc..103S Much of the observed activity on M dwarfs (e.g., spots, flares, chromospheric and coronal emission) has been attributed to the interaction of magnetic fields with the stellar atmosphere. Since data on the magnetic field parameters of M dwarfs can potentially reveal much about the physical mechanisms behind these phenomena and, additionally, about stellar dynamos and the evolution of stellar angular momentum, the authors have begun a program to measure the mean magnetic field strength in stellar active regions, and the surface filling factor of these regions for a sample of M dwarfs. In this paper some preliminary results of this survey are discussed. Title: Non-Axisymmetric Winds in T Tauri Stars Authors: Giampapa, Mark S. Bibcode: 1987iue..prop.2782G Altcode: We propose to obtain high dispersion, large aperture LWP observations of the Mg II h and k lines of a T Tauri star during the course of its rotation period in order to determine the empirical relationship between surface magnetic field regions and winds and mass loss in T Tauri stars. More specifically, we propose to monitor the Mg II hand k line profiles during the rotation period of a T Tauri star to search for evidence of rotational modulation in the blue wings. Such modulation (in both position and the intensity of the wind absorption) would be expected if the wind regions are intimately linked to magnetic field configurations, similar to solar coronal holes, on or near the stellar surface. This phenomenon has recently been observed with the IUE by Praderie at al. (1986) in the wind of AB Aur and thus constitutes the first direct evidence of a non-axisymmetric wind in an A type pre-main sequence star. Clearly, it would be extremely interesting to determine if this phenomenon is present in the precursors of late-type, solar-like stars, namely, the T Tauri stars. The detection of a nonaxisymmetric wind component in a T Tauri star would strongly support the hypothesis that mass loss in T Tauri stars is associated with nonradiative heating. Magnetic field related mass loss mechanisms, such as the Alfven wave driven winds, would consequently become more applicable in the context of mass loss from T Tauri stars. Our previous work indicates that the Mg II 2800 lines are the best diagnostics of physical conditions in the wind acceleration region between the lower chromosphere and the more extended regions in the wind. In addition, we will supplement these IUE observations with simultaneous ground-based observations of the H-alpha profile. In this way we can discern the radial extent of magnetic-field-related variability in the wind component of the profile as modulated by rotation. This additional component of the proposed program may provide a valuable constraint on the lower bound for the Alfven radius in a pre-main sequence star. We propose to acquire high dispersion LWP observations of the Mg II h and k lines in the T Tauri star SU Aurigae. The upper limit to its rotation period is 3.8 days; hence, we request 4 shifts to completely cover a rotation period. The choice of SU Aur is dictated by the fact that this T Tauri star exhibits both strong X-ray emission and evidence for strong mass loss that Is variable. Thus, both open and closed magnetic field regions are likely present on the stellar surface if the solar analogy is applicable. The feasibility of this IUE program has been demonstrated by two previous high dispersion observations of SU Aur. In order to obtain adequate signal-to-noise, an exposure of 7 hr is required. We must therefore request US1 shifts entirely. If approved, this program would represent the first time a T Tauri star has been monitored for line profile variations during a rotation period. Title: MOST: Multiple Object Spectroscopic Telescope. Authors: Pilachowski, C.; Giampapa, M.; Barden, S.; Green, R.; Osmer, P. Bibcode: 1987inco.conf...53P Altcode: MOST is a multiple object spectroscopic telescope based on the anticipated available of a 4 m, f/1.5 mirror from the NNTT mirror development program. The authors describe the MOST concept and give examples of how it can be applied to cosmological problems. Title: The McMath Solar-Stellar Synoptic Program Authors: Smith, Myron A.; Giampapa, Mark S. Bibcode: 1987LNP...291..477S Altcode: 1987LNP87.291..477S; 1987csss....5..477S No abstract at ADS Title: Synoptic Observations of the He I λ5876 Line in Active, Solar-Type Stars Authors: Giampapa, M. S. Bibcode: 1986BAAS...18..982G Altcode: No abstract at ADS Title: IUE observations of the eruptive pre-main sequence object FU Orionis. Authors: Ewald, R.; Imhoff, C. L.; Giampapa, M. S. Bibcode: 1986ESASP.263..205E Altcode: 1986NIA86......205E; 1986niia.conf..203E IUE observations have been used to examine the nature of the eruptive pre-main sequence object FU Orionis. The Mg II emission line is quite strong, with a surface flux of about 1.8×108erg/cm2sec, and probably arises in a wind and extended envelope. The Mg II h and k line profiles appear to be P Cygni, indicating that a substantial wind persists 50 years after the original outburst in the star. The ultraviolet spectrum, aside from the Mg II emission, resembles F2 Ia standard star spectra. Title: High-Resolution H alpha Observations of M Dwarf Stars: Implications for Stellar Dynamo Models and Stellar Kinematic Properties at Faint Magnitudes Authors: Giampapa, M. S.; Liebert, J. Bibcode: 1986ApJ...305..784G Altcode: We present high-dispersion observations of the Hα spectral region for a sample of very late M dwarf stars, as obtained with the Multiple Mirror Telescope echelle spectrograph and Reticon detector. Radial velocities and total space motions are derived. The Hα emission line properties of our sample are thereby examined according to membership in stellar kinematic populations. We find that, contrary to previous assertions, M dwarf stars exist later than spectral type M5.5 which do not exhibit Hα line emission. In fact, there are comparable numbers showing and not showing Hα emission for Mv > + 15 in this sample of large proper motion stars. Thus, the onset of full convection along the main sequence does not necessarily imply an enhanced level of magnetic field related chromospheric activity. However, we do find for the small and biased sample considered in this investigation that dMe stars are the dominant class of objects for absolute magnitudes Mv > + 17. The dMe stars tend to exhibit the small total space motions and (U, V, W) velocity dispersions that are indicative of young disk kinematics, while nearly all the M dwarfs lacking Hα emission are members of either the old disk or halo kinematic populations. The faintest subdwarf included in this investigation has Mv ≍ +14.8. The implications for stellar dynamo theory and for the nature of the stellar luminosity function at faint magnitudes are discussed. In particular, the results constitute corroborative evidence for a rotation-dependent distributed dynamo as a viable model for the generation of magnetic flux in the very low mass stars. Our results also suggest no significant difference between the kinematic properties of the stellar population that is brighter than the likely maximum in the luminosity function and that which is fainter. Title: The Surface Magnetic Fields of dM and dMe Stars Authors: Saar, S. H.; Linsky, J. L.; Giampapa, M. S. Bibcode: 1986BAAS...18..670S Altcode: No abstract at ADS Title: The Nature of the Dynamo in the Very Late M Dwarf Stars Authors: Giampapa, Mark S.; Liebert, James Bibcode: 1986LNP...254...62G Altcode: 1986csss....4...62G The results demonstrate that there are non-dMe stars with spectral types later than M5.5. We also confirm the occurrence of dMe stars at very late spectral types that, on the basis of current models, correspond to fully convective interiors. Hence, the results support a rotation-dependent distributed dynamo (or some variation thereof) as a viable model for the generation of magnetic flux in the very low mass stars. Future work should include v sin i determinations in order to further extend the investigation of the properties of dynamos, the kinematics, and the occurrence of binaries in the very low mass stars. The acquisition of Ca II H and K line data for the old disk and halo population stars in order to verify if any chromospheric activity is at all present would prove valuable. Many of the known low luminosity M dwarfs should be targeted for observation with future X-ray satellite observatories. A monitoring program to determine whether cycles occur in the fully convective M dwarf stars would provide valuable input on the location of dynamo processes in the stellar interior, as suggested by Dr. P. Gilman during the course of this workshop. Title: Prospects for a new synoptic high resolution spectroscopic observing facility Authors: Giampapa, Mark S. Bibcode: 1986pnsh.conf.....G Altcode: No abstract at ADS Title: Summary of the Synoptic Spectroscopic Facility Workshop Authors: Giampapa, M. S. Bibcode: 1986tswo.work..145G Altcode: No abstract at ADS Title: SHIRSOG Workshop / National Solar Observatory, Tucson,AZ., 1986 Authors: Giampapa, Mark S. Bibcode: 1986tswo.work.....G Altcode: No abstract at ADS Title: T Tauri stars: flare characteristics and flare models. Authors: Giampapa, M. S. Bibcode: 1986RALR...85..232G Altcode: The author notes the results of some recent work concerning surface magnetic activity on T Tauri stars. Then he discusses the flare properties of T Tauri stars. Title: The SHIRSOG Workshop. Proceedings of a workshop on prospects for a new synoptic high resolution spectroscopic observing facility, held at the National Solar Observatory, National Optical Astronomy Observatories, Tucson, Arizona, USA, 3 September 1986. Authors: Giampapa, M. S.; Jefferies, J. T.; Linsky, J. L. Bibcode: 1986swpw.book.....G Altcode: No abstract at ADS Title: Synoptic Studies of T-Tauri Stars Authors: Giampapa, M. S. Bibcode: 1986tswo.work...53G Altcode: The synoptic study of pre-main sequence stars at non-redundant wavelengths throughout the electromagnetic spectrum can elucidate critical problems in stellar evolution. Among these problems are: (1) The process of star formation in molecular clouds. (2) The redistribution of angular momentum as cloud collapse occurs. (3) The evolution of stellar magnetic activity up to the ZAMS. (4) The origin of chromospheres and coronae, including the operative heating mechanisms in the atmosphere and the associated mass flows. These processes may ultimately influence the structure of the star forming region and thereby play a role in regulating star formation rates. Title: Chromospheric and Coronal Emission in DM Stars Authors: Giampapa, Mark S. Bibcode: 1986iue..prop.2455G Altcode: We propose to obtain low dispersion, large aperture LWP spectra of the Mg II h+k chromospheric resonance lines for a volume limited sample of mainly single dM (i.e., nondMe) stars for which X-ray data are available. The combination of the IUE data-set we propose herein to obtain and the previously acquired X-ray data-set (Bookbinder 1985) will yield further insights on the nature of chromospheric and coronal heating in the ordinary, inactive (quiescent) dM stars. In particular, if the X-ray heating hypothesis for the source of chromospheric heating in the dMe stars, as advanced by Cram (1982), is also applicable to the dM stars then we would expect to find a linear correlation between the luminosity in the Mg II lines and the X-ray luminosity. In general, if a common source of in situ heating in the chromospheres and coronae of the dM stars is present then we would expect to find a linear relationship between the observed Mg II emission and the X-ray emission. Conversely, if the sources of chromospheric and coronal heating are different between these atmospheric regions in the dM stars then we expect to find a departure from a simple linear relationship. The results to be obtained in this program will yield critical observational constraints on the possible mechanisms for atmospheric heating in the dM stars. Title: The filling factor of active regions on the surfaces of the dM stars. Authors: Giampapa, M. S. Bibcode: 1985ApJ...299..781G Altcode: According to the appearance of the H-alpha line in their spectra, the M dwarf stars are subdivided into two classes, including the dMe stars and the dM stars. Arguments, based on the unique properties of H-alpha line formation in the M dwarf stars, are presented to demonstrate that the surfaces of the dM stars must be characterized by a significant areal coverage (or 'filling factor') of presumably magnetic field-related active regions. In addition, an estimate regarding the lower limit to the filling factor of chromospheric regions on dM stars is obtained, and an empirical relation is provided for the upper limit to the intrinsic Ca II (and Mg II) emission in these stellar surface regions. The discussion utilizes general model results obtained by Cram and Mullan (1979) and Giampapa et al. (1982). Title: Stellar magnetic field measurements utilizing infrared spectral lines. Authors: Gondoin, Ph.; Giampapa, M. S.; Bookbinder, J. A. Bibcode: 1985ApJ...297..710G Altcode: High-resolution spectra obtained with the KPNO 4 m telescope and FTS in the infrared H and K bands are examined in order to select spectral lines suitable for measurements of stellar magnetic field strengths and filling factors. Only four lines are found suitable for the magnetic field measurement technique adopted in this study. The authors analyze the co-added spectra of the active stars ξ Boo A (G8 V), 61 UMa (G8 V) and λ And (G8 IV-III) as obtained during four consecutive nights. The analysis technique involves the Fourier deconvolution of magnetically sensitive and insensitive line profiles in a single spectrum. No evidence for the presence of magnetic fields is detected in the co-added spectra of either ξ Boo A or 61 UMa. The data for λ And suggest magnetic fields of ≡600 G extending over at least 20% of the visible hemisphere. However, these values are near the detection limit for the spectrum of λ And. Title: Synoptic Observations of the Li I λ6707 Line in a Sample of Solar-Type Stars Authors: Giampapa, M. S. Bibcode: 1985BAAS...17..902G Altcode: No abstract at ADS Title: Simultaneous observations of CA II K and MG II K in T TAuri stars. Authors: Calvet, N.; Basri, G.; Imhoff, C. L.; Giampapa, M. S. Bibcode: 1985ApJ...293..575C Altcode: The first simultaneous, calibrated observations of the Ca II K and Mg II k resonance lines in T Tauri stars are presented. It is found that for T Tauri stars with mass greater than 1.5 solar mass, which have radiative cores and tend to be fast rotators, the k line seems to arise in an extended region (probably also responsible for the H-alpha emission), whereas the K line apparently originates closer to the highly inhomogeneous stellar surface. The lower mass stars, which are fully convective and tend to be slow rotators, are more easily described by a largely chromospheric model, consistent with main-sequence activity structures but at greater values of the nonradiative flux. The strongest emission-line stars in the low-mass group, however, are also likely to have extended k line regions. Title: Closed coronal structures. VI. Far-ultraviolet and X-ray emission from active late-type stars and the applicability of coronal loop models. Authors: Giampapa, M. S.; Golub, L.; Peres, G.; Serio, S.; Vaiana, G. S. Bibcode: 1985ApJ...289..203G Altcode: We present far-ultraviolet line fluxes of prominent transition region emission lines, as obtained with the International Ultraviolet Explorer satellite, for a sample of solar-type stars. We combine the ultraviolet observations with existing soft X-ray measurements obtained by the Einstein Observatory (HEAO 2). We utilize the resulting data set and a new coronal loop model numerical code developed at the Harvard-Smithsonian Center for Astrophysics to perform a preliminary investigation of the applicability of coronal loop models to solar-type stars. In a few cases, reasonable agreement between the predictions of single-component, coronal loop model atmospheres and the observational data is achieved for a relatively well-defined, plausible range of values in the pressure-filling factor (p, f) plane. In general, however, we find that the addition of non- simultaneous ultraviolet observations to a previously acquired soft X-ray data set does not provide a sufficient constraint on the range of possible loop filling factors and pressures for loop model atmospheres that may be producing the observed X-ray and transition region emissions. We discuss the origins of the discrepancies between the model results and the observations within the context of (1) stellar variability, (2) multiple coronal components, and (3) the presence of relatively low temperature loops that give rise to far-ultraviolet emission but not to coronal X-ray emission. We suggest on the basis of the results presented in this investigation that in order to verify the applicability of coronal loop models to solar-type stars, simultaneous far-ultraviolet and moderate spectral resolution X-ray observations will eventually have to be obtained. Title: The ambient radiation field of young solar systems: ultraviolet and X-ray emission from T Tauri stars. Authors: Giampapa, M. S.; Imhoff, C. L. Bibcode: 1985prpl.conf..386G Altcode: The authors review the principal results that have emerged from ultraviolet and X-ray observations of T Tauri stars. They emphasize that, as seen in the ultraviolet, T Tauri stars are characterized by strongly enhanced emission. The X-ray emission and its variability, when detected, is also enhanced and indicate of the occurrence of violent flare activity near the stellar surface. The authors discuss possible effects of these enhanced emissions on conditions in early solar systems and the chemical evolution of early planetary atmospheres. Title: Profiles of the MG II H and K Lines in Selected Red Dwarfs Authors: Giampapa, Mark S. Bibcode: 1985iue..prop.2149G Altcode: We propose to obtain high dispersion, large aperture, flux-calibrated LWP observations of the Mg II h and k resonance lines for a selected sample of 8 red dwarf stars in the spectral range dK7 - dM4.5. The sample includes 6 active chromosphere emission line stars and 1 quiet chromosphere comparison dwarf. Furthermore, we will apply to arrange for simultaneous, high spectral resolution, flux-calibrated observations of the Ca II H and K lines and the H-alpha line using the KPNO 4m echelle spectrograph and CCD. The resulting data-set will be used to (1) develop self-consistent, semi-empirical model chromospheres with the eventual goal of gaining insight on the Possible atmospheric heating mechanisms operative in the chromospheres of these stars and the relative geometries of the line emitting regions, (2) testing the applicability of specific chromospheric scaling laws (Ayres 1979) to the Mg II lines in these stars, and (3) determine if the Wilson-Bappu effect persists through these late spectral types as seen in the Mg II lines as well as the Ca II and H-alpha lines. We will utilize a fully general, non-LTE transfer code at Berkeley to develop semi-empirical model chromospheres according to the techniques employed by Giampapa et al. (1982). The Mg II resonance lines in M dwarfs are particularly interesting since they are formed at a level between the lower chromospheric Ca II h and k lines and the upper chromospheric Balmer lines. Thus the Mg II lines represent a crucial "bridge" between these diagnostics. Moreover, the Mg II lines are significantly more optically thick than the Ca II lines by virtue of the greater (~ 10) abundance of magnesium relative to calcium. Thus they are potentially a more sensitive test of chromospheric scaling laws (Ayres 1979) for optically thick lines. Finally, an active star and a quiet chromosphere star of the same spectral types (dK7) are included in the observing program as a further test of the applicability of the Wilson-Bappu law to red dwarfs. According to this law, the widths should be identical within errors. Significant differences would be investigated within the context of differences in chromospheric structure which would, in turn, lead to new insights on chromospheric line formation and the Wilson-Bappu effect. The feasibility of this IUE program has been demonstrated by high dispersion, LWR observations of AU Mic (dM1.6e) of 4 hr duration during a US2 shift (Ayres et al. 1983). We use this result and low resolution Mg II flux measurements tabulated by Linsky et al. (1982) to obtain reliable LWP-high dispersion exposure estimates for the targets in our sample. We will precede each LWP - high with a LWP - low for accurate flux calibration purposes. In addition, we wish to bracket all exposures with FES visual magnitude estimates to check for flare activity. The LWP - high exposures for the more flare active stars in our program will be obtained in segments bracketed by FES magnitudes. Title: Stellar surface inhomogeneities and the interpretation of stellar spectra. Authors: Giampapa, M. S. Bibcode: 1985ASIC..152..305G Altcode: 1985pssl.proc..305G The author discusses manifestations of stellar surface thermal inhomogeneities in stellar spectra. He illustrates the effects of multi-components in stellar atmospheres on the interpretation of line diagnostics and single-component models as well as on the treatment of line transfer problems. The examples offered involve metal abundance determinations, chromospheric line diagnostics, the realistic representation of pre-main sequence atmospheres and stellar magnetic fields. Title: Coordinated Magnetic and Chromospheric Observations of Stars Authors: Giampapa, Mark S. Bibcode: 1985iue..prop.2147G Altcode: We propose to obtain time-resolved, coordinated observations of magnetic flux and the associated chromospheric and transition region line emissions for selected active chromosphere stars. The unique data to be obtained in this program will provide a crucial input to theories that describe the heating of stellar atmospheres. In essence, the results to be acquired through the observations will establish a preliminary empirical relationship between stellar photospheric magnetic field strengths and magnetic flux, and stellar outer atmospheric line emission. We are presently utilizing demonstrated methods to directly detect magnetic fields on stellar surfaces. Magnetic results indicate the existence of strong (a few kilogauss) fields that may cover up to 80% of the stellar surface. Moreover, these fields are observed to rapidly (2-3 days) vary in surface coverage, suggesting a single large magnetic spot complex on only one hemisphere of the star. We therefore propose a coordinated IUE/ground-based synoptic program to obtain chromospherictransition region data (with IUE), and photospheric magnetic field and flux measurements (ground-based observations) for several stars that exhibit rapidly varying surface field coverages over their rotational periods. Our IUE observing pattern will primarily consist of low dispersion, SWP observations and high-dispersion, LWR exposures. These data will be obtained simultaneously (or near simultaneously) with ground-based optical and IR observations. The ground-based data will be used to infer magnetic field strengths and flux in the photosphere. We also require that the IUE shifts be scheduled every third day to insure that we examine the entire stellar surface over 10-15 day rotational periods. We require two separate observing periods in order to have access to all objects in the target list from ground-based observing sites. Title: Active late-type stars and the applicability of coronal loop models. Authors: Giampapa, M. S.; Golub, L.; Peres, G.; Serio, S.; Vaiana, G. S. Bibcode: 1984NASCP2349..454G Altcode: 1984fiue.rept..454G; 1984IUE84......454G Far ultraviolet IUE observations of a sample of solar type stars were combined with existing soft X-ray measurements obtained by HEAO B. The resulting data set was utilized and a new coronal loop model numerical code was developed to perform a preliminary investigation of the applicability of coronal loop models to solar-type stars. Reasonable agreement was found to exist between the predictions of single-component coronal loop model atmospheres. It was demonstrated that semi-empirical, coronal loop models can be applied to account for observed stellar transition region and coronal emission. This result is corroborative evidence for the presence of magnetic field structures analogous to solar coronal loops on the surfaces of solar-type stars. It is suggested that stellar transition region emission arises predominantly from the base of quiescent coronal loop configurations. Title: The appearance of magnetic flux on the surfaces of the early main-sequence F stars Authors: Giampapa, M. S.; Rosner, R. Bibcode: 1984ApJ...286L..19G Altcode: Available chromospheric, transition region, and coronal observations of the early main-sequence F stars are examined in order to find that while these objects exhibit enhanced levels of magnetic field-related radiative emissions, significant inhomogeneities in surface activity are not present. This phenomenon is discussed within the context of the calculations published by Schmitt and Rosner (1983) for the production of flux ropes of various spatial scales at a given rotation rate at the bottom of a stellar convection zone. It is found that the spatial scales and area contrast of emergent magnetic flux in these stars that, as a class, are characterized by rapid rotation and thin convection zones are substantially reduced relative to that of the sun. Title: The Filling Factor of Active Regions on non-dMe Stars Authors: Giampapa, M. S. Bibcode: 1984BAAS...16..940G Altcode: No abstract at ADS Title: A Transition from Chromosphere to Wind for MgII in T Tauri Stars Authors: Basri, G.; Calvet, N.; Imhoff, C. L.; Giampapa, M. S. Bibcode: 1984BAAS...16..938B Altcode: No abstract at ADS Title: Ultraviolet Continuum and Mg II Emission Rotational Modulation in Three Pre-Main Sequence Stars Authors: Imhoff, C. L.; Giampapa, M. S. Bibcode: 1984BAAS...16..997I Altcode: No abstract at ADS Title: Simultaneous IUE, Voyager, and Optical Observation of Epsilon Persei Authors: Giampapa, Mark Bibcode: 1984iue..prop.1947G Altcode: No abstract at ADS Title: New spectrophotometry of the extremely cool proper motion star LHS 2924. Authors: Liebert, J.; Boroson, T. A.; Giampapa, M. S. Bibcode: 1984ApJ...282..758L Altcode: Improved spectrophotometric scans are presented for this very faint, red, large-proper motion star which has a peculiar spectrum. The Palomar Observatory 5 meter CCD spectrum shows the clear presence of VO λ7400 and λ7900. However, the TiO and hydride bands and the Na I and K I lines appear relatively weaker over the spectrum of LHS 2924 than they do in the benchmark low-luminosity star VB 10. A high-resolution observation with the MMT echelle spectrograph shows very weak Hα emission, at best. These and other recent results eliminate all previously considered explanations of the nature of LHS 2924 other than a very cool, main-sequence star or sub-stellar-mass "brown dwarf." The weakness of Hα emission tends to indicate that the star is an old, main-sequence object. Title: The Transition Regions of X-Ray Emitting Main-Sequence A Stars Authors: Giampapa, Mark S. Bibcode: 1984iue..prop.1812G Altcode: We propose to obtain low dispersion, large aperture SWP and high dispersion, large aperture LWR observations of two (2) X-ray emitting, single main-sequence A stars:: HR 7160 (A8V, log Lx = 29) and HD 117721 (A3V, log Lx = 30.4). These stars were strongly detected by HEAO-B (Golub et al. 1983) and, unlike many of the other A stars detected by Einstein, these objects appear to be single stars. lie thus propose to verify the presence of hot plasma in these stars by searching for the occurrence of transition region and chromospheric line emission. The detection of transition region line emission (i.e. C IV, N V, Si IV, etc.) in main sequence A stars would have important implications for (1) our understanding of the precise location on the main sequence of the onset of convection, and (2) the role of convection zone depth and surface turbulence in the generation of stellar chromospheric and coronal activity. Title: Photometric variations of solar-type stars: results of the Cloudcroftsurvey. Authors: Giampapa, M. S. Bibcode: 1984NASCP2310..173G Altcode: 1984siva.work..173G The author summarizes the results of a synoptic program conducted at the Cloudcroft Observatory to search for the occurrence of photometric variability in solar-type stars as seen in continuum band photometry. The survey disclosed the existence of photometric variability in solar-type stars that is, in turn, related to the presence of spots on the stellar surface. Moreover, the observed variability detected in solar-type stars is at enhanced levels (≡1%) compared to that observed for the Sun. Title: Lithium abundances and chromospheric activity. I. Empirical results. Authors: Giampapa, M. S. Bibcode: 1984ApJ...277..235G Altcode: An empirical analysis is presented of the effects of chromospheric activity on lithium abundance determinations, as deduced from high signal-to-noise, high spectral resolution solar observations of the Li I resonance doublet at 6707.8 A. In particular, solar active (plage) regions and quiet comparison regions were observed to find a maximum relative change in the Li I 6707 equivalent width of -0.53 among the limited number of solar plage observations available for this investigation. The relative weakening of the lithium resonance doublet is attributed to the increased ionization of neutral lithium due to the enhanced nonradiative heating that characterizes solar plages. The strong enhancement of the 6707 line in sunspot umbrae is confirmed and it is emphasized that the presence of stellar surface thermal inhomogeneities analogous to solar plages and sunspots can substantially alter the equivalent width of this feature in stellar spectra. Thus the effects of stellar chromospheric activity will introduce ambiguities into lithium abundance determinations that, in turn, can contribute significantly to the scatter in investigations that utilize this diagnostic. Title: Results from Ultraviolet Observations of T Tauri Stars Authors: Giampapa, Mark S. Bibcode: 1984LNP...193...14G Altcode: 1984csss....3...14G No abstract at ADS Title: The response of chromospheric emission lines to flares on YZ Canis Minoris. Authors: Worden, S. P.; Schneeberger, T. J.; Giampapa, M. S.; Deluca, E. E.; Cram, L. E. Bibcode: 1984ApJ...276..270W Altcode: Six flares of the dMe star YZ CMi have been observed with simultaneous photometry and high-dispersion, time-resolved spectroscopy.The spectra have temporal resolutions of 3 minutes with spectral resolutions of 0.24 Å. The largest observed flare had a U band amplitude of 1.5 mag. Hα and Hβ line profiles did not broaden during any of the observed flares, although the line center intensity increased by over a factor of 2 during some flares. After the initial increase in intensity, the emission line strength decreases but remains at enhanced levels for hours following U band flares. The Hα flare luminosity and total energy are compared to corresponding properties of solar flares. Title: Direct and Indirect Methods of Measurement of Stellar Magnetic Fields Authors: Giampapa, M. S. Bibcode: 1984srps.conf..309G Altcode: Standard polarization methods for measuring stellar magnetic fields are inappropriate for solar-type field topologies. The author is therefore utilizing a "white-light" method that involves the interpretation of spectral line shapes as seen in high spectral resolution data. Through the application of Fourier deconvolution techniques, the field strength and area coverage on a stellar surface can be ascertained. The applicability and results of this method for both solar and stellar magnetic field measurements are discussed. Besides the aforementioned direct method, there potentially exist complementary indirect methods. They are less satisfactory than direct methods. They require a knowledge of the underlying physics that relates on observable radiative emission to the local magnetic field strength or flux. Title: Some Relevant Topics in Solar-Stellar Physics Authors: Giampapa, M. S. Bibcode: 1984ssdp.conf..457G Altcode: No abstract at ADS Title: Combined ultraviolet studies of astronomical sources Authors: Dupree, A. K.; Giampapa, M. S.; Huchra, J. P.; Noyes, R. W.; Hartmann, L. W.; Raymond, J. C.; Blair, W. P.; Bothun, G. D.; Patterson, J. O.; Baliunas, S. L. Bibcode: 1983sao..reptR....D Altcode: Ultraviolet spectra of non-radiataive shock waves grain destruction and elemental abundances in interstellar shocks, carbon abundance in M33 and M31 from supernova remnants, determination of the mass function in the large Magellanic cloud, UV spectra of white dwarf pulsars, stellar flares, availability of the double quasar Q 0957 + 56' AB, spectra of late-F dwarfs and their relation to rotation, dynamics of hot gas surrounding hybrid stars, high resolution study of epsilon coronae Austriual, active regions on solar-type dwarfs as a function of rotation rate and age, coordinated chromospheric synoptic observations of selected late-type stars, the two-component atmosphere of Lambda Andromedae, and activity in Hyades giants are discussed. Title: Magnetic Field Measurements on the Sun and Synthesis of Stellar Spectrum from Solar Data Authors: Sun, W.; Giampapa, M. S.; Worden, S. P. Bibcode: 1983BAAS...15..952S Altcode: No abstract at ADS Title: The UV Variability of RW Aur Authors: Imhoff, C. L.; Giampapa, M. S. Bibcode: 1983BAAS...15..928I Altcode: No abstract at ADS Title: The Young Sun and The Atmosphere and Photochemistry of the Early Earth Authors: Giampapa, M. S.; Canuto, V. M.; et al. Bibcode: 1983Natur.305..281G Altcode: No abstract at ADS Title: Concerning Spot Formation in the Early Main Sequence F Stars Authors: Giampapa, M. S. Bibcode: 1983BAAS...15..947G Altcode: No abstract at ADS Title: The young Sun and the atmosphere and photochemistry of the early Earth Authors: Canuto, V. M.; Levine, J. S.; Augustsson, T. R.; Imhoff, C. L.; Giampapa, M. S. Bibcode: 1983Natur.305..281C Altcode: The origin and evolution of the Earth's early atmosphere depend crucially on the dissipation time tN of the primitive solar nebula, SN. Using different theories of turbulence, we estimate that for a 0.1 Msolar SN, tN is 2.5-8.3Myr. Because accretion times are usually much longer, we conclude that most planetary accretion must have occurred in a gas-free environment. Using new IUE data, a wavelength-dependent UV flux is constructed for the young Sun which is then used to study the photochemistry and concentrations of O, O2, O3, OH, H, HCO and formaldehyde H2CO in the Earth's early prebiological atmosphere. Title: High Resolution Ultraviolet and Optical Observations of T-Tauri Stars Authors: Giampapa, M. S. Bibcode: 1983RMxAA...7..195G Altcode: No abstract at ADS Title: Ultraviolet Observations of the T-Tauri Stars - Inferences Regarding Their Chromospheres Transition Regions and Coronae Authors: Imhoff, C. L.; Giampapa, M. S. Bibcode: 1983RMxAA...7..191I Altcode: No abstract at ADS Title: Ultraviolet Observations of the T Tauri Stars: Inferences Regarding their Chromospheres, Transition Regions, and Coronae Authors: Giampapa, M. S. Bibcode: 1983RMxAA...7..191G Altcode: No abstract at ADS Title: New Spectrophotometry of the Extremely Red Proper-Motion Star LHS2924 Authors: Liebert, J. W.; Boroson, T. A.; Giampapa, M. S. Bibcode: 1983nssl.conf..361L Altcode: 1983IAUCo..76..361L; 1983LDP.....4..361L LHS 2924 (LP 271-25) is the uniquely-red, faint proper motion star recently reported to have a peculiar spectrum and colors by Probst and Liebert (1983). This paper reports briefly the results of two follow-up observations: an excellent red spectrum covering 5000 - 9000 Å, and a high dispersion spectrum of the important Hα region. Title: The photometric variability of solar-type stars. II. Stars selected from Wilson's chromospheric activity survey. Authors: Radick, R. R.; Wilkerson, M. S.; Worden, S. P.; Africano, J. L.; Klimke, A.; Ruden, S.; Rogers, W.; Armandroff, T. E.; Giampapa, M. S. Bibcode: 1983PASP...95..300R Altcode: The authors have observed eleven solar-type main-sequence stars to search for continuum variability. Stars were selected from Wilson's chromospheric activity survey, and were observed for periods of three to six months with intermediate-band Stroemgren uvby photometry. The authors find evidence that two of these eleven stars are variable and that one other may be. Comparison with contemporaneous Ca II H + K emission flux measurements shows that the amplitude of photometric variability correlates strongly with both the mean emission flux and the amplitude of its variation. Variations in continuum light and emission flux tend to correlate in time, as well, with continuum minima coinciding with emission maxima and vice-versa. The authors infer that the surface activity of these stars tends to be confined to localized activity centers that include both emission plages and dark spots, similar to the active regions observed on the sun. Title: The magnetic field on the RS Canum Venaticorum star lambda Andromeda. Authors: Giampapa, M. S.; Golub, L.; Worden, S. P. Bibcode: 1983ApJ...268L.121G Altcode: A program to detect and measure magnetic flux on the surfaces of late-type stars is discussed. A technique is adopted to deconvolve magnetically insensitive lines from similar, magnetically sensitive lines to infer the degree of Zeeman splitting in the latter lines. These measurements yield values for the magnetic field strength and filling factor (flux). To illustrate the approach, observations of the RS CVn star Lambda And are presented. At the epoch of observation, 1981 April 26, a field strength of 1290 + or - 320 gauss covering 48 + or - 7 percent of this star's surface is found. This measurement compares with an estimate of coronal magnetic flux in the cooler component of the stellar corona of 1110 gauss with a coronal volume filling factor of 75 percent, based on X-ray data for Lambda And. Title: Methods and results for detecting magnetic fields on late-type stars. Authors: Giampapa, M. S.; Worden, S. P. Bibcode: 1983IAUS..102...29G Altcode: A program to detect and measure magnetic flux on the surfaces of late-type stars is discussed. A novel technique is adopted to deconvolve magnetically insensitive lines from similar, magnetically sensitive lines to infer the degree of Zeeman splitting in the latter lines. These measurements yield values for the magnetic field strength and filling factor (flux). To illustrate the approach multiple observations are presented of the RS CVn star Lambda And. At the epoch of observation 26 April 1981 a field strength of 1290 + or - 50 gauss covering 48 + or - 2 percent of this stars's surface is found. Observations at other epochs clearly demonstrate magnetic flux variability on Lambda And. Title: Fractional stellar convection-zone depth and the generation of magnetic flux - an empirical approach Authors: Giampapa, M. S. Bibcode: 1983IAUS..102..187G Altcode: Preliminary results of an observational investigation of very late M dwarf stars utilizing the Multiple Mirror Telescope facility are presented. It is found that dwarf stars later than spectral type M5 do not necessarily exhibit H-alpha line emission, contrary to the assertion by Joy and Abt (1974). The preliminary results tentatively suggest, but do not prove, that the generation of significant magnetic fields and magnetic flux is severely inhibited in fully convective stars. Title: Observations of Flare Activity on Selected DME Flare Stars Authors: Giampapa, Mark S. Bibcode: 1983iue..prop.1442G Altcode: Optical and ultraviolet spectroscopy can enable the assessment of the physical conditions characterizing a stellar flare atmosphere and thereby potentially elucidate the possible radiative and hydrodynamic transport mechanisms operative during stellar flares. Observations of flares on M dwarf stars offers the opportunity to obtain detailed information on a solar-like phenomenon as it presumably occurs on many stars, but can presently only be observed on the cool dMe stars due to the highly favorable contrast between the UV and near UV bright flare emission and the faint quiescent background. We therefore propose to acquire timeresolved, low dispersion, large aperture SWP and LWR observations simultaneously with moderate resolution (3-4A) spectrophotometric optical observations of stellar flare events. We also will attempt to coordinate simultaneous VLA (radio corona) observations. We intend to monitor two highly flare active systems; the binary UV Ceti (GL65AB) system and the single flare star YZ CMi (GL 285). We wish to ascertain the dominant radiative transport mechanism that gives rise to the UV and optical continuum emission during flares as well as assess the relative energy balance in these wavelength regions. Furthermore, we will utilize density diagnostics and emission mesure analysis techniques developed for solar observations. In addition, we will infer flare X-ray luminosities from the enhancement of the He II 1640 recombination line. The UV data and inferred X-ray data will ultimately be used to determine the applicability of flare loop models. All data obtained in this program will be used as input for the construction of semiempirical flare atmospheres. Title: Results from optical and UV stellar flare spectroscopy Authors: Giampapa, M. S. Bibcode: 1983ASSL..102..223G Altcode: 1983ards.proc..223G; 1983IAUCo..71..223G Optical and ultraviolet spectroscopy can enable the assessment of the physical conditions characterizing a stellar flare atmosphere and thereby potentially elucidate the possible radiative and hydrodynamic transport mechanisms operative during stellar flares. In this review, illustrative examples are presented of the spectroscopic diagnostic techniques that can be applied to the analysis of stellar flare spectroscopic data and the resulting inferences concerning stellar flare properties for M dwarf flare events. Title: Outer atmospheres of cool stars. XII. A survey of IUE ultraviolet emission line spectra of cool dwarf stars. Authors: Linsky, J. L.; Bornmann, P. L.; Carpenter, K. G.; Wing, R. F.; Giampapa, M. S.; Worden, S. P.; Hege, E. K. Bibcode: 1982ApJ...260..670L Altcode: Quantitative information is obtained on the chromospheres and transition regions of M dwarf stars, in order to determine how the outer atmospheres of dMe stars differ from dM stars and how they compare with the outer atmospheres of quiet and active G and K type dwarfs. IUE spectra of six dMe and four dM stars, together with ground-based photometry and spectroscopy of the Balmer and Ca II H and K lines, show no evidence of flares. It is concluded, regarding the quiescent behavior of these stars, that emission-line spectra resemble that of the sun and contain emission lines formed in regions with 4000-20,000 K temperatures that are presumably analogous to the solar chromosphere, as well as regions with temperatures of 20,000-200,000 K that are presumably analogous to the solar transition region. Emission-line surface fluxes are proportional to the emission measure over the range of temperatures at which the lines are formed. Title: Fractional Stellar Convection Zone Depth and the Generation of Magnetic Flux Authors: Giampapa, M. S. Bibcode: 1982BAAS...14..865G Altcode: No abstract at ADS Title: Stellar model chromospheres. XIII. M dwarf stars. Authors: Giampapa, M. S.; Worden, S. P.; Linsky, J. L. Bibcode: 1982ApJ...258..740G Altcode: Single-component, homogeneous model chromospheres that are consistent with high-resolution profiles of the Ca II K line calibrated in surface flux units for three dMe and 2 dM stars observed at quiescent times are constructed. The models reveal several systematic trends. Large values of the ratio of T(min) to T(eff) are derived, indicating a large amount of nonradiative heating present in the upper photospheres of M dwarf stars. It is also found that the lower chromospheric temperature gradient is similar for all the M dwarf stars. Since for the models here the chromospheric K line emission strength is most sensitive to the total amount of chromospheric material present within the approximate temperature range T(min)-6000 K, increasing the emission strength is not simply due to increasing chromospheric temperature gradients. It is also found that both the electron density and electron temperature at one thermalization length in the K line below the top of the chromospheres are greater in the dMe stars than in the dM stars. The M dwarf models here have microturbulent velocities between 1 and 2 km/sec, which are much smaller than for solar chromosphere models. Title: Observations of rapid line profile variability in the spectra of T Tau stars. Authors: Mundt, R.; Giampapa, M. S. Bibcode: 1982ApJ...256..156M Altcode: Observation of six T Tauri stars, having a spectral resolution of 240,000 and temporal resolutions in the 300-900 sec range, are presented. In addition to presenting evidence for the existence of rapid line profile variability in the spectrum of RW Aurigae, this object's line spectrum properties in the vicinity of the H-alpha, H-gamma, and Na D lines are discussed in view of three high-quality spectra, with the result that photospheric absorption features are identified and a rotational velocity of about 25 km/sec is tentatively estimated. The data set acquired for RW Aur also reveals the existence of mass motions with antiparallel velocity components in the line-emitting region of the object. A spectral type for this previously unclassified T Tauri star of K1 + or - 2 subclasses is determined. Title: Combined ultraviolet studies of astronomical sources Authors: Dupree, A. K.; Giampapa, M. S.; Huchra, J. P.; Noyes, R. W.; Hartmann, L. W.; Raymond, J. C. Bibcode: 1982sao..reptQ....D Altcode: Ultraviolet studies of astronomical sources are discussed. Some studies utilized IVE data. Non-radiative shock at the edge of the Cygnses Loop, stellar flares, local interestellar medium, hot galaxies, stellar mass ejection, contact binaries, double quasars, and stellar chromosphere and coronae are discussed. Title: A heating mechanism for the chromospheres of M dwarf stars. Authors: Giampapa, M. S.; Golub, L.; Rosner, R.; Vaiana, G. S.; Linsky, J. L.; Worden, S. P. Bibcode: 1982SAOSR.392A..73G Altcode: 1982csss....2...73G The atmospheric structure of the dwarf M-stars which is especially important to the general field of stellar chromospheres and coronae was investigated. The M-dwarf stars constitute a class of objects for which the discrepancy between the predictions of the acoustic wave chromospheric/coronal heating hypothesis and the observations is most vivid. It is assumed that they represent a class of stars where alternative atmospheric heating mechanisms, presumably magnetically related, are most clearly manifested. Ascertainment of the validity of a hypothesis to account for the origin of the chromospheric and transition region line emission in M-dwarf stars is proposed. Title: Second Cambridge workshop on cool stars, stellar systems, and the sun. Vol. 1. Proceedings of a workshop held at the Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, October 21 - 23, 1981. Authors: Giampapa, M. S.; Golub, L. Bibcode: 1982SAOSR.392A....G Altcode: 1982csss....2A....G No abstract at ADS Title: Cool stars, stellar systems and the sun : 2 : 1981 Authors: Giampapa, M. S.; Golup, L. Bibcode: 1982SAOSR.392B....G Altcode: 1982csss....2B....G No abstract at ADS Title: Preface Authors: Giampapa, Mark; Golub, Leon Bibcode: 1982SAOSR.392D...9G Altcode: 1982csss....2D...9G No abstract at ADS Title: Far-ultraviolet and X-ray evidence concerning the chromospheres and coronae of the T Tauri stars. Authors: Imhoff, C. L.; Giampapa, M. S. Bibcode: 1982SAOSR.392B.175I Altcode: 1982csss....2..175I No abstract at ADS Title: Coordinated X-ray, optical and radio observations of flaring activityon YZ Canis Minoris. Authors: Kahler, S.; Golub, L.; Harnden, F. R.; Liller, W.; Seward, F.; Vaiana, G.; Lovell, B.; Davis, R. J.; Spencer, R. E.; Whitehouse, D. R.; Feldman, P. A.; Viner, M. R.; Leslie, B.; Kahn, S. M.; Mason, K. O.; Davis, M. M.; Crannell, C. J.; Hobbs, R. W.; Schneeberger, T. J.; Worden, S. P.; Schommer, R. A.; Vogt, S. S.; Pettersen, B. R.; Coleman, G. D.; Karpen, J. T.; Giampapa, M. S.; Hege, E. K.; Pazzani, V.; Rodono, M.; Romeo, G.; Chugainov, P. F. Bibcode: 1982ApJ...252..239K Altcode: The YZ Canis Minoris (Gliese 285), a late-type dwarf star with Balmer emission (dM4.5e), is a member of the UV Ceti class of flare stars. Obtaining good X-ray observations of a dMe star flare is important not only for understanding the physics of flares but also for testing current ideas regarding the similarity between stellar and solar flares. The Einstein X-ray Observatory has made it possible to conduct X-ray observations of dMe stars with unprecedented sensitivity. A description is presented of the results of a program of ground-based optical and radio observations of YZ CMi coordinated with those of the Einstein Observatory. The observations were carried out as part of a coordinated program on October 25, 26, and 27, 1979, when YZ CMi was on the dawn side of the earth. Comprehensive observational data were obtained of an event detected in all three wavelength regions on October 25, 1979. Title: The relevance of the IUE results on young stars for earth's paleoatmosphere. Authors: Canuto, V. M.; Levine, J. S.; Augustsson, T. R.; Imhoff, C. L.; Giampapa, M. S. Bibcode: 1982NASCP2238..293C Altcode: 1982auva.nasa..293C; 1982NASCP2338..293C Using the latest IUE results for seven T Tauri stars, which are believed to represent the young Sun and a detailed photochemical chemical model of the paleoatmosphere, the vertical distribution of Oxygen and Ozone in the early atmosphere was calculated. The calculations indicate that the surface Oxygen mixing ratio is as much as six orders of magnitude larger than previously estimated, but appears low enough for the formation of amino acids via the Urey-Miller type of experiments. It is believed that the quantification of the oxygen level in the Earth's paleoatmosphere presented can reconcile the demands of both biological and geological considerations. Title: Magnetic & Chromospheric Synoptic Observations of Late-Type Stars Authors: Giampapa, Mark S. Bibcode: 1982iue..prop.1099G Altcode: We propose to obtain time-resolved, coordinated observations of magnetic flux and the associated chromospheric and transition region line emission for selected active chromosphere stars. The unique data to be obtained in this program will provide a crucial input to theories that describe the heating of stellar chromospheres and coronae. In essence, the results to be acquired through the observations proposed herein will (for the first time) establish a preliminary empirical relationship between stellar magnetic field strengths and magnetic flux, and stellar outer atmospheric line emission. We are presently utilizing a now and successfully demonstrated method to directly detect magnetic fields on stellar surfaces. These results indicate the existence of strong (~ a few kilogauss) magnetic fields that may cover up to 80% of the stellar surface. Moreover, these fields are observed to rapidly (2-3 days) vary in surface coverage. We therefore propose a coordinated IUE ground-based synoptic program to obtain chromospheric-transition region data (with IUE) and magnetic field and flux measurements (ground-based observations) for several stars that exhibit rapidly varying surface field coverages over their rotational periods. Our IUE observing pattern will primarily consist of low dispersion, SWP observations and high-dispersion, LWR exposures. These data will be obtained simultaneously (or near simultaneously) with groundbased optical and infrared observations. The groundbased data will Title: Chromospheres and coronae in the T Tauri stars. Authors: Imhoff, C. L.; Giampapa, M. S. Bibcode: 1982NASCP2238..456I Altcode: 1982NASCP2338..456I; 1982auva.nasa..456I The Tauri stars exhibit strong far ultraviolet emission lines of C II, III, IV; OI; Si II, III; IV; and sometimes N V and He II. Surface fluxes of the lines for several T Tauri stars were computed, drawing upon both International Ultraviolet Explorer observations and published spectra. The surface fluxes are quite high. The FUV lines together account for 0.1% of the stellar luminosity. These results indicate the presence of active relatively dense chromospheres. The Tauri stars showing very strong visual emission spectra exhibit weakened high temperature FUV lines of C IV and N V, as well as He II which may be produced by X-rays. In the same stars, no X-ray emission was detected with Einstein. Among all the T Tauri stars the X-ray luminosities are deficient by factors of 100 to 1000 compared to the FUV lines. It is argued that the X-ray flux has not been heavily absorbed by circumstellar gas, as has been previously suggested, but that the X-rays are truly underluminous, perhaps due to the stellar wind. It is suggested that the birth and development of the chromosphere and corona may be occurring during the T Tauri stage of protostellar evolution. Title: A preflare diminution in the quiescent flux of EQ Pegasi. Authors: Giampapa, M. S.; Africano, J. L.; Klimke, A.; Parks, J.; Quigley, R. J.; Robinson, R. D.; Worden, S. P. Bibcode: 1982ApJ...252L..39G Altcode: The occurrence of a remarkable flare event on EQ Peg is reported as recorded by high speed photometry in the Johnson U band: a stellar flare event is immediately preceded by a well-defined decline in the quiescent flux of the star. The U band flux decays to a minimum level that is 75% of the stellar quiescent flux, and the duration of the so-called negative flare event is 2.7 minutes. A description of the observation is presented and hypotheses are discussed that may eventually account for this phenomenon. Title: IUE observations of pre-main-sequence stars. I. MG II and CA II resonance line fluxes for T Tau stars. Authors: Giampapa, M. S.; Calvet, N.; Imhoff, C. L.; Kuhi, L. V. Bibcode: 1981ApJ...251..113G Altcode: IUE satellite and Lick 3 m reflector image tube scanner measurements of the Mg II and Ca II resonance lines in a sample of T Tauri stars are the basis of a discussion of the Mg II h and k line emission and the Ca II H and K line emission, within the context of stellar chromospheres. Corroborative evidence is presented for the chromospheric origin of these resonance lines, and chromospheric radiative loss rates in the Mg II and Ca II resonance lines are derived. It is found that the degree of nonradiative heating present in the outer atmospheres of T Tauri stars generally exceeds that of the RS CVn systems, as well as the dMe stars and other active chromospheric dwarfs, and it is inferred that the surfaces of such pre-main sequence stars are covered by regions similar to solar plages. The mean chromospheric electron density of T Tauri stars is determined as 10 to the 11th/cu cm. Title: High-resolution profiles of chromospheric lines in M dwarf stars. Authors: Worden, S. P.; Schneeberger, T. J.; Giampapa, M. S. Bibcode: 1981ApJS...46..159W Altcode: Forty-six hydrogen and sodium line profiles are presented for 17 selected dwarf M and dwarf M emission line stars. These profiles, derived from echelle spectrograms, typically have 0.25 A spectral resolution. Most of the dMe stars show hydrogen emission lines with central reversals. Central emission features in the cores of the Na D lines are often observed, and the presence of these emission features is strongly correlated with hydrogen line emission. Title: Stellar model chromospheres. XII. High-resolution, absolute flux profiles of the CaII H and K lines in dMe and non-dMe stars. Authors: Giampapa, M. S.; Worden, S. P.; Schneeberger, T. J.; Cram, L. E. Bibcode: 1981ApJ...246..502G Altcode: We present 142 mÅ resolution spectra of the cores and wings of the Ca II H and K lines in three dMe and four comparison dwarf M stars, obtained with the KPNO 4 m echelle spectrograph and blue image tube. The narrow-band photometry of Willstrop and the Barnes and Evans relations for stellar angular diameters convert the observed relative flux to absolute surface flux units with an estimated uncertainty of ± 15 %. We derive chromospheric radiative loss rates in the H and K lines and discuss trends in these loss rates with effective temperature. Monochromatic surface fluxes are tabulated for different features in the H and K lines, and radiation temperatures are derived from the mean surface fluxes at K1 and H1, respectively. We find TR(H1) > TR(K1), consistent with partial redistribution theory. The TR(K1)/Teff ratio is higher in these M dwarfs than the giants studied in Paper X, and it is anomalously high for the dMe flare star YZ CMi. If TR(K1)/Teff is an empirical age indicator, then the result for YZ CMi implies that flare activity and youth are directly correlated, as has been suggested by other investigators. Moreover, the result implies that a high degree of nonradiative heating is present in the upper photospheres of dMe stars. Measurements of line widths at H1 and K1 are presented together with FWHM data for the H and K lines. We find that the scaling law proposed by Ayres generally agrees with the observed trend exhibited by the K1 widths. We also discuss chromospheric radiative loss rates in the Hɛ line compared with loss rates in the H and K lines, and present corrected FWHM(K) widths and compare them to the widths predicted by the Wilson-Bappu relation as calibrated by Lutz. Title: High Resolution, Absolute Flux Profiles of the Mg II h and k Lines for T Tauri Stars Authors: Giampapa, M. S.; Morossi, C.; Ramella, M.; Imhoff, C. L. Bibcode: 1981BAAS...13..811G Altcode: No abstract at ADS Title: The Mg II h and k lines in a sample of dMe and dM stars. Authors: Giampapa, M. S.; Pornmann, P. L.; Ayres, T. R.; Linsky, J. L.; Worden, S. P. Bibcode: 1981NASCP2171..279G Altcode: 1981uviu.nasa..279G; 1981NASCP3171..279G; 1980IUE80......279G Both Mg II h and k line fluxes are presented for a sample of 4 dMe and 3 dM stars obtained with the IUE satellite in the long wavelength, low dispersion mode. The observed fluxes are converted to stellar surface flux units and the importance of chromospheric non radiative heating in this sample of M dwarf stars is intercompared. In addition, the net chromospheric radiative losses due to the Ca II H and K lines in those stars in the sample for which calibrated Ca II H and K line data exist are compared. Active region filling factors which likely give rise to the observed optical and ultraviolet chromospheric emission are estimated. The implications of the results for homogeneous, single component stellar model chromospheres analyses are discussed. Title: The ultraviolet variability of the T Tauri star RW Aurigae. Authors: Imhoff, C. L.; Giampapa, M. S. Bibcode: 1981NASCP2171..185I Altcode: 1981uviu.nasa..185I; 1980IUE80......185I; 1981NASCP3171..185I Between 1978 and 1979 the visible brightness of RW Aurigae increased by 0.9 mag. During this time (1) CIV and SiIV increased by factors of 2 to 4 while the lower ionization lines remained unchanged; (2) the fluorescent OI line increased by a factor of 8; (3) the shell spectrum changed from emission to absorption; and (4) the ultraviolet continuum brightened by 2.3 mag. On a time scale of a week the continuum varied by as much as 0.8 mag., but the MgII emission lines showed no variability over 10 percent. An active chromosphere, transition region, and envelope cooled by mass loss are hypothesized in order to explain the ultraviolet observations of RW Aur. Title: The Transition Regions & Coronae of Solar-Type Stars Authors: Giampapa, Mark S. Bibcode: 1981iue..prop..751G Altcode: We propose to obtain low dispersion, high signal-to-noise, short wavelength spectra for a sample of solar-type stars for which X-ray data are available. The transition region pressures, as inferred from the short wavelength spectra to be obtained with the IUE satellite, will be compared to the values of the transition region pressures predicted by the scaling laws advanced by Rosner, Tucker and Vaiana (1978) and Golub et al. (1980) on the basis of HEAO-B soft X-ray observations. In addition, we will assess the energy balance in the outer atmospheres of solar-type stars by comparing the total transition region and chromospheric line luminosities to the X-ray luminosities for the stars considered in this proposal. Title: UV chromospheric and circumstellar diagnostic features among F supergiant stars. Authors: Stencel, R. E.; Worden, S. P.; Giampapa, M. S. Bibcode: 1981NASCP2171..311S Altcode: 1981NASCP3171..311S; 1980IUE80......311S; 1981uviu.nasa..311S A survey of F supergiant stars to evaluate the extension of chromospheric and circumstellar characteristics commonly observed in the slightly cooler G, K, and M supergiant is discussed. An ultraviolet survey was elected since UV features of Mg II and Fe II might persist in revealing outer atmosphere phenomena even among F supergiants. The encompassed spectral types F0 to G0, and luminosity classes Ib, Ia, and Ia-0. In addition, the usefulness of the emission line width-to-luminosity correlation for the G-M stars in both the Ca II and Mg II lines is examined. Title: High Dispersion, Long Wavelength Studies of T Tauri Stars Authors: Giampapa, Mark S. Bibcode: 1981iue..prop..762G Altcode: We propose to obtain high dispersion, high quality, long wavelength spectra as well as some low dispersion, short wavelength spectra for a sample of T Tauri stars. The data to be obtained in this program will be supplemented with ground-based, high spectral resolution optical observations to be acquired simultaneously with the IUE observations. These data will be used for a comprehensive study of the structure, energy balance, velocity fields and mass loss rates that characterize the atmospheres of T Tauri stars. More specifically, we will develop semi-empirical models for the chromospheres and transition regions of specific T Tauri stars in order to parameterize the atmospheres Of these pre-main sequence objects and to attempt to discover why the T Tauri stars do not obey the Wilson-Bappu relation. Title: IUE observations of the Mg II emission lines in T Tauri stars. Authors: Imhoff, C. L.; Giampapa, M. S. Bibcode: 1980PASP...92..548I Altcode: No abstract at ADS Title: The Chromospheres of M Dwarf Stars Authors: Giampapa, M. S.; Worden, S. P.; Linsky, J. L. Bibcode: 1980BAAS...12..807G Altcode: No abstract at ADS Title: The ultraviolet spectrum of the T Tau star RW Aur. Authors: Imhoff, C. L.; Giampapa, M. S. Bibcode: 1980ApJ...239L.115I Altcode: Ultraviolet spectra of the T Tauri star RW Aurigae have been obtained with the International Ultraviolet Explorer. Emission lines include Mg II, Fe II, Cr II, Si I, Si II, Si III, Si IV, C II, C IV, and L alpha. The spectrum roughly resembles the solar chromospheric spectrum, but the surface fluxes are 200 times greater. N V and He II appear to be absent, a possible indication of either an extended chromosphere cooled by mass loss or an optically thick, hot shocked region. The ultraviolet excess in RW Aur is strong, consistent with Balmer continuum emission. The observed continuum may be used to set limits on the type and amount of extinction affecting the star. Title: Emission measures derived from far ultraviolet spectra of T Tau stars. Authors: Cram, L. E.; Giampapa, M. S.; Imhoff, C. L. Bibcode: 1980ApJ...238..905C Altcode: Spectroscopic diagnostics based on UV emission line observations have been developed to study the solar chromosphere, transition region, and corona. The atmospheric properties that can be inferred from observations of total line intensities include the temperature, by identifying the ionic species present; the temperature distribution of the emission measure, from the absolute intensities; and the electron density of the source, from line intensity ratios sensitive to the electron density. In the present paper, the temperature distribution of the emission measure is estimated from observations of far UV emission line fluxes of the T Tauri stars, RW Aurigae and RU Lupi, made on the IUE. A crude estimate of the electron density of one star is obtained, using density-sensitive line ratios. Title: An Estimate of Active Region Filling Factors for Dme-Stars and Dm-Stars Authors: Giampapa, M. S. Bibcode: 1980SAOSR.389..119G Altcode: 1980csss....1..119G No abstract at ADS Title: The chromospheres of M dwarf stars Authors: Giampapa, Mark Steven Bibcode: 1980PhDT.......127G Altcode: No abstract at ADS Title: The chromospheres of M Dwarf Stars Authors: Giampapa, Mark S. Bibcode: 1980cmds.book.....G Altcode: No abstract at ADS Title: The Chromospheres of M Dwarf Stars. Authors: Giampapa, M. S. Bibcode: 1980PhDT.........5G Altcode: Single-component, homogeneous, quiescent semi-empirical model chromospheres are constructed, based upon high resolution, well-calibrated profiles of the Ca II K line in 3 dMe and 2 dM stars. The results of the atmospheric models inferred from the observed Ca II K line profiles reveal several systematic trends which characterize the chromospheres of M dwarf stars. In particular, high values of T min/Teff are deduced for the stars considered, thus indicating an unusually large degree of nonradiative heating present in the upper photospheres of M dwarf stars. Hence dissipation of mechanical energy is an important parameter in the control of the energy balance in the upper photospheres of M dwarf stars. The value of the lower chromospheric temperature gradient, dT/d log m, is similar for the M dwarf stars considered. Chromospheric K-line emission strength is most sensitive to the total amount of chromospheric material present within the approximate temperature range Tmin-6000K. Title: The Evolution of the Chromospheres and Transition Regions in Dwarf Stars Authors: Giampapa, Mark S. Bibcode: 1980iue..prop..445G Altcode: We propose to study the active chromosphere stars xi Boo A and 70 Oph A. These are solar type stars which exhibit much larger levels of chromospheric activity than the sun. There are two complementary aspects of this proposal. Our first objective is to obtain high spectral resolution observations of upper chromospheric and transition region spectral diagnostics. These data will be used to model the quiescent states of these stars and compare their upper atmospheric structure to the sun and other quiet chromosphere G dwarf stars. Our second objective is to perform a coordinated optical, X-ray, radio, and IUE ultraviolet spectral monitoring of these two stars to study flare events. In particular we hope to observe flare events, model flare structure, and compare the derived physical conditions in stellar flares to solar events. We have recently observed extensive large magnetic fields on these stars, and we believe they exhibit frequent flares. We are confident that time resolved data needed to model the stellar flares is obtainable in the required spectral bands, including the IUE ultraviolet region. The results of these studies will improve our understanding of solar and stellar chromospheric and non-radiative phenomena. Title: IUE Observations of T. Tauri Stars Authors: Imhoff, C. L.; Giampapa, M. S. Bibcode: 1979BAAS...11..681I Altcode: No abstract at ADS Title: High Resolution Spectra of Stellar Flares Authors: Worden, S. P.; Schneeberger, T. J.; Deluca, E.; Giampapa, M. Bibcode: 1979BAAS...11..628W Altcode: No abstract at ADS Title: The Ca II H and K Lines in dMe and non-dMe Stars Authors: Giampapa, M. S.; Worden, S. P.; Schneeberger, T. J.; Cram, L. E. Bibcode: 1979BAAS...11..625G Altcode: No abstract at ADS Title: The effect of chromospheric activity on metallicity measurements. Authors: Giampapa, M. S.; Gilliam, L. B.; Worden, S. P. Bibcode: 1979ApJ...229.1143G Altcode: The intermediate band uvby-beta photometric system is used to observe solar active (plage) regions and quiescent regions in an effort to determine the effect of chromospheric activity on photometric metallicity measurements. It is found that the active regions appear metal deficient with respect to the quiet sun by approximately 35%. Title: Compact variable extragalactic objects and small-pitch-angle synchrotron theory. Authors: Cocke, W. J.; Giampapa, M. S.; Pacholczyk, A. G. Bibcode: 1979ApJ...229..503C Altcode: A small-pitch-angle synchrotron radiation model of luminous compact variable radio sources is applied to a large class of such objects. The model consists of a massive spinning object endowed with an extended magnetosphere. The electrons are accelerated near its surface by a strong electric field, spiral along the field lines, and lose their energy by the small-pitch-angle synchrotron process responsible for the observed centimeter and infrared radiation. The model adequately explains the observed variability of the majority of compact sources for (rest frame) frequencies greater than about 10 GHz. The model is not able to account for the variability of sources at lower frequencies, indicating clearly that an investigation of alternative radiation mechanisms or relativistic effects resulting from bulk motion is necessary. Title: A Survey of Astronomy Graduate Students Authors: Giampapa, M. S. Bibcode: 1979AstQ....3....5G Altcode: No abstract at ADS Title: Chromospheric emission lines in the red spectrum of AD Leonis. I. The nonflare spectrum. Authors: Giampapa, M. S.; Linsky, J. L.; Schneeberger, T. J.; Worden, S. P. Bibcode: 1978ApJ...226..144G Altcode: High-resolution red (5300-7300 A) spectra of the flare star AD Leonis were obtained with the Kitt Peak 4 m echelle spectrograph system at a spectral resolution of 0.22 A at Ha. A series of time-trailed plates with 5 hours integration in total were averaged together to obtain a representation of the star's nonflaring spectrum with high signal-to-noise ratio. The He i A5876 triplet line and A6678 singlet line appear in emission with measured equivalent widths of 0.312 + 0.016 A and 0.058 + 0.029 A, respectively. The corresponding triplet-to-singlet line flux ratio is 3.7, close to the ratio of the level statistical weights. We argue that the He i lines are not produced by recombination and cascade following photoionization by A < 504 A coronal photons, but are instead collisionally excited. We suggest that these lines are formed in a geometrically thin chromospheric layer at 20,000-50,000 K with a column density of nel 6 x 1018 . The sodium D emission lines (A5890, AS 896) are found to be stellar in origin, with measured FWHM of 0.7 A for both lines, and the Ha line has a FWHM of 1.4 A. No other chromospheric emission lines were found in this spectral region. Subject headings: stars: chromospheres - stars: emission-line - stars: flare - stars: individual Title: The Effects of Stellar Chromospheric Activity on Metallicity Measurements. Authors: Giampapa, M. S.; Worden, S. P. Bibcode: 1978BAAS...10..458G Altcode: No abstract at ADS Title: Application of the Small-Pitch Angle Synchrotron Theory to a Wide Class of Variable Compact Extragalactic Objects. Authors: Cocke, W. J.; Giampapa, M. S.; Pacholczyk, A. G. Bibcode: 1978BAAS...10R.404C Altcode: No abstract at ADS Title: On the polarization and mass of BL Lac objects. Authors: Angel, J. R. P.; Boroson, T. A.; Adams, M. T.; Duerr, R.; Giampapa, M. S.; Gresham, M. S.; Gural, P. S.; Hubbard, E. N.; Kopriva, D. A.; Moore, R. L.; Peterson, B. M.; Schmidt, G. D.; Turnshek, D. A.; Wilkerson, M. S.; Zotov, N. V.; Maza, J.; Kinman, T. D. Bibcode: 1978bllo.conf..117A Altcode: 1978blo..conf..117A Optical polarization measurements have been obtained for 12 BL Lac objects, including many repeated observations during a night. It is found that the shortest time scale for substantial changes in polarization is about 10 hours. Fluctuations with a 1-day characteristic time are common. This time is identified with the dynamical time scale of the most luminous material close to a black hole. It follows that the typical mass is about 2 billion solar masses. Observations over several years show that five out of 12 objects have a preferred orientation of position angle, perhaps defined by the angular-momentum vector of accreted material. Title: Chromospheric Emission Lines in the Quiescent Spectrum of the Flare Star AD Leo Authors: Giampapa, M. S.; Linsky, J. L.; Schneeberger, T. J.; Worden, S. P. Bibcode: 1977BAAS....9..593G Altcode: No abstract at ADS