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Author name code: kostogryz
ADS astronomy entries on 2022-09-14
author:Kostogryz, Nadiia M.
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Title: Stellar limb darkening. A new MPS-ATLAS library for Kepler,
TESS, CHEOPS, and PLATO passbands
Authors: Kostogryz, N. M.; Witzke, V.; Shapiro, A. I.; Solanki, S. K.;
Maxted, P. F. L.; Kurucz, R. L.; Gizon, L.
2022arXiv220606641K Altcode:
The detection of the first exoplanet paved the way into the era of
transit photometry space missions with a revolutionary photometric
precision that aim at discovering new exoplanetary systems around
different types of stars. With this high precision, it is possible
to derive very accurately the radii of exoplanets which is crucial
for constraining their type and composition. However, it requires an
accurate description of host stars, especially their center-to-limb
variation of intensities (so called limb darkening) as it affects the
planet-to-star radius ratio determination. We aim at improving the
accuracy of limb darkening calculations for stars with a wide range
of fundamental parameters. We used the recently developed 1D MPS-ATLAS
code to compute model atmosphere structures and to synthesize stellar
limb darkening on a very fine grid of stellar parameters. For the
computations we utilized the most accurate information on chemical
element abundances and mixing length parameters including convective
overshoot. The stellar limb darkening was fitted using the two most
accurate limb darkening laws: the power-2 and 4-parameters non-linear
laws. We present a new extensive library of stellar model atmospheric
structures, the synthesized stellar limb darkening curves, and the
coefficients of parameterized limb-darkening laws on a very fine grid of
stellar parameters in the Kepler, TESS, CHEOPS, and PLATO passbands. The
fine grid allows overcoming the sizable errors introduced by the need
to interpolate. Our computations of solar limb darkening are in a
good agreement with available solar measurements at different view
angles and wavelengths. Our computations of stellar limb darkening
agree well with available measurements of Kepler stars. A new grid of
stellar model structures, limb darkening and their fitted coefficients
in different broad filters is provided in CDS.
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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.
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").
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Title: Modelling continuum intensity perturbations caused by solar
acoustic oscillations
Authors: Kostogryz, N. M.; Fournier, D.; Gizon, L.
2021A&A...654A...1K Altcode: 2021arXiv210707220K
Context. Helioseismology is the study of the Sun's interior
using observations of oscillations at the surface. It suffers
from systematic errors, for instance a center-to-limb error in
travel-time measurements. Understanding these errors requires an
adequate understanding of the nontrivial relationship between wave
displacement and helioseismic observables (intensity or velocity). <BR
/> Aims: The wave displacement causes perturbations in the atmospheric
thermodynamical quantities which, in turn, perturb the opacity, the
optical depth, the source function, and the local ray geometry, thus
affecting the emergent intensity. We aim to establish the most complete
relationship achieved to date between the wave displacement and the
emergent intensity perturbation by solving the radiative transfer
problem in the perturbed atmosphere. <BR /> Methods: We derived an
expression for the emergent intensity perturbation caused by acoustic
oscillations at any point on the solar disk by applying a first-order
perturbation theory. As input perturbations, we considerd adiabatic
modes of oscillation of different degrees in a spherically-symmetric
solar model. The background and the perturbed intensities are computed
by solving the radiative transfer equation considering the main sources
of opacity in the continuum (absorption and scattering). <BR /> Results:
We find that for all modes, the perturbations to the thermodynamical
quantities are not sufficient to model the intensity perturbations:
the geometrical effects due to the wave displacement must always
be taken into account as they lead to a difference in amplitude and
a phase shift between temperature perturbations at the surface and
emergent intensity perturbations. The closer to the limb, the greater
the differences. For modes with eigenfrequencies around 3 mHz, we found
that the radial and horizontal components of the wave displacement are
important, in particular, for high-degree modes. <BR /> Conclusions:
This work presents improvements for the computation of the intensity
perturbations, in particular, for high-degree modes. Here, we explain
the differences in intensity computations seen in earlier works. The
phase shifts and amplitude differences between the temperature and
intensity perturbations increase toward the limb. This should prove
helpful when interpreting some of the systematic centre-to-limb
effects observed in local helioseismology. The computations are fast
(3 s for 2000 positions and one frequency for one core) and can be
parallelised. This work can be extended to models of the line-of-sight
velocity observable.
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Title: MPS-ATLAS: A fast all-in-one code for synthesising stellar
spectra
Authors: Witzke, V.; Shapiro, A. I.; Cernetic, M.; Tagirov, R. V.;
Kostogryz, N. M.; Anusha, L. S.; Unruh, Y. C.; Solanki, S. K.; Kurucz,
R. L.
2021A&A...653A..65W Altcode: 2021arXiv210513611W
Context. Stellar spectral synthesis is essential for various
applications, ranging from determining stellar parameters to
comprehensive stellar variability calculations. New observational
resources as well as advanced stellar atmosphere modelling, taking three
dimensional effects from radiative magnetohydrodynamics calculations
into account, require a more efficient radiative transfer. <BR /> Aims:
For accurate, fast and flexible calculations of opacity distribution
functions (ODFs), stellar atmospheres, and stellar spectra, we developed
an efficient code building on the well-established ATLAS9 code. The new
code also paves the way for easy and fast access to different elemental
compositions in stellar calculations. <BR /> Methods: For the generation
of ODF tables, we further developed the well-established DFSYNTHE code
by implementing additional functionality and a speed-up by employing
a parallel computation scheme. In addition, the line lists used can be
changed from Kurucz's recent lists. In particular, we implemented the
VALD3 line list. <BR /> Results: A new code, the Merged Parallelised
Simplified ATLAS, is presented. It combines the efficient generation of
ODF, atmosphere modelling, and spectral synthesis in local thermodynamic
equilibrium, therefore being an all-in-one code. This all-in-one code
provides more numerical functionality and is substantially faster
compared to other available codes. The fully portable MPS-ATLAS code
is validated against previous ATLAS9 calculations, the PHOENIX code
calculations, and high-quality observations.
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Title: Accurate Short-Characteristics Radiative Transfer in A
Numerical Tool for Astrophysical RESearch (ANTARES)
Authors: Kostogryz, Nadiia M.; Kupka, Friedrich; Piskunov, Nikolai;
Fabbian, Damian; Krüger, Daniel; Gizon, Laurent
2021SoPh..296...46K Altcode:
We aim to improve the accuracy of radiative energy transport in
three-dimensional radiation hydrodynamical simulations in ANTARES
(A Numerical Tool for Astrophysical RESearch). We implement in the
ANTARES short-characteristics numerical schemes a modification of
the Bézier interpolant solver. This method yields a smoother surface
structure in simulations of solar convection and reduces the artifacts
appearing due to the limited number of rays along which the integration
is done. Reducing such artifacts leads to increased stability of the
code. We show that our new implementation achieves a better agreement
of the temperature structure and its gradient with a semi-empirical
model derived from observations, as well as of synthetic spectral-line
profiles with the observed solar spectrum.
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Title: On long-duration 3D simulations of stellar convection using
ANTARES
Authors: Kupka, F.; Fabbian, D.; Krüger, D.; Kostogryz, N.; Gizon, L.
2020IAUGA..30..373K Altcode:
We present initial results from three-dimensional (3-D) radiation
hydrodynamical simulations for the Sun and targeted Sun-like stars. We
plan to extend these simulations up to several stellar days to study
p-mode excitation and damping processes. The level of variation of
irradiance on the time scales spanned by our 3-D simulations will
be studied too. Here we show results from a first analysis of the
computational data we produced so far.
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Title: Shine BRITE: shedding light on stellar variability through
advanced models
Authors: Fabbian, D.; Kupka, F.; Krüger, D.; Kostogryz, N. M.;
Piskunov, N.
2020svos.conf..155F Altcode: 2020arXiv200201560F
The correct interpretation of the large amount of complex data from
next-generation (in particular, space-based) observational facilities
requires a very strong theoretical underpinning. One can predict
that, in the near future, the use of atmospheric models obtained with
three-dimensional (3-D) radiation magneto-hydrodynamics (RMHD) codes,
coupled with advanced radiative transfer treatment including non-local
thermodynamic equilibrium (non-LTE) effects and polarisation, will
become the norm. In particular, stellar brightness variability in cool
stars (i.e., spectral types F-- M) can be caused by several different
effects besides pulsation. In this review we have briefly discussed
some published results, and mentioned aspects of recent progress. It
then attempted to peek into what the future may hold for understanding
this important aspect of the lives of stars.
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Title: The inner dust shell of Betelgeuse detected by polarimetric
aperture-masking interferometry
Authors: Haubois, X.; Norris, B.; Tuthill, P. G.; Pinte, C.; Kervella,
P.; Girard, J. H.; Kostogryz, N. M.; Berdyugina, S. V.; Perrin, G.;
Lacour, S.; Chiavassa, A.; Ridgway, S. T.
2019A&A...628A.101H Altcode: 2019arXiv190708594H
Context. Theory surrounding the origin of the dust-laden winds
from evolved stars remains mired in controversy. Characterizing the
formation loci and the dust distribution within approximately the
first stellar radius above the surface is crucial for understanding
the physics that underlie the mass-loss phenomenon. <BR /> Aims:
By exploiting interferometric polarimetry, we derive the fundamental
parameters that govern the dust structure at the wind base of a red
supergiant. <BR /> Methods: We present near-infrared aperture-masking
observations of Betelgeuse in polarimetric mode obtained with the
NACO/SAMPol instrument. We used both parametric models and radiative
transfer simulations to predict polarimetric differential visibility
data and compared them to SPHERE/ZIMPOL measurements. <BR /> Results:
Using a thin dust shell model, we report the discovery of a dust halo
that is located at only 0.5 R<SUB>⋆</SUB> above the photosphere
(i.e. an inner radius of the dust halo of 1.5 R<SUB>⋆</SUB>). By
fitting the data under the assumption of Mie scattering, we estimate
the grain size and density for various dust species. By extrapolating
to the visible wavelengths using radiative transfer simulations,
we compare our model with SPHERE/ZIMPOL data and find that models
based on dust mixtures that are dominated by forsterite are most
favored. Such a close dusty atmosphere has profound implications for
the dust formation mechanisms around red supergiants. <P />Based on
SAMPol data obtained at the ESO VLT Yepun telescope (090.D-0898(A)).
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Title: Modeling observables for local helioseismology.
Authors: Kostogryz, Nadiia; Fournier, Damien; Gizon, Laurent
2019AAS...23430705K Altcode:
Local helioseismology provides different techniques to study flows
in the solar interior. However, all of them suffer from systematic
errors, which occur because of the nontrivial relationship between
wave displacement and helioseismic observables, such as intensity
and Doppler velocity. In this study, we solve the radiative transfer
equation in a perturbed solar atmosphere including flows caused by
acoustic oscillations. The adiabatic oscillations for normal modes
of low and high degree are computed using the ADIPLS code that
solves an eigenvalue problem in a standard solar model assuming
spherically symmetric background quantities. The wave displacement
causes perturbations in atmospheric thermodynamical quantities that,
in turn, perturb opacity and emergent intensity. These perturbations
depend on the center to the limb distance. In addition, the oscillations
modify the shape of the solar surface and thus the direction of the
normal to the surface. For low-degree modes this geometrical effect
is negligible, however, this effect matters for high-degree modes with
a large horizontal component of wave displacement. We investigate the
contribution of such perturbations on emergent intensity and velocity
and estimate their impact on helioseismic observables.
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Title: Center-to-Limb Continuum Polarization in Solar and Stellar
Atmospheres
Authors: Kostogryz, N. M.; Berdyugina, S. V.; Yakobchuk, T. M.;
Milić, I.
2019ASPC..526..139K Altcode:
The center-to-limb variation of the intensity (CLVI) and of the linear
polarization (CLVP) of stellar radiation arise when the scattering
and absorption processes are important in the stellar atmosphere. We
model the CLVI and CLVP of continuum radiation, taking into account
different contributions of scattering and absorption opacity for
a variety of spectral type stars with plane-parallel and spherical
PHOENIX atmosphere models. We show how the polarization depends on
the effective temperature and surface gravity of a star and how the
considered geometry of the stellar atmosphere affects the polarization
signal. For the Sun, we compare existing measurements with our
theoretical predictions for different solar models (FALA, FALC, FALP,
HSRA, and Phoenix). The CLVI and CLVP of stellar atmospheres are also
needed to interpret the light curves of transiting exoplanets. Here we
present the variation of the polarization in exoplanetary systems caused
by transits and grazing transits and discuss how the considered geometry
of stellar atmosphere models affect the transit curves of exoplanets.
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Title: Polarimetry of transiting planets: Differences between
plane-parallel and spherical host star atmosphere models
Authors: Kostogryz, N. M.; Yakobchuk, T. M.; Berdyugina, S. V.;
Milic, I.
2017A&A...601A...6K Altcode:
Context. To properly interpret photometric and polarimetric observations
of exoplanetary transits, accurate calculations of center-to-limb
variations of intensity and linear polarization of the host star are
needed. These variations, in turn, depend on the choice of geometry of
stellar atmosphere. <BR /> Aims: We want to understand the dependence
of the flux and the polarization curves during a transit on the choice
of the applied approximation for the stellar atmosphere: spherical
and plane-parallel. We examine whether simpler plane-parallel models
of stellar atmospheres are good enough to interpret the flux and the
polarization light curves during planetary transits, or whether more
complicated spherical models should be used. <BR /> Methods: Linear
polarization during a transit appears because a planet eclipses
a stellar disk and thus breaks left-right symmetry. We calculate
the flux and the polarization variations during a transit with given
center-to-limb variations of intensity and polarization. <BR /> Results:
We calculate the flux and the polarization variations during transit for
a sample of 405 extrasolar systems. Most of them show higher transit
polarization for the spherical stellar atmosphere. Our calculations
reveal a group of exoplanetary systems that demonstrates lower maximum
polarization during the transits with spherical model atmospheres of
host stars with effective temperatures of T<SUB>eff</SUB> = 4400-5400
K and surface gravity of log g = 4.45-4.65 than that obtained with
plane-parallel atmospheres. Moreover, we have found two trends of the
transit polarization. The first trend is a decrease in the polarization
calculated with spherical model atmosphere of host stars with effective
temperatures T<SUB>eff</SUB> = 3500-5100 K, and the second shows an
increase in the polarization for host stars with T<SUB>eff</SUB> =
5100-7000 K. These trends can be explained by the relative variation
of temperature and pressure dependences in the plane-parallel and
spherical model atmospheres. <BR /> Conclusions: For most cases of
known transiting systems the plane-parallel approximation of stellar
model atmospheres may be safely used for calculation of the flux and
the polarization curves because the difference between two models
is tiny. However, there are some examples where the spherical model
atmospheres are necessary to get proper results, such as the systems
with grazing transits, with Earth-size planets, or for the hot host
stars with effective temperatures higher than 6000 K.
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Title: Haze and cloud distribution in Uranus' atmosphere based on
high-contrast spatially resolved polarization measurements
Authors: Kostogryz, Nadiia; Berdyugina, Svetlana; Gisler, Daniel;
Berkefeld, Thomas
2017EGUGA..1918092K Altcode:
In planetary atmospheres, main sources of opacity are molecular
absorption and scattering on molecules, hazes and aerosols. Hence,
light reflected from a planetary atmosphere can be linearly
polarized. Polarization study of inner solar system planets and
exoplanets is a powerful method to characterize their atmospheres,
because of a wide range of observable phase angles. For outer solar
system planets, observable phase angles are very limited. For instance,
Uranus can only be observed up to 3.2 degrees away from conjunctions,
and its disk-integrated polarization is close to zero due to the
back-scattering geometry. However, resolving the disk of Uranus and
measuring the center-to-limb polarization can help constraining the
vertical atmospheric structure and the nature of scattering aerosols and
particles. In October 2016, we carried out polarization measurements
of Uranus in narrow-band filters centered at methane bands and the
adjacent continuum using the GREGOR Planet Polarimeter (GPP). The GPP is
a high-precision polarimeter and is mounted at the 1.5-m GREGOR solar
telescope, which is suitable for observing at night. In order to reach
a high spatial resolution, the instrument uses an adaptive-optics system
of the telescope. To interpret our measurements, we solve the polarized
radiative transfer problem taking into account different scattering
and absorption opacities. We calculate the center-to-limb variation of
polarization of Uranus' disk in the continuum spectrum and in methane
bands. By varying the vertical distribution of haze and cloud layers,
we derive the vertical structure of the best-fit Uranus atmosphere.
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Title: Center-to-limb variation of intensity and polarization in
continuum spectra of FGK stars for spherical atmospheres
Authors: Kostogryz, N. M.; Milic, I.; Berdyugina, S. V.; Hauschildt,
P. H.
2016A&A...586A..87K Altcode: 2015arXiv151107213K
<BR /> Aims: One of the necessary parameters needed for the
interpretation of the light curves of transiting exoplanets or
eclipsing binary stars (as well as interferometric measurements of a
star or microlensing events) is how the intensity and polarization
of light changes from the center to the limb of a star. Scattering
and absorption processes in the stellar atmosphere affect both the
center-to-limb variation of intensity (CLVI) and polarization (CLVP). In
this paper, we present a study of the CLVI and CLVP in continuum
spectra, taking into consideration the different contributions of
scattering and absorption opacity for a variety of spectral type stars
with spherical atmospheres. <BR /> Methods: We solve the radiative
transfer equation for polarized light in the presence of a continuum
scattering, taking into consideration the spherical model of a stellar
atmosphere. To cross-check our results, we developed two independent
codes that are based on Feautrier and short characteristics methods,
respectively, <BR /> Results: We calculate the center-to-limb variation
of intensity (CLVI) and polarization (CLVP) in continuum for the
Phoenix grid of spherical stellar model atmospheres for a range of
effective temperatures (4000-7000 K), gravities (log g = 1.0-5.5), and
wavelengths (4000-7000 Å), which are tabulated and available at the
CDS. In addition, we present several tests of our codes and compare our
calculations for the solar atmosphere with published photometric and
polarimetric measurements. We also show that our two codes provide
similar results in all considered cases. <BR /> Conclusions: For
sub-giant and dwarf stars (log g = 3.0-4.5), the lower gravity and
lower effective temperature of a star lead to higher limb polarization
of the star. For giant and supergiant stars (log g = 1.0-2.5), the
highest effective temperature yields the largest polarization. By
decreasing the effective temperature of a star down to 4500-5500 K
(depending on log g), the limb polarization decreases and reaches a
local minimum. It increases again with a corresponding decrease in
temperature down to 4000 K. For the most compact dwarf stars (log g =
5.0-5.5), the limb polarization degree shows a maximum for models with
effective temperatures in the range 4200-4600 K (depending on log g) and
decreases toward higher and lower temperatures. <P />The intensity and
polarization profiles are only available at the CDS via anonymous ftp to
<A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/586/A87">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/586/A87</A>
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Title: VizieR Online Data Catalog: Center-to-limb polarization of
FGK stars (Kostogryz+, 2016)
Authors: Kostogryz, N. M.; Milic, I.; Berdyugina, S. V.; Hauschildt,
P. H.
2016yCat..35860087K Altcode:
Calculated center-to-limb variations of intensity (limb darkening)
for different stellar parameters with spherical atmosphere model
approximation. All intensities are normalized to the intensity in
the center of stellar disks, therefore, in the centre of the disks
(mu=1.0), I(mu)/I(1.0)=1.0. The parameters of spherical Phoenix
stellar model atmospheres we considered here are the following:
effective temperature is in the range of 4000K-7000K with the step of
100K and for logg=1.0-5.5 with the step of 0.5. All calculations are
made for such wavelengths: 4000Å, 4500Å, 5000Å, 6000Å, 7000Å. We
also present the position of the stellar limb and calculated stellar
radius. <P />Calculated center-to-limb variations of polarization
(CLVP) for different stellar parameters with spherical atmosphere model
approximation. All intensities are normalized to the intensity in the
center of stellar disks, therefore, in the centre of the disks (mu=1.0),
I(mu)/I(1.0)=1.0. The parameters of spherical Phoenix model atmosphere
we considered here are the following: effective temperature is in
the range of 4000K-7000 K with the step of 100K and for logg=1.0-5.5
with the step of 0.5. All calculations are made for such wavelengths:
4000Å, 4500Å, 5000Å, 6000Å, 7000Å. We also present the position
of the stellar limb. <P />(2 data files).
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Title: Investigations on physics of planetary atmospheres and small
bodies of the Solar system, extrasolar planets and disk structures
around the stars
Authors: Vidmachenko, A. P.; Delets, O. S.; Dlugach, J. M.; Zakhozhay,
O. V.; Kostogryz, N. M.; Krushevska, V. M.; Kuznyetsova, Y. G.;
Morozhenko, O. V.; Nevodovskyi, P. V.; Ovsak, O. S.; Rozenbush, O. E.;
Romanyuk, Ya. O.; Shavlovskiy, V. I.; Yanovitskij, E. G.
2015ippa.book.....V Altcode:
The history and main becoming stages of Planetary system physics
Department of the Main astronomical observatory of National academy of
Sciences of Ukraine are considered. Fundamental subjects of department
researches and science achievements of employees are presented. Fields
of theoretical and experimental researches are Solar system planets
and their satellites; vertical structures of planet atmospheres;
radiative transfer in planet atmospheres; exoplanet systems of Milky
Way; stars having disc structures; astronomical engineering. Employees
of the department carry out spectral, photometrical and polarimetrical
observations of Solar system planets, exoplanet systems and stars
with disc structures. 1. From the history of department 2. The main
directions of department research 3. Scientific instrumentation
4. Telescopes and observation stations 5. Theoretical studies 6. The
results of observations of planets and small Solar system bodies and
their interpretation 7. The study of exoplanets around the stars of our
galaxy 8. Spectral energy distribution of fragmenting protostellar
disks 9. Cooperation with the National Technical University of
Ukraine (KPI) and National University of Ukraine "Lviv Polytechnic"
to study the impact of stratospheric aerosol changes on weather and
climate of the Earth 10. International relations. Scientific and
organizational work. Scientific conferences, congresses, symposia
11. The main achievements of the department 12. Current researches
13. Anniversaries and awards
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Title: Polarization in Exoplanetary Systems Caused by Transits,
Grazing Transits, and Starspots
Authors: Kostogryz, N. M.; Yakobchuk, T. M.; Berdyugina, S. V.
2015ApJ...806...97K Altcode: 2015arXiv150402943K
We present results of numerical simulations of flux and linear
polarization variations in transiting exoplanetary systems, caused by
host star disk symmetry breaking. We consider different configurations
of planetary transits depending on orbital parameters. The starspot
contribution to the polarized signal is also estimated. Applying the
method to known systems and simulating observational conditions, a
number of targets is selected where transit polarization effects could
be detected. We investigate several principal benefits of the transit
polarimetry, particularly for determining orbital spatial orientation
and distinguishing between grazing and near-grazing planets. Simulations
show that polarization parameters are also sensitive to starspots,
and they can be used to determine spot positions and sizes.
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Title: Disentangling 2:1 resonant radial velocity orbits from
eccentric ones and a case study for HD 27894
Authors: Kürster, Martin; Trifonov, Trifon; Reffert, Sabine;
Kostogryz, Nadiia M.; Rodler, Florian
2015A&A...577A.103K Altcode: 2015arXiv150307769K
Context. In radial velocity (RV) observations, a pair of extrasolar
planets near a 2:1 orbital resonance can be misinterpreted as
a single eccentric planet, if data are sparse and measurement
precision insufficient to distinguish between these models. <BR />
Aims: Using the Exoplanet Orbit Database (EOD), we determine the
fraction of alleged single-planet RV detected systems for which
a 2:1 resonant pair of planets is also a viable model and address
the question of how the models can be disentangled. <BR /> Methods:
By simulation we quantified the mismatch arising from applying the
wrong model. Model alternatives are illustrated using the supposed
single-planet system HD 27894 for which we also study the dynamical
stability of near-2:1 resonant solutions. <BR /> Results: Using EOD
values of the data scatter around the fitted single-planet Keplerians,
we find that for 74% of the 254 putative single-planet systems,
a 2:1 resonant pair cannot be excluded as a viable model, since the
error due to the wrong model is smaller than the scatter. For 187 EOD
stars χ<SUP>2</SUP>-probabilities can be used to reject the Keplerian
models with a confidence of 95% for 54% of the stars and with 99.9%
for 39% of the stars. For HD 27894 a considerable fit improvement is
obtained when adding a low-mass planet near half the orbital period
of the known Jovian planet. Dynamical analysis demonstrates that this
system is stable when both planets are initially placed on circular
orbits. For fully Keplerian orbits a stable system is only obtained if
the eccentricity of the inner planet is constrained to < 0.3. <BR />
Conclusions: A large part of the allegedly RV detected single-planet
systems should be scrutinized in order to determine the fraction of
systems containing near-2:1 resonant pairs of planets. Knowing the
abundance of such systems will allow us to revise the eccentricity
distribution for extrasolar planets and provide direct constraints
for planetary system formation. <P />This research has made use of
the Exoplanet Orbit Database and the Exoplanet Data Explorer at <A
href="http://www.exoplanets.org">http://www.exoplanets.org</A>
---------------------------------------------------------
Title: Spectrophotometric properties of Moon's and Mars's surfaces
exploration by shadow mechanism
Authors: Morozhenko, Alexandr; Vidmachenko, Anatolij; Kostogryz, Nadiia
2015HiA....16..182M Altcode:
Typically, to analyze the data of the phase dependence of brightness
atmosphereless celestial bodies one use some modification of the
shadow mechanism involving the coherent mechanism. There are several
modification of B.Hapke [2] model divided into two groups by the
number of unknown parameters: the first one with 4 parameters [3,4]
and the second one with up to 10 unknown parameters [1] providing
a good agreement of observations and calculations in several
wavelengths. However, they are complicated by analysing of the
colorindex C(α) dependence and photometric contrast of details with
phase K(α) and on the disk (μ o = cos i). We have got good agreement
between observed and calculated values of C(α) = U(α)-I(α), K(α),
K(muo) for Moon and Mars with a minimum number of unknown parameters
[4]. We used an empirical dependence of single scattering albedo
(ω) and particle semi-transparency(æ): æ = (1-ω)n. Assuming that
[χ (0°)/χ(5°)] = χ (5°)/χ (0°)], where χ(α) is scattering
function, using the phase dependence of brightness and opposition effect
in a single wavelength, we have defined ω,χ(α),g (particle packing
factor), and the first term expansion of χ(α) in a series of Legendre
polynomials x1. Good agreement between calculated and observed data of
C(α) = U(α)-I(α) for the light and dark parts of the lunar surface
and the integral disk reached at n ~ 0,25, g = 0,4 (porosity 0,91), x1 =
-0,93, ω = 0,137 at λ = 359nm and 0,394 at λ = 1064nm;, for Mars with
n ~ 0,25,g = 0,6 (porosity 0,84), x1 ~ 0, ω = 0,210 at λ = 359nm and
ω = 0,784 at λ = 730nm. <P />1. Bowell E., Hapke B., Domingue D.,
Lumme K., et al. Applications of photometric models to asteroids,
in Asteroids II. Tucson: Univ. Arizona Press. p.524-556. (1989)
<P />2. Hapke B. A theoretical function for the lunar surface,
J.Geophys.Res. 68, No.15., 4571-4586(1963). <P />3. Irwine W. M.,
The shadowing effect in diffuse reflection, J.Geophys.Res. 71,No.12,
2931-2937(1966). <P />4. Morozhenko A. V., Yanovitskij E.G., An
optical model of the Martian surface in the visible region of spectrum,
Astronomy Reports 48, No.4, 795-809(1971).
---------------------------------------------------------
Title: Center-to-limb polarization in continuum spectra of F, G,
K stars
Authors: Kostogryz, N. M.; Berdyugina, S. V.
2015A&A...575A..89K Altcode: 2014arXiv1408.5019K
Context. Scattering and absorption processes in stellar atmosphere
affect the center-to-limb variations of the intensity (CLVI) and the
linear polarization (CLVP) of stellar radiation. <BR /> Aims: There are
several theoretical and observational studies of CLVI using different
stellar models, however, most studies of CLVP have concentrated on the
solar atmosphere and have not considered the CLVP in cooler non-gray
stellar atmospheres at all. In this paper, we present a theoretical
study of the CLV of the intensity and the linear polarization in
continuum spectra of different spectral type stars. <BR /> Methods: We
solve the radiative transfer equations for polarized light iteratively
assuming no magnetic field and considering a plane-parallel model
atmospheres and various opacities. <BR /> Results: We calculate the
CLVI and the CLVP for Phoenix stellar model atmospheres for the range
of effective temperatures (4500 K-6900 K), gravities (log g = 3.0-5.0),
and wavelengths (4000-7000 Å), which are tabulated and available at
the CDS. In addition, we present several tests of our code and compare
our results with measurements and calculations of CLVI and the CLVP
for the Sun. The resulting CLVI are fitted with polynomials and their
coefficients are presented in this paper. <BR /> Conclusions: For the
stellar model atmospheres with lower gravity and effective temperature
the CLVP is larger. <P />Full Tables 1 and 2, and coefficients of
polynomials are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A89">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A89</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: Center-to-limb polarization of
FGK stars (Kostogryz+, 2015)
Authors: Kostogryz, N. M.; Berdyugina, S. V.
2015yCat..35750089K Altcode: 2015yCat..35759089K
The stellar parameters we considered here are the following: effective
temperature is in the range of 4500K-6900K with the step of 100K and
for logg=3.0, 3.5, 4.0, 4.5, 5.0. All calculations are made for such
wavelengths: 4000Å, 4500Å, 5000Å, 6000Å, 7000Å. <P />table1.dat:
Calculated center-to-limb variations of intensity (limb darkening)
for different stellar parameters with plane-parallel atmosphere model
approximation. All intensities are normalized to the intensity in the
center of stellar disks, therefore, in the centre of the disks (mu=1.0),
I(mu)/I(1.0)=1.0. <P />table2.dat: Calculated center-to-limb variations
of linear polarization (Stokes parameter Q/I) for different stellar
parameters with plane-parallel atmosphere model approximation. The
radiation coming from the centre of the stellar disk is nonpolarized,
so all values of Q/I(1.0)=0.0. <P />table3.dat: Calculated polynomial
coefficients of center-to-limb variations of intensity (limb darkening)
fits for different stellar parameters with plane-parallel atmosphere
model approximation. <P />(3 data files).
---------------------------------------------------------
Title: Transit Polarimetry of Exoplanetary System HD 189733
Authors: Kostogryz, N. M.; Berdyugina, S. V.; Yakobchuk, T. M.
2015csss...18..773K Altcode: 2014arXiv1408.5023K
We present and discuss a polarimetric effect caused by a planet
transiting the stellar disk thus breaking the symmetry of the light
distribution and resulting in linear polarization of the partially
eclipsed star. Estimates of this effect for transiting planets have
been made only recently. In particular, we demonstrate that the maximum
polarization during transits depends strongly on the centre-to-limb
variation of the linear polarization of the host star. However,
observational and theoretical studies of the limb polarization
have largely concentrated on the Sun. Here we solve the radiative
transfer problem for polarized light and calculate the centre-to-limb
polarization for one of the brightest transiting planet host HD 189733
taking into account various opacities. Using that we simulate the
transit effect and estimate the variations of the flux and the linear
polarization for HD 189733 during the event. As the spots on the stellar
disk also break the limb polarization symmetry we simulate the flux
and polarization variation due to the spots on the stellar disk.
---------------------------------------------------------
Title: On the efficiency of polarization measurements while studying
aerosols in the terrestrial atmosphere
Authors: Morozhenko, A. V.; Vidmachenko, A. P.; Nevodovskiy, P. V.;
Kostogryz, N. M.
2014KPCB...30...11M Altcode:
It has been shown that the orbital polarization measurements of the
Earth in the spectral range λ > 300 nm do not allow the sets of the
Stokes parameters satisfying the homogeneity requirement for the optical
properties of the "atmosphere + surface" system to be retrieved. Due to
this, the atmospheric and surface contributions cannot be correctly
separated and the physical properties of the atmospheric aerosol
cannot be determined. This is caused by the optical heterogeneity of
the system, the different nature of aerosol above different relief
features, and the poorly predictable temporal changes of the optical
properties of the "atmosphere + surface" system. Observations at λ <
300 nm are more acceptable, since not only the surface but also the
tropospheric layer of the atmosphere, which are both mostly subjected
to the effects of horizontal inhomogeneity and temporal variations,
become practically invisible due to a high absorption by the ozone
layer. Because of this, from the scans along specified latitude zones,
one may obtain the quasi-homogeneous dependences of the second Stokes
parameter Q(α) (U(α) = 0) suitable for estimating the physical
characteristics of the stratospheric aerosol and revealing their
horizontal and temporal variations.
---------------------------------------------------------
Title: A spectral differential approach to characterizing low-mass
companions to late-type stars
Authors: Kostogryz, N. M.; Kürster, M.; Yakobchuk, T. M.; Lyubchik,
Y.; Kuznetsov, M. K.
2013AN....334..648K Altcode: 2013arXiv1303.5254K
In this paper, we develop a spectral differential technique with which
the dynamical mass of low-mass companions can be found. This method
aims at discovering close companions to late-type stars by removing
the stellar spectrum through a subtraction of spectra obtained at
different orbital phases and discovering the companion spectrum in the
difference spectrum in which the companion lines appear twice (positive
and negative signal). The resulting radial velocity difference of these
two signals provides the true mass of the companion, if the orbital
solution for the radial velocities of the primary is known. We select
the CO line region in the K band for our study, because it provides
a favourable star-to-companion brightness ratio for our test case
GJ 1046, an M2V dwarf with a low-mass companion that most likely is
a brown dwarf. Furthermore, these lines remain largely unblended
in the difference spectrum so that the radial velocity amplitude
of the companion can be measured directly. Only if the companion
rotates rapidly and has a small radial velocity due to a high mass,
does blending occur for all lines so that our approach fails. We
also consider activity of the host star, and show that the companion
difference flux can be expected to have larger amplitude than the
residual signal from the active star so that stellar activity does
not inhibit the determination of the companion mass. In addition to
determining the companion mass, we restore the single companion spectrum
from the difference spectrum using singular value decomposition.
---------------------------------------------------------
Title: A spectral differential characterization of low-mass companions
Authors: Kostogryz, N.; Kürster, M.; Yakobchuk, T.; Lyubchik, Y.;
Kuznetsov, M.
2013EPJWC..4713003K Altcode:
We present a new approach with which the dynamical mass of low-mass
companions around cool stars can be found. In order to discover
companions to late-type stars the stellar spectrum is removed. For
this we substract two spectra obtained at different orbital phases
from each other in order to discover the companion spectrum in the
difference spectrum in which the companion lines appear twice (positive
and negative signal). The resulting radial velocity difference of
these two signals provides the true mass of the companion. For our
test case GJ1046, an M2V dwarf with a low-mass companion that most
likely is a brown dwarf we select the CO line region in the K-band. We
show that the dynamical mass of a faint companion to an M dwarf can
be determined using our spectral differential technique. Only if the
companion rotates rapidly and has a small radial velocity amplitude due
to a high mass, does blending occur for all lines so that our approach
fails. In addition to determining the companion mass, we restore the
single companion spectrum from the difference spectrum using singular
value decomposition.
---------------------------------------------------------
Title: Time variations of aerosol properties in the atmosphere
of uranus
Authors: Kostogryz, N. M.
2013SoSyR..47...24K Altcode:
In the present paper, variations in the vertical structure of the cloud
layer of the atmosphere of Uranus in 1981, 1993, and 1995 were analyzed
from the data on the geometric albedo of Uranus in the profiles of the
absorption bands of methane at λ = 543, 619, 702, 727, 842, 864, 887
nm (Neff, et al., 1984; Karkoschka, 1994; 1998). We used Morozhenko's
method that allows us to identify how much the vertical structure of the
atmosphere diverges from the conditions of homogeneity. This method is
based on the estimation of the optical depths of the layers which form
the intensity in the optically-thick vertically homogeneous gasaerosol
atmosphere, i.e., the effective optical depths. It has been shown that,
at the depths of formation of these absorption bands, there are two
extensive cloud layers, the strength of which was maximum in 1981 and
minimum in 1995. They are approximately positioned at the levels that
correspond to the pressure intervals from 1.4 to 2 bar and from 3.5
to 5.8 bar.
---------------------------------------------------------
Title: Stellar activity, difference spectra, and the dynamical masses
of M dwarf companions
Authors: Kostogryz, N. M.; Kürster, M.; Lyubchik, Y.
2013MmSAI..84.1047K Altcode:
We provide a differential technique that aims at discovering companions
to late-type stars by removing the stellar spectrum through subtraction
of spectra obtained at different orbital phases and identifying the
companion spectrum in the difference spectrum. As we need to observe
at different observational epochs our approach may be susceptible
to changes in the stellar surface temperature distribution arising
from appearing and disappearing star spots. For very active stars
the temperature difference between the spots and the photosphere
remains a rather unknown parameter. In our simulations we assume a
single spot that can have different values of surface filling factor,
spot-to-photosphere temperature ratio, and instantaneous radial
velocity on the rotating star. For our test case, the M dwarf/brown
dwarf binary GJ 1046, we show that the companion difference flux has a
larger amplitude than the residual signal from the active star unless
extreme spot filling factors and spot-to-photosphere temperature
differences are assumed.
---------------------------------------------------------
Title: Simulation of polarimetric effects in planetary system
HD 189733
Authors: Frantseva, K.; Kostogryz, N. M.; Yakobchuk, T. M.
2012AASP....2..146F Altcode:
In this paper we present results of linear polarization modelling for HD
189733 in the U filter using the Monte Carlo method. Our simulations
are based on the well known effect that linear polarization of a
centrosymmetric unresolved star becomes non-zero during the planet
transit or in the presence of spots on its surface. HD 189733 is
currently the brightest (m_{V}=7.67^{m}) known star to harbour a
transiting exoplanet. This fact, along with the short orbital period
(2.2 d), makes it very suitable for different types of observations
including polarimetry. Since we are interested in occultation effects,
a very important parameter is the ratio of the planet to star radii,
which is also very large (0.15). As the host star is active and spots
may cover up to 1% of the planetary surface, we perform our simulations
for different spot parameters such as sizes, locations on the stellar
disk, and temperatures.
---------------------------------------------------------
Title: Polarimetry of Exoplanetary System CoRoT-2
Authors: Kostogryz, N. M.; Yakobchuk, T. M.; Vidmachenko, A. P.
2012IAUS..282..209K Altcode:
We present the results of modelling the polarization resulting from
the planetary transits and stellar spots in the system Corot-2 using
the Monte Carlo method. The planetary transit was estimated to produce
a polarization maximum at the limb of ~5 × 10<SUP>-6</SUP>, adopting
solar center-to-limb polarization. Assuming different parameters of
the spots, we evaluated the flux and polarization changes due to the
stellar activity.
---------------------------------------------------------
Title: Spectropolarimetric Observations of Transiting Extrasolar
Planetary System HD189733
Authors: Vidmachenko, A. P.; Ivanov, Yu. S.; Kostogryz, N. M.
2012LPI....43.1280V Altcode:
Spectropolarimetric observations were carried out with
spectropolarimeter mounted in the Cassegrain focus at the 70-cm
telescope of Golosiiv (Kyiv). We observed the extrasolar planetary
system HD189733 during the planet-crossing of the host star.
---------------------------------------------------------
Title: Asymmetry of reflective properties of the hemispheres of
Jupiter satellite Europa
Authors: Vidmachenko, Anatoliy; Morozhenko, A.; Klyanchin, A.;
Shavlovskiy, V.; Ivanov, Yu.; Kostogryz, N.
2011AstSR...7..133V Altcode:
Rotation around the central planet of Europa is synchronous. Leading
hemisphere - is much brighter and less polluted by "no ice" material
than the trailing one. The high albedo of the satellite may indicates
that the ice on the surface is clean enough and is formed recently:
1,5-30 million years ago. Comparison of surface images of spacecrafts
"Voyager" and "Galileo" with a low spatial resolution did not detect
any significant changes during 20 years. But a detailed analysis of
observational data with high resolution points to a number of features
on the surface, which may indicate a change in the geological structures
during this time. Spectral geometric albedo in the wavelength range
346-750 nm of leading and trailing hemispheres of Galilean satellites
were defined using of our spectral observations in 2009 and 2010 and
the observations of the other authors at different values of orbital
and solar phase angles. The high geometric albedo in the red region of
Io and Europa spectrum are confirmed; albedo of Io decreases sharply
with decreasing of wavelength for ? < 500 nm; albedo of Ganymede and
Callisto - reduced smoothly; albedo of Europa - have an intermediate
gradient of reduction. Such behavior of the spectral variation of
Europa surface albedo can be explained by deposition of sulfur from
Io. Moreover, the sulfur absorption is more strongly on the trailing
hemisphere. This indicates that the sulfur on the leading hemisphere is
"processed" by meteoritic bombardment much faster and is gone to the
the sub-surface regolith layer.
---------------------------------------------------------
Title: Polarimetric study of transiting extrasolar planets
Authors: Kostogryz, N. M.; Yakobchuk, T. M.; Morozhenko, O. V.;
Vid'Machenko, A. P.
2011MNRAS.415..695K Altcode: 2011MNRAS.tmp..646K
We present the results of modelling the polarization produced
during planetary transits in the systems HD 189733, TrES-3, Wasp-4
and Wasp-25, using the Monte Carlo method. Polarization maxima at
the limb are calculated to be ∼0.022 per cent for HD 189733 with
stellar polarization according to Chandrasekhar. The polarization for
the system HD 189733 of ∼0.022 per cent is close to that previously
published, although this was attributed to scattering of starlight,
rather than produced in transit. Using three-dimensional modelling
data for the linear polarization of the Sun's continuous spectrum,
the limb polarization of the solar-type stars Wasp-25 was calculated to
be ∼0.00018 per cent, ∼0.00024 per cent for TrES-3 and ∼0.00016
per cent for Wasp-4 in the B band. It is noted that observations of
the Sun-like stars in the Ti I 4536 Å spectral line are particularly
suitable for distinguishing between different contributions to the
polarization. Also, the shape of the polarization curves, at the near
limb transits, can be used for obtaining the inclination of the planet
orbit, as a good alternative to standard transit methods.
---------------------------------------------------------
Title: Vertical cloud distribution in the Uranian atmosphere
Authors: Kostogryz, N. M.
2011ysc..conf...77K Altcode:
In this work, the vertical cloud distribution in the Uranian atmosphere
is investigated. We used the method of determinination of the deviation
scope of the real atmosphere from homogeneity conditions. The idea
of this methods is that the diffusely reflected radiations form at
different effective depths in the atmosphere, namely: the strong
absorption bands form higher in the atmosphere than weak ones. The
same is for separate absorption bands: their centres form in higher
atmospheric layers than other points of bands or lines contours. The
relative methane concentration for all points of the contours of
absorption bands will be the same only for a homogeneous atmosphere
and will show the systematic deviation in the center and near the edge
of the absorption bands in the case of an inhomogeneous atmosphere. It
was obtained that Uranus' atmosphere has two cloud layers: the first
one in the region with pressure within the range 1.5-1.8 bar, and the
second one in the region with the pressure 3.5-5.5 bar. We also can
conclude that aerosol was more abundant in 1981 compared to 1993 and
1995 which was found in our previous work.
---------------------------------------------------------
Title: The first experience of solar eclipse observations with a
miniature torsion balance
Authors: Pugach, A. F.; Medvedskii, M. M.; Peretyatko, N. N.;
Shavlovskii, V. I.; Karbovskii, V. L.; Nikityuk, T. V.; Lazorenko,
P. F.; Zolotukhina, A. V.; Vorobyev, D. P.; Pap, V. A.; Lazorenko,
G. A.; Vedenicheva, I. P.; Shatokhina, S. V.; Kostogryz, N. M.
2008KPCB...24..253P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Study of the Reasons for the Geometric Albedo Variations
of Uranus
Authors: Kostogryz, N. M.
2007ysc..conf...44K Altcode: 2007arXiv0712.1492K
The method of the optical parameter estimations of the nonisothermal
giant planet atmospheres by using intensity data of Raman scattering
features was used. We applied this method to the observational data
of Uranus' geometric albedo spectra from 1981, 1993 and 1995 and
obtained the spectral values of the optical depth, namely, τ_a/τ_R
and τ_κ/τ_S (where τ_a, τ_R are aerosol and gas components,
τ_S=τ_a+τ_R and τ_κ is absorption component of the effective
optical depth of the intensity of diffuse - reflected irradiation
forming). We showed that these ratios are different for the three
years. The conclusion is that this effect can be due to the horizontal
inhomogeneity of aerosol component of optical depth over the Uranus'
disk.
---------------------------------------------------------
Title: Probable causes of long-period variations in the Uranian
geometrical albedo
Authors: Kostogryz, N. M.
2007KPCB...23..214K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The possible reason of the optical parameters changing in
the Uranus's atmosphere.
Authors: Kostogryz, N. M.
2006IAUJD..10E..38K Altcode:
In recent years there has been increasing amount of interest
in the influence of Raman scattering on the spectra of planetary
atmospheres. Raman scattering is the incoherent non-resonance scattering
of photons by molecules. If an incident solar photon of frequency
"ν_0" is scattered, it will emerge at frequency "ν_0 + δν " and
"ν_0 - δν", where "δν" is the frequency of the Raman transition of
the molecule. Raman scattering is a second-order effect in the overall
atmospheric radiative transfer problem. It does have several important
observable effects on the visible and ultraviolet spectrum of planet,
which may provide new information on the composition and structure of
these atmospheres. In 1997 Morozhenko demonstrated that the observed
geometric albedo for wavelength corresponding to Fraunhofer lines and
their "ghosts" was able to be used for estimating values of the ratios
of the aerosol and gas optical thicknesses ("τ_a/τ_R") as well as the
ratios of the absorbing and scattering components in the aerosol optical
thicknesses ("τ_κ/τ_R"). But in this method was considered the model
of isothermal atmosphere of giant planets. This method was taken as a
basis. We developed a method of the optical parameters estimation of the
nonisothermal giant planet atmosphere by using detailed intensity data
of Raman scattering. In such a way using observational data of Uranus
atmosphere the spectral mean of ratios of the optical thicknesses
components: aerosol and gas components ("τ_a/τ_R"), absorbing and
scattering components ("τ_κ/τ_R"), and also a single scattering
albedo ω of aerosol component were obtained. Applied this calculation
code to observational data in 1993 and 1995, observed by Karkoshka, we
obtained different values. The average value of ratio τ_&?/τ_R is
0.96 using observation from 1993 in the spectral region of 350-450nm,
and value of ratio τ_?/τ_R is 0.82 using observation from 1995
in the same spectral region. In the presence of Raman scattering,
albedos are not physical properties of the planets since the albedo is
quite dependent on the shape of the solar spectrum. So we obtained a
"physical" albedo of Uranus, its albedo corrected for Raman scattering.
---------------------------------------------------------
Title: Raman scattering in Uranus's spectrum with regard to
nonisothermal atmosphere
Authors: Kostogryz, N. M.
2006KFNT...22..254K Altcode:
A method for optical parameter estimation of the nonisothermal giant
planet atmospheres is developed by using detailed intensity data on
Raman scattering. Morozhenko's method was taken as a basis. Using
observational data on Uranus's atmosphere, the spectral values for
ratio of the components of the optical depth were obtained, namely,
aerosol and gas components (τ<SUB>a</SUB>/ τ<SUB>R</SUB>, absorbing
and scattering constituent components τ<SUB>κ</SUB>/(τ<SUB>a</SUB>
+ τ<SUB>R</SUB>), and single scattering albedo omega of aerosol
constituent ratio (where τ<SUB>a</SUB>, τ<SUB>R</SUB> are aerosol and
gas components, and τ<SUB>κ</SUB> is absorbing component of effective
optical depth of the formation of the intensity of diffuse reflected
radiation). The average value of the ratio τ<SUB>a</SUB>/τ<SUB>R</SUB>
is 0.96 but it decreases slowly in the spectral region from 350 to
450 nm.
---------------------------------------------------------
Title: Optical parameters of the nonisothermal Uranus's and Neptune's
atmospheres
Authors: Kostogryz, N.
2006yosc.conf...61K Altcode: 2006astro.ph..7182K
A method of the calculation of optical parameters of the nonisothermal
giant planet atmospheres was developed using detailed intensity data of
Raman scattering. We have used the model of Morozhenko (A.V. Morozhenko,
1997) as a baseline. In such a way, using observational data of Uranus
and Neptune (E.Karkoschka, 1994), the spectral values of ratio of
optical depth components: aerosol and gas components ?a/?R, absorbing
and scattering components ??/?R, and also single scattering albedo
of aerosol component corrected for Raman scattering ? were obtained
(where ?a, ?R are aerosol and gas components, and ?? is absorbing
components of effective optical depths of the formation of diffusely
reflected irradiation). The averaged value of ratio ?a/?R is 0.96 but
it slowly decreases in the spectral range of 350-450nm for Uranus and
?a/?R is 1.35 for Neptune.
---------------------------------------------------------
Title: Determination of the optical parameters of the nonisothermal
Uranus atmosphere via Raman scattering.
Authors: Kostogryz, N.
2006epsc.conf....7K Altcode:
Raman scattering. N. Kostogryz Main Astronomical Observatory of NAS
of Ukraine, Kyiv, Ukraine (kosn@mao.kiev.ua) Raman scattering is the
incoherent non-resonance scattering of photons by molecules. If an
incident solar photon of frequency ν0 is scattered, it will emerge
at frequency ν0 ± ?ν, where ?ν is the frequency of the Raman
transition of the molecule. It does have several important observable
effects on the visible and ultraviolet spectrum of planet, which may
provide new information on the composition and structure of these
atmospheres. In most of the blue and UV region, the solar flux drops
almost exponentially with increasing frequency. Many fewer photons
will be scattered into a spectral interval than will be scattered out
of it. This results in a decrease in geometric albedo of the planet
in the blue and UV. A second noticeable aspect of RS results from
the absorption lines present in the solar spectrum. Let us consider
a spectral element in the center of Fraunhofer line and one in the
adjacent continuum. In the core of the line, there are very few incident
photons to be Raman scattered out, while there are still just as many
photons being scattered in as for the adjacent continuum. This results
in a net filling in of the line in the reflected spectrum of the
planet. The geometric albedo of Uranus in 350-450nm spectral region
is analyzed using a code which explicitly treats Raman scattering
of solar photons by H2 . We have used the model of A.V.Morozhenko
(1997) as a baseline model. The baseline model demonstrated that the
observed geometric albedo for wavelength corresponding to Fraunhofer
lines and their "ghosts" was able to be used for estimating values
of the ratios of the aerosol and gas optical thicknesses τa/τR as
well as the ratios of the absorbing and scattering components in the
aerosol optical thicknesses τk/τR . But in this method the model of
isothermal atmosphere of giant planets was considered. We developed
a code of the optical parameters estimation of the nonisothermal
giant planet atmosphere by using detailed intensity data of Raman
scattering. The values of aerosol and gas ratios of optical thicknesses
components were obtained τa for Uranus τR = 0.96 .We obtained that
errors of determination of atmosphere parameters could be near 50% when
we don't take into account it experimental temperature profile. And
also we corrected single scattering albedo for Raman scattering for
nonisothermal atmospheres of Uranus for spectral region 350-450 nm.
---------------------------------------------------------
Title: Some features of formation of details of raman scattering in
a non-isothermal atmosphere
Authors: Morozhenko, O. V.; Kostogryz, N. M.
2005KFNT...21..114M Altcode:
The influence of non-isothermal atmosphere on the intensity of details
of the Raman scattering is computed for a spectrum of Neptune. The
following inferences are made: the intensity of this scattering depends
on the depth of the level of its formation in an optical homogeneous
non-isothermal atmosphere; neglect of real temperature profiles during
the analysis of observation data leads to large errors in the parameters
of the atmosphere upper levels.
---------------------------------------------------------
Title: The manifestations of Raman scattering in the non-isothermic
Neptune atmosphere
Authors: Kostogryz, N.
2005ysc..conf...73K Altcode: 2005yosc.conf...73K
Raman scattering is observing in the UV spectrum of giant planets
even with low (1nm) resolution. Since it condition is scattering on
the hydrogen molecules that, it is obviously, the intensity of Raman
scattering details are lesser when the relative hydrogen concentration
is lesser and when the role of aerosol constituent of atmosphere is
increaser. Undoubtedly, the appearance of Raman scattering will lead
to changing the single-scattering albedo. Raman scattering in the giant
planets atmosphere lead to such effect as intensity of Fraunhofer-lines
in the diffuse reflected by planets atmosphere are lesser than in the
Solar spectrum. This effect leads to pseudo-emission in the UV spectra
of giant planet. Raman scattering in the isothermic giant planet
atmospheres were considered by Morozhenko (1997). But the planetary
atmospheres are gas-aerosol medium, and the optical parameters are
changing with altitude. We were computed the influence of non-isothermic
atmosphere to intensity of Raman Scattering details in the Neptune
atmosphere. There were shown that the intensity of Raman scattering will
depend on the depth of its forming level in the optical homogeneous
non-isothermic atmosphere and that the mistakes will be large when we
don't take into account real temperature profile in the upper levels
of atmosphere. Sun spectrum in the interval of wavelengthes ?? =
320 - 400 nm with resolution 0,004 ? was taking. Standard temperature
profile of Neptune atmosphere was obtained from the observation data
at space vehicle.
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Title: Appearance of Second Harmonic in the Jupiter Spectrum
Authors: Kostogryz, N. M.; Vidmachenko, A. P.
2004LPI....35.1034K Altcode:
Such nonlinear atmospheric effect as appearance of second harmonic of
the methane bands in the Jupiter spectrum was obtained. The spectral
observations received by E. Karkoshka in 1993 and 1995 on the ESO from
300 to 1000 nm were used.
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Title: Raman scattering in the Jupiter's atmosphere and optical
properties of atmospheric aerosol
Authors: Kostogryz, N.; Morozhenko, A.; Vidmachenko, A.
2004cosp...35..275K Altcode: 2004cosp.meet..275K
The basis of nonlinear atmospheric optic is considered here. When
Sun radiation cross the Jupiter's atmosphere, such nonlinear optical
effect as Raman scattering will be appear. For our investigations,
we used the spectral observations received by E.Karkoshka in 1993
and 1995 on the ESO (European Southern Observatory) from 300 to 1000
nm. We received such nonlinear optical effects as Raman scattering of
the methane bands in the Jupiter's spectrum. The vibration-rotation
methane bands were considered here. The atmosphere's spectrum is formed
on the different height where phisical characteristics of atmosphere
are substantial different. That's why we are calculated the influence
of Raman scattering effects as function of changing temperature
with height in the Jupiter's atmosphere. We demonstrate that for
wavelengths corresponding to Fraunhofer lines and their "ghosts",
geometric albedo is observed may be used for estimating probable
values of the ratios of the aerosol and gas optical thicknesses as
well as the ratios of the absorbing and scattering components in the
aerosol optical thickness. The ratios of the aerosol and gas optical
thicknesses obtained for the Jupiter atmosphere (20±3) agree well
with the estimates derived from the analysis of methane absorption
bands intensity distributions over the planetary disk.
