Author name code: neven
ADS astronomy entries on 2022-09-14
author:Neven, Luc
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Title: Atlas photometrique du spectre solaire de [lambda] 3000 a
[lambda] 10000
Authors: Delbouille, L.; Roland, G.; Neven, L.
Bibcode: 1990apds.book.....D
Altcode:
No abstract at ADS
Title: Atlas photometrique du spectre solaire de [lambda] 3000 a
[lambda] 10000. Vol.2
Authors: Delbouille, L.; Roland, G.; Neven, L.
Bibcode: 1989apds.book.....D
Altcode:
No abstract at ADS
Title: The Photospheric Velocity Field of Procyon
Authors: de Jager, C.; Neven, L.
Bibcode: 1982Ap&SS..84..297D
Altcode:
BUSS observations of the profiles of two well observed spectral lines
in the ultraviolet spectrum of αCMi (Procyon; F5 IV V) are analysed
with a Fourier transform method in order to determine values of various
parameters of the velocity field of the upper photosphere. We find a
microturbulent line-of-sight velocity componentL μ = 0.9 ±
0.4 km s-1, a macroturbulent velocity componentL M
= 5.3 ± 0.2 km s-1, and a rotational velocity componentv
R sini=10.0±1.2 km s-1. In these calculations a
single-moded sinusoidal isotropic macroturbulent velocity function was
assumed. The result appears to be sensitive to the assumed shape of the
macroturbulence function: for an assumed Gaussian shape the observations
can be described withv R sini=4 km s-1 andL
M = 11.6 ± 2.7 km s-1. A comparison is made
with other results and theoretical predictions.
Title: Stellar Atmospheric Velocity Fields - the Beta-Cephei Variables
Gamma-Pegasi and Beta-Cephei
Authors: de Jager, C.; Sato, N.; Burger, M.; Neven, L.
Bibcode: 1982Ap&SS..83..411D
Altcode:
The shape parameters of a number of selected ultraviolet lines in
BUSS-spectra of the Beta Cephei stars γ Peg and β Cep have been
analyzed to determine the principal parameters of the atmospheric
velocity field. We find for both stars a fairly high value (∼5
km s-1) for the microturbulent line-of-sight velocity
component, which confirms an earlier result based on lower resolution
UV spectra. Macroturbulent and rotational velocities are virtually zero
in the atmosphere of γ Peg; for β Cep we findv rotsini=40
km s-1.
Title: The ultraviolet spectrum of BET CMa stars.
Authors: Burger, M.; de Jager, C.; Kamperman, T. M.; Neven, L.
Bibcode: 1980A&A....90..170B
Altcode:
Ultraviolet spectra of 15 beta Canis Majoris stars in wavelength bands
of approximately 100 A around 2100, 2500, and 2800 A (resolution 1.8
A), obtained with the Ultraviolet Stellar Spectrophotometer S 59 on
board the ESRO TD-1A satellite are discussed. In general the spectra
are similar to those of 'normal' stars, only the star alpha Vir has He
I, C II, and Mg II lines slightly weaker than normal. Comparison with
theoretical computations shows that the Fe abundance in the beta CMa
stars is solar and that the average microturbulent velocity is about 4
km/sec. The UV spectral lines of beta Cep do not show any significant
variations in equivalent width with phase.
Title: Analysis of spectra of α CMi and α Cen A observed with
the orbiting stellar ultraviolet spectrophotometer S59 in ESRO's
TD1A satellite
Authors: de Jager, C.; Kamperman, T. M.; Neven, L.
Bibcode: 1978Ap&SS..54..343D
Altcode:
Ultraviolet spectra of α CMi and α Cen A taken with moderate
spectral resolution (approx. 1.8 Å) are used to analyse whether
a determination of stellar chemical abundances of Fe and Cr and of
the photospheric parameters is possible. For αCMi, for which good
spectral data are available, we findT eff=7660±110 K;
logg eff=3.05±0.1. Further, Δlogɛ(Fe)=-0.06±0.09; Δ log
ɛ(Cr)=-0.01±0.09 with regard to ‘standard’ (solar) abundances. For
α Cen A the resulting data — particularly the photospheric ones —
are less certain, but it seems that the Fe abundance may be smaller
than the ‘standard’ value.
Title: The Radiation Field in Photospheric Models for Extreme
Supergiants
Authors: de Jager, C.; Neven, L.
Bibcode: 1975Ap&SS..33..295D
Altcode:
On the basis of assumed photospheric temperature models for 36
extreme supergiants (logg e -values of 1, 0.5 and 0;T
e ranging from approx. 3700 33 000 K) photospheric
fluxesS(τλ) were computed for 36 wavelengths ranging
from 100 Å to 60 000 Å. The hot models are in perfect radiative
equilibrium; the cooler show deviations up to 10%, sometimes even
larger. Only in the relatively deep parts of the photospheres
(τ5≳1) the radiation field at each geometrical level
can be characterized by one unique radiation temperature; for smaller
τ5-values there are large deviations from local thermal
equilibrium. The influence of deviations from local thermodynamical
equilibrium on the fluxes is briefly examined, and appears small but
for the shortest wavelengths. In tables and graphs we give for these
models πF(γ)-values, integrated fluxes, effective temperatures,
coloursU, B andV, and the Balmer discontinuityD.
Title: Atlas photometrique du spectre solaire de [lambda] 3000 a
[lambda] 10000
Authors: Delbouille, L.; Roland, G.; Neven, L.
Bibcode: 1973apds.book.....D
Altcode: 1973QB551.D423.....
No abstract at ADS
Title: The empirical determination of line source functions, β
L -values, and the microturbulent and convective velocity
components as functions of depth in the photosphere-chromosphere
transition region
Authors: De Jager, C.; Neven, L.
Bibcode: 1972SoPh...25..277D
Altcode:
An empirical method for determining line source functions, previously
applied by us to the cores of infrared lines has now been extended to
the whole line profile and was applied to centre-limb observations of
sixteen lines of five infrared multiplets, mainly of high excitation
potential (Table I). The present investigation was performed in two
steps. In the first part of the paper approximate values are derived
for the depth dependence of the four functions named in the title of
this paper, where βL is the ratio between the actual and
the LTE population of the lower level of the transitions involved. In
the second part of the paper we use these empirically derived functions
to compute the line profiles. From the remaining differences between
observed and computed profiles, corrections are derived to the four
functions. The main results are: (a) Convective velocities: see Table
IV.(b)(Micro-)turbulent velocities: see Figure 8. Between τ5
= 10-4 and 10-1: «υτ» ≈ 1.4 km
s-1, which is an upper limit since an unknown contribution of
macroscopic motions could not be separated, (c) Line source functions:
see Figures 9, 15 and 16. The source functions are close to the
black-body function for τ5≳ 10-3, slight
deviations occur in higher levels. The interesting behaviour of the
CaII source function near τ5 = 10-5 should be
noted. (d) Non LTE-functions: first approximations for the functions
log βL (τ5) were derived empirically in the
first part, and are shown in Figure 10; the second approximation shows
them to be too large and the real values seem to be closer to one-half
or one-third of these functions.
Title: On the Applicability of Goldberg and Unno's Method to the
Determination of Microturbulent Velocities in an Atmosphere with
Convection
Authors: De Jager, C.; Neven, L.
Bibcode: 1972SoPh...22...49D
Altcode:
The method of Goldberg and Unno for the determination of microturbulent
velocities in a stellar atmosphere is only applicable if there are no
macroturbulent or convective motions.
Title: Damping Constants for Infrared Fraunhofer Lines
Authors: De Jager, C.; Neven, L.
Bibcode: 1970SoPh...11....3D
Altcode:
Empirical values of solar damping constants and their variation with
optical depth were derived according to a method developed earlier by
the authors. The damping constants refer to six infrared multiplets
(24 lines). The average optical depths range from τ0 =
0.5 to 2.2. Corresponding theoretical damping constants were computed,
mainly on the basis of Van der Waals damping, and with the help of
detailed computations of the mean square radii of the atomic levels by
Van Rensbergen. The empirical values are systematically larger than
the theoretical ones, with factors ranging between 1.8 and 4.9. Some
speculations about the source of this discrepancy are given.
Title: On the Occurrence of Convective Motions in the Upper
Photosphere
Authors: De Jager, C.; Neven, L.
Bibcode: 1968SoPh....4..379D
Altcode:
We have examined whether the motion field in the photosphere in the
range of optical depths 0.25< τ0< 0.6 is dominated
by thermal convection or by vibrations. The observed asymmetries
of infrared Fraunhofer lines indicate the presence of motions, and
the fact that the asymmetry is zero for lines of low excitation and
increases with the excitation potential shows that these motions are
chiefly convective in this part of the photosphere: upward moving
elements appear to be hotter than downward moving ones.
Title: Source Functions in the Cores of Infrared Fraunhofer Lines
Authors: De Jager, C.; Neven, L.
Bibcode: 1968SoPh....3..159D
Altcode:
No abstract at ADS
Title: Errata
Authors: de Jaher, C.; Neven, L.
Bibcode: 1968BANS....2..291D
Altcode:
No abstract at ADS
Title: A Systematic Method for the Analysis of High-Resolution
Fraunhofer Line Profiles
Authors: De Jager, C.; Neven, L.
Bibcode: 1967SoPh....1...27D
Altcode:
A fraunhofer line profile depends on various parameters, partly
related to the photospheric structure (T, Pg, Pe,
vconv, vturb), partly to the atom or ion involved
(such as oscillator strength, energy levels), partly also resulting
from the interaction of the relevant kind of particles with the
photosphere, and the photospheric radiation field. In this paper we
shall mainly pay attention to the determination of: the macroturbulent
(convective) velocities, vconv (τ); the damping constant
γ (τ); the abundance, Ael; the distribution function
ϕ(vconv, τ) of the convective velocities at each depth
τ; the source function, S (τ); the microturbulent velocities,
vturb (τ).
Title: Observation of solar line profiles. I. The centre-to-limb
variation of profiles of fifty lines in the near infrared solar
spectrum
Authors: de Jager, C.; Neven, L.
Bibcode: 1967BANS....1..325D
Altcode: 1966BANS....1..325N; 1966BANS....1..325D
No abstract at ADS
Title: Spectroscopic data for sixty new model photospheres
Authors: de Jager, C.; Neven, L.
Bibcode: 1967BANS....2..125D
Altcode:
No abstract at ADS
Title: Observation of solar line profiles. I. The centre-to-limb
variation of profiles of fifty lines in the near infrared solar
spectrum (Abstract)
Authors: de Jager, C.; Neven, L.
Bibcode: 1967BAN....19..160D
Altcode:
No abstract at ADS
Title: Spectroscopic data for sixty new model photospheres
Authors: de Jager, Cornelis; Neven, L.
Bibcode: 1967sdsn.book.....D
Altcode: 1967QB1.B94v2n4....
No abstract at ADS
Title: Note on the influence of the apparatus profile on spectral
line profiles
Authors: de Jager, C.; Neven, L.
Bibcode: 1966BAN....18..306D
Altcode:
No abstract at ADS
Title: Deviations from LTE in the Catom and the Abundance of C in
the Solar Photosphere
Authors: de Jager, C.; Neven, L.
Bibcode: 1966IAUS...26..149D
Altcode:
No abstract at ADS
Title: The profile of the infrared He I lines over the undisturbed
solar disk
Authors: de Jager, C.; Namba, O.; Neven, L.
Bibcode: 1966BAN....18..128D
Altcode:
No abstract at ADS
Title: The Computation of Spectroscopic Data for 60 New Model
Photopheres
Authors: de Jager, C.; Neven, L.
Bibcode: 1964SAOSR.167..270D
Altcode:
No abstract at ADS
Title: The abundance of lead in the Sun
Authors: de Jager, C.; Neven, L.
Bibcode: 1962BAN....16..307D
Altcode:
No abstract at ADS
Title: Tables and graphs enabling the computation of the profiles of H
[gamma] and H [delta] in stellar spectra
Authors: de Jager, Cornelis; Neven, L.
Bibcode: 1962AnOB....9.....D
Altcode: 1962AnBel...9.....D
No abstract at ADS
Title: The Ultra-Violet and X-Ray Spectra of the Stars
Authors: de Jager, C.; Neven, L.
Bibcode: 1961LIACo..10..552D
Altcode: 1961MSRSL...4..551D; 1961LIACo..10..551D
No abstract at ADS
Title: Observations of infrared solar line profiles
Authors: Delbouille, L.; de Jager, C.; Neven, L.
Bibcode: 1960AnAp...23..949D
Altcode:
No abstract at ADS
Title: The computation of partition functions in a stellar atmosphere
Authors: de Jager, C.; Neven, L.
Bibcode: 1960BAN....15...55D
Altcode:
No abstract at ADS
Title: A program for the computation of bn tables for H
and He
Authors: de Jager, C.; Kanno, M.; Neven, L.
Bibcode: 1960AnAp...23..843D
Altcode:
No abstract at ADS
Title: Saturation effects in very faint Fraunhofer lines
Authors: de Jager, C.; Neven, L.
Bibcode: 1959Obs....79..102D
Altcode:
No abstract at ADS
Title: 36. The Influence of the Metal Abundance on the Continuous
Stellar Spectra
Authors: De Jager, C.; Neven, L.
Bibcode: 1959LIACo...9..413D
Altcode: 1959MSRSL...3..413D
No abstract at ADS
Title: Spectroscopic data for 50 model photospherese
Authors: de Jager, Cornelis; Neven, L.
Bibcode: 1957sdfm.book.....D
Altcode: 1957QB4.U8l13p4....
No abstract at ADS
Title: Spectroscopic data for 50 model photospheres
Authors: de Jager, Cornelis; Neven, L.
Bibcode: 1957AnOB....8.....D
Altcode: 1957AnBel...8.....D
No abstract at ADS
Title: The Abundances of Diatomic Molecules of H, C, N, and O and
of H2O in Stellar Atmospheres
Authors: de Jager, C.; Neven, L.
Bibcode: 1957LIACo...7..357D
Altcode:
No abstract at ADS
Title: The profile of the Brackett α line in the solar spectrum
Authors: de Jager, C.; Migeotte, M.; Neven, L.
Bibcode: 1956AnAp...19....9D
Altcode:
No abstract at ADS
Title: Observational models and helium abundances of the atmospheres
of four B-type stars
Authors: Neven, L.; de Jager, C.
Bibcode: 1954BAN....12..103N
Altcode:
No abstract at ADS
Title: La détermination de l'abondance relative de l'hélium dans
les étoiles chaudes
Authors: Neven, L.
Bibcode: 1954LIACo...5..358N
Altcode: 1954MSRSL...1..358N; 1954pna..conf..358N
No abstract at ADS
Title: High-Dispersion Solar Spectrograms Between 15μ and 24μ.
Authors: Migeotte, M.; Neven, L.
Bibcode: 1952ApJ...115..326M
Altcode:
No abstract at ADS
Title: The interpretation of the observed hydrogen lines in the
infrared solar spectrum II.
Authors: de Jager, C.; Neven, L.
Bibcode: 1952PRNAA..55..165D
Altcode: 1952RNAAS..55..165D
No abstract at ADS
Title: Récents progrès dans l'observation du spectre infra-rouge
du soleil a la station scientifique du Jungfraiijoch (Suisse)
Authors: Migeotte, M.; Neven, L.
Bibcode: 1952LIACo...3..165M
Altcode:
No abstract at ADS
Title: The model of the solar atmosphere and the continuous absorption
coefficient in the infrared
Authors: Neven, L.; de Jager, C.
Bibcode: 1951BAN....11..291N
Altcode:
No abstract at ADS
Title: Nouvelles raies du méthane tellurique
Authors: Migeotte, Marcel; Neven, L.
Bibcode: 1951AnAp...14..315M
Altcode:
No abstract at ADS
Title: The profiles of the lines of the Paschen and Brackett series
of hydrogen in the solar spectrum.
Authors: de Jager, C.; Neven, L.
Bibcode: 1950PRNAA..53..157D
Altcode: 1950RNAAS..53..157D
No abstract at ADS
Title: Mesures Micrometriques D'Etoiles Doubles
Authors: Neven, L.
Bibcode: 1949AnOB....4..201N
Altcode:
No abstract at ADS
Title: Mesures micrometriques d'etoiles doubles
Authors: Neven, L.
Bibcode: 1948AnOB....4..201N
Altcode: 1948AnBel...4..201N
No abstract at ADS
Title: Mesures micrometriques d'etoiles doubles
Authors: Neven, L.
Bibcode: 1948AnOB....4..277N
Altcode:
No abstract at ADS