J/A+A/609/A108 Stellar parameters of Be stars with X-shooter (Shokry+, 2018)
Stellar parameters of Be stars observed with X-shooter.
Shokry A., Rivinius T., Mehner A., Martayan C., Hummel W., Townsend R.H.D.,
Merand A., Mota B., Faes D.M., Hamdy M.A., Beheary M.M., Gadallah K.A.K.,
Abo-Elazm M.S.
<Astron. Astrophys. 609, A108 (2018)>
=2018A&A...609A.108S 2018A&A...609A.108S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, Be ; Stars, masses ; Effective temperatures
Keywords: circumstellar matter - stars: emission-line, Be - stars: activity
Abstract:
The X-shooter archive of several thousand telluric star spectra was
skimmed for Be and Be-shell stars to derive the stellar fundamental
parameters and statistical properties, in particular for the less
investigated late type Be stars, and the extension of the Be
phenomenon into early A stars.
An adapted version of the BCD method is used, utilizing the Balmer
discontinuity parameters to determine effective temperature and
surface gravity. This method is optimally suited for late B stars. The
projected rotational velocity was obtained by profile fitting to the
Mgii lines of the targets, and the spectra were inspected visually for
the presence of peculiar features such as the infrared Ca ii triplet
or the presence of a double Balmer discontinuity. The Balmer line
equivalent widths were measured, but due to uncertainties in
determining the photospheric contribution are useful only in a
subsample of Be stars for determining the pure emission contribution.
A total of 78 Be stars, mostly late type ones, were identified in the
X-shooter telluric standard star archive, out of which 48 had not been
reported before. The general trend of late type Be stars having more
tenuous disks and being less variable than early type ones is
confirmed. The relatively large number (48) of relatively bright
(V>8.5) additional Be stars casts some doubt on the statistics of late
type Be stars; they are more common than currently thought: The Be/B
star fraction may not strongly depend on spectral subtype.
Description:
All spectra have been acquired with the VLT/X-shooter instruments.
Most data were taken as telluric standard stars for other
observations, from the commissioning of X-shooter in 2007 until 2015.
Once the value of this database for science on its own was realized,
additional spectra of stars of interest were acquired in a dedicated
observing program in ESO period 93. A few datasets for stars of
interest were also taken under a number of different program IDs, and
were downloaded from the archive as well. The main program IDs under
which data was observed for this work, however, are 60.A-9022,
60.A-9024, and 093.D-0415.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table6.dat 84 3450 Parameters of stellar models used to measure the
theoretical values of the Balmer discontinuity
parameters used in the BCD method, D_star and
lambda_1
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 30 A30 --- Ident Approximate spectral type (ident)
32- 36 F5.3 [Lsun] Lstar log of the stellar luminosity (L_star)
38- 42 F5.2 Msun Mstar Stellar mass (M_star)
44- 47 F4.2 --- Rpole Polar radius (R_pole)
49- 53 I5 K Teff Stellar effective temperature (T_eff)
55- 59 F5.3 [cm/s2] loggpole log of polar gravity (logg_pole)
61- 65 F5.3 --- omega Critical fraction in linear velocity (omega)(1)
67- 69 I3 km/s vsini Stellar projected rotational velocity (vsini)
71- 74 F4.3 --- Dstar BCD parameter D_star (D_star)
76- 79 F4.1 0.1nm lambda1 BCD parameter lambda_1 (lambda1)
81- 84 I4 --- respow Spectral resolving power for which the BCD
parameters were measured (respow)
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Note (1): note that the values in the paper are given as fraction of angular
velocity. See epns. 7 and 8 of 2013A&ARv..21...69R 2013A&ARv..21...69R for conversion)
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Acknowledgements:
Ahmed Shokry, ahmedsh2911(at)gmail.com
(End) Patricia Vannier [CDS] 16-Nov-2017