J/A+A/665/A36 FEROS spectroscopy of B-type stars (Gebruers+, 2022)
Analysis of high-resolution FEROS spectroscopy for a sample of variable B-type
stars assembled from TESS photometry.
Gebruers S., Tkachenko A., Bowman D.M., Van Reeth T., Burssens S.,
IJspeert L., Mahy L., Straumit I., Xiang M., Rix H-.W., Aerts C.
<Astron. Astrophys. 665, A36 (2022)>
=2022A&A...665A..36G 2022A&A...665A..36G (SIMBAD/NED BibCode)
ADC_Keywords: Asteroseismology ; Stars, variable ; Stars, B-type ;
Stars, peculiar ; Spectroscopy ; Photometry, classification
Keywords: stars: fundamental parameters - stars: variables: general -
stars: oscillations - asteroseismology - techniques: spectroscopic
Abstract:
Spectroscopic data are necessary to break degeneracies in
asteroseismic modelling of the interior structure in high- and
intermediate-mass stars. With the TESS mission, the number of bright
intermediate-mass B-type stars with long photometric light curves,
that are therefore suitable for detailed asteroseismic studies, has
increased substantially compared to the pre-TESS era.
We derive precise photospheric stellar parameters for a sample of 166
B-type stars with TESS light curves through a homogeneous
spectroscopic analysis. The variability types of these sample stars
are also classified based on all currently available TESS sectors and
ultimately prioritised according to their astrophysical potential.
We obtained high-resolution spectra for all 166 targets with the FEROS
spectrograph in the context of a large program.The spectra are reduced
with the CERES pipeline, that we adapted to improve the quality of the
reduced spectra. These spectra are subsequently analysed with the
zeta-Payne, a machine learning-based spectrum analysis algorithm, to
infer precise stellar labels for all stars in the sample. Furthermore,
the Least-Squares Deconvolution (LSD) method is employed to
investigate spectral line profile variability (LPV) and isolate binary
systems from presumably single stars.
The LSD profile analysis identified 26 spectroscopic double-lined
binaries; the remainder of the sample are 42 supergiants in the Large
Magellanic Cloud galaxy and 98 Galactic stars, both with and without
apparent LPV. For the Galactic single stars and single-lined
spectroscopic binaries, we determine their five main surface
parameters: effective temperature (Teff), surface gravity (logg),
global metallicity ([M/H]), projected rotational velocity (vsini), and
microturbulent velocity (vmicro) with average formal precisions of
70K, 0.03dex, 0.07dex, 8km/s, and 0.7km/s respectively. The average
internal uncertainties we find for FEROS spectra with our spectrum
analysis method are 430K (Teff), 0.12dex (logg), 0.13dex ([M/H]),
12km/s (vsini), and 2km/s (vmicro).
We find spectroscopic evidence that eight of the 98 galactic single or
SB1 variables are fast rotating gravity-mode pulsators occurring in
between the slowly pulsating B (SPB) stars and delta Scuti instability
strips. The g-mode frequencies of these pulsators are shifted to
relatively high frequency values due to their rotation, and their
apparently too low Teff relative to the SPB instability region can in
most cases be explained by the gravity darkening effect. We also
discover 13 new HgMn stars in the Galactic sample of which only one is
found in a spectroscopic binary, resulting in a biased and therefore
unreliable low binary rate of only 8%.
Description:
We study a sample of 166 B-type stars for which we obtained spectra
with the FEROS spectrograph attached to the ESO/MPG 2.2-m telescope at
La Silla, Chile. We classify the stars based on the photometric
variability detected in their available TESS light curves.
The spectra of the single stars and the single-lined spectroscopic
binaries in our sample are analysed with the zeta-Payne, a machine
learning-based spectrum analysis algorithm, that determines the
surface parameters of each target.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 95 124 Photometric classification of the Galactic
single stars, Galactic SB1 systems,
and SB2 systems considered in this work
tablea2.dat 94 98 Spectroscopic information and surface parameters
for the 98 Galactic stars in this work analysed
with the zeta-Payne
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See also:
IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Name Star name
19 A1 --- n_Name [*] * for LMC members
20- 29 I10 --- TIC TIC identifier
31- 69 A39 --- Sectors Number of used TESS sectors
71- 91 A21 --- Var Variability type (1)
93- 95 A3 --- SB2 [SB2 ] Double-lined spectroscopic binaries
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Note (1): Variability type abbreviations as follows:
rot = rotational modulation
SPB = slowly pulsating B star
const= constant star
EB = eclipsing binary
EV = ellipsoidal variable
beta Cep = beta Cephei star
delta Sct = delta Scuti star
SLF = stochastic low-frequency variability
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Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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1- 11 A11 --- Name Star name
13 I1 --- N Number of FEROS spectra
15- 17 I3 --- S/N Signal-to-noise ratio of averaged spectrum
19- 28 A10 --- Spect Spectroscopic information (1)
30- 34 I5 K Teff Effective temperature
36- 38 I3 K e_Teff Statistical uncertainty on Teff
40- 42 I3 K ei_Teff Statistical+internal uncertainty on Teff
44- 47 F4.2 [cm/s2] logg Surface gravity
49- 52 F4.2 [cm/s2] e_logg Statistical uncertainty on logg
54- 57 F4.2 [cm/s2] ei_logg Statistical+internal uncertainty on logg
59- 61 I3 km/s vsini Projected rotational velocity
63- 64 I2 km/s e_vsini Statistical uncertainty on vsini
66- 67 I2 km/s ei_vsini Statistical+internal uncertainty on vsini
69- 72 F4.1 km/s vmicro Microturbulent velocity
74- 76 F3.1 km/s e_vmicro Statistical uncertainty on vmicro
78 I1 km/s ei_vmicro Statistical+internal uncertainty on vmicro
80- 84 F5.2 [-] [M/H] Metallicity
86- 89 F4.2 [-] e_[M/H] Statistical uncertainty on [M/H]
91- 94 F4.2 [-] ei_[M/H] Statistical+internal uncertainty on [M/H]
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Note (1): Spectroscopic information abbreviations as follows:
SB1 = single-lined spectroscopic binary
HgMn = chemically peculiar mercury-manganese star
LPV = line profile variability, where we do not make a distinction
between the true nature of the observed variability
LPV* = very narrow lined stars with strong line profile variations
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Acknowledgements:
Sarah Gebruers, sarah.gebruers(at)kuleuven.be
(End) Sarah Gebruers [IvS, Leuven], Patricia Vannier [CDS] 23-Jun-2022