J/A+A/661/A113 Hot subdwarf stars Radial velocity variability (Geier+, 2022)
Radial velocity variability and the evolution of hot subdwarf stars.
Geier S., Dorsch M., Pelisoli I., Reindl N., Heber U., Irrgang A.
<Astron. Astrophys. 661, A113 (2022)>
=2022A&A...661A.113G 2022A&A...661A.113G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, subdwarf ; Effective temperatures ; Abundances ;
Radial velocities ; Optical
Keywords: subdwarfs - binaries: spectroscopic - stars: horizontal-branch
Abstract:
Hot subdwarf stars represent a late and peculiar stage in the
evolution of low-mass stars, since they are likely formed by close
binary interactions. In this work, we perform a radial velocity (RV)
variability study of a sample of 646 hot subdwarfs with multi-epoch
radial velocities based on spectra from Sloan Digital Sky Survey
(SDSS) and Large Sky Area Multi-Object Fibre Spectroscopic Telescope
(LAMOST). The atmospheric parameters and RVs were taken from the
literature. For stars with archival spectra but without literature
values, we determined the parameters by fitting model atmospheres. In
addition, we redetermined the atmospheric parameters and RVs for all
the He-enriched sdO/Bs. This broad sample allowed us to study
RV-variability as a function of the location in the Teff-logg- and
Teff-logn(He)/n(H) diagrams in a statistically significant way. We
used the fraction of RV-variable stars and the distribution of the
maximum RV variations {DELTA}RVmax as diagnostics. Both indicators
turned out to be quite inhomogeneous across the studied parameter
ranges. A striking feature is the completely dissimilar behaviour of
He-poor and He-rich hot subdwarfs. While the former have a high
fraction of close binaries, almost no significant RV variations could
be detected for the latter. This has led us to the conclusion that
there is likely no evolutionary connection between these subtypes. On
the other hand, intermediate He-rich- and extreme He-rich sdOB/Os are
more likely to be related. Furthermore, we conclude that the vast
majority of this population is formed via one or several binary merger
channels. Hot subdwarfs with temperatures cooler than ∼24000K
tend to show fewer and smaller RV-variations. These objects might
constitute a new subpopulation of binaries with longer periods and
late-type or compact companions. The RV-variability properties of the
extreme horizontal branch (EHB) and corresponding post-EHB populations
of the He-poor hot subdwarfs match and confirm the predicted
evolutionary connection between them. Stars found below the canonical
EHB at somewhat higher surface gravities show large RV variations and
a high RV variability fraction. These properties are consistent with
most of them being low-mass EHB stars or progenitors of low-mass
helium white dwarfs in close binaries.
Description:
Radial velocity variability and spectroscopic parameters for a sample
of 646 hot subdwarf stars with multi-epoch radial velocities based on
spectra from Sloan Digital Sky Survey (SDSS) and Large Sky Area
Multi-Object Fibre Spectroscopic Telescope (LAMOST). Helium abundances
without uncertainty are upper (if negative) or lower limits (if
positive).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 165 646 Catalogue
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 25 A25 --- Name Target name
27- 34 A8 --- --- [Gaia DR2]
36- 54 I19 --- GaiaDR2 ? Gaia DR2 designation (source_id)
56- 66 F11.7 deg RAdeg Right ascension (J2000)
68- 77 F10.7 deg DEdeg Declination (J2000)
79- 85 A7 --- SpClass Spectroscopic classification
87- 88 I2 --- NEpoch Number of single RV epochs
90- 93 I4 km/s RVav Inverse-variance weighted mean RV
95- 96 I2 km/s e_RVav Inverse-variance weighted mean RV error
98-100 I3 km/s dRVmax Maximum RV shift
102-103 I2 km/s e_dRVmax Maximum RV shift error
105-113 F9.4 [-] logP LOG10 of false-alarm probability
115-119 I5 K Teff Effective temperature
121-124 I4 K e_Teff Effective temperature error
125 A1 --- l_logg Lower limit flag on logg
126-129 F4.2 [cm/s2] logg log10 surface gravity
131-134 F4.2 [cm/s2] e_logg ? Error on log10 surface gravity
136-140 F5.2 [-] logY log10 helium abundance n(He)/n(H)
142-145 F4.2 [-] e_logY Error log10 helium abundance
147-165 A19 --- Ref Reference for atmo parameters (Bibcode)
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Acknowledgements:
Stephan Geier, sgeier(at)astro.physik.uni-potsdam.de
(End) Patricia Vannier [CDS] 13-Mar-2022