J/A+A/693/A121 Hot subdwarf stars radial velocity variability (He+, 2025)
Radial velocity variability fractions of different types of hot subdwarf stars.
He R., Meng X., Lei Z., Yan H., Lan S.
<Astron. Astrophys. 693, A121 (2025)>
=2025A&A...693A.121H 2025A&A...693A.121H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, subdwarf ; Stars, double and multiple ;
Radial velocities ; Optical
Keywords: binaries: close - stars: evolution - subdwarfs
Abstract:
It is generally thought that hot subdwarfs are helium-core- or
helium-shell-burning objects with extremely thin hydrogen envelopes
and that binary interactions are always needed in their formation.
Different types of hot subdwarfs may have different origins, which
will cause them to present different radial velocity (RV) variability
properties.
We plan to study the RV-variability fractions of different types of
hot subdwarfs, as well as their distributions in the Teff-logg
diagram. This provides insights into the formation of hot subdwarfs.
The cross-correlation function method was adopted to measure RV
variations in 434 hot subdwarfs based on spectra obtained with the
Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST).
Light curves from the Transiting Exoplanet Survey were also used to
search for short-period binary hot subdwarfs.
Only 6±4% of our single-lined He-rich hot subdwarfs that only show
spectroscopic features of hot subdwarfs are found to be RV variable,
which is lower than the fraction of single-lined He-poor sdB stars
(31±3%). Single-lined sdB stars with effective temperatures
(Teff)∼25000-33000K show an RV-variability fraction of 34±5%, while
lower RV-variability fractions are observed for single-lined sdB stars
cooler than about 25000K (11±4%), single-lined sdB/OB stars with
Teff∼33000-40000K and surface gravities ∼5.7-6.0(13±3%), as well as
single-lined sdO/B stars with Teff∼45000-70000K (10±7%).
Single-lined hot subdwarfs with Teff∼35000-45000K located above the
extreme horizontal branch (EHB) show a similar RV-variability fraction
of 34±9% as single-lined sdB stars at about 25000-33000K. The
largest RV-variability fraction of 51±8% is found in single-lined
hot subdwarfs below the canonical EHB. The detected RV-variability
fraction of our composite hot subdwarfs with an infrared excess in
their spectral energy distributions is 9±3%, which is lower than
that fraction of single-lined hot subdwarfs. Since the average RV
uncertainty we measured in the LAMOST spectra is about 7.0km/s, the
lower detected RV-variability fraction for composite hot subdwarfs is
expected because the RV amplitudes associated with long-period systems
are lower.
The results here are generally consistent with the canonical binary
evolution channels for forming hot subdwarfs. Most single-lined
He-rich hot subdwarfs may form through merger channels, while the
stable Roche-lobe overflow channel could play an important role in the
formation of composite hot subdwarfs. Single-lined hot subdwarfs with
Teff∼35000-45000K located above the EHB may have an evolutionary
connection to the sdB stars at about 25000-33000K. The different
detected RV-variability fractions for the different subclasses of
single-lined hot subdwarfs indicate that their formation channels may
differ.
Description:
Radial velocity variations and atmospheric parameters for a sample of
434 hot subdwarfs with multi-epoch radial velocities. We denote the
false-alarm probability whose Log10 is smaller than -15 (logP←15)
as "---" in the text. Since some of the atmospheric parameters of
composite hot subdwarfs are derived through the single-lined models,
and these situations result in their being misclassified as
single-lined hot subdwarfs, they may not be reliable. Therefore, we
just list the atmospheric parameters of composite hot subdwarfs as a
reference.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 83 434 The RV variations and atmospheric parameters of
434 hot subdwarfs
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See also:
V/156 : LAMOST DR7 catalogs (Luo+, 2019)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 11 F11.7 deg RAdeg LAMOST Right ascension (J2000)
13- 22 F10.7 deg DEdeg LAMOST Declination (J2000)
24- 28 I5 K Teff Effective temperature
30- 34 I5 K e_Teff Effective temperature error
36- 39 F4.2 [cm/s2] logg log10 surface gravity
41- 44 F4.2 [cm/s2] e_logg Error on log10 surface gravity
46- 50 F5.2 [-] logY log10 helium abundance n(He)/n(H)
52- 55 F4.2 [-] e_logY Error on log10 n(He)/n(H)
57- 58 A2 --- Single-lined [is no] Single-lined or composite
60- 66 A7 --- SpClass Spectroscopic classification
68- 73 F6.2 [-] logP ?=- Log10 of false-alarm probability
75- 76 I2 --- NEpoch Number of single RV epochs
78- 80 I3 km/s dRVmax Maximum RV shift
82- 83 I2 km/s e_dRVmax Error on maximum RV shift
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Acknowledgements:
Ruijie He, heruijie(at)ynao.ac.cn
(End) Patricia Vannier [CDS] 18-Dec-2024