J/A+A/707/A6 Hot subluminous stars 500pc volume-limited sample (Dawson+, 2026)
A 500 pc volume-limited sample of hot subluminous stars.
II. Atmospheric parameters, mass distribution, and kinematics.
Dawson H., Dorsch M., Geier S., Munday J., Pritzkuleit M., Heber U.,
Mattig F., Benitez-Palacios D., Vuckovic M., Pelisoli I., Deshmukh K.,
Bhat A., Kufleitner L., Uzundag M., Schaffenroth V., Reindl N., Culpan R.,
Raddi R., Antunes Amaral L., Istrate A.G., Justham S., Ostensen R.H.,
Telting J.H., Steinmetz T., Rodriguez-Segovia N., Fernandez-Schlosser P.,
Duran-Reyes A., Arancibia-Rojas E., Latour M., Jones G.T., O'Brien M.,
Sahu S., Elms A.
<Astron. Astrophys. 707, A6 (2026)>
=2026A&A...707A...6D 2026A&A...707A...6D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, subdwarf ; Spectral types ; Space velocities ;
Stars, masses ; Optical
Keywords: catalogs - binaries: general - stars: evolution -
Hertzsprung-Russell and C-M diagrams - stars: statistics / subdwarfs
Abstract:
We present a quantitative spectroscopic and kinematic analysis of a
volume-complete sample of hot subluminous stars within 500 pc of the
Sun, assembled using accurate parallax measurements from the Gaia
space mission Data Release 3 (DR3). In total, 3226 spectra of 253 hot
subdwarf stars were analysed to derive atmospheric parameters (Teff,
logg, and helium abundance) and radial velocities. Spectral energy
distributions (SEDs) with Gaia parallaxes were used to measure stellar
radii, luminosities, and masses. The derived atmospheric parameters
reveal a consistent alignment between sdB and sdO stars in the Kiel
diagram when compared to theoretical evolutionary models. Notably, we
find a substantial population (about 10%) of hot subdwarfs located
below the 0.45M☉ zero-age extreme horizontal branch (EHB) in both
the Kiel and Hertzsprung-Russell diagrams (HRDs), which likely
originate from intermediate-mass progenitors (1.8-8M☉). The
overall mass distribution peaks at 0.48-0.100.14M☉, while hot
subdwarfs below the EHB peak at 0.43-0.090.11M☉, supporting a
scenario of non- or semi-degenerate helium ignition for these objects
characteristic of intermediate-mass stars. Interpolation of EHB and
post-EHB tracks yields theoretical mass distributions consistent with
our estimates based on SED and parallax. By assuming a mass range
between 0.40 and 0.50M☉ during the interpolation, we further find
that the post-EHB birthrate in our sample is 2-3 times higher than
the EHB birthrate, which may suggest overestimated EHB lifetimes in
theoretical tracks or contamination from other formation and
evolutionary channels. Our kinematic analysis shows that 86±2%
of the stars belong to the Galactic thin disk, with 13±1% and
1±1% associated with the thick disk and halo, respectively. The
below-EHB population is exclusively found in the thin disk, the only
Galactic population young enough to harbour intermediate-mass stars.
The below-EHB population seems to be absent in other large samples,
which generally include more thick disk and halo members. These
findings suggest that non-degenerate formation channels may play a
more prominent role in the Galactic disk than previously thought.
Description:
Here we present a spectroscopically complete 500pc volume-limited
sample of hot subluminous stars using data from Gaia EDR3 (Gaia
Collaboration, 2021A&A...649A...1G 2021A&A...649A...1G, Cat. I/350). Spectroscopic classes
are given for all sources in this sample.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 86 253 Atmospheric parameters
table3.dat 187 253 SED and HRD parameters
table4.dat 126 247 Kinematic/membership parameters
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See also:
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 34 A34 --- Name Name of object
36- 43 F8.4 deg RAdeg Right ascension (J2000)
45- 52 F8.4 deg DEdeg Declination (J2000)
54- 62 A9 --- Class Spectral classification
64- 68 I5 K Teff Effective temperature
70- 73 F4.2 [cm/s2] logg Surface gravity
75- 79 F5.2 --- logm(He)/m(H) Helium abundance
81- 84 I4 km/s RV Radial velocity
86 A1 --- Flag [A/B] Quality flag
(A = reliable parameters)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 34 A34 --- Name Name of object
36- 43 F8.4 deg RAdeg Right ascension (J2000)
45- 52 F8.4 deg DEdeg Declination (J2000)
54- 71 F18.16 Msun MSED SED mass
73- 76 F4.2 Msun E_MSED SED mass upper error
78- 81 F4.2 Msun e_MSED SED mass lower error
83-101 F19.15 Lsun LSED SED luminosity
103-107 F5.2 Lsun E_LSED SED luminosity upper error
109-113 F5.2 Lsun e_LSED SED luminosity lower error
115-119 F5.3 Rsun RSED SED radius
121-125 F5.3 Rsun E_RSED SED radius upper error
127-131 F5.3 Rsun e_RSED SED radius lower error
133-137 F5.3 mag E(44-55) Extinction (Stilism)
139-143 F5.3 mag E_E(44-55) Extinction (Stilism) upper error
145-149 F5.3 mag e_E(44-55) Extinction (Stilism) lower error
151-154 F4.2 Msun MHDR ?=- HDR mass
156-159 F4.2 Msun E_MHDR ?=- HDR mass upper error
161-164 F4.2 Msun e_MHDR ?=- HDR mass lower error
166-171 F6.2 Myr tauHRD ?=- HRS age
173-178 F6.2 Myr E_tauHRD ?=- HDR age upper error
180-185 F6.2 Myr e_tauHRD ?=- HDR age lower error
187 A1 --- Flag [A/B] Quality flag (A = reliable parameters)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 34 A34 --- Name Name of object
36- 43 F8.4 deg RAdeg Right ascension (J2000)
45- 52 F8.4 deg DEdeg Declination (J2000)
54- 59 F6.1 km/s Uvel U velocity
61- 64 F4.1 km/s E_Uvel U velocity upper error
66- 69 F4.1 km/s e_Uvel U velocity lower error
71- 76 F6.1 km/s Vvel V velocity
78- 81 F4.1 km/s E_Vvel V velocity upper error
83- 86 F4.1 km/s e_Vvel V velocity lower error
88- 93 F6.1 km/s Wvel W velocity
95- 98 F4.1 km/s E_Wvel W velocity upper error
100-103 F4.1 km/s e_Wvel W velocity lower error
105-108 F4.2 --- pthin Thin probability
110-113 F4.2 --- pthick Thick probability
115-118 F4.2 --- phalo Halo probability
120-124 A5 --- Memb Menbership
126 A1 --- Flag [A/B] Quality flag (A = reliable parameters)
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Acknowledgements:
Harry Dawson, hdawson(at)uni-potsdam.de
(End) Patricia Vannier [CDS] 15-Jan-2026