J/A+A/690/A368 Fast hot subdwarfs spectroscopy and kinematics (Geier+, 2024)
A spectroscopic and kinematic survey of fast hot subdwarfs.
Geier S., Heber U., Irrgang A., Dorsch M., Bastian A., Neunteufel P.,
Kupfer T., Bloemen S., Kreuzer S., Moller L., Schindewolf M., Schneider D.,
Ziegerer E., Pelisoli I., Schaffenroth V., Barlow B.N., Raddi R.,
Geier S.J., Reindl N., Rauch T., Nemeth P., Gansicke B.T.
<Astron. Astrophys. 690, A368 (2024)>
=2024A&A...690A.368G 2024A&A...690A.368G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, subdwarf ; Supernovae ; Space velocities ;
Effective temperatures ; Stars, diameters
Keywords: stars: kinematics and dynamics - subdwarfs - supernovae: general
Abstract:
Hot subdwarfs (sdO/B) are the stripped helium cores of red giants
formed via binary interactions. Close hot subdwarf binaries with
massive white dwarf companions have been proposed as possible
progenitors of thermonuclear supernovae type Ia (SN Ia). If the
supernova is triggered by stable mass transfer from the helium star,
the companion should survive the explosion and should be accelerated
to high velocities. The hypervelocity star US 708 is regarded as the
prototype for such an ejected companion. To find more of those objects
we conducted an extensive spectroscopic survey. Candidates for such
fast stars have been selected from the spectroscopic database of the
Sloan Digital Sky Survey (SDSS) and several ground-based proper-motion
surveys. Follow-up spectroscopy has been obtained with several 4m- to
10m-class telescopes. Combining the results from quantitative
spectroscopic analyses with space-based astrometry from Gaia Early
Data Release 3 (EDR3) we determined the atmospheric and kinematic
parameters of 53 fast hot subdwarf stars. None of these stars is
unbound to the Galaxy, although some have Galactic restframe
velocities close to the Galactic escape velocity. 21 stars are
apparently single objects, that crossed the Galactic disc within their
lifetimes in the sdO/B stage and could be regarded as potential
candidates for the SN Ia ejection scenario. However, the properties of
the full sample are more consistent with a pure old Galactic halo
population. We therefore conclude that the fast sdO/B stars we found
are likely to be extreme halo stars.
Description:
To substantially increase the sample of high-velocity sdO/Bs and to
find unbound objects similar to the prototype US 708, we performed an
extended and more systematic survey, including archival
spectroscopic and ground-based astrometric data. Our aim was to select
candidates with high Galactic-restframe velocities, for which we
wanted to obtain spectroscopic follow-up observations for detailed
analyses. This part of the project was mostly conducted between 2015
and 2018 with the data and methods available to us at that time. A
follow-up campaign was conducted to obtain higher-quality spectra and
to improve the accuracy of the derived spectroscopic parameters.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 43 53 Spectroscopic data overview
tablea3.dat 104 53 Classifications and spectroscopic parameters
tablea4.dat 79 53 Astrometric parameters
tablea5.dat 70 53 Results of the SED analysis
tablea6.dat 114 53 Kinematic parameters of the fast star candidates
tablea7.dat 139 53 Parameters of the fast star candidates at the
last Galactic disc passage
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name SDSS name (JHHMMSS.ss+DDMMSS.s)
22 I1 --- SDSS ? Number of SDSS available spectra
24- 25 I2 --- BOSS ? Number of BOSS available spectra
27 I1 --- ISIS ? Number of ISIS available spectra
29 I1 --- LAMOST ? Number of LAMOST available spectra
31- 32 I2 --- XSHO ? Number of XSHO available spectra
35 I1 -- FORS1 ? Number of FORS1 available spectra
37 I1 --- EFOSC2 ? Number of EFOSC2 available spectra
39 I1 --- DBSP ? Number of DBSP available spectra
41 I1 --- TWIN ? Number of TWIN available spectra
43 I1 --- LRIS ? Number of LRIS available spectra
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name SDSS name (JHHMMSS.ss+DDMMSS.s)
20 A1 --- n_Name [a] Note on SDSS name (1)
22- 29 A8 --- Class Spectral types (defined in Section 4.1)
31- 35 I5 K Teff Effective temperature
36 A1 --- --- [+]
37- 40 I4 K E_Teff Effective temperature error
(upper value) (2)
41 A1 --- --- [-]
42- 45 I4 K e_Teff Effective temperature error
(lower value) (2)
47- 51 F5.3 [cm/s2] logg Surface gravity
52 A1 --- --- [+]
53- 57 F5.3 [cm/s2] E_logg Surface gravity error (upper value) (2)
58 A1 --- --- [-]
59- 63 F5.3 [cm/s2] e_logg Surface gravity error (lower value) (2)
65 A1 --- l_logn(He/H) Limit flag on logn(He/H)
66- 72 F7.4 --- logn(He/H) Helium abundance
73 A1 --- --- [+]
74- 78 F5.3 --- E_logn(He/H) ? Helium abundance (upper value) (2)
79 A1 --- --- [-]
80- 85 F6.4 --- e_logn(He/H) ? Helium abundance (lower value) (2)
87- 90 I4 km/s RV Mean radial velocity
92- 93 I2 km/s e_RV Mean radial velocity standard deviation (2)
95- 99 F5.2 --- logp log p value to indicate radial velocity
variability
101-102 I2 --- Nspec Number of spectra used
104 I1 --- Cat [1/4] Category as defined in Sect. 4.4 (3)
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Note (1): a = Atmospheric parameters derived with a tailored grid for BHB stars.
Note (2): The uncertainties in the table are statistical uncertainties only.
Systematic uncertainties of ±3% in Teff and ±0.1 in logg and logn(He)/n(H)
should be added in quadrature for a more realistic estimate of the
uncertainties.
Note (3): categories as follows:
1 = stars have follow-up observations taken with different instruments
usually several years after the SDSS epochs.
2 = stars have SDSS spectra only, but these were again taken at several
distinct epochs separated by at least one day.
3 = stars only have individual SDSS spectra, which were taken back-to-back
usually within less than one hour, but their longer term RV variability
can be checked with follow-up spectra taken with different instruments.
4 = stars only has individual SDSS spectra taken back-to-back within less
than one hour of each other. Since the typical orbital periods of sdBs
range from hours to days, these stars can only probe the closest binary
systems with the shortest periods.
Non-detections of RV variations in category 4 stars are therefore not
suited to excluding close binarity in general.
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Byte-by-byte Description of file: tablea4.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name SDSS name (JHHMMSS.ss+DDMMSS.s)
21- 39 I19 --- GaiaDR3 GaiaDR3 identifier
41- 45 F5.3 mas plx ? Parallax (1)
47- 51 F5.3 mas e_plx ? Parallax error
53- 59 F7.3 mas/yr pmRA Proper motion in right ascension, pmRA*cosDE
61- 65 F5.3 mas/yr e_pmRA Proper motion in right ascension error
67- 73 F7.3 mas/yr pmDE Proper motion in declination
75- 79 F5.3 mas/yr e_pmDE Proper motion in declination error
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Note (1): Only parallaxes with uncertainties better than 20% are listed.
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Byte-by-byte Description of file: tablea5.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name SDSS name (JHHMMSS.ss+DDMMSS.s)
21- 27 F7.3 [rad] log(theta) Angular diameter
29- 33 F5.3 [rad] E_log(theta) Angular diameter error (upper value)
35- 39 F5.3 [rad] e_log(theta) Angular diameter error (lower value)
41- 45 F5.3 mag E(44-55) Interstellar reddening parameter E(44-55)
47- 51 F5.3 mag E_E(44-55) Interstellar reddening parameter E(44-55)
error (upper value)
53- 57 F5.3 mag e_E(44-55) Interstellar reddening parameter E(44-55)
error (lower value)
59- 62 F4.1 kpc Dspec Spectroscopic distance
64- 66 F3.1 kpc E_Dspec Spectroscopic distance error (upper value)
68- 70 F3.1 kpc e_Dspec Spectroscopic distance error (lower value)
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Byte-by-byte Description of file: tablea6.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name SDSS name (JHHMMSS.ss+DDMMSS.s)
23- 28 F6.2 kpc X X position
30- 33 F4.2 kpc E_X X position error (upper value)
35- 38 F4.2 kpc e_X X position error (lower value)
40- 44 F5.2 kpc Y
46- 49 F4.2 kpc E_Y Y position error (upper value)
51- 54 F4.2 kpc e_Y Y position error (lower value)
56- 60 F5.2 kpc Z Z position
62- 65 F4.2 kpc E_Z Z position error (upper value)
67- 70 D4.2 kpc e_Z Z position error (lower value)
72- 75 I4 km/s U Galactic U velocity
77- 78 I2 km/s E_U Galactic U velocity error (upper value)
80- 81 I2 km/s e_U Galactic U velocity error (lower value)
83- 86 I4 km/s V Galactic V velocity
88- 90 I3 km/s E_V Galactic V velocity error (upper value)
92- 93 I2 km/s e_V Galactic V velocity error (lower value)
95- 98 I4 km/s W Galactic W velocity
100-101 I2 km/s E_W Galactic W velocity error (upper value)
103-104 I2 km/s e_W Galactic W velocity error (lower value)
106-108 I3 km/s vgrf Galactic rest-frame velocity
110-111 I2 km/s E_vgrf Galactic rest-frame velocity error
(upper value)
113-114 I2 km/s e_vgrf Galactic rest-frame velocity error
(lower value)
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Byte-by-byte Description of file: tablea7.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name SDSS name (JHHMMSS.ss+DDMMSS.s)
21- 26 F6.2 kpc Xdisc Disc X position
27 A1 --- --- [+]
28- 32 F5.2 kpc E_Xdisc Disc X position error (upper value)
33 A1 --- --- [-]
34- 38 F5.2 kpc e_Xdisc Disc X position (lower value)
40- 45 F6.2 kpc Ydisc Disc Y position
46 A1 --- --- [+]
47- 51 F5.2 kpc E_Ydisc Disc Y position error (upper value)
52 A1 --- --- [-]
53- 57 F5.2 kpc e_Ydisc Disc Y position error (lower value)
59- 63 F5.2 kpc Rdisc Disc radius
64 A1 --- --- [+]
65- 69 F5.2 kpc E_Rdisc Disc radius error (upper value)
70 A1 --- --- [-]
71- 75 F5.2 kpc e_Rdisc Disc radius error (lower value)
77- 79 I3 km/s Vej Ejection velocity
80 A1 --- --- [+]
81- 83 I3 km/s E_Vej Ejection velocity error (upper value)
84 A1 --- --- [-]
85- 87 I3 km/s e_Vej Ejection velocity error (lower value)
89- 93 F5.1 Myr tdisc Disc age
94 A1 --- --- [+]
95- 99 F5.1 Myr E_tdisc Disc age error (upper value)
100 A1 --- --- [-]
101-105 F5.1 Myr e_tdisc Disc age error (lower value)
107-111 F5.3 --- e Ellipticity
112 A1 --- --- [+]
113-117 F5.3 --- E_e Ellipticity error (upper value)
118 A1 --- --- [-]
119-123 F5.3 --- e_e Ellipticity error (lower value)
125-129 F5.2 10+3kpc.km/s Lz Angular momentum in z-direction
130 A1 --- --- [+]
131-134 F4.2 10+3kpc.km/s E_Lz Angular momentum in z-direction error
(upper value)
135 A1 --- --- [-]
136-139 F4.2 10+3kpc.km/s e_Lz Angular momentum in z-direction error
(lower value)
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 26-Mar-2025