J/A+A/576/A44 Hot subdwarf binaries from MUCHFUSS (Kupfer+, 2015)
Hot subdwarf binaries from the MUCHFUSS project. Analysis of 12 new systems
and a study of the short-period binary population.
Kupfer T., Geier S., Heber U., Ostensen R.H., Barlow B.N., Maxted P.F.L.,
Heuser C., Schaffenroth V., Gaensicke B.T.
<Astron. Astrophys., 576, A44-44 (2015)>
=2015A&A...576A..44K 2015A&A...576A..44K
ADC_Keywords: Stars, subdwarf ; Stars, double and multiple ; Photometry ;
Radial velocities ; Effective temperatures
Keywords: subdwarfs - binaries: close
Abstract:
The project Massive Unseen Companions to Hot Faint Underluminous Stars
from SDSS (MUCHFUSS) aims at finding hot subdwarf stars with massive
compact companions like massive white dwarfs (M>1.0M☉), neutron
stars, or stellar-mass black holes. The existence of such systems is
predicted by binary evolution theory, and recent discoveries indicate
that they exist in our Galaxy. We present orbital and atmospheric
parameters and put constraints on the nature of the companions of 12
close hot subdwarf B star (sdB) binaries found in the course of the
MUCHFUSS project. The systems show periods between 0.14 and 7.4days.
In nine cases the nature of the companions cannot be constrained
unambiguously whereas three systems most likely have white dwarf
companions. We find that the companion to SDSSJ083006.17+475150.3 is
likely to be a rare example of a low-mass helium-core white dwarf.
SDSSJ095101.28+034757.0 shows an excess in the infrared that probably
originates from a third companion in a wide orbit, which makes this
system the second candidate hierarchical triple system containing an
sdB star. SDSSJ113241.58-063652.8 is the first helium deficient sdO
star with a confirmed close companion. This study brings to 142 the
number of sdB binaries with orbital periods of less than 30 days and
with measured mass functions. We present an analysis of the minimum
companion mass distribution and show that it is bimodal. One peak
around 0.1M☉ corresponds to the low-mass main sequence (dM) and
substellar companions. The other peak around 0.4M☉ corresponds
to the white dwarf companions. The derived masses for the white dwarf
companions are significantly lower than the average mass for single
carbon-oxygen white dwarfs. In a Teff-logg diagram of sdB+dM
companions, we find signs that the sdB components are more massive
than the rest of the sample. The full sample was compared to the known
population of extremely low-mass white dwarf binaries as well as
short-period white dwarfs with main sequence companions. Both samples
show a significantly different companion mass distribution indicating
either different selection effects or different evolutionary paths. We
identified 16 systems where the dM companion will fill its Roche Lobe
within a Hubble time and will evolve into a cataclysmic variable; two
of them will have a brown dwarf as donor star. Twelve systems with
confirmed white dwarf companions will merge within a Hubble time, two
of them having a mass ratio to evolve into a stable AMCVn-type binary
and another two which are potential supernova Ia progenitor systems.
The remaining eight systems will most likely merge and form RCrB stars
or massive C/O white dwarfs depending on the structure of the white
dwarf companion.
Description:
Follow-up medium resolution spectroscopy of 12 sdB binaries was
obtained using different instruments including the CAHA-3.5m
telescope with the TWIN spectrograph, the ESO-NTT telescope with the
EFOSC2 spectrograph, the SOAR telescope with the Goodman spectrograph,
the Gemini-North/South telescopes with the GMOS-N/S spectrographs and
the William Herschel telescope (WHT) with the ISIS spectrograph.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea2.dat 102 142 Orbital parameters of all published helium
burning hot subdwarf binaries
tablea3.dat 94 142 Photometry, spectroscopic distances and
companion types
refs.dat 123 81 References
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See also:
J/A+A/530/A28 : Priority targets for the MUCHFUSS project (Geier+, 2011)
J/A+A/559/A35 : FBS 0117+396 pulsating sdB star photometry (Ostensen+, 2013)
J/A+A/577/A26 : MUCHFUSS RV variable hot subluminous stars (Geier+, 2015)
Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1 A1 --- n_Object [*] * for SDSS troncated names
3- 18 A16 --- Object Object name
20- 24 I5 K Teff [20300/46400]?=- Effective temperature
26- 29 I4 K e_Teff [0/1800]? rms uncertainty on Teff
31- 35 F5.3 [cm/s2] logg [4.9/6.1]?=- Surface gravity
37- 41 F5.3 [cm/s2] e_logg [0.02/0.2]? rms uncertainty on logg
43- 56 F14.10 d Per [0.04/28] Orbital Period
58- 70 F13.11 d e_Per [0/0.2]? rms uncertainty on Per
72- 78 F7.2 km/s gamma [-113/136]?=- System velocity γ
80- 84 F5.2 km/s e_gamma [0.08/20]? rms uncertainty on gamma
86- 91 F6.2 km/s K [12/377]Semi-amplitude radial velocity K
93- 96 F4.2 km/s e_K [0.04/8.6]? rms uncertainty on K
98-106 A9 --- Ref1 References, in refs.dat file
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- n_Object [*] * for SDSS truncated names
3- 18 A16 --- Object Object name
23- 28 F6.3 mag Vmag [9.8/18.3]?=- V magnitude
30- 34 F5.3 mag e_Vmag ? rms uncertainty on Vmag
36- 41 F6.3 mag Jmag [10.3/18.5]?=- J magnitude
43- 47 F5.3 mag e_Jmag [0/0.15]? rms uncertainty on Jmag
48 A1 --- q_Jmag [BCD] 2MASS colours of quality B, C or D
which were excluded from the analysis
50- 55 F6.3 mag Hmag [10.4/18.3]?=- H magnitude
57- 61 F5.3 mag e_Hmag [0/0.23]? rms uncertainty on Hmag
62 A1 --- q_Hmag [BCD] 2MASS colours of quality B, C or D
which were excluded from the analysis
64- 67 F4.2 kpc Dist [0.1/5.8]?=- Distance
69- 72 F4.2 kpc E_Dist [0/0.74]? Error on Dist (upper value)
74- 77 F4.2 kpc e_Dist [0/0.51]? Error on Dist (lower value)
79- 83 A5 --- Type Companion type: MS=MainSequence,
WD=WhiteDwarf, BD=BrownDwarf
84- 85 A2 --- n_Type [lc ] lc: type identified photometrically
87- 94 A8 --- Ref2 References, in refs.dat file
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Ref Reference number
4- 22 A19 --- BibCode Bibcode
24- 43 A20 --- Aut Author's name
45-123 A79 --- Com Comments
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 04-Jun-2015