J/ApJ/723/1072 The ELM survey. I. Low-mass white dwarfs (Brown+, 2010)
The ELM survey.
I. A complete sample of extremely low-mass white dwarfs.
Brown W.R., Kilic M., Prieto C.A., Kenyon S.J.
<Astrophys. J., 723, 1072-1081 (2010)>
=2010ApJ...723.1072B 2010ApJ...723.1072B
ADC_Keywords: Stars, white dwarf ; Radial velocities ; Photometry, SDSS ;
Binaries, spectroscopic ; Stars, masses
Keywords: Galaxy: stellar content - stars: individual (J211921.96-001825.8,
SDSS J075552.40+490627.9, SDSS J081822.34+353618.9,
SDSS J092345.60+302805.0, SDSS J123316.20+160204.6,
SDSS J143948.40+100221.7, SDSS J151225.70+261538.5) - white dwarfs
Abstract:
We analyze radial velocity observations of the 12 extremely low-mass
(ELM), with ≤0.25M☉, white dwarfs (WDs) in the MMT
Hypervelocity Star Survey. Eleven of the twelve WDs are binaries with
orbital periods shorter than 14hr; the one non-variable WD is possibly
a pole-on system among our non-kinematically selected targets. Our
sample is unique: it is complete in a well-defined range of apparent
magnitude and color. The orbital mass functions imply that the unseen
companions are most likely other WDs, although neutron star companions
cannot be excluded. Six of the eleven systems with orbital solutions
will merge within a Hubble time due to the loss of angular momentum
through gravitational wave radiation. The quickest merger is
J0923+3028, a g=15.7 ELM WD binary with a 1.08hr orbital period and a
≤130Myr merger time. The chance of a supernova Ia event among our ELM
WDs is only 1%-7%, however. Three binary systems (J0755+4906,
J1233+1602, and J2119-0018) have extreme mass ratios and will most
likely form stable mass-transfer AM CVn systems. Two of these objects,
SDSS J1233+1602 and J2119-0018, are the lowest surface gravity WDs
ever found; both show CaII absorption likely from accretion of
circumbinary material. We predict that at least one of our WDs is an
eclipsing detached double WD system, important for constraining helium
core WD models.
Description:
Here we present 12 extremely low-mass (ELM) WDs with ≤0.25M☉
found in the Hypervelocity Star (HVS) Survey of Brown et al.
(2005ApJ...622L..33B 2005ApJ...622L..33B, 2006ApJ...640L..35B 2006ApJ...640L..35B, 2006, Cat. J/ApJ/647/303,
2007, Cat. J/ApJ/660/311, 2007, Cat. J/ApJ/671/1708,
2009ApJ...690.1639B 2009ApJ...690.1639B, 2009ApJ...690L..69B 2009ApJ...690L..69B), 10 of which are new
discoveries.
With the exception of J0923+3028, we obtained all observations at the
6.5m MMT telescope using the Blue Channel Spectrograph (wavelength
coverage: 3650-4500Å and spectral resolution of 1.0-1.2Å). We
obtained spectroscopy for J0923+3028 at the Fred Lawrence Whipple
Observatory 1.5m Tillinghast telescope using the FAST spectrograph
(wavelength coverage: 3600-5500Å and spectral resolution of 2.3Å).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 83 12 White dwarf physical parameters
table2.dat 87 12 Binary orbital parameters
table3.dat 34 184 Radial velocity measurements (also named A.1 in
the paper)
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See also:
II/306 : The SDSS Photometric Catalog, Release 8 (Adelman-McCarthy+, 2011)
J/MNRAS/413/1121 : SDSS post-common envelope binaries. X (Rebassa-Mansergas+
2011)
J/ApJ/671/1708 : Hypervelocity stars. III (Brown+, 2007)
J/ApJ/660/311 : Hypervelocity stars. II. (Brown+, 2007)
J/ApJ/647/303 : Spectroscopic survey of hypervelocity stars (Brown+, 2006)
J/ApJS/167/40 : SDSS4 confirmed white dwarfs catalog (Eisenstein+, 2006)
J/AJ/132/1221 : VJHK and SDSS photometry of DA white dwarfs (Holberg+, 2006)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Whide dwarf name (JHHMM+DDMM)
11 A1 --- r_Name [abc] Reference (G1)
13- 18 F6.3 mag gmag0 Corrected g-band magnitude
20- 24 F5.3 mag e_gmag0 Corrected g-band magnitude uncertainty
26- 30 F5.3 mag (u-g)0 Corrected (u-g) color index
32- 36 F5.3 mag e_(u-g)0 Corrected (u-g) color index uncertainty
38- 43 F6.3 mag (g-r)0 Corrected (g-r) color index
45- 49 F5.3 mag e_(g-r)0 Corrected (g-r) color index uncertainty
51- 55 I5 K Teff Effective temperature
57- 59 I3 K e_Teff Effective temperature uncertainty
61- 64 F4.2 [cm/s2] logg Surface gravity
66- 69 F4.2 [cm/s2] e_logg Surface gravity uncertainty
71- 73 F3.1 mag gMAG Absolute g-band magnitude
75- 78 F4.2 kpc Dist Heliocentric distance
80- 83 F4.2 Msun Mass Mass
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name WD name (JHHMM+DDMM)
11 A1 --- r_Name [abc] Reference or note (G1)
13- 19 F7.5 d Per ? Orbital period
21- 27 F7.5 d e_Per ? Per uncertainty
29- 31 I3 km/s K Radial velocity semi-amplitude (K)
33 I1 km/s e_K K uncertainty
35- 38 I4 km/s Vsys Systemic velocity
40 I1 km/s e_Vsys Systemic velocity uncertainty
42- 51 F10.5 d T0 ? Time of spectroscopic conjunction (-2450000)(1)
53- 59 F7.5 d e_T0 ? T0 uncertainty
61- 65 F5.3 Msun f(M) ? Binary mass function (2)
67- 71 F5.3 Msun e_f(M) ? Binary mass function uncertainty
73- 74 A2 --- l_M2 [≥ ] Limit flag on M2
75- 78 F4.2 Msun M2 ? Minimum secondary mass (assuming i=90°)
80- 81 A2 --- l_tau [≤ ] Limit flag on tau
82- 87 F6.2 Gyr tau ? Merger time (3)
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Note (1): the time when the object passes through 0km/s as it approaches the
observer.
Note (2): the binary mass function is given by Eq.(1):
f(M) = (M23sin3i)/(M1+M2)2 = PK3/(2πG)
if M1 is the mass of the white dwarf, M2 the companion mass, i the
inclination of the orbit, P the period and K the velocity amplitude.
Note (3): Short-period binaries must eventually merge due to angular
momentum loss due to gravitational wave radiation. The merger time
is given by Eq.(2):
τ = (M1+M2)1/3/(M1M2)P8/3x10-2Gyr
if masses are in solar mass, and period P in hours.
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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- 10 A10 --- Name WD name (JHHMM+DDMM)
12- 22 F11.6 d HJD Heliocentric Julian Date (HJD-2450000)
24- 29 F6.1 km/s HRV Heliocentric radial velocity
31- 34 F4.1 km/s e_HRV Uncertainty in HRV
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Global notes:
Note (G1): Flag as follows:
a = Kilic et al. (2007ApJ...664.1088K 2007ApJ...664.1088K).
b = Kilic et al. (2010ApJ...716..122K 2010ApJ...716..122K).
c = The measurements are formally consistent with no variation.
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History:
From electronic version of the journal
References:
Kilic et al. Paper II. 2011ApJ...727....3K 2011ApJ...727....3K
Brown et al. Paper III. 2012ApJ...744..142B 2012ApJ...744..142B
Kilic et al. Paper IV. 2012ApJ...751..141K 2012ApJ...751..141K
Brown et al. Paper V. 2013ApJ...769...66B 2013ApJ...769...66B Cat. J/ApJ/769/66
Gianninas et al. Paper VI. 2015ApJ...812..167G 2015ApJ...812..167G Cat. J/ApJ/812/167
Brown et al. Paper VII. 2016ApJ...818..155B 2016ApJ...818..155B Cat. J/ApJ/818/155
Brown et al. Paper VIII. 2020ApJ...889...49B 2020ApJ...889...49B Cat. J/ApJ/889/49
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 24-Jul-2012