J/MNRAS/449/3966 Ultracool white dwarfs (Gianninas+, 2015)
Ultracool white dwarfs and the age of the Galactic disc.
Gianninas A., Curd B., Thorstensen J.R., Kilic M., Bergeron P.,
Andrews J.J., Canton P., Agueros M.A.
<Mon. Not. R. Astron. Soc., 449, 3966-3980 (2015)>
=2015MNRAS.449.3966G 2015MNRAS.449.3966G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, white dwarf ; Parallaxes, trigonometric ; Proper motions ;
Space velocities ; Photometry, infrared
Keywords: techniques: photometric - stars: atmospheres - stars: evolution -
white dwarfs - Galaxy: disc
Abstract:
We present parallax observations and a detailed model atmosphere
analysis of 54 cool and ultracool (Teff<4000K) white dwarfs
(WDs) in the solar neighbourhood. For the first time, a large number
of cool and ultracool WDs have distance and tangential velocities
measurements available. Our targets have distances ranging from 21pc
to >100pc, and include five stars within 30pc. Contrary to
expectations, all but two of them have tangential velocities smaller
than 150km/s thus suggesting Galactic disc membership. The oldest WDs
in this sample have WD cooling ages of 10Gyr, providing a firm lower
limit to the age of the thick disc population. Many of our targets
have uncharacteristically large radii, indicating that they are
low-mass WDs. It appears that we have detected the brighter population
of cool and ultracool WDs near the Sun. The fainter population of
ultracool CO-core WDs remain to be discovered in large numbers. The
Large Synoptic Survey Telescope should find these elusive, more
massive ultracool WDs in the solar neighbourhood.
Description:
All our parallax data are from the 2.4m Hiltner telescope at
Michigan-Dartmouth-MIT (MDM) Observatory on Kitt Peak, Arizona. We
used a thinned SITe CCD (named 'echelle'); at the f7.5 focus, each
24um pixel subtended 0.275-arcsec, giving a field of view
9.4arcmin2. For all our parallax data, we used a 4-inch-square
Kron-Cousins I-band filter, which did not vignette the CCD. Exposure
times varied with the brightness of the object, but were typically a
few hundred seconds. Our data were taken on numerous observing runs
between 2007 and 2011.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 216 52 Journal of Parallax Observations
table2.dat 94 54 Astrometry of cool WDs
table3.dat 111 57 Optical and near-infrared photometry of cool WDs
table4.dat 104 54 Properties of cool WDs
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See also:
J/MNRAS/382/515 : SDSS ultracool and halo WD candidates (Vidrih+, 2007)
J/ApJ/723/684 : NIRSPEC ultracool dwarf radial velocity survey (Blake+, 2010)
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 SDSS name (JHHMM-DDMM)
12- 14 I3 --- Nref Number of reference stars used to define
the plate solution
16- 18 I3 --- Nmeas Total number of stars measured
20- 22 I3 --- Npix Number of images used
24-216 A193 --- Epochs Different observing runs, and the numbers in
parentheses are the number of images included
from each run (YYYY.yy(NN), separated by comma)
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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- 11 A11 --- Name SDSS name (JHHMM+DDMMN)
12 A1 --- n_Name [b] Note on Name (1)
14- 15 I2 h RAh Right ascension (J2000)
17- 18 I2 min RAm Right ascension (J2000)
20- 24 F5.2 s RAs Right ascension (J2000)
26 A1 --- DE- Declination sign (J2000)
27- 28 I2 deg DEd Declination (J2000)
30- 31 I2 arcmin DEm Declination (J2000)
33- 36 F4.1 arcsec DEs Declination (J2000)
38- 41 F4.1 mas/yr plxabs Absolute parallax
43- 45 F3.1 mas/yr e_plxabs rms uncertainty on plxabs
47- 50 I4 mas/yr pmRA Proper motion along RA
52- 55 I4 mas/yr pmDE Proper motion along DE
57- 59 I3 pc Dist Distance
61- 62 I2 pc E_Dist Error on Dist (upper value)
64- 65 I2 pc e_Dist Error on Dist (lower value)
67- 69 I3 km/s Vtan Tangential velocity
71- 72 I2 km/s e_Vtan rms uncertainty on Vtan
74- 76 I3 km/s Uvel U velocity (2)
78- 79 I2 km/s e_Uvel rms uncertainty on Uvel
81- 84 I4 km/s Vvel V velocity
86- 87 I2 km/s e_Vvel rms uncertainty on Vvel
89- 91 I3 km/s Wvel W velocity
93- 94 I2 km/s e_Wvel rms uncertainty on Wvel
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Note (1): b: For these two binary systems, a weighted mean was adopted in the
determination of their astrometric measurements.
Note (2): Since we do not have any radial velocity measurements for our targets,
the U component has been computed assuming vrad=0km/s.
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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- 11 A11 --- Name SDSS SDSS name (JHHMM+DDMMN)
12 A1 --- n_Name [ab] Note on Name (1)
14- 18 F5.2 mag umag SDSS u magnitude
20- 23 F4.2 mag e_umag rms uncertainty on umag
25- 29 F5.2 mag gmag SDSS g magnitude
31- 34 F4.2 mag e_gmag rms uncertainty on gmag
36- 40 F5.2 mag rmag SDSS r magnitude
42- 45 F4.2 mag e_rmag rms uncertainty on rmag
47- 51 F5.2 mag imag SDSS i magnitude
53- 56 F4.2 mag e_imag rms uncertainty on imag
58- 62 F5.2 mag zmag SDSS z magnitude
64- 67 F4.2 mag e_zmag rms uncertainty on zmag
69- 73 F5.2 mag Ymag ?=- UKIDSS Y magnitude
75- 78 F4.2 mag e_Ymag ? rms uncertainty on Ymag
80- 84 F5.2 mag Jmag ?=- UKIDSS J magnitude
86- 89 F4.2 mag e_Jmag ? rms uncertainty on Jmag
91- 95 F5.2 mag Hmag ?=- UKIDSS H magnitude
97-100 F4.2 mag e_Hmag ? rms uncertainty on Hmag
102-106 F5.2 mag Kmag ?=- UKIDSS K magnitude
108-111 F4.2 mag e_Kmag ? rms uncertainty on Kmag
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Note (1): Notes as follows:
a = IR photometry from UKIDSS
b = IR photometry from 2MASS
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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- 9 A9 --- Type Type of WD
11- 21 A11 --- Name SDSS name (JHHMM+DDMMN)
24- 27 I4 K Teff Effective temperature
29- 31 I3 K e_Teff rms uncertainty on Teff
33- 36 F4.2 [cm/s2] logg Surface gravity
38- 41 F4.2 [cm/s2] e_logg rms uncertainty on logg
43- 46 F4.2 Msun Mass Mass
48- 51 F4.2 Msun e_Mass rms uncertainty on Mass
53- 57 F5.3 Rsun Rad Radius
59- 63 F5.3 Rsun e_Rad rms uncertainty no Rad
65- 69 A5 ---- Comp Composition (H, He or value of logHe/H)
71- 75 F5.2 mag gMAG Absolute SDSS g magnitude
77- 80 F4.2 mag e_gMAG rms uncertainty on gMAG
82- 84 F3.1 Gyr tcoolCO Cooling time from CO
86- 88 F3.1 Gyr E_tcoolCO Error on tcoolCO (upper value)
90- 92 F3.1 Gyr e_tcoolCO Error on tcoolCO (lower value)
94- 96 F3.1 Gyr tcoolHe ? Cooling time from He
98-100 F3.1 Gyr E_tcoolHe ? Error on tcoolHe (upper value)
102-104 F3.1 Gyr e_tcoolHe ? Error on tcoolHe (lower value)
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 14-Dec-2015