J/AJ/138/1681 WD within 20pc of the Sun (Sion+, 2009)
The white dwarfs within 20 parsecs of the Sun: kinematics and statistics.
Sion E.M., Holberg J.B., Oswalt T.D., McCook G.P., Wasatonic R.
<Astron. J., 138, 1681-1689 (2009)>
=2009AJ....138.1681S 2009AJ....138.1681S
ADC_Keywords: Stars, white dwarf ; Stars, distances ; Space velocities ;
Stars, ages ; Spectral types ; Stars, nearby
Keywords: stars: kinematics - stars: statistics - techniques: photometric -
techniques: spectroscopic - white dwarfs
Abstract:
We present the kinematical properties, distribution of spectroscopic
subtypes, and stellar population subcomponents of the white dwarfs
within 20pc of the Sun. We find no convincing evidence of halo white
dwarfs in the total 20pc sample of 129 white dwarfs nor is there
convincing evidence of genuine thick disk subcomponent members within
20 parsecs. Virtually, the entire 20pc sample likely belongs to the
thin disk. The total DA to non-DA ratio of the 20pc sample is 1.6, a
manifestation of deepening envelope convection which transforms DA
stars with sufficiently thin H surface layers into non-DAs. The
addition of five new stars to the 20pc sample yields a revised local
space density of white dwarfs of (4.9±0.5)x10-3pc-3 and a
corresponding mass density of (3.3±0.3)x10-3M☉pc-3. We
find that at least 15% of the white dwarfs within 20 parsecs of the
Sun (the DAZ and DZ stars) have photospheric metals that possibly
originate from accretion of circumstellar material (debris disks)
around them. If this interpretation is correct, this suggests the
possibility that the same percentage have planets or asteroid-like
bodies orbiting them.
Description:
The local sample of 129 white dwarfs within 20pc is mainly the same as
in Holdberg et al., 2008, Cat. J/AJ/135/1225 (124 stars). In this
work, we use the enlarged local sample to examine the kinematical
properties, distribution of spectroscopic subtypes, and stellar
population subcomponents of the white dwarfs sampled in this volume of
space around the Sun.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 56 129 Observational data used in space motions
table3.dat 45 129 Space motions of white dwarfs within 20pc
table4.dat 33 126 Cooling ages of white dwarfs within 20pc
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See also:
B/wd : Spectroscopically Identified White Dwarfs (McCook+, 2008)
V/32 : Stars within 25pc of the Sun (Woolley+ 1970)
J/AJ/135/1225 : Parameters of the local white dwarfs (Holberg+, 2008)
J/AJ/135/1239 : Spectral distances to DA white dwarfs (Holberg+, 2008)
J/AJ/134/252 : New nearby white dwarf systems (Subasavage+, 2007)
J/ApJ/643/402 : Cool white dwarfs in the solar neighborhood (Kawka+, 2006)
J/ApJ/571/512 : Distances of white dwarf stars (Holberg+, 2002)
http://www.astro.umontreal.ca/~bergeron/CoolingModels/ : Synthetic colors and
evolutionary sequences of H- and He-atmosphere WD
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- WD WD designation (HHMM+DDd.N; B1950)
12- 18 A7 --- SpT Spectral type
20- 26 F7.3 deg RAdeg Right ascension in decimal degrees (J2000)
28- 34 F7.3 deg DEdeg Declination in decimal degrees (J2000)
36- 40 F5.2 pc Dist Distance (1)
42- 46 F5.3 arcsec/yr pm Proper motion (2)
48- 54 F7.3 deg pmPA Position angle of proper motion
56 A1 --- n_Dist [psa] Method of distance determination (3)
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Note (1): Distance estimates are taken from Holdberg et al., 2008,
Cat. J/AJ/135/1225 which are based on both trigonometric parallaxes
and spectrophotometric distances. Whenever possible, preference was
given to trigonometric parallax distances. In Holdberg et al., 2008,
Cat. J/AJ/135/1225, the photometric distances were computed based upon
spectroscopic and photometric measurements using the techniques
described in Holberg et al. (2008, Cat. J/AJ/135/1239).
Note (2): Proper motions are taken from the McCook and Sion Catalog, or
where available, were determined from NOMAD.
Note (3): Method is one of:
p = trigonometric parallax,
s = spectrophotometric distances,
a = a weighted average of the parallax and photometric distances according to
their respective uncertainties.
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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 --- WD WD designation (HHMM+DDd.N; B1950)
12- 18 A7 --- SpT White dwarf spectral type
20- 25 F6.1 km/s Uvel U-component (4)
27- 32 F6.1 km/s Vvel V-component (4)
34- 39 F6.1 km/s Wvel W-component (4)
41- 45 F5.1 km/s Tvel The total space velocity
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Note (4): For the local white dwarfs with sufficient kinematical
information (photometric or trigonometric parallax, proper motion,
position angle), we have computed the vector components of the space
motion U, V, and W relative to the Sun in a right-handed system
following Wooley et al. (1970, Cat. V/32) where U is measured positive
in the direction of the Galactic anti-center, V is measured positive
in the direction of the Galactic rotation, and W is measured positive
in the direction of the north Galactic pole.
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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- 2 A2 --- --- [WD]
3- 12 A10 --- WD WD designation (HHMM+DDd.N; B1950)
14- 18 I5 K Teff Effective temperature
20- 24 F5.3 [cm/s2] logg Surface gravity
26- 33 E8.3 yr Age Cooling age
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 24-Jan-2012