J/MNRAS/399/699 Parameters of atmospheres of white dwarfs (Mortlock+, 2009)
Photometric constraints on white dwarfs and the identification of extreme
objects.
Mortlock D.J., Peiris H.V., Ivezic Z.
<Mon. Not. R. Astron. Soc., 399, 699-714 (2009)>
=2009MNRAS.399..699M 2009MNRAS.399..699M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, white dwarf ; Models, atmosphere
Keywords: methods: statistical - surveys - white dwarfs
Abstract:
It is possible to reliably identify white dwarfs (WDs) without
recourse to spectra, instead using photometric and astrometric
measurements to distinguish them from main-sequence stars and quasars.
WDs' colours can also be used to infer their intrinsic properties
(effective temperature, surface gravity, etc.), but the results
obtained must be interpreted with care. The difficulties stem from the
existence of a solid angle degeneracy, as revealed by a full
exploration of the likelihood, although this can be masked if a simple
best-fitting approach is used. Conversely, this degeneracy can be
broken if a Bayesian approach is adopted, as it is then possible to
utilize the prior information on the surface gravities of WDs implied
by spectroscopic fitting. The benefits of such an approach are
particularly strong when applied to outliers, such as the candidate
halo and ultracool WDs identified by Vidrih et al. A reanalysis of
these samples confirms their results for the latter sample, but
suggests that most of the halo candidates are thick-disc WDs in the
tails of the photometric noise distribution.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 92 34 *Estimated H atmosphere model parameters of the
34 V07 candidate halo WDs, obtained using the
informative prior defined in Eq. (9)
table2.dat 92 34 *Estimated He atmosphere model parameters of the
34 V07 candidate halo WDs, obtained using the
informative prior defined in Eq. (9)
table3.dat 104 34 Model selection quantities for the 34 V07
candidate halo WDs
table4.dat 48 20 *Estimated model parameters of the 17 V07
candidate halo WDs with spectroscopic fits
presented by Eisenstein et al.
(2006, Cat. J/ApJS/167/40)
table5.dat 92 24 *Estimated H atmosphere model parameters of the
24 V07 candidate ultra-cool WDs, obtained
using the informative prior defined in Eq. (9)
table6.dat 92 24 *Estimated He atmosphere model parameters of the
24 V07 candidate ultra-cool WDs, obtained
using the informative prior defined in Eq. (9)
table7.dat 99 24 Model selection quantities for the 24 V07
candidate ultra-cool WDs
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Note on table1.dat, table2.dat, table5.dat, table6.dat: obtained using the
informative prior defined in Eq. (9),
Eq (9): PI(g, Teff,D)=PI(g)PI(Teff)PI(D),
i.e., the reduced prior is separable.
Note on table4.dat: Three WDs, SDSS J024837.53-003123.9,
SDSS J024837.53-003123.9 and SDSS J234110.13+003259.5, were observed twice.
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See also:
J/ApJS/167/40 : SDSS4 confirmed white dwarfs catalog (Eisenstein+, 2006)
Byte-by-byte Description of file: table[15].dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [SDSS]
6- 24 A19 --- SDSS SDSS name (JHHMMSS.ss+DDMMSS+s)
26- 32 E7.3 K Te(H) Effective temperature for H atmosphere
34- 40 E7.3 K e_Te(H) rms uncertainty on Teff
42- 45 F4.2 [cm/s2] logg(H) Surface gravity for H atmosphere
47- 50 F4.2 [cm/s2] e_logg(H) rms uncertainty on logg
52- 55 F4.2 Msun M(H) Mass for H atmosphere
57- 60 F4.2 Msun e_M(H) rms uncertainty on Mass
62- 69 E8.3 yr Age(H) Age for H atmosphere
71- 78 E8.3 yr e_Age(H) rms uncertainty on Age
80- 82 I3 pc r(H) Distance for H atmosphere
84- 85 I2 pc e_r(H) rms uncertainty in r(H)
87- 89 I3 km/s Vt(H) Tangential velocity for H atmosphere
91- 92 I2 km/s e_Vt(H) rms uncertainty on Vtan
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Byte-by-byte Description of file: table[26].dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [SDSS]
6- 24 A19 --- SDSS SDSS name (JHHMMSS.ss+DDMMSS+s)
26- 32 E7.3 K Te(He) Effective temperature for He atmosphere
34- 40 E7.3 K e_Te(He) rms uncertainty on Teff
42- 45 F4.2 [cm/s2] logg(He) Surface gravity for He atmosphere
47- 50 F4.2 [cm/s2] e_logg(He) rms uncertainty on logg
52- 55 F4.2 Msun M(He) Mass for He atmosphere
57- 60 F4.2 Msun e_M(He) rms uncertainty on Mass
62- 69 E8.3 yr Age(He) Age for He atmosphere
71- 78 E8.3 yr e_Age(He) rms uncertainty on Age
80- 82 I3 pc r(He) Distance for He atmosphere
84- 85 I2 pc e_r(He) rms uncertainty in r(He)
87- 89 I3 km/s Vt(He) Tangential velocity for He atmosphere
91- 92 I2 km/s e_Vt(He) rms uncertainty on Vtan
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Byte-by-byte Description of file: table[37].dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [SDSS]
6- 24 A19 --- SDSS SDSS name (JHHMMSS.ss+DDMMSS+s)
26- 29 F4.2 [cm/s2] gb(H) Best-fit log g values estimated using the
uninformative g prior for H (1)
31- 34 F4.2 [cm/s2] gb(He) Best-fit log g values estimated using the
uninformative g prior for He (1)
36- 40 F5.1 --- chi2(H) Miminum chi2 value for H
42- 46 F5.1 --- chi2(He) Miminum chi2 value for He
48- 54 E7.2 --- Ev(H) Evidence value for H (2)
56- 62 E7.2 --- Ev(He) Evidence value for He (2)
64- 70 E7.4 --- Pr(H) Probability that the WD atmosphere is H
72-104 A33 --- Notes Indicates whether the model selection result
is driven by the data, the informative g
prior, or the 10:1 model prior
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Note (1): UKIDSS data have been used where available
Note (2): Evidence is the integral over the Np model parameters.
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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- 4 A4 --- --- [SDSS]
6- 24 A19 --- SDSS SDSS name (JHHMMSS.ss+DDMMSS+s)
26- 27 A2 --- Type WD type
29- 32 F4.2 [cm/s2] logg Surface gravity
34- 37 F4.2 [cm/s2] e_logg rms uncertainty on logg
39- 43 I5 K Teff Effective temperature
45- 48 I4 K e_Teff rms uncertainty on Teff
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 09-Mar-2010