J/ApJ/934/36 IR-faint WDs from Gaia, NIR phot. and opt. sp. (Bergeron+, 2022)
On the nature of ultracool white dwarfs: not so cool after all.
Bergeron P., Kilic M., Blouin S., Bedard A., Leggett S.K., Brown W.R.
<Astrophys. J., 934, 36 (2022)>
=2022ApJ...934...36B 2022ApJ...934...36B
ADC_Keywords: Stars, white dwarf; Photometry, ugriz; Spectra, optical
Keywords: White dwarf stars ; Stellar properties ; Hertzsprung Russell diagram ;
Stellar remnants ; Stellar atmospheric opacity
Abstract:
A recent analysis of the 100pc white dwarf sample in the SDSS
footprint demonstrated for the first time the existence of a
well-defined ultracool --or IR-faint-- white dwarf sequence in the
Hertzsprung-Russell diagram. Here we take advantage of this discovery
to enlarge the IR-faint white dwarf sample threefold. We expand our
selection to the entire Pan-STARRS survey footprint as well as the
Montreal White Dwarf Database 100pc sample and identify 37 candidates
with strong flux deficits in the optical. We present follow-up Gemini
optical spectroscopy of 30 of these systems and confirm all of them as
IR-faint white dwarfs. We identify an additional set of 33 objects as
candidates based on their colors and magnitudes. We present a detailed
model atmosphere analysis of all 70 newly identified IR-faint white
dwarfs together with 35 previously known objects reported in the
literature. We discuss the physics of model atmospheres and show that
the key physical ingredient missing in our previous generation of
model atmospheres was the high-density correction to the He-
free-free absorption coefficient. With new model atmospheres
calculated for the purpose of this analysis, we now obtain
significantly higher effective temperatures and larger stellar masses
for these IR-faint white dwarfs than the Teff and M values reported
in previous analyses, thus solving a two-decade-old problem. In
particular, we identify in our sample a group of ultramassive white
dwarfs in the Debye cooling phase with stellar parameters never
measured before.
Description:
We obtained optical spectroscopy (range 3730-6920Å, with a
resolution of 2.05Å per pixel and range 4770-7980Å) for
12 targets using the 8-m Gemini North telescope equipped with the
Gemini Multi-Object Spectrograph (GMOS) as part of the program
GN-2020B-FT-104. We observed 18 additional objects as part of the
queue programs GN-2021A-Q-203 and GS-2021A-Q-300 with a central
wavelength of 6350Å. In total, we obtained spectra for
30 candidates at Gemini. See Section 3.
We use the photometric technique as detailed in
Bergeron+ (2019ApJ...876...67B 2019ApJ...876...67B) and follow the same approach and use
the SDSS u, Pan-STARRS grizy photometry, and Gaia EDR3 parallaxes to
analyze 105 IR-faint white dwarfs (WDs). See Sections 4 and 6.
In particular, we identified 37 new IR-faint white dwarfs with strong
flux deficits in the optical, 30 of which have follow-up Gemini
optical spectroscopy, and 33 additional white dwarfs with milder deficits.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 136 37 Newly identified IR-faint white dwarfs with strong
flux deficits in the optical bands
table3.dat 78 33 Additional IR-faint white dwarf candidates
table4.dat 58 106 *Best-fit parameters for IR-faint white dwarfs
sp/* . 30 Individual spectra in ASCII format
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Note on table4.dat: As discussed in Section 5.3, we provide in Table 4 two
solutions for J1238+3502, including one with the J magnitude omitted
from the fit (see Figure 20). In both cases, the solutions appear way
too cool for the inferred mass, which leads to cooling ages that are
largely extrapolated. See Section 6.2.
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See also:
B/wd : Spectroscopically identified white dwarfs (McCook+, 2014)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
II/367 : The VISTA Hemisphere Survey (VHS) catalog DR5 (McMahon+, 2020)
V/154 : Sloan Digital Sky Surveys (SDSS), Release 16 (DR16) (Ahumada+, 2020)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
II/371 : The Dark Energy Survey (DES): Data Release 2 (Abbott+, 2021)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/other/Sci/292.698 : Candidate halo dark matter (Oppenheimer+, 2001)
J/AJ/131/582 : Cool white dwarfs in the SDSS (Kilic+, 2006)
J/ApJ/663/1291 : DZ stars in SDSS DR4 (Dufour+, 2007)
J/A+A/465/249 : Age and colors of massive white dwarf stars (Althaus+, 2007)
J/ApJS/190/77 : Detailed analysis of cool WDs in the SDSS (Kilic+, 2010)
J/A+A/557/A19 : Mass & age of extreme low-mass white dwarfs (Althaus+, 2013)
J/other/SCPMA/57.176 : Carbon stars & DZ white dwarfs in SDSS sp. (Si+ 2014)
J/MNRAS/449/3966 : Ultracool white dwarfs (Gianninas+, 2015)
J/A+A/595/A35 : Low-mass helium WDs evolutionary models (Istrate+, 2016)
J/MNRAS/467/4970 : Cool DZ white dwarfs. I. (Hollands+, 2017)
J/A+A/616/A10 : Open clusters GaiaDR2 HR diagrams (Gaia Collaboration, 2018)
J/ApJS/239/26 : NOFS measurements for distant WDs (Leggett+, 2018)
J/ApJ/872/199 : Cand. spectrophotometric standard DA WDs (Calamida+, 2019)
J/ApJ/878/63 : Cool WD atm. models. IV. Spectral evolution (Blouin+, 2019)
J/ApJ/901/93 : Model atm. analysis of hot WDs from SDSS (Bedard+, 2020)
J/ApJ/898/84 : Sp. follow-up of 100pc WDs in SDSS & Gaia (Kilic+, 2020)
J/MNRAS/497/130 : Gaia white dwarfs within 40pc. I (Tremblay+, 2020)
J/MNRAS/499/1890 : Gaia white dwarfs within 40pc. II. (McCleery+, 2020)
http://www.montrealwhitedwarfdatabase.org/ : Montreal WD database homepage
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 White dwarf identifier (JHHMM+DDMM)
12- 20 A9 --- --- [Gaia EDR3]
22- 40 I19 --- Gaia Gaia EDR3 identifier
42- 46 F5.2 mas plx [8.49/30.64] Gaia EDR3 parallax
48- 52 F5.1 mas/yr pm [22.3/487.7] Gaia EDR3 proper motion
54- 75 A22 --- OName Pan-STARRS or DES identifier
77- 81 F5.2 mag gmag [18.2/21.1] Apparent g band AB magnitude (1)
83- 87 F5.2 mag rmag [17.77/20.64] Apparent r band AB magnitude (1)
89- 93 F5.2 mag imag [17.88/21.1]? Apparent i band AB magnitude (1)
95- 99 F5.2 mag zmag [18.2/21.62]? Apparent z band AB magnitude (1)
101-105 F5.2 mag ymag [18.4/21.3]? Apparent y band AB magnitude (1)
107-108 A2 --- SpT White dwarf spectral type ("DC" or
1 occurrence of "DZ")
110-115 A6 --- Inst Spectral source (2)
117-136 A20 --- FileName Name of the spectrum file in subdirectory "sp";
column added by CDS
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Note (1): From Pan-STARRS or Dark Energy Survey.
Note (2): Source as follows:
Gemini = 8-m Gemini North telescope with Multi-Object Spectrograph (GMOS)
observations; see the "Description" section.
SDSS = Sloan Digital Sky Survey spectroscopy (Gates+ 2004ApJ...612L.129G 2004ApJ...612L.129G
and Harris+ 2008ApJ...679..697H 2008ApJ...679..697H).
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name White dwarf identifier (JHHMM+DDMM)
12- 19 A8 --- --- [Gaia DR2]
21- 39 I19 --- Gaia Gaia EDR3 identifier
41- 42 A2 --- SpT Spectral type
44- 48 F5.2 mas plx [9.6/28.3] Gaia EDR3 parallax
50- 54 F5.2 mag gmag [18.2/20.62] Apparent g band AB magnitude (1)
56- 60 F5.2 mag rmag [17.7/20.1] Apparent r band AB magnitude (1)
62- 66 F5.2 mag imag [17.5/20.02] Apparent i band AB magnitude (1)
68- 72 F5.2 mag zmag [17.59/20.21] Apparent z band AB magnitude (1)
74- 78 F5.2 mag ymag [17.7/20.64]? Apparent y band AB magnitude (1)
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Note (1): From Pan-STARRS or Dark Energy Survey.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name White dwarf identifier
12- 15 I4 K Teff [3021/5561] Effective temperature
17- 20 I4 K e_Teff [17/3639]? Uncertainty in Teff
22- 26 F5.3 Msun Mass [0.2/1.3] Mass
28- 32 F5.3 Msun E_Mass [0/0.08] Upper uncertainty in Mass
34- 38 F5.3 Msun e_Mass [0/0.1] Lower uncertainty in Mass
40- 44 F5.2 [-] logH/He [-4.8/0.2] log H/He number abundance
46- 51 F6.3 [Lsun] logL [-5.1/-3.7] log luminosity
53- 58 F6.3 Gyr CAge [3.6/23.96] Cooling age
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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1- 16 F16.11 0.1nm lambda Wavelength in Angstroms
18- 30 E13.8 mW/m2/Hz Flux Flux, f_nu, in ergs/cm2/s/Hz
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Acknowledgements:
Pierre Bergeron [pierre.bergeron.1 at umontreal.ca]
History:
From electronic version of the journal for the tables
Spectra were kindly sent by the author and are also available on:
http://www.montrealwhitedwarfdatabase.org/
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 14-May-2024