J/MNRAS/475/2480 Extremely-low mass white dwarf star (Pelisoli+, 2018)
The sdA problem. I. Physical properties.
Pelisoli I., Kepler S.O., Koester D.
<Mon. Not. R. Astron. Soc., 475, 2480-2495 (2018)>
=2018MNRAS.475.2480P 2018MNRAS.475.2480P (SIMBAD/NED BibCode)
ADC_Keywords: Stars, dwarfs ; Stars, subdwarf ; Stars, white dwarf ;
Effective temperatures
Keywords: binaries: general - stars: evolution -
stars: kinematics and dynamics - subdwarfs - white dwarfs
Abstract:
The so-called sdA stars are defined by having H-rich spectra and
surface gravities similar to hot subdwarf stars, but effective
temperature below the zero-age horizontal branch. Their evolutionary
history is an enigma: their surface gravity is too high for
main-sequence stars, but too low for single evolution white dwarfs.
They are most likely byproducts of binary evolution, including
blue-stragglers, extremely-low mass white dwarf stars (ELMs) and their
precursors (pre-ELMs). A small number of ELMs with similar properties
to sdAs is known. Other possibilities include metal-poor A/F dwarfs,
second generation stars, or even stars accreted from dwarf galaxies.
In this work, we analyse colours, proper motions, and spacial
velocities of a sample of sdAs from the Sloan Digital Sky Survey to
assess their nature and evolutionary origin. We define a probability
of belonging to the main sequence and a probability of being a
(pre-)ELM based on these properties. We find that 7 per cent of the
sdAs are more likely to be (pre-)ELMs than main-sequence stars.
However, the spacial velocity distribution suggests that over 35 per
cent of them cannot be explained as single metal-poor A/F stars.
Description:
We have analysed a sample of narrow-line hydrogen spectra identified
in the SDSS, estimating Teff and logg from their spectra using new
spectral models derived from solar abundance atmospheric models.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 63 408 Obtained values of Teff and logg for the 408
analysed SDSS objects in the range
5.5≤logg<7.0 and 7000≤Teff≤20000K
table2.dat 66 1150 Objects with a higher probability of being
(pre-)ELM compared to main sequence
tablec1.dat 50 62 Objects for which our fit indicated Teff>20000K and
logg<6.5, which are possible hot subdwarfs not
listed in Geier et al. (2017, Cat. J/A+A/600/A50)
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See also:
J/A+A/600/A50 : Catalog of hot subdwarf stars (Geier+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- SDSS SDSS designation (HHMMSS.ss+DDMMSS.s)
20- 34 A15 --- PMF SDSS Plate-MJD-Fiber identifier
36- 41 F6.2 --- SNRg Signal-to-noise ratio in g band
43- 47 I5 K Teff Effective temperature
49- 51 I3 K e_Teff rms uncertainty on Teff (1)
53- 57 F5.3 [cm/s2] logg Surface gravity
59- 63 F5.3 [cm/s2] e_logg rms uncertainty on logg (1)
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Note (1): The quoted uncertainties are formal fitting errors; external
uncertainties in the models are 5-10 per cent in Teff and 0.25dex in logg.
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- SDSS SDSS designation (HHMMSS.ss+DDMMSS.s)
20- 34 A15 --- PMF SDSS Plate-MJD-Fiber identifier
36- 40 I5 K Teff Effective temperature
42- 44 I3 K e_Teff rms uncertainty on Teff
46- 50 F5.3 [cm/s2] logg Surface gravity
52- 56 F5.3 [cm/s2] e_logg rms uncertainty on logg
58- 61 F4.2 --- pMS Probability of being main sequence
63- 66 F4.2 --- pELM Probability of being extremely-low mass
white dwarf star (ELM)
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Byte-by-byte Description of file: tablec1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- SDSS SDSS designation (HHMMSS.ss+DDMMSS.s)
20- 34 A15 --- PMF SDSS Plate-MJD-Fiber identifier
35 A1 --- --- [,]
36- 50 A15 --- PMF2 Second SDSS Plate-MJD-Fiber identifier
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History:
From electronic version of the journal
References:
Pelisoli et al., Paper II 2018MNRAS.478..867P 2018MNRAS.478..867P
Pelisoli et al., Paper III 2019MNRAS.482.3831P 2019MNRAS.482.3831P
(End) Patricia Vannier [CDS] 08-Apr-2021