2018A&A...617A...6B


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.04CEST00:43:14

2018A&A...617A...6B - Astronomy and Astrophysics, volume 617A, 6-6 (2018/9-1)

The McDonald Observatory search for pulsating sdA stars. Asteroseismic support for multiple populations.

BELL K.J., PELISOLI I., KEPLER S.O., BROWN W.R., WINGET D.E., WINGET K.I., VANDERBOSCH Z., CASTANHEIRA B.G., HERMES J.J., MONTGOMERY M.H. and KOESTER D.

Abstract (from CDS):


Context. The nature of the recently identified "sdA" spectroscopic class of stars is not well understood. The thousands of known sdAs have H-dominated spectra, spectroscopic surface gravity values between main sequence stars and isolated white dwarfs, and effective temperatures below the lower limit for He-burning subdwarfs. Most are likely products of binary stellar evolution, whether extremely low-mass white dwarfs and their precursors or blue stragglers in the halo.
Aims. Stellar eigenfrequencies revealed through time series photometry of pulsating stars sensitively probe stellar structural properties. The properties of pulsations exhibited by sdA stars would contribute substantially to our developing understanding of this class.
Methods. We extend our photometric campaign to discover pulsating extremely low-mass white dwarfs from the McDonald Observatory to target sdA stars classified from SDSS spectra. We also obtain follow-up time series spectroscopy to search for binary signatures from four new pulsators.
Results. Out of 23 sdA stars observed, we clearly detect stellar pulsations in 7. Dominant pulsation periods range from 4.6min to 12.3h, with most on timescales of approximately one hour. We argue specific classifications for some of the new variables, identifying both compact and likely main sequence dwarf pulsators, along with a candidate low-mass RR Lyrae star.
Conclusions. With dominant pulsation periods spanning orders of magnitude, the pulsational evidence supports the emerging narrative that the sdA class consists of multiple stellar populations. Since multiple types of sdA exhibit stellar pulsations, follow-up asteroseismic analysis can be used to probe the precise evolutionary natures and stellar structures of these individual subpopulations.

Abstract Copyright: © ESO 2018

Journal keyword(s): stars: oscillations - stars: variables: general - subdwarfs - white dwarfs - Galaxy: stellar content

VizieR on-line data: <Available at CDS (J/A+A/617/A6): stars.dat list.dat lc/*>

Simbad objects: 12

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Number of rows : 12

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 V* ZZ Cet WD* 01 36 13.6155835488 -11 20 32.631811638   14.328 14.16 14.4   DA4.0 260 0
2 [DCD2013] CSS J075644.3+502741 RR* 07 56 44.3458977332 +50 27 40.958204096     16.68     ~ 3 0
3 SDSS J082900.96+084645.4 BS* 08 29 00.9609438287 +08 46 45.509834217           ~ 2 0
4 SDSS J093003.42+054815.5 BS* 09 30 03.4254085736 +05 48 15.652571488           ~ 2 0
5 LINEAR 1781225 dS* 11 31 43.4583011257 -07 42 20.402943534           ~ 2 0
6 CHSS 1999 HB* 11 42 24.6192474949 +37 47 03.630704554           A9.9 3 0
7 SDSS J131011.60-014233.1 BS* 13 10 11.6071247648 -01 42 33.070810946           ~ 2 0
8 UCAC2 33946702 Pu* 16 04 10.8108396469 +06 27 05.541077660   15.13 14.73 14.83   ~ 1 0
9 SDSS J161831.69+385415.1 WD* 16 18 31.6880253224 +38 54 15.208581739   20.0   20.1   DA 7 0
10 OGLE BLG-ECL-108266 RR* 17 47 38.2072770984 -35 31 07.161960373     17.079   15.734 ~ 29 0
11 SDSS J223716.61+052228.3 WD* 22 37 16.6145414627 +05 22 28.497693385           DA 2 0
12 SDSS J223831.91+125318.3 HB* 22 38 31.9118699691 +12 53 18.318512833           ~ 3 0

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2020.07.04-00:43:14

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