Query : 2007A&A...461..585O

2007A&A...461..585O - Astronomy and Astrophysics, volume 461, 585-591 (2007/1-2)

PG1657+416: a new fast pulsating sdB star. Photometric observations and theoretical model comparison.


Abstract (from CDS):

Since the discovery in 1997 of stellar oscillations in some B-type hot subdwarfs (sdBs), much effort is being made both observationally and theoretically to characterize this new group of pulsating objects. To increase the number of members of such pulsators and to perform a theoretical analysis of new pulsating stars.The Nordic Optical Telescope was used to measure the brightness as function of time for a list of selected sdBs. Pulsator candidates were selected by deriving the effective temperatures and gravities of sdB stars from various spectroscopic surveys, and picking targets in the instability region. Pulsational properties were investigated by Fourier analysis. For the theoretical analysis, the predicted frequencies of sdB structural models in the Teff-logg region of interest were computed.From our list of candidates we detected one, PG1657+416, as a new oscillating star. Follow-up photometry revealed at least four frequencies in the range 6.9-7.9mHz, whose amplitudes vary from one data set to another. The theoretical comparison indicates that the observed periods are well reproduced by structural models whose physical parameters are in good agreement with the effective temperature and gravity estimates from a spectral energy distribution fit, which also shows that the sdB has a G5 main sequence companion with Teff∼5500K.

Abstract Copyright:

Journal keyword(s): stars: early-type - stars: subdwarfs - stars: oscillations - stars: individual: PG 1657+416

Simbad objects: 4

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Number of rows : 4
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 PG 1219+534 HS* 12 21 29.0914917288 +53 04 36.796062144   12.41       sdB 81 1
2 PG 1618+563B * 16 19 26.5988937384 +56 05 58.593549588   12.16 12.34 12.71   F3 13 0
3 PG 1657+416 HS* 16 58 41.8362739056 +41 31 15.512739888   16.07 16.23 16.45   sdB 13 0
4 V* LS Dra HS* 18 24 52.4115107856 +57 47 23.528193612           sdOB 18 0

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