Detection of Long-Period Variations in the Subdwarf B Star PG 0101+039 on the Basis of Photometry from the MOST Satellite

Details Detection of Long-Period Variations in the Subdwarf B Star PG 0101+039 on the Basis of Photometry from the MOST Satellite Detection of Long-Period Variations in the Subdwarf B Star PG 0101+039 on the Basis of Photometry from the MOST Satellite

Nov 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005apj...633..460r&link_type=abstract

The Astrophysical Journal, Volume 633, Issue 1, pp. 460-464.

Astronomy and Astrophysics

Astronomy

19

Stars: Interiors, Stars: Oscillations, Stars: Subdwarfs

Scientific paper

We report the detection of three discrete pulsation frequencies in the long-period variable subdwarf B star PG 0101+039 on the basis of ~400 hr of MOST wide-band photometry. The periodicities uncovered lie at 7235, 5227, and 2650 s, respectively, and are associated with amplitudes between 0.03% and 0.06% of the mean brightness, lower than those measured in any other variable of this kind. We also find evidence for luminosity variations consistent with an ellipsoidal deformation of the subdwarf in the rotationally locked short-period binary system predicted from radial velocity measurements and evolutionary models. Our atmospheric modeling of two independent time-averaged optical spectra of PG 0101+039 yields Teff~=28,300 K and logg~=5.52, making it one of the hottest long-period variable subdwarf B stars known. The fact that we nevertheless detect brightness variations in the data is in conflict with predictions from current models, which place the theoretical blue edge for observable long-period instabilities at a temperature around 4000 K cooler than that of PG 0101+039.
Based on data from MOST, a Canadian Space Agency mission operated jointly by Dynacon, Inc., the University of Toronto Institute of Aerospace Studies, and the University of British Columbia, with assistance from the University of Vienna.
Observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution.

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