Reed, M. D.; Baran, A. S.; Østensen, R. H.; Telting, J. H.; Kern, J. W.; Bloemen, S.; Blay, P.; Pursimo, T.; Kuutma, T.; Slumstrup, D.; Saajasto, M.; Nielsen, L. D.; Harmanen, J.; Winans, A. J.; Foster, H. M.; Rowe, L.
A pulsation analysis of K2 observations of the subdwarf B star PG 1142-037 during Campaign 1: A subsynchronously rotating ellipsoidal variable,
Monthly Notices of the Royal Astronomical Society, Vol. 458, Issue 2.
We report a new subdwarf B pulsator, PG 1142-037, discovered during the first full-length campaign of K2, the two-gyro mission of the Kepler space telescope. 14 periodicities have been detected between 0.9 and 2.5 hr with amplitudes below 0.35 parts-per-thousand.
We have been able to associate all of the pulsations with low-degree, ℓ ≤ 2 modes. Follow-up spectroscopy of PG 1142 has revealed it to be in a binary with a period of 0.54 d. Phase-folding the K2 photometry reveals a two-component variation including both Doppler boosting and ellipsoidal deformation. Perhaps the most surprising and interesting result is the detection of an ellipsoidal, tidally distorted variable with no indication of rotationally induced pulsation multiplets. This indicates that the rotation period is longer than 45 d, even though the binary period is near 13 h.
Key words: stars: oscillations / subdwarfs