Radial velocities of pulsating subdwarf B stars: KPD 2109+4401 and PB 8783 |
| |
Authors: | C. Simon Jeffery Don Pollacco |
| |
Affiliation: | Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland;Isaac Newton Group, Apartado de correos 321, E‐38700 Santa Cruz de la Palma, Tenerife, Spain; Queens University Belfast, Belfast BT7 1NN |
| |
Abstract: | High-speed spectroscopy of two pulsating subdwarf B stars, KPD 2109+4401 and PB 8783, is presented. Radial motions are detected with the same frequencies as reported from photometric observations and with amplitudes of ∼2 km s−1 in two or more independent modes. These represent the first direct observations of surface motion arising from multimode non-radial oscillations in subdwarf B stars. In the case of the sdB+F binary PB 8783, the velocities of both components are resolved; high-frequency oscillations are found only in the sdB star and not the F star. There also appears to be evidence for mutual motion of the binary components. If confirmed, it implies that the F-type companion is ≳1.2 times more massive than the sdB star, while the amplitude of the F-star acceleration over 4 h would constrain the orbital period to lie between 0.5 and 3.2 d. |
| |
Keywords: | stars: individual: KPD 2109+4401 stars: individual: PB 8783 stars: oscillations subdwarfs stars: variables: other |
|
|