Free access article

A&A 369, 986-992 (2001)
DOI: 10.1051/0004-6361:20010181

CCD-based observations of PG 0856+121 and a theoretical analysis of its oscillation modes

A. Ulla¹, M. R. Zapatero Osorio^{2, 3}, F. Pérez Hernández^{2, 4} and J. MacDonald<sup>5

1</sup>  Universidade de Vigo, Departamento de Física Aplicada, Área de Física da Terra, Astronomía e Astrofísica, Facultade de Ciencias, Campus Lagoas-Marcosende, 36200 Vigo, Spain
²  Instituto de Astrofísica de Canarias, c/ Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain
³  CALTECH, MS 150-21, Pasadena, CA 91125, USA
⁴  Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain
⁵  Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA

(Received 5 July 2000 / Accepted 29 January 2001 )

Abstract
BVRI CCD-based and near-IR (J) imaging, together with unfiltered photometry of the hot subdwarf B star PG 0856+121, are reported. Two close, faint, red, point-like sources are resolved. They account for the previously reported IR excess observed in this hot subdwarf. In addition, the new unfiltered differential photometry of PG 0856+121 confirms its previously reported pulsational nature. A comparison with the oscillation modes of stellar models suggests the presence of g modes.

Key words: binaries: close -- stars: individual: PG 0856+121 -- stars: oscillations -- subdwarfs

Offprint request: A. Ulla, ulla@uvigo.es

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