A survey of hot subdwarf pulsators in ω Cen

¹ ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
² Osservatorio Astronomico di Roma, Istituto Nazionale de Astrofisica, via Frascati 33, 0040 Monte Porzio Catone, Italy
³ Département de Physique, Université de Montréal, CP. 6128, Succ. Centre-Ville, Montréal, QC H3C 3J7, Canada
⁴ Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
⁵ Instituto de Astrofísica de Canarias, Calle Via Lactea s/n, 38205 La Laguna, Tenerife, Spain
⁶ Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain
⁷ Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
⁸ Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago, Chile
⁹ The Milky Way Millennium Nucleus, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago, Chile
¹⁰ Department of Physics, Università di Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Rome, Italy
¹¹ Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
¹² Department of Physics, University of Warwick, Coventry CV4 7AL, UK

Abstract

We recently discovered an apparently new class of pulsating Extreme Horizontal Branch (EHB) star in ω Cen. Tightly clustered around ∼50,000 K, these H-rich sdO stars exhibit rapid, multi-periodic oscillations on a timescale of 100 s. While four such objects have been detected in ω Cen, no counterparts have yet been found among the field population. Conversely, the rapid sdB pulsators around 31,000 K that are well-studied in the Galactic field have yet to be found in a globular cluster. We discuss the implications of this and also report the discovery of a fifth EHB pulsator in ω Cen.