Spectroscopic and photometric studies of white dwarfs in the Hyades

¹ Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, 69117 Heidelberg, Germany
e-mail: ptremblay@lsw.uni-heidelberg.de; hludwig@lsw.uni-heidelberg.de
² Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstrasse 12 − 14, 69120 Heidelberg, Germany
e-mail: elena@ari.uni-heidelberg.de; roeser@ari.uni-heidelberg.de; jordan@ari.uni-heidelberg.de
³ Max-Planck-Institut für Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
e-mail: goldman@mpia.de

Received: 19 July 2012
Accepted: 18 September 2012

Abstract

The Hyades cluster is known to harbour ten so-called classical white dwarf members. Numerous studies through the years have predicted that more than twice this amount of degenerate stars should be associated with the cluster. Using the PPMXL Catalog of proper motions and positions, a recent study proposed 17 new white dwarf candidates. We review the membership of these candidates by using published spectroscopic and photometric observations, as well as by simulating the contamination from field white dwarfs. In addition to the ten classical Hyades white dwarfs, we find six white dwarfs that may be of Hyades origin and three more objects that have an uncertain membership status due to their unknown or imprecise atmospheric parameters. Among those, two to three are expected as field stars contamination. Accurate radial velocity measurements will confirm or reject the candidates. One consequence is that the longstanding problem that no white dwarf older than  ~340 Myr appears to be associated with the cluster remains unsolved.