Faint Sources in the EUVE Survey: Identification of White Dwarfs, Active Late-Type Stars and Galactic Nuclei

E. Polomski, S. Vennes, J.R. Thorstensen, M. Mathioudakis, and E.E. Falco

To appear in Astrophysical Journal. [CEA publication #785]

Abstract

We report the classification of 23 new extreme ultraviolet sources from the Lampton et al. (1997) catalog. The optical spectra presented identify the objects as 14 active late-type stars (including a possible T Tauri star), three white dwarf stars, and six active galactic nuclei (a Seyfert galaxy, a BL Lac object 1ES 1028+511 [or EUVE J1031+508], and four quasi-stellar objects). We have detected Ca II absorption lines in the BL Lac object and measured its redshift. Two of the white dwarf stars are unusually massive (M > 1.1 M_sun. Our sample of late-type stars includes five previously known high proper motion objects (EUVE J1004+503, EUVE J2244-332A+B, EUVE J1802+642, EUVE J1131-346) of which one is the well known flare star TX PsA (EUVE J2244-332B). We report an unusually high level of activity for the primary component of the TX PsA system (EUVE J2244-332A), which may indicate flare activity. The group of late-type stars is on average almost 3 magnitudes fainter ( ~ 13) than the typical member of the Extreme Ultraviolet Explorer (EUVE) all-sky survey catalog (Bowyer et al. 1994). All Galactic and extragalactic objects were also detected in the Rontgen Satellite (ROSAT) Position Sensitive Proportional Counter (PSPC) survey, and most are at the faint limit of the EUVE detectors. These identifications expand the list of known EUV sources to 557 and increase the list of detected extragalactic sources by nearly a third (from 22 to 28).

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