[ITAL]EXTREME ULTRAVIOLET EXPLORER[/ITAL][ITAL]Extreme Ultraviolet Explorer[/ITAL] Optical Identification Campaign. IV. A Northern Hemisphere Sample of Active Late-Type Stars and Typical EUV Sources

Abstract

We present new optical identiÐcations of previously unidentiÐed faint extreme ultraviolet sources. Our total sample of 30 identiÐed sources, of which 22 are new identiÐcations, includes 24 late-type stars, three white dwarfs, two cataclysmic variables (CVs), and one active galactic nucleus. These sources are joint detections of the faint sources from the all-sky surveys of the Extreme Ultraviolet Explorer (EUV E) in the 58È174 (0.071È0.214 keV) EUV band and of the ROSAT Position Sensitive Proportional Counter A in the 5È120 (0.1È2.4 keV) X-ray band. We obtained medium-resolution spectra of the possible optical A counterparts with the Shane 3 m telescope at Lick Observatory using the Kast double spectrograph covering a bandpass of 3600È7500 Our sample of active late-type stars is dominated by K and M A. stars showing strong Balmer and Ca II emission lines. The white dwarfs are fairly typical for those detected in the EUV E survey with and log g ranging from 35 to 53 kK and 7.6 to 8.7, respectively. T eff We found strong H and He emission lines typical of cataclysmic variables (CVs) for EUVE J0854]390 and EUVE J1802]180. EUVE J0854]390 is a newly identiÐed cataclysmic variable showing radial velocity shifts to the red as large as B400 km s~1. We associate EUVE J1802]180 with the previously identiÐed CV, V884 Her (RX J1802.1]1804). Including the present work (22 new identiÐcations), EUV E optical identiÐcation campaigns have identiÐed B28% of the presently cataloged NOID sources.

Chromospheric activity, lithium and radial velocities of single late-type stars possible members of young moving groups

“…These variations can be associated with photospheric spots that disturb the line profile of this rapidly rotating star. Bidelman (1985) and Christian et al (2001) reported moderate Ca ii H & K emission and the Hα line in emission in this star. Chromospheric and transition region UV emission fluxes have been reported by Ambruster et al (1998) and Wood et al (2000).…”

Rotational modulation of the photospheric and chromospheric activity in the young, single K2-dwarf PW And

“…It was included in the Henry Draper Catalogue as a G5 type star. However, other studies show that the spectral type is more similar to the Fehrenbach & Burnage (1982) classification of PW And as K3 while Christian et al (2001) have it as a K0 type star with emission. No clear luminosity classification has been proposed but Hooten & Hall (1990) suggest it is a main sequence star due to its short-period photometric variations (P ∼ 1.75 days).…”

“…Chromospheric and transition region UV emission fluxes have been reported by Ambruster et al (1998) and Wood et al (2000). In addition, it has been detected by the ROSAT-satellite as the 2RE J001820+305 source (Pye et al 1995;Kreysing et al 1995;Thomas et al 1998;Rutledge et al 2000), and by the EUVE-satellite as the EUVE J0018+309 source (Malina et al 1994;Christian et al 2001).…”

“…No clear luminosity classification has been proposed but Hooten & Hall (1990) suggest it is a main sequence star due to its short-period photometric variations (P ∼ 1.75 days). Christian et al (2001) identify the EUVE source EUVE J0018+308 as PW And. This star was classified as a neighborhood Pleiades-age K2 dwarf by Ambruster et al (1998).…”

Cataclysmic Variables from Sloan Digital Sky Survey. IV. The Fourth Year (2003)

“…Christian et al (2001) showed three spectra of this source that also reveal large variability. Their spectra all have about a factor of 10 larger flux than the SDSS spectrum and have much stronger He ii, implying a higher state of accretion at that time.…”