Extreme Ultraviolet Explorer optical identification campaign. IV. A northern hemisphere sample of active late-type stars and typical EUV sources

We present new optical identifications of previously unidentified faint ext reme ultraviolet sources. Our total sample of 30 identified sources, of whi ch 22 are new identifications, includes 24 late-type stars, three white dwa rfs, two cataclysmic variables (CVs), and one active galactic nucleus. Thes e sources are joint detections of the faint sources from the all-sky survey s of the Extreme Ultraviolet Explorer (EUV E) in the 58-174 Angstrom (0.071 -0.214 keV) EUV band and of the ROSAT Position Sensitive Proportional Count er in the 5-120 Angstrom (0.1-2.4 keV) X-ray band. We obtained medium-resol ution spectra of the possible optical counterparts with the Shane 3 m teles cope at Lick Observatory using the Kast double spectrograph covering a band pass of 3600-7500 Angstrom Our sample of active late-type stars is dominate d by K and M stars showing strong Balmer and Ca II emission lines. The whit e dwarfs are fairly typical for those detected in the EUV E survey with T-e ff and log g ranging from 35 to 53 kK and 7.6 to 8.7, respectively. We foun d 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 identified ca taclysmic variable showing radial velocity shifts to the red as large as ap proximate to 400 km s(-1). We associate EUVE J1802+180 with the previously identified CV, V884 Her (RX J1802.1+1804). Including the present work (22 n ew identifications), EUV E optical identification campaigns have identified approximate to 28% of the presently cataloged NOID sources.