Optical Identification of Quasar 0917+7122 in the Direction of an Extreme-Ultraviolet Source

Abstract

We report the optical identification of an $R=18.3$ mag, $z=2.432$ quasar at the position of a 6 cm radio source and a faint \rosat PSPC X-ray source. The quasar lies within the error circles of unidentified extreme-UV (EUV) detections by the \euve and \rosat WFC all-sky surveys at $\sim 400$ Ã and $\sim 150$ Ã , respectively. A 21 cm H I emission measurement in the direction of the quasar with a $21^{\prime }$-diameter beam yields a total H I column density of $N_H=3.3\times 10^{20}$ cm${}^{-2}$, two orders of magnitude higher than the maximum allowed for transparency through the Galaxy in the EUV. The source of the EUV flux is therefore probably nearby ($\ltorder 100$ pc), and unrelated to the quasar.

9 pages, compressed, uuencoded postscript, including figures. Accepted by A&A (Research Note)