The ROSAT deep survey. II. Optical identification, photometry and spectra of X-ray sources in the Lockman field

M. Schmidt, G. Hasinger, J. Gunn, D. Schneider, R. Burg, R. Giacconi, I. Lehmann, J. MacKenty, J. Trumper, G. Zamorani

Research output: Contribution to journalArticlepeer-review

Abstract

The ROSAT Deep Survey includes a complete sample of 50 X-ray sources with fluxes in the 0.5 - 2 keV band larger than 5.510(-15) erg cm(-2) s(-1) in the Lockman field (Hasinger et al., Paper I). We have obtained deep broad-band CCD images of the field and spectra of many optical objects near the positions of the X-ray sources. We define systematically the process leading to the optical identifications of the X-ray sources. For this purpose, we introduce five identification (ID) classes that characterize the process in each case. Among the 50 X-ray sources, we identify 39 AGNs, 3 groups of galaxies, 1 galaxy and 3 galactic stars. Four X-ray sources remain unidentified so far; two of these objects may have an unusually large ratio of X-ray to optical flux.
Original languageEnglish (US)
Pages (from-to)495-503
JournalAstronomy and Astrophysics
Volume329
StatePublished - Jan 1 1998
Externally publishedYes

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