An AGN sample with high X-ray-to-optical flux ratio from RASS

J. Y. Wei; D. W. Xu; X. Y. Dong; J. Y. Hu

doi:10.1051/aas:1999514

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Volume 139 / No 3 (November I 1999)

Astron. Astrophys. Suppl. Ser., 139 3 (1999) 575-599

Abstract

Free Access

Issue		Astron. Astrophys. Suppl. Ser. Volume 139, Number 3, November I 1999


Page(s)		575 - 599
DOI		https://doi.org/10.1051/aas:1999514
Published online		15 November 1999

Astron. Astrophys. Suppl. Ser. 139, 575-599 (1999)

I. The optical identification

J. Y. Wei¹^,2, D. W. Xu¹^,2, X. Y. Dong¹^,2 and J. Y. Hu¹^,2

¹ Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100012, PR China
² National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China

Received: 21 June 1999
Accepted: 26 August 1999

Abstract

We present the first results of a program to identify the unknown bright active galactic nuclei (AGN) in the ROSAT All Sky Survey Bright Source Catalog (RASS-BSC). We have used as an alternative expression for , where C is X-ray count rate and R stands for R magnitude. Then a high X-ray-to-optical flux ratio criterion has been used to select an AGN sample with 165 unidentified X-ray sources for optical spectroscopy. Those 165 X-ray sources have been identified in the following classes: 115 emission line AGN (QSOs and Seyferts), 2 BL Lac objects and 4 BL Lac candidates, 22 clusters of galaxies, 12 Galactic stars and 10 objects remain unidentified. This represent a success rate of about 73% for detecting AGN using our selection criteria. Plausibility is based upon the optical classification and X-ray characteristics of the sources.

Key words: surveys / X-rays: general / X-rays: galaxies / galaxies: active