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Astron. Astrophys. 318, L67-L70 (1997)

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1. Introduction

The phenomenon of gravitational lensing allows a new insight into many fundamental astrophysics problems: dark matter problem (Tyson et al. 1990), value of [FORMULA] (Chang & Refsdal 1979), existence of a cosmological constant (Fukugita & Turner 1991), etc.

The Second Byurakan Survey (SBS) is a low resolution objective prism survey with a limiting magnitude of [FORMULA]. It covers 1000 square degrees in the range [FORMULA] and [FORMULA]. The observing techniques and selection criteria for the SBS objects are described by Markarian & Stepanian (1983). Data for 7 fields of the SBS have been published (Stepanian et al. 1990 and references therein), the data for the remaining 58 fields will be presented in the General Catalog of SBS Objects.

QSO candidates for follow-up spectroscopy were selected from the list of SBS objects. The spectral observations were carried out at both the 6m telescope of the Special Astrophysical Observatory (SAO), and at the 2.6m telescope of the Byurakan Astrophysical Observatory (BAO) (Stepanian et al. 1993 and references therein). The BV CCD photometric observations were carried out with the 1m telescope of SAO (Chavushyan et al. 1995). To date, more than 300 QSOs have been discovered in this survey.

In this Letter we report the discovery of a new gravitationally lensed system SBS 1520+530, which is found among SBS quasars.

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© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998