Five nights of intensive R- and V-band photometry of QSO 0957+561A,B

Authors: Ovaldsen J.E.¹; Teuber J.; Stabell R.¹; Evans A.K.D.¹

Source: Monthly Notices of the Royal Astronomical Society, Volume 345, Number 3, November 2003 , pp. 795-799(5)

Publisher: Blackwell Publishing

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Abstract:

We present R- and V-band photometry of the gravitational lens system QSO 0957+561 from five nights (one in 2000 January and four in 2001 March, corresponding to the approximate time delay for the system) of uninterrupted monitoring at the Nordic Optical Telescope. In the photometry scheme we have stressed careful magnitude calibration as well as corrections for the lens galaxy contamination and the crosstalk between the twin (A and B) quasar images. The resulting, very densely sampled, light curves are quite stable, in conflict with earlier claims derived from the same data material. We estimate high-precision timelag-corrected B/A flux ratios in both colour bands, as well as V–R colour indices for A and B, and discuss the short time-scale variability of the system.

Keywords: gravitational lensing; methods: data analysis; techniques: photometric; quasars: individual: QSO 0957+561; cosmology: observations

Document Type: Research article

DOI: 10.1046/j.1365-8711.2003.06989.x

Affiliations: 1: Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029, Blindern, N-0315 Oslo, Norway

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