BVRI photometry of QSO 0957+561A, B: Observations, new reduction method and time delay

Abstract

CCD observations of the gravitational lens system Q0957+561A,B in the BVRI bands are presented in this paper. The observations, taken with the 82 cm IAC-80 telescope, at Teide Observatory, Spain, were made from the beginning of 1996 February to 1998 July, as part of an on-going lens monitoring program. Accurate photometry was obtained by simultaneously fitting a stellar two-dimensional profile on each component by means of DAOPHOT software. This alternative method equals and even improves the results obtained with previous techniques. The final dataset is characterized by its high degree of homogeneity as it was obtained using the same telescope and instrumentation during a period of almost 3 years. The resulting delay, obtained with a new method, the delta2-test, is of 425 +/- 4 days, slightly higher than the value previously accepted (417 days), but concordant with the results obtained by Pelt et al. (1996); Oscoz et al. (1997); Pijpers (1997); and Goicoechea et al. (1999).

arXiv comment31 pages, 16 figures, accepted for publication in ApJ

References in corpus (6)

• A Robust Determination of the Time Delay in 0957+561A,B and a Measurement of the Global Value of Hubble's Constant
• Improved Parameters and New Lensed Features for Q0957+561 from WFPC2 Imaging
• Signatures of Accretion Disks in Quasar Microlensing
• The 6 cm Light Curves of B0957+561, 1979-1994: New Features and Implications for the Time Delay
• Magnification Ratio of the Fluctuating Light in Gravitational Lens 0957+561
• Precision Photometry for Q0957+561 Images A and B

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• A New Microlensing Event in the Doubly-Imaged Quasar Q0957+561
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• Multiple delays in QSO 0957+561: observational evidence and interpretation
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• Revealing the structure of the lensed quasar Q 0957+561: I. Accretion disk size
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• New VR magnification ratios of QSO 0957+561
• A Large Brightness Enhancement of the QSO 0957+561 A Component
• A 5.5-year robotic optical monitoring of Q0957+561: substructure in a non-local cD galaxy
• GLITP Optical Monitoring of QSO 0957+561: VR Light Curves and Variability
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