QSO 2237+0305 VR Light Curves from Gravitational LensES International Time Project Optical Monitoring
Surdej, J.; Serra-Ricart, M.; Muñoz, J. A.; McLeod, B. A.; Mediavilla, E.; Gil-Merino, R.; Goicoechea, L. J.; Libbrecht, C.; Motta, V.; Barrena, R.; Oscoz, A.; Puga, E.; Moreau, O.; De Rop, Y.; Alcalde, D.
Spain, Belgium, France, Germany, United States, Uruguay
Abstract
We present VR observations of QSO 2237+0305 conducted by the Gravitational Lensing International Time Project collaboration from 1999 October 1 to 2000 February 3. The observations were made with the 2.56 m Nordic Optical Telescope at Roque de los Muchachos Observatory, La Palma (Spain). The point-spread function (PSF) fitting method and an adapted version of the ISIS subtraction method have been used to derive the VR light curves of the four components (A-D) of the quasar. The mean errors range in the intervals 0.01-0.04 mag (PSF fitting) and 0.01-0.02 mag (ISIS subtraction), with the faintest component (D) having the largest uncertainties. We address the relatively good agreement between the A and D light curves derived using different filters, photometric techniques, and telescopes. The new VR light curves of component A extend the time coverage of a high-magnification microlensing peak, which was discovered by the OGLE team.