Optical monitoring of the gravitationally lensed quasar Q2237+0305 from APO between June 1995 and January 1998^*

¹ Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
² Universität Potsdam, Institut für Physik, Am Neuen Palais 10, 14469 Potsdam, Germany
³ Renaissance Technologies, 600 Route 25A, East Setauket, NY 11733, USA
⁴ Canadian Institute of Theoretical Astrophysics, 60 St. George St., Toronto, M5S 3H8, Canada
⁵ Princeton University Observatory, Peyton Hall, Princeton, NJ 08544, USA
⁶ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁷ Lincoln Laboratory, Massachusetts Institute of Technology, 244 Wood Street, Lexington, MA 02420, USA
⁸ National Optical Astronomy Observatory, PO Box 26732, Tucson, AZ 85726, USA
⁹ Apache Point Observatory, 2001 Apache Point Rd, Sunspot NM 88349, USA
¹⁰ Mesa Community College, 1833 West Southern Ave., Mesa, Arizona 85202-4866, USA
¹¹ Johns Hopkins University, Charles and 34th Street, Bloomberg Center, Baltimore, MD 21210, USA
¹² Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

Corresponding author: R. W. Schmidt, rschmidt@ast.cam.ac.uk

Received: 31 January 2002
Accepted: 20 June 2002

Abstract

We present a data set of images of the gravitationally lensed quasar Q2237+0305, that was obtained at the Apache Point Observatory (APO) between June 1995 and January 1998. Although the images were taken under variable, often poor seeing conditions and with coarse pixel sampling, photometry is possible for the two brighter quasar images A and B with the help of exact quasar image positions from HST observations. We obtain a light curve with 73 data points for each of the images A and B. There is evidence for a long (100 day) brightness peak in image A in 1996 with an amplitude of about 0.4 to 0.5 mag (relative to 1995), which indicates that microlensing has been taking place in the lensing galaxy. Image B does not vary much over the course of the observation period. The long, smooth variation of the light curve is similar to the results from the OGLE monitoring of the system (Woźniak et al. [CITE]).