PG 1115+080: variations of the A2/A1 flux ratio and new values of the time delays

Abstract

We report the results of our multicolor observations of PG 1115+080 with the\n1.5-m telescope of the Maidanak Observatory (Uzbekistan, Central Asia) in\n2001-2006. Monitoring data in filter R spanning the 2004, 2005 and 2006 seasons\n(76 data points) demonstrate distinct brightness variations of the source\nquasar with the total amplitude of almost 0.4 mag. Our R light curves have\nshown image C leading B by 16.4d and image (A1+A2) by 12d that is inconsistent\nwith the previous estimates obtained by Schechter et al. in 1997 - 24.7d\nbetween B and C and 9.4d between (A1+A2) and C. The new values of time delays\nin PG 1115+080 must result in larger values for the Hubble constant, thus\nreducing difference between its estimates taken from the gravitational lenses\nand with other methods. Also, we analyzed variability of the A2/A1 flux ratio,\nas well as color changes in the archetypal "fold" lens PG 1115+080. We found\nthe A1/A2 flux ratio to grow during 2001-2006 and to be larger at longer\nwavelengths. In particular, the A2/A1 flux ratio reached 0.85 in filter I in\n2006. We also present evidence that both the A1 and A2 images might have\nundergone microlensing during 2001-2006, with the descending phase for A1 and\ninitial phase for A2. We find that the A2/A1 flux ratio anomaly in PG 1115 can\nbe well explained both by microlensing and by finite distance of the source\nquasar from the caustic fold.\n