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

14 pages, 7 figures, 8 tables, Accepted for publication in MNRAS

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Cited by in corpus (7)

• COSMOGRAIL XVII: Time delays for the quadruply imaged quasar PG 1115+080
• $H_0$ from ten well-measured time delay lenses
• Constraining the microlensing effect on time delays with new time-delay prediction model in $H_0$ measurements
• A Spectroscopic Survey of the Fields of 28 Strong Gravitational Lenses: The Redshift Catalog
• Light versus dark in strong-lens galaxies: Dark matter haloes that are rounder than their stars
• The Extreme Ultraviolet Variability of Quasars
• Using strong lensing to understand the microJy radio emission in two radio quiet quasars at redshift 1.7