A New Microlensing Event in the Doubly-Imaged Quasar Q0957+561

TL;DR

This study reports evidence of ultraviolet/optical microlensing in the gravitationally lensed quasar Q0957+561, revealing a flux ratio change over five years and estimating the quasar's accretion disk size.

Contribution

The paper introduces a new microlensing event detection in Q0957+561 and provides an estimate of the quasar's accretion disk size using Monte Carlo analysis.

Findings

Flux ratio increased by ~0.1 magnitudes over five years.

Estimated accretion disk size log {(r_s/cm)[cos(i)/0.5]^{1/2}} = 16.2^{+0.5}_{-0.6}.

Accretion disk size consistent with black hole mass relation.

Abstract

We present evidence for ultraviolet/optical microlensing in the gravitationally lensed quasar Q0957+561. We combine new measurements from our optical monitoring campaign at the United States Naval Observatory, Flagstaff (USNO) with measurements from the literature and find that the time-delay-corrected r-band flux ratio m_A - m_B has increased by ~0.1 magnitudes over a period of five years beginning in the fall of 2005. We apply our Monte Carlo microlensing analysis procedure to the composite light curves, obtaining a measurement of the optical accretion disk size, log {(r_s/cm)[cos(i)/0.5]^{1/2}} = 16.2^{+0.5}_{-0.6}, that is consistent with the quasar accretion disk size - black hole mass relation.