Publication

Simultaneous estimation of time delays and quasar structure

Abstract

We expand our Bayesian Monte Carlo method for analyzing the light curves of gravitationally lensed quasars to simultaneously estimate time delays and the sizes of quasar continuum emission regions including their mutual uncertainties. We apply the method to HE1104 - 1805 and QJ0158 - 4325, two doubly imaged quasars with microlensing and intrinsic variability on comparable timescales. For HE1104 - 1805 the resulting time delay of Delta t(AB) = t(A) - t(B) = 162: 2(-5.9)(+6: 3) days and accretion disk size estimate of log {(r(s)/cm) cos (i)/ 0:5](1/2) = 15:7(-0.5)(+0.4) at 0.2 mu m in the rest frame and for inclination i are consistent with earlier estimates but suggest that existing methods for estimating time delays in the presence of microlensing underestimate the uncertainties. We are unable to measure a time delay for QJ0158 - 4325, but the accretion disk size is log[(r(s)/cm) cos(i)/ 0: 5 = 14: 9 +/- 0: 3 at 0.3 mu m in the rest frame.

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An accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The central body is most frequently a star. Friction, uneven irradiance, magnetohydrodynamic effects, and other forces induce instabilities causing orbiting material in the disk to spiral inward toward the central body. Gravitational and frictional forces compress and raise the temperature of the material, causing the emission of electromagnetic radiation.
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Propagation delay is the time duration taken for a signal to reach its destination. It can relate to networking, electronics or physics. In computer networks, propagation delay is the amount of time it takes for the head of the signal to travel from the sender to the receiver. It can be computed as the ratio between the link length and the propagation speed over the specific medium. Propagation delay is equal to d / s where d is the distance and s is the wave propagation speed. In wireless communication, s=c, i.
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