Response from Irwin, <i>et al.</i>

Irwin, Kathleen L.; Ballard, Jane; Kobayashi, John M.; Veazie, Mark A.; Grendon, John; Yuen, Gale

doi:10.2105/ajph.79.12.1678-a

Cited by 30 publications

(48 citation statements)

References 4 publications

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“…This quasar has been observed to undergo Ñuctuations due to microlensing roughly once per year (Irwin et al 1989 ;R. Webster 1998, private communication).…”

Section: Microlensing L Aboratory : T He Einstein Crossmentioning

confidence: 99%

Imaging a Quasar Accretion Disk with Microlensing

Agol

Krolik

1999

ApJ

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We show how analysis of a quasar high-magniÐcation microlensing event may be used to construct a map of the frequency-dependent surface brightness of the quasar accretion disk. The same procedure also allows determination of the disk inclination angle, the black hole mass (modulo the caustic velocity), and possibly the black hole spin. This method depends on the validity of one assumption : that the optical and ultraviolet continuum of the quasar is produced on the surface of an azimuthally symmetric, Ñat equatorial disk, whose gas follows prograde circular orbits in a Kerr spacetime (and plunges inside the marginally stable orbit). Given this assumption, we advocate using a variant of Ðrst-order linear regularization to invert multifrequency microlensing light curves to obtain the disk surface brightness as a function of radius and frequency. The other parameters can be found by minimizing s2 in a fashion consistent with the regularized solution for the surface brightness. We present simulations for a disk model appropriate to the Einstein Cross quasar, an object uniquely well suited to this approach. These simulations conÐrm that the surface brightness can be reconstructed quite well near its peak and that there are no systematic errors in determining the other model parameters. We also discuss the observational requirements for successful implementation of this technique.

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“…This quasar has been observed to undergo Ñuctuations due to microlensing roughly once per year (Irwin et al 1989 ;R. Webster 1998, private communication).…”

Section: Microlensing L Aboratory : T He Einstein Crossmentioning

confidence: 99%

Imaging a Quasar Accretion Disk with Microlensing

Agol

Krolik

1999

ApJ

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“…This will give intensity fluctuations in one but not both images (Gott 1981), the timescale of the fluctuations being ∼ 40(M/M ⊙ ) 1/2 y. There is already evidence of this effect for the quasar 2237+0305 (Irwin et al 1989), the observed timescale possibly indicating a mass below 0.1 M ⊙ (Webster et al 1991). However, because the optical depth is high, the mass estimate is rather uncertain and a more recent analysis suggests that it could be in the higher range 0.1 − 10 M ⊙ ( Lewis et al 1998), in which case the lens could be an ordinary star.…”

Section: Microlensing Of Stars In M31mentioning

confidence: 96%

Recent Developments in the Search for Baryonic Dark Matter

Carr

2001

Phase Transitions in the Early Universe: Theory and Observations

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Abstract. Cosmological nucleosynthesis calculations imply that many of the baryons in the Universe must be dark. We discuss the likelihood that some of these dark baryons may reside in galaxies as Massive Compact Halo Objects (MACHOs), the remnants of a first generation of pregalactic or protogalactic stars. Various candidates have been proposed for such remnants and we review the many types of observations which can be used to detect or exclude them. Claims to have found positive evidence for some of the candidates have generally turned out to be spurious or questionable, so the status of the MACHO scenario remains controversial. However, it would be premature to reject MACHOs altogether and further observations are likely to resolve the issue soon.

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“…In 1989, evidence for cosmological microlensing was found by Irwin et al (1989) in the quadruple quasar Q2237+0305: one of the components showed fluctuations, whereas the others stayed constant. In the mean time, Q2237+0305 has been monitored by many groups (Corrigan et al 1991;Ostensen et al 1996; ).…”

Section: The Einstein Cross: Quadruple Quasar Q2237+0305mentioning

confidence: 99%

Gravitational Microlensing

Wambsganß

Saas-Fee Advanced Courses

106

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This review forms the microlensing part of the 33rd Saas-Fee Advanced Course "Gravitational Lensing: Strong, Weak & Micro'', which was held in April 2003 in Les Diablerets. It contains an introduction to the lensing effects of single and binary stars and it summarizes the state-of-the-art of microlensing observations and prospects at the time of the meeting. Stellar microlensing as well as quasar microlensing are covered.Comment: 93 pages, 51 figures; to appear (April 2006) in: Kochanek, C.S., Schneider, P., Wambsganss, J.: "Gravitational Lensing: Strong, Weak & Micro", Proceedings of the 33rd Saas-Fee Advanced Course; G. Meylan, P. Jetzer, P. North, eds. (Springer-Verlag, Heidelberg); pp. 45

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Response from Irwin, et al.

Cited by 30 publications

References 4 publications

Imaging a Quasar Accretion Disk with Microlensing

Imaging a Quasar Accretion Disk with Microlensing

Recent Developments in the Search for Baryonic Dark Matter

Gravitational Microlensing

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