1999/01/29 by Edward A. Baltz, Joseph Silk · 1 citation
Engineering · Physics and Astronomy · #Adaptive optics and wavefront sensing #CCD and CMOS Imaging Sensors #Photocathodes and Microchannel Plates #astro-ph
paper · pdf · doi:10.1086/308385
published as Astrophys.J. 530 (2000) 578 · 18 pages, 30 figures, uses emulateapj
arxiv created 1999/01/29 · openalex publication_date 2000/02/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
In previous work it has been shown that a flux-weighted FWHM timescale of a microlensing event can be used as an unbiased estimator of the optical depth. For the first time, this allows the optical depth, which is effectively the microlensing probability, to be easily estimated from pixel microlensing data. In this paper we derive analytic expressions for the observed rate of pixel lensing events as a function of the FWHM timescale. This contrasts works in the literature that express rates in terms of an "event duration" or Einstein time, which require knowledge of the magnification, which is difficult to determine in a pixel event. The FWHM is the most directly measured timescale. We apply these results to possible pixel lensing surveys, using the Hubble Space Telescope ( HST ) for M87 and the Canada-France-Hawaii Telescope (CFHT) for M31. We predict M87 microlensing rates for the HST Advanced Camera and for the Next-Generation Space Telescope ( NGST ), and demonstrate that one will be able to probe the stellar initial mass function (IMF). Next, we describe a new method by which a crude measurement of the magnification can be made in the regime of magnifications A ~ 10-100. This in turn gives a crude measurement of the Einstein time. This program requires good photometry and sampling in the low-magnification tails of an event, but is feasible with today's technology.