2001/02/28 by Julio Chanamé, Julio Chaname, Andrew Gould +2 · 3 citations
Engineering · Physics and Astronomy · #Adaptive optics and wavefront sensing #Astrophysical Phenomena and Observations #Mechanics and Biomechanics Studies #astro-ph
paper · pdf · doi:10.1086/323986
published as ApJ 563, 793-799 (2001) · 19 pages, 4 figures; replaced with version published in ApJ
openalex publication_date 2001/12/20 · arxiv created 2002/01/15 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/01
We show that at any given time, the Galactocentric black hole Sgr A* is expected to be microlensing N lens ~ 1.7 bulge stars if the threshold of detectability of the fainter image is K thr = 21, and N lens ~ 8 sources if K thr = 23. The lensed images then provide a unique way to detect stellar-mass black holes predicted to cluster around Sgr A*. If a black hole passes close to a microlensed image, it will give rise to a short (weeks long) microlensing event. We show that the mass and projected velocity of the stellar-mass black hole can both be measured unambiguously from such an event, provided that either a caustic crossing is observed or the astrometric displacement is measured. For K thr = 23 and moderate magnifications by Sgr A*, the microlensing event rate from a cluster of 20000 black holes within a radius of 0.7 pc is only 0.06 yr - 1 ; however, if highly magnified images of a star were found, the rate of events by the stellar black holes would be much higher. In addition, the N lens sources lensed by Sgr A* provide a unique probe of extinction behind the Galactic center along 2 N lens lines of sight.