Spin 3/5 Black Hole in GRO J1655-40?

1999/10/19 by Andrei Gruzinov, Gruzinov, Andrei
Engineering · Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics (astro-ph) #FOS: Physical sciences #Mechanics and Biomechanics Studies #Pulsars and Gravitational Waves Research #astro-ph

paper · pdf · doi:10.48550/arxiv.astro-ph/9910335

4 pages, submitted to ApJ

openalex publication_date 1999/10/19 · arxiv created 1999/10/28 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

When a bright spot in a high-inclination disk orbits a black hole, its light is periodically lensed and Doppler shifted. If the spots occupy a narrow range of radii, a quasi-periodic oscillation (QPO) will result. I calculate the QPO frequency assuming that the spots appear near r_max - the radius of the maximal proper radiation flux from the disk. The calculated frequency depends on the black hole mass and spin. For the microquasar GRO J1655-40, the black hole mass is known and a 300 Hz QPO was observed. The inferred black hole spin is about 60% of the maximal. The orbit precession frequency at r_max is 20Hz, this QPO was also observed in GRO J1655-40. An approximate formula for r_max is given.

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