2004/10/19 by Sergei Nayakshin · 2 citations
Earth and Planetary Sciences · Physics and Astronomy · #Astrophysical Phenomena and Observations #High-pressure geophysics and materials #Nuclear Physics and Applications #astro-ph
paper · pdf · doi:10.1051/0004-6361:200400101
published as Astron.Astrophys. 429 (2005) L33-L36 · submitted to A&A Letters. 4 pages and 2 figures
arxiv created 2004/10/19 · openalex publication_date 2004/12/17 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
The extremely hot and tenuous accretion flow in the immediate vicinity of Sgr A* is believed to be invisible (too dim) in the X-ray band, except for short X-ray flares. Here we point out that during pericenter passages, close brightest stars irradiate the inner region of the accretion flow, providing a plenty of optical/UV photons. These seed photons are Compton up-scattered by the hot electrons of the accretion flow to higher frequencies, some into the X-ray band, potentially making the innermost accretion flow much brighter in X-rays than usual. We propose to use coordinated near infra-red and X-ray observations of close star passages to put constraints onto Sgr A* accretion theories. The absence of a noticeable change in the steady emission of Sgr A* as observed by Chandra in the year 2002, when the star named S2 passed through a pericenter of its orbit, already rules out the hotter of the “standard” Advection-Dominated Accretion Flows. The less dense accretion flows, in particular the model of [CITE], passes the test and is constrained to accretion rates no larger than ~ few 10 year-1.