Query : 2005A&A...429L..33N

2005A&A...429L..33N - Astronomy and Astrophysics, volume 429, L33-36 (2005/1-2)

Using close stars as probes of hot accretion flow in Sgr A*.


Abstract (from CDS):

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 Yuan et al. (2003ApJ...598..301Y), passes the test and is constrained to accretion rates no larger than ∼few x10–7M/year.

Abstract Copyright:

Journal keyword(s): accretion, accretion disks - black hole physics - Galaxy: center - radiation mechanisms: general

CDS comments: Star S2 = [GKM98] S0-2

Simbad objects: 4

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Number of rows : 4
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
1 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 12984 0
2 GCIRS 16 Cl* 17 45 40.0 -29 00 28           ~ 330 0
3 NAME Sgr A* X 17 45 40.03599 -29 00 28.1699           ~ 3890 3
4 [EG97] S2 * 17 45 40.0442 -29 00 27.975           B0/2V 327 1

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