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*.
NAYAKSHIN S.
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
Full paper
View the references in ADS
To bookmark this query, right click on this link: simbad:2005A&A...429L..33N and select 'bookmark this link' or equivalent in the popup menu