2007ApJ...660L.113F -
Astrophys. J., 660, L113-L116 (2007/May-2)
Spectral evolution of NGC 1313 X-2: evidence against the cool disk model.
FENG H. and KAARET P.
Abstract (from CDS):
The presence of a cool multicolor disk component with an inner disk temperature kT≃0.1-0.3 keV at a luminosity L>1040 ergs/s has been interpreted as evidence that the ultraluminous X-ray source NGC 1313 X-2 harbors an intermediate-mass black hole (IMBH). The temperature of a disk component should vary with luminosity as L∝T4. However, upon investigating the spectral evolution with multiple XMM-Newton observations, we found that the cool disk component failed to follow this relation, with a confidence level of 0.999964. Indeed, the luminosity decreases as the temperature increases, and the luminosities at high temperatures are more than an order of magnitude less than expected from the L∝T4 extrapolation of luminosities at low temperatures. This places a strong constraint against the validity of modeling the X-ray spectra of NGC 1313 X-2 as emission from the accretion disk of an IMBH. The decrease in luminosity with increasing temperature of the soft component follows the trend suggested by a model in which the soft emission arises from an outflow from a stellar mass black hole with super-Eddington accretion viewed along the symmetry axis. Alternatively, the spectra can be adequately fitted by a p-free disk model with kT~2 keV and p~0.5. The spectral evolution is consistent with the L∝T4 relation and appears to be a high-luminosity extension of the L-kT relation of Galactic black holes. This, again, would suggest that the emission is from a super-Eddington accreting stellar mass black hole.
Abstract Copyright:
∼
Journal keyword(s):
Accretion, Accretion Disks - Black Hole Physics - X-Rays: Binaries - X-Rays: Galaxies - X-rays: individual (NGC 1313 X-2)
Simbad objects:
8
Full paper
View the references in ADS
To bookmark this query, right click on this link: simbad:2007ApJ...660L.113F and select 'bookmark this link' or equivalent in the popup menu