N. D. Vagshette, P. K. Pawar, M. K. Patil. Ultraluminous X-ray sources in dusty early-type galaxies
Natural Sciences / Astronomy / Astrophysics
Submitted on: Jun 26, 2012, 07:00:42
Description: We present properties of 34 ULX sources detected within D$_{25}$ region of 15 dusty early-type galaxies. All these sources have X-ray luminosity greater than 10$^{39}$ lum, implying that they are resulted due to the accretion of matter on to compact object with mass $ge$ 10Msun. Spectra of X-ray photons extracted from individual ULX are well represented by an absorbed power law with photon indices lying between 0.81 to 2.64, with their spectral properties closely matching with the hard-state spectra of the Galactic black hole binaries. The combined XLF of all the 34 ULXs is consistent with that reported earlier for early-type galaxies and is adequately described by a power-law with slope equal to -1.34pms0.12. The X-ray color-color plot of ULXs exhibit significant difference of their spectral properties with X-ray colors lying in the range between (-0.5, -0.5) to (+1.0, +1.0). We have quantified mass of a accreting sources on the basis of measured values of X-ray luminosities of individual ULXs and found to lie in the range between 20 Msun, $lesssim$ {bf M} $lesssim$ 100 Msun.