Abstract Details
| Name: Jithesh V Affiliation: IUCAA, Pune Conference ID: ASI2019_390 Title : Long-term X-ray spectral variability of the ultra-luminous X-ray source M81 X-6 Authors and Co-Authors : V.Jithesh and Ranjeev Misra Abstract Type : Oral Abstract Category : Extragalactic Astronomy Abstract : We present the long-term X-ray spectral variability of the ultra-luminous X-ray source (ULX) M81 X-6 using {\it Suzaku} and {\it XMM-Newton} observations performed during 2001--2015. The observed spectra were first fitted by a standard multi-temperature disk plus a thermal Comptonization component which revealed spectral variability of the source with a change in the optical depth of the Comptonizing component similar to the other ULXs. We further investigated the spectral evolution of M81 X-6 using the relativistic accretion disk emission plus a power law component. The parameters for the black hole mass and spin were found to be degenerate, but the high spin and larger mass (20 - 100 solar mass) solutions provided near Eddington accretion rates consistent with the assumptions of the model. The source exhibits three different spectral shapes during these observations and the spectral variation is found to be driven by accretion rate changes, where the derived mass accretion rate varies by more than an order of magnitude in these observations. Thus, these results indicate the presence of a dominant relativistic disk emission component in some of the spectral states of the source. |