Spectral and timing study of the newly detected Ultraluminous X-Ray Sources in NGC 3585 using different Chandra observations.

Abstract

The present work aims to study the previously unstudied Ultraluminous X-ray sources (ULXs) in the galaxy NGC 3585 at its various epochs of Chandra observation. We report here the detection of two new ULXs viz. CXOUJ111306.0-264825 (X-1) and CXOUJ111325.3-264732 (X-2) with their bolometric luminosity > 1039erg s−1 in its various Chandra observations. X-1 was found to be a spectrally hard ULX in both the epochs where it was detected. However in the ULX, X-2, a slight hardening of the spectra was observed within a period of 17 years. Assuming isotropic emission and explained by disk blackbody model, the spectrally softer epoch of X-2 with an inner disk temperature, kTin ∼ 0.79 keV and bolometric luminosity ∼ 2.51 × 1039erg s−1 implies for X-2 to be powered by a compact object, necessarily a black hole of mass, MBH ∼ 44.85+82.11−25.92M⊙ accreting at ∼ 0.42 times the Eddington limit. The Lightcurve of X-1 and X-2 binned at 500s, 1ks, 2ks and 4ks has shown no signature of short-term variability in both the ULXs in kilo-seconds time scales. Overall, both the detected ULXs seem to be almost static sources both in long-term (years) as well as short-term (kilo-seconds) time scales with the presently available Chandra Observations.

Keywords

• Accretion
• Accretion disks
• Galaxies: individual(NGC 3585)
• X-rays: binaries