Spectral study of X-ray sources in some galaxies recently observed by Chandra
Abstract
With the aim to study the spectral properties of some X-ray sources from recently observed Chandra data, 9 galaxies which have been observed by Chandra ACIS-S during the year 2018 to 2022 have been considered for the present work. 27 sources with net source counts ≥100 have been considered. The spectra of all the sources were fitted using two empirical models-an absorbed powerlaw and an absorbed disk blackbody. Based on their estimated bolometric luminosities, the 27 X-ray sources have been classified into 6 X-ray binaries (XRBs) and 21 Ultraluminous X-ray sources (ULXs). All the six XRBs are found to be in the spectrally hard state (Γ ∼1.52 -2.29 ) which indeed may be due to thermal comptonization. Only one ULX-CXOUJ032251.2-370950 (X-5) was found to be spectrally soft while the remaining 20 ULXs were spectrally hard. The spectral parameters of X-5 with an inner disk temperature (kTin) ∼ 0.5 keV and an estimated bolometric luminosity, LX∼3.26 ×1039 erg s-1 requires a black hole of mass, MBH∼137 .86-47.41+66.62M⊙ accreting at ∼0.19 times its Eddington limit. 8 ULXs-X-4, X-8, X-9, X-10, X-11, X-12, X-20 and X-21 were found to be in the Extremely luminous X-ray sources (ELXs) regime with even their lower limit of luminosity >1040 erg s-1. Softening/Hardening of spectra with or without changes in the luminosity were also observed in some ULXs/ELXs. In the hard ELX, X-8, spectral softening with almost consistent luminosity was observed. While in the ULXs-X-20 and X-25 spectral softening with increasing luminosity was observed. However, spectral hardening with increase in luminosity were observed in the ULXs-X-21 and X-26.
- Publication:
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Indian Journal of Physics
- Pub Date:
- March 2024
- DOI:
- 10.1007/s12648-024-03120-8
- Bibcode:
- 2024InJPh.tmp...74C
- Keywords:
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- Accretion;
- Accretion disks;
- Galaxies: general-X-rays:binaries