Spectral Analysis of the Black Hole X-Ray Binary Maxi J1820+070 Using Astrosat/SXT Observations

MAXI J1820+070 is one of the brightest Galactic black hole X-ray transients discovered in recent years and has been extensively studied because of its remarkable spectral and timing behaviour. In the present work, we present timing (light-curve) and spectral analyses of MAXI J1820+070 using archival observations obtained with the Soft X-ray Telescope (SXT) onboard AstroSat. The analysis is based on a combined effective exposure of approximately 12 ks obtained from multiple orbital segments corresponding to Observation ID A05_142T01_9000002904. The source light curve exhibits significant variability, indicating active accretion processes around the compact object. Spectral fitting was performed in the 0.7–7.0 keV energy range using the model TBabs × (diskbb + powerlaw). The best-fit parameters are NH = 0.15 × 1022 cm-2 (fixed), inner disk temperature Tin = 0.145 ± 0.011 keV, and photon index Г= 0.94 ± 0.15. The fit yields χ2 = 59.39 for 38 degrees of freedom (reduced χ2 = 1.56), indicating an acceptable fit to the observed spectrum. The results indicate the presence of a relatively cool accretion disk together with a dominant hard X-ray component, suggesting that coronal emission contributes significantly to the observed X-ray spectrum. The observed variability and spectral characteristics are consistent with an active accretion state during the observation. These findings provide insight into the accretion geometry and X-ray emission mechanisms operating in MAXI J1820+070.

AstroSat, SXT, MAXI J1820+070, Black Hole X-ray Binary, X-ray Spectroscopy, Accretion Disk

1. M.A. Tucker et al., The Astronomer’s Telegram, No. 11529, 2018. [Google Scholar] [Crossref]

2. D. J. K. Buisson, et al., Monthly Notices of the Royal Astronomical Society, vol. 490, pp. 1350-1362, 2019. [Google Scholar] [Crossref]

3. J. Frank, A. King, & D. J. Raine, Accretion Power in Astrophysics, 3rd ed., Cambridge University Press, Cambridge, U.K., 2002. [Google Scholar] [Crossref]

4. C. Done, M. Gierliński, & A. Kubota, “Modelling the behaviour of accretion flow in X-ray binaries: A review,” The Astronomy and Astrophysics Review, vol. 15, pp. 1-66, 2007. [Google Scholar] [Crossref]

5. M. A. P. Torres et al., The Astrophysical Journal, vol. 893, Art. No. L37, 2020. [Google Scholar] [Crossref]

6. K. P. Singh et al., “The Soft X-ray Telescope (SXT) aboard AstroSat,” Proceedings of SPIE, vol. 9144, p. 91441S, 2014. [Google Scholar] [Crossref]

7. K. P. Singh et al., “The Soft X-ray Telescope (SXT) onboard AstroSat,” Journal of Astrophysics and Astronomy, vol. 38, Art. no. 29, 2017. [Google Scholar] [Crossref]

8. K. A. Arnaud, “XSPEC: The First Ten Years,” in Astronomical Data Analysis Software and Systems V (ASP Conference Series), vol. 101, p. 17, 1996. [Google Scholar] [Crossref]

9. T. M. Belloni, S. E. Motta, & T. Muñoz-Darias, “Black Hole Transients,” Bulletin of the Astronomical Society of India, vol. 39, pp. 409-428, 2011. [Google Scholar] [Crossref]

10. R.A. Remillard & J. E. McClintock, “X-ray Properties of Black-Hole Binaries,” Annual Review of Astronomy and Astrophysics, vol. 44, pp. 49-92, 2006. [Google Scholar] [Crossref]

11. A. A. Zdziarski & M. Gierliński, “Radiative Processes, Spectral States and Variability of Black-Hole Binaries,” Progress of Theoretical Physics Supplement, vol.155, pp. 99-119, 2004. [Google Scholar] [Crossref]

12. M. Shidatsu, S. Nakahira, K. L. Murata et al., The Astrophysical Journal, vol.874, Art. no. 183, 2019. [Google Scholar] [Crossref]

13. E. Kara, J. E. Steiner, A. C. Fabian et al., “The corona contracts in a black-hole transient,” Nature, vol. 565, pp. 198-201,2019. [Google Scholar] [Crossref]

14. A. C. Fabian, J. Wang, M. L. Parker et al., “The soft state of the black hole transient source MAXI J1820+070: Emission from the edge of the plunge region?” Monthly Notices of the Royal Astronomical Society, vol.493, pp. 5389-5408, 2020. [Google Scholar] [Crossref]

15. S. K. Chakrabarti and L. G. Titarchuk, “Spectral Properties of Accretion Disks around Galactic and Extragalactic Black Hole,” The Astrophysical Journal, vol.455, pp. 623-639, 1995. [Google Scholar] [Crossref]

16. J. Wilms, A. Allen & R. McCray, “On the Absorption of X-ray in the Interstellar Medium,” The Astrophysical Journal, vol.542, pp. 914-924, 2000. [Google Scholar] [Crossref]

17. K. Mitsuda, H. Inoue, K. Koyama et al., “Energy Spectra of Low-Mass Binary X-ray Source Observed from TENMA,” Publications of the Astronomical Society of Japan, vol.36, pp. 741-759, 1984. [Google Scholar] [Crossref]

• Assessment of the Role of Artificial Intelligence in Repositioning TVET for Economic Development in Nigeria
• Teachers’ Use of Assure Model Instructional Design on Learners’ Problem Solving Efficacy in Secondary Schools in Bungoma County, Kenya
• “E-Booksan Ang Kaalaman”: Development, Validation, and Utilization of Electronic Book in Academic Performance of Grade 9 Students in Social Studies
• Analyzing EFL University Students’ Academic Speaking Skills Through Self-Recorded Video Presentation
• Major Findings of The Study on Total Quality Management in Teachers’ Education Institutions (TEIs) In Assam – An Evaluative Study