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arXiv · 2206.04473

Decoding the X-ray flare from MAXI J0709-159 using optical spectroscopy and multi-epoch photometry

Suman Bhattacharyya·Blesson Mathew·Savithri H Ezhikode·S Muneer·Selvakumar G·Maheswer G·R. Arun·Hema Anilkumar·Gourav Banerjee·Pramod Kumar S·Sreeja S Kartha·KT Paul·C. Velu
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Abstract

We present a follow-up study on the recent detection of two X-ray flaring events by MAXI/GSC observations in soft and hard X-rays from MAXI J0709-159 in the direction of HD 54786 (LY CMa), on 2022 January 25. The X-ray luminosity during the flare was around 10^(37) erg/s (MAXI), which got reduced to 10^(32) erg/s (NuSTAR) after the flare. We took low-resolution spectra of HD 54786 from HCT and VBT facilities in India, on 2022 February 1 and 2. In addition to H-alpha emission, we found emission lines of He I in the optical spectrum of this star. By comparing our spectrum of the object with those from literature we found that He I lines show variability. Using photometric study we estimate that the star is having effective temperature of 20000 K. Although HD 54786 is reported as a supergiant in previous studies, our analysis favours it to be evolving off the main sequence in the Color-Magnitude Diagram. We could not detect any infrared excess, ruling out the possibility of IR emission from a dusty circumstellar disc. Our present study suggests that HD 54786 is a Be/X-ray binary system with a compact object companion, possibly a neutron star.

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Suman Bhattacharyya, Blesson Mathew, Savithri H Ezhikode, S Muneer, Selvakumar G, Maheswer G, R. Arun, Hema Anilkumar, Gourav Banerjee, Pramod Kumar S, Sreeja S Kartha, KT Paul, C. Velu. 2022-06-09. Decoding the X-ray flare from MAXI J0709-159 using optical spectroscopy and multi-epoch photometry. https://doi.org/10.3847/2041-8213%2Fac7b8a

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