Determining the nature of IC 10 X-2: A comprehensive study of the Optical/Infrared emission from an extragalactic BeHMXB

Jwaher Alnaqbi; Joseph D. Gelfand; Payaswini Saikia; Craig Heinke; M. C. Baglio; David M. Russell; Guobao Zhang; Antonios Manousakis; Ivan Yu. Katkov; Fraser Lewis

arXiv · 2501.06626

Determining the nature of IC 10 X-2: A comprehensive study of the Optical/Infrared emission from an extragalactic BeHMXB

Jwaher Alnaqbi·Joseph D. Gelfand·Payaswini Saikia·Craig Heinke·M. C. Baglio·David M. Russell·Guobao Zhang·Antonios Manousakis·Ivan Yu. Katkov·Fraser Lewis

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Abstract

We present a comprehensive analysis of the optical and infrared (IR) properties of high-mass X-ray binary (HMXB) IC 10 X-2, classified as a super-giant HMXB and super-fast X-ray transient (SFXT) by previous work. Our analysis of regular (daily and weekly) observations by both the Zwicky Transient Factory and Las Cumbres Observatory over a ~5 year period indicates both periodic flares and variations in the apparent magnitude and color with a $\sim26.5$~d period -- likely the orbital period of this binary system. The periodic flaring suggests the stellar companion is a Be star, with flares resulting from increased accretion onto the neutron star when it enters the stellar decretion disk. The periodic variations in the optical/IR brightness and color likely result from orbital variations in the Hydrogen column density along the line of sight or a transient accretion disk around the neutron star. Lastly, the numerous, short duration, episodes where IC 10 X-2 is significantly ``redder'' or ``bluer'' than normal likely result from from clumps within this system -- which can accrete onto the neutron star (causing IC 10 X-2 to appear bluer), or pass through the line of sight (causing IC 10 X-2 to appear redder). These results substantially increase our understanding of the evolution of this source, a significant source of ionizing photons in its host galaxy IC 10, a low mass, metal-poor starburst galaxy similar in many respect to those thought to be common in the early Universe.

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Jwaher Alnaqbi, Joseph D. Gelfand, Payaswini Saikia, Craig Heinke, M. C. Baglio, David M. Russell, Guobao Zhang, Antonios Manousakis, Ivan Yu. Katkov, Fraser Lewis. 2025-01-11. Determining the nature of IC 10 X-2: A comprehensive study of the Optical/Infrared emission from an extragalactic BeHMXB. https://arxiv.org/abs/2501.06626

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