Two Optical Counterpart Candidates of M82-X1 from HST Observations

TL;DR

This study identifies two potential optical counterparts to the ULX M82 X-1 using HST data, suggesting possible accretion disks and stellar types, but further spectroscopic follow-up is required for confirmation.

Contribution

First identification of optical counterpart candidates for M82 X-1 using HST, highlighting potential accretion disks and stellar types, advancing understanding of ULX systems.

Findings

Two optical candidates show flux excess indicating possible accretion disks.

Spectral energy distributions match supergiant spectra of specific stellar types.

Further spectroscopic studies are needed to confirm the true companion.

Abstract

Optical counterparts can provide significant constraints on the physical nature of ultraluminous X-ray sources (ULXs). In this letter, we identify six point sources in the error circle of a ULX in M82, namely M82 X-1, by registering Chandra positions onto Hubble Space Telescope images. Two objects are considered as optical counterpart candidates of M82 X-1, which show F658N flux excess compared to the optical continuum that may suggest the existence of an accretion disk. The spectral energy distributions of the two candidates match well with the spectra for supergiants, with stellar types as F5-G0 and B5-G0, respectively. Deep spatially resolved spectroscopic follow-up and detailed studies are needed to identify the true companion and confirm the properties of this BH system.