Identification of a Helium Donor Star in NGC 247 ULX-1
Abstract
With Very Large Telescope Multi Unit Spectroscopic Explorer (MUSE) observations, we detected highly variable helium emission lines from the optical counterpart of the supersoft ultraluminous X-ray source (ULX) NGC 247 ULX-1. No Balmer lines can be seen in the source spectrum. This is the first evidence for the presence of a helium donor star in ULXs, consistent with a prediction that helium donor stars may be common in ULXs. The helium lines with an FWHM of about 200 km s-1 are likely produced on the outer accretion disk. Their strong variation implies that the central X-ray source can be significantly obscured to the outer disk. Also, a ring or a double-ring structure is revealed in the MUSE image. It is unknown whether or not it is related to the progenitor of the ULX binary.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2023
- DOI:
- 10.3847/1538-4357/acc5eb
- arXiv:
- arXiv:2303.11639
- Bibcode:
- 2023ApJ...947...52Z
- Keywords:
-
- Ultraluminous x-ray sources;
- X-ray binary stars;
- Companion stars;
- Hydrogen deficient stars;
- Stellar accretion disks;
- 2164;
- 1811;
- 291;
- 769;
- 1579;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- accepted for publication in ApJ