WR 138: new results from X-ray and optical spectroscopy
Abstract
Context. Massive-binary evolution models predict that some systems will go through an evolutionary phase where the original primary has become a supernova and left a compact object behind that then orbits a Wolf-Rayet (WR) star. WR 138 is an X-ray bright WR star that has been described as a triple system, including a compact companion in a short-period orbit.
Aims: Our goal is to search for spectroscopic evidence of a compact companion around WR 138.
Methods: We used optical and X-ray spectra to search for signatures of a compact companion, which can be revealed by systematic variations in WR optical spectral lines induced by orbital motion of the compact companion or by hard, luminous X-rays from accretion onto this companion.
Results: The optical spectra display emission-line profile variations that are most probably caused by clumps inside the stellar winds. The radial velocities do not vary on a short time-scale compatible with the suggested orbital period of a putative compact companion. The X-ray spectra are found to be normal for a WN5-6+OB system with no indication of accretion by a compact companion.
Conclusions: There is no evidence for the presence of a compact companion, and we therefore conclude that WR 138 is a normal long-period (P ~ 1521 d) eccentric WR+OB system.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- December 2013
- DOI:
- 10.1051/0004-6361/201322162
- arXiv:
- arXiv:1310.3929
- Bibcode:
- 2013A&A...560A..27P
- Keywords:
-
- stars: early-type;
- stars: Wolf-Rayet;
- stars: massive;
- stars:;
- individual: WR 138 (HD 193077);
- X-rays: stars;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- A&