Weakly broadened iron line in the X-ray spectrum of the ultraluminous X-ray source M82 X-1
Abstract
We present the best quality XMM-Newton and Suzaku data from M82 X-1 so far. We analyse the spectra of this remarkable ultraluminous X-ray (ULX) source in a self-consistent manner. We have disentangled emission from the host galaxy, responsible for the soft X-ray emission (E≤ 2.5 keV), which is successfully described by a two-temperature thermal emission from a hot plasma in multiphase state, plus a narrow Fe line emission at 6.7 keV. This allowed us to properly study the intrinsic continuum emission from M82 X-1. The continuum of the Suzaku spectrum is curved, and the high-quality data of the Suzaku spectrum allowed us to significantly detect a weakly broadened Fe Kα emission line. The equivalent width is in the range 30-80 eV and it does not depend on the model applied for the continuum. Assuming that this line is coming from the ULX via disc fluorescence, the data indicate a disc truncation at a radius of 6-20 gravitational radii. This value is comparable to or even larger than the innermost stable circular orbit of a non-spinning (Schwarzschild) black hole. Future longer observations might test this scenario.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 2011
- DOI:
- 10.1111/j.1365-2966.2011.19615.x
- arXiv:
- arXiv:1108.2139
- Bibcode:
- 2011MNRAS.418.1973C
- Keywords:
-
- black hole physics;
- line: formation;
- X-rays: galaxies;
- X-rays: general;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- Accepted (09/08/2011) for publication in MNRAS. (7 pages, including 6 figures and 3 tables)