Chandra detection of sn2010da four months after outburst: Evidence for a high-mass X-ray binary in NGC300

Abstract

We present the results of a 63 ks Chandra observation of the "supernova impostor" SN2010da four months after it was first observed on 2010 May 24. We detect an X-ray source at 7σ confidence coincident with the optical location of the outburst. Our imaging analysis has revealed a hard central point source, surrounded by soft diffuse emission extending 8″ north of the central source. The diffuse emission has a hardness ratio (-0.4), 0.35-2keV luminosity (6 × 1035ergs-1), and size (70pc) consistent with that of a supernova remnant, although the low number of counts prohibits detailed spectral modeling. The 0.5-6keV spectrum of the central point source is well described by both a power law with Γ 0 and a blackbody with kT 1.8keV, with no evidence for intrinsic absorption beyond the Galactic column. We estimate the 0.3-10keV luminosity to be 2 × 10 37ergs-1, a factor of 25 decrease since the initial outburst. The high X-ray luminosity and slow fading rate is not consistent with this object being a single massive star undergoing an outburst. When combined with the optical and infrared properties of the outburst and progenitor systems, our X-ray observations suggest the SN2010da system may be a Be X-ray binary system which experienced an extremely bright optical outburst near simultaneously with a bright, TypeII X-ray outburst. © 2011. The American Astronomical Society. All rights reserved.