X-Ray, UV, and Optical Observations of Supernova 2006bp with Swift: Detection of Early X-Ray Emission
Abstract
We present results on the X-ray and optical/UV emission from the Type II-P supernova (SN) 2006bp and the interaction of the SN shock with its environment, obtained with the X-Ray Telescope (XRT) and UV/Optical Telescope (UVOT) on board Swift. SN 2006bp is detected in X-rays at a 4.5 σ level of significance in the merged XRT data from days 1 to 12 after the explosion. If the 0.2-10 keV band X-ray luminosity of L0.2-10=(1.8+/-0.4)×1039 ergs s-1 is caused by interaction of the SN shock with circumstellar material (CSM) deposited by a stellar wind from the progenitor's companion star, a mass-loss rate of M˙~(1×10-5 Msolar yr-1)(vw/10 km s-1) is inferred. The mass-loss rate is consistent with the nondetection in the radio with the VLA on days 2, 9, and 11 after the explosion and is characteristic of a red supergiant progenitor with a mass of ~12-15 Msolar prior to the explosion. The Swift data further show a fading of the X-ray emission starting around day 12 after the explosion. In combination with a follow-up XMM-Newton observation obtained on day 21 after the explosion, an X-ray rate of decline of LX~t-n with index n=1.2+/-0.6 is inferred. Since no other SN has been detected in X-rays prior to the optical peak, and since Type II-P SNe have an extended ``plateau'' phase in the optical, we discuss the scenario that the X-rays might be due to inverse Compton scattering of photospheric optical photons off relativistic electrons produced in circumstellar shocks. However, due to the high required value of the Lorentz factor (~10-100), which is inconsistent with the ejecta velocity inferred from optical line widths, we conclude that inverse Compton scattering is an unlikely explanation for the observed X-ray emission.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2007
- DOI:
- 10.1086/518466
- arXiv:
- arXiv:astro-ph/0703765
- Bibcode:
- 2007ApJ...664..435I
- Keywords:
-
- Stars: Circumstellar Matter;
- supernovae: individual (SN 2006bp);
- Ultraviolet: ISM;
- X-Rays: General;
- X-rays: individual (SN 2006bp);
- X-Rays: ISM;
- Astrophysics
- E-Print:
- 8 pages, 5 figures, accepted for publication in ApJ