* Astronomy

Title: The progenitor of SN 2011ja: Clues from circumstellar interaction
Authors: Sayan Chakraborti, Alak Ray, Randall Smith, Stuart Ryder, Naveen Yadav, Firoza Sutaria, Vikram V. Dwarkadas, Poonam Chandra, David Pooley, Rupak Roy

Massive stars, possibly red supergiants, which retain extended hydrogen envelopes until the time of core collapse produce Type IIP (Plateau) supernovae. The ejecta from these explosions shock the circumstellar matter originating from the mass loss of the progenitor during the final phases of its life. This interaction accelerates particles to relativistic energies which then lose energy via synchrotron radiation in the shock-amplified magnetic fields and inverse Compton scattering against optical photons from the supernova. These processes produce different signatures in the radio and X-ray part of the electromagnetic spectrum. Observed together, they allow us to break the degeneracy between shock acceleration and magnetic field amplification. In this work we use X-rays observations from the Chandra and radio observations from the ATCA to study the relative importance of particle acceleration and magnetic fields in producing the non-thermal radiation from SN 2011ja. We use radio observations to constrain the explosion date. Multiple Chandra observations allow us to probe the history of variable mass loss from the progenitor. The ejecta expands into a low density bubble followed by interaction with a higher density wind from a red supergiant consistent with M>16 solar masses. Our results suggest that a fraction of type IIP supernovae may interact with circumstellar media set up by non-steady winds.

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