The amounts of X-rays they found were small—they counted 33 photons in the first observation a year and a half after the supernova exploded, and ten in another about 200 days later—but present.
“This certainly appears to be a Ia supernova with substantial circumstellar material, and it looks as though it’s very dense,” he said. “What we saw suggests a density about a million times higher what we thought was the maximum around Ia’s.”
It’s thought that white dwarfs don’t lose mass before they explode. The usual explanation for the circumstellar material is that it would have come from a companion star in the system, but the amount of mass suggested by this measurement was very large, Dwarkadas said—far larger than one could expect from most companion stars. “Even the most massive stars do not have such high mass-loss rates on a regular basis,” he said. “This once again raises the question of how exactly these strange supernovas form.”
“If it’s truly a Ia, that’s a very interesting development because we have no idea why it would have so much circumstellar material around it,” he said.
“It is surprising what you can learn from so few photons,” said lead author and Caltech graduate student Chris Bochenek; his work on the study formed his undergraduate thesis at UChicago. “With only tens of them, we were able to infer that the dense gas around the supernova is likely clumpy or in a disk.”
More studies to look for X-rays, and even radio waves coming off these anomalies, could open a new window to understanding such supernovas and how they form, the authors said.
Citation: “X-ray Emission from SN 2012ca: A Type Ia-CSM Supernova Explosion in a Dense Surrounding Medium.” Bochenek et al, Monthly Notices of the Royal Astronomical Society. Aug. 23, 2017. https://academic.oup.com/mnras/article/doi/10.1093/mnras/stx2029/4091449/X-ray-Emission-from-SN-2012ca-A-Type-Ia-CSM)
Funding: NASA, National Science Foundation, TABASGO Foundation, Miller Institute for Basic Research in Science, Christopher R. Redlich Fund.