Astronomers explain behaviour of 'chameleon supernova'
An international team of astronomers, including Manos Zapartas and Selma de Mink of the University of Amsterdam, has found two possible explanations for the behaviour of chameleon supernova SN 2014C. Either the star threw of its hydrogen-rich material late in life in a sort of last breath, or the star was stripped by an accompanying star. The researchers base their explanations on data collected by three telescopes.
The astronomers discovered supernova SN2014C in 2014 in spiral galaxy at a distance of between 36 million and 46 million light years from Earth. At the time, it appeared the star had lost its hydrogen-rich outer layer just after explosion.
A year later, in 2015, the star was nicknamed Chameleon. Normal supernovas would gradually grow weaker, but this supernova underwent a surprising make-over. It started to look more and more like a hydrogen-rich supernova. A change like this had never been observed before.
In recent years, a team of astronomers led by Raffaella Margutti (Northwestern University), studied the star in more detail with the use of three NASA space telescopes (Swift, Chandra and NuSTAR).
UvA PhD-student Manos Zapartas and Assistent Professor Selma de Mink contributed to the project with computer simulations. De Mink: 'From the data we could glean that there is a think layer of hydrogen-rich gas around the former star. This cocoon is at a considerable distance from the star: about 4,000 times the distance from Earth to the sun. The big question is why the star exploded in a cocoon of hydrogen gas. The star would have somehow lost that material shortly before explosion.'
Zapartas explains that there are two possible explanations: 'The first is that the star threw of its hydrogen-rich material late in life in a sort of last breath. The second possibility, for which I did the calculations, is that the star was part of a double star system. In that scenario, it would have been stripped completely by its accompanying star.'
The astromers furthermore show that exploding stars are possibly surrounded by a cocoon more often. About 1 in 10 stripped supernovas show indications for this theory.
The researchers will continue to monitor the chameleon supernova for the time to come. They also wish to study other supernovas in more detail.
Ejection of the massive Hydrogen-rich envelope timed with the collapse of the stripped SN2014C. Door: R. Margutti, A. Kamble, D. Milisavljevic, E. Zapartas, S. E. de Mink, M. Drout, R. Chornock, G. Risaliti, B. A. Zauderer, M. Bietenholz, M. Cantiello, S. Chakraborti, L. Chomiuk, W. Fong, B. Grefenstette, C. Guidorzi, R. Kirshner, J. T. Parrent, D. Patnaude, A. M. Soderberg, N. C. Gehrels, F. Harrison. In: Astrophysical Journal (in press) (free preprint)
Accompanying article about the theoretical simulations
Delay-time distribution of core-collapse supernovae with late events resulting from binary interaction. Door: E. Zapartas, S.E. de Mink, R.G. Izzard, S.-C. Yoon, C. Badenes, Y. Gotberg, A. de Koter, C.J. Neijssel, M. Renzo, A. Schootemeijer, and T.S. Shrotriya. Accepted for publication in Astronomy & Astrophysics (free preprint)