Time-resolved Polarimetry of the Superluminous SN 2015bn with the Nordic Optical Telescope

DOI: 
10.3847/2041-8213/aa6157
Publication date: 
01/03/2017
Main author: 
Leloudas G.
IAA authors: 
De Ugarte Postigo, A.
Authors: 
Leloudas G., Maund J.R., Gal-Yam A., Pursimo T., Hsiao E., Malesani D., Patat F., De Ugarte Postigo A., Sollerman J., Stritzinger M.D., Wheeler J.C.
Journal: 
Astrophysical Journal Letters
Refereed: 
Yes
Publication type: 
Article
Volume: 
837
Pages: 
Number: 
L14
Abstract: 

We present imaging polarimetry of the superluminous supernova SN 2015bn, obtained over nine epochs between -20 and +46 days with the Nordic Optical Telescope. This was a nearby, slowly evolving Type I superluminous supernova that has been studied extensively and for which two epochs of spectropolarimetry are also available. Based on field stars, we determine the interstellar polarization in the Galaxy to be negligible. The polarization of SN 2015bn shows a statistically significant increase during the last epochs, confirming previous findings. Our well-sampled imaging polarimetry series allows us to determine that this increase (from ∼0.54% to ≳1.10%) coincides in time with rapid changes that took place in the optical spectrum. We conclude that the supernova underwent a 'phase transition' at around +20 days, when the photospheric emission shifted from an outer layer, dominated by natal C and O, to a more aspherical inner core, dominated by freshly nucleosynthesized material. This two-layered model might account for the characteristic appearance and properties of Type I superluminous supernovae. © 2017. The American Astronomical Society. All rights reserved.

Database: 
SCOPUS
ADS
URL: 
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85014970638&doi=10.3847%2f2041-8213%2faa6157&partnerID=40&md5=5c840a670b5b265b9d023100ebb07d50
ADS Bibcode: 
2017ApJ...837L..14L
Keywords: 
supernovae: general; supernovae: individual (SN 2015bn)