A1 Refereed original research article in a scientific journal
SN 2017ens: The Metamorphosis of a Luminous Broadlined Type Ic Supernova into an SN IIn
Authors: Chen T.-W., Inserra C., Fraser M., Moriya T.J., Schady P., Schweyer T., Filippenko A.V., Perley D.A., Ruiter A.J., Seitenzahl I., Sollerman J., Taddia F., Anderson J.P., Foley R.J., Jerkstrand A., Ngeow C.-C., Pan Y.-C., Pastorello A., Points S., Smartt S.J., Smith K.W., Taubenberger S., Wiseman P., Young D.R., Benetti S., Berton M., Bufano F., Clark P., Valle M.D., Galbany L., Gal-Yam A., Gromadzki M., Gutiérrez C.P., Heinze A., Kankare E., Kilpatrick C.D., Kuncarayakti H., Leloudas G., Lin Z.-Y., Maguire K., Mazzali P., McBrien O., Prentice S.J., Rau A., Rest A., Siebert M.R., Stalder B., Tonry J.L., Yu P.-C.
Publisher: IOP PUBLISHING LTD
Publication year: 2018
Journal: Astrophysical Journal Letters
Journal name in source: ASTROPHYSICAL JOURNAL LETTERS
Journal acronym: ASTROPHYS J LETT
Article number: ARTN L31
Volume: 867
Issue: 2
Number of pages: 8
ISSN: 2041-8205
DOI: https://doi.org/10.3847/2041-8213/aaeb2e
We present observations of supernova (SN) 2017ens, discovered by the ATLAS survey and identified as a hot blue object through the GREAT program. The redshift z = 0.1086 implies a peak brightness of M-g = -21.1 mag, placing the object within the regime of superluminous supernovae. We observe a dramatic spectral evolution, from initially being blue and featureless, to later developing features similar to those of the broadlined Type Ic SN 1998bw, and finally showing 2000 km s(-1) wide H alpha and H beta emission. Relatively narrow Balmer emission (reminiscent of a SN IIn) is present at all times. We also detect coronal lines, indicative of a dense circumstellar medium. We constrain the progenitor wind velocity to similar to 50-60 km s(-1) based on P-Cygni profiles, which is far slower than those present in Wolf-Rayet stars. This may suggest that the progenitor passed through a luminous blue variable phase, or that the wind is instead from a binary companion red supergiant star. At late times we see the similar to 2000 km s(-1) wide H alpha emission persisting at high luminosity (similar to 3 x 10(40) erg s(-1)) for at least 100 day, perhaps indicative of additional mass loss at high velocities that could have been ejected by a pulsational pair instability.
