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SN 2017ens: The metamorphosis of a luminous broadlined type Ic supernova into an SN IIn

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. Della, 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. and Yu, P.-C. 2018. SN 2017ens: The metamorphosis of a luminous broadlined type Ic supernova into an SN IIn. Astrophysical Journal Letters 867 (2) , -. 10.3847/2041-8213/aaeb2e

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Abstract

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 Hα and Hβ 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 ~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 ~2000 km s−1 wide Hα emission persisting at high luminosity (~3 × 1040 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.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: American Astronomical Society
ISSN: 2041-8205
Date of First Compliant Deposit: 2 July 2019
Date of Acceptance: 20 October 2018
Last Modified: 04 Jul 2019 09:30
URI: http://orca.cf.ac.uk/id/eprint/123923

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