iPTF 16asu: A Luminous, Rapidly Evolving, and High-velocity Supernova

December 2017 • 2017ApJ...851..107W

Authors • Whitesides, L. • Lunnan, R. • Kasliwal, M. M. • Perley, D. A. • Corsi, A. • Cenko, S. B. • Blagorodnova, N. • Cao, Y. • Cook, D. O. • Doran, G. B. • Frederiks, D. D. • Fremling, C. • Hurley, K. • Karamehmetoglu, E. • Kulkarni, S. R. • Leloudas, G. • Masci, F. • Nugent, P. E. • Ritter, A. • Rubin, A. • Savchenko, V. • Sollerman, J. • Svinkin, D. S. • Taddia, F. • Vreeswijk, P. • Wozniak, P.

Abstract • Wide-field surveys are discovering a growing number of rare transients whose physical origin is not yet well understood. Here we present optical and UV data and analysis of intermediate Palomar Transient Factory (iPTF) 16asu, a luminous, rapidly evolving, high-velocity, stripped-envelope supernova (SN). With a rest-frame rise time of just four days and a peak absolute magnitude of {M}_{{g}}=-20.4 mag, the light curve of iPTF 16asu is faster and more luminous than that of previous rapid transients. The spectra of iPTF 16asu show a featureless blue continuum near peak that develops into an SN Ic-BL spectrum on the decline. We show that while the late-time light curve could plausibly be powered by ⁵⁶Ni decay, the early emission requires a different energy source. Nondetections in the X-ray and radio strongly constrain the energy coupled to relativistic ejecta to be at most comparable to the class of low-luminosity gamma-ray bursts (GRBs). We suggest that the early emission may have been powered by either a rapidly spinning-down magnetar or by shock breakout in an extended envelope of a very energetic explosion. In either scenario a central engine is required, making iPTF 16asu an intriguing transition object between superluminous SNe, SNe Ic-BL, and low-luminosity GRBs.

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David Cook

Assistant Scientist

Frank Masci

Senior Scientist