iPTF16asu: A Luminous, Rapidly-Evolving, and High-Velocity Supernova
astro-ph.HE
/ Authors
L. Whitesides, R. Lunnan, M. M. Kasliwal, D. A. Perley, A. Corsi, S. B. Cenko, N. Blagorodnova, Y. Cao, D. O. Cook, G. B. Doran
and 16 more authors
D. D. Frederiks, C. Fremling, K. Hurley, E. Karamehmetoglu, S. R. Kulkarni, G. Leloudas, F. Masci, P. E. Nugent, A. Ritter, A. Rubin, V. Savchenko, J. Sollerman, D. S. Svinkin, F. Taddia, P. Vreeswijk, P. Wozniak
/ 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 iPTF16asu, a luminous, rapidly-evolving, high velocity, stripped-envelope supernova. With a rest-frame rise-time of just 4 days and a peak absolute magnitude of $M_{\rm g}=-20.4$ mag, the light curve of iPTF16asu is faster and more luminous than previous rapid transients. The spectra of iPTF16asu show a featureless, blue continuum near peak that develops into a Type Ic-BL spectrum on the decline. We show that while the late-time light curve could plausibly be powered by $^{56}$Ni decay, the early emission requires a different energy source. Non-detections in the X-ray and radio strongly constrain any associated gamma-ray burst to be low-luminosity. 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 iPTF16asu an intriguing transition object between superluminous supernovae, Type Ic-BL supernovae, and low-energy gamma-ray bursts.