1110.2363 (Nathan E. Sanders et al.)

SN 2010ay is a Luminous and Broad-lined Type Ic Supernova within a Low-metallicity Host Galaxy    [PDF]

Nathan E. Sanders, A. M. Soderberg, S. Valenti, L. Chomiuk, E. Berger, S. Smartt, K. Hurley, S. D. Barthelmy, R. Chornock, R. J. Foley, E. M. Levesque, G. Narayan, R. P. Kirshner, M. T. Botticella, M. S. Briggs, V. Connaughton, Y. Terada, N. Gehrels, S. Golenetskii, E. Mazets, T. Cline, A. von Kienlin, W. Boynton, K. C. Chambers, T. Grav, J. N. Heasley, K. W. Hodapp, R. Jedicke, N. Kaiser, R. -P. Kudritzki, G. A. Luppino, R. H. Lupton, E. A. Magnier, D. G. Monet, J. S. Morgan, P. M. Onaka, P. A. Price, C. W. Stubbs, J. L. Tonry, R. J. Wainscoat, M. F. Waterson

[abridged] We report on our serendipitous pre-discovery detection and detailed follow-up of the broad-lined Type Ic supernova SN 2010ay at z\approx0.067 imaged by the Pan-STARRS1 3{\pi} survey just \sim3 days after explosion. We estimate the explosion date and the peak luminosity of the SN, MR\approx-20.2 mag, significantly brighter than known GRB-SNe and one of the most luminous SNe Ic ever discovered. We measure the photospheric expansion velocity of the explosion, v_ph\approx19.2x10^3 km/s at \sim40 days after explosion. In comparison with other broad-lined SNe, the characteristic velocity of SN 2010ay is 2-5x higher and similar to the measurements for GRB-SNe at comparable epochs. Moreover the velocity declines two times slower than other SNe Ic-BL and GRB-SNe. Assuming that the optical emission is powered by radioactive decay, the peak magnitude implies the synthesis of an unusually large mass of 56 Ni, M_Ni=0.9+0.2 M_solar. Our modeling of the light-curve points to a total ejecta mass, Mej\approx4.7M_solar, and total kinetic energy, E_K,51\approx11. Thus the ratio of MNi to Mej is at least twice as large for SN 2010ay than in GRB-SNe and may indicate an additional energy reservoir. We also measure the metallicity (log(O/H)+12=8.19) of the explosion site within the host galaxy, placing this SN in the low-metallicity regime populated by GRB-SNe, and \sim 0.2(0.5) dex lower than that typically measured for the host environments of normal (broad-lined) Ic supernovae. Despite striking similarities to the recent GRB-SN 100316D/2010bh, we show that gamma-ray observations rule out an associated GRB with a flux, F_gamma>6x10^-7 erg/cm^2 (25-150 keV). Similarly, our deep radio follow-up observations with the EVLA rule out relativistic ejecta with energy, E>10^48 erg. These observations challenge the importance of progenitor metallicity for the production of a GRB, and suggest that other parameters also play a key role.

View original: http://arxiv.org/abs/1110.2363