Abstract
We present extensive multiwavelength (radio to X-ray) observations of the Type Ib/c supernova (SN Ib/c) SN 2013ge from -13 to +457 days relative to maximum light, including a series of optical spectra and Swift UV-optical photometry beginning 2-4 days post-explosion. This data set makes SN 2013ge one of the best-observed normal SNe Ib/c at early times-when the light curve is particularly sensitive to the progenitor configuration and mixing of radioactive elements-and reveals two distinct light curve components in the UV bands. The first component rises over 4-5 days and is visible for the first week post-explosion. Spectra of the first component have blue continua and show a plethora of moderately high. velocity (similar to 15,000 km s(-1)) but narrow (similar to 3500 km s(-1)) spectroscopic features, indicating that the line-forming region is restricted. The explosion parameters estimated for the bulk explosion (M-ej similar to 2-3 M-circle dot; E-K similar to (1-2) x 10(51) erg) are standard for SNe Ib/c, and there is evidence for weak He features at early times-in an object that. would have otherwise been classified as Type Ic. In addition, SN 2013ge exploded in a low-metallicity environment (similar to 0.5 Z(circle dot)), and we have obtained some of the deepest radio and X-ray limits for an SN Ib/c to date, which constrain the progenitor mass-loss rate to be (M) over dot < 4 x 10(-6) M-circle dot yr(-1). We are left with two distinct progenitor scenarios for SN 2013ge, depending on our interpretation of the early emission. If the first component is cooling envelope emission, then the progenitor of SN 2013ge either possessed an extended (greater than or similar to 30 R-circle dot) envelope or ejected a portion of its envelope in the final less than or similar to 1 yr before core. collapse. Alternatively, if the first component is due to outwardly mixed Ni-56, then our observations are consistent with the asymmetric ejection of a distinct clump of nickel-rich material at high velocities. Current models for the collision of an. SN. shock with a binary companion cannot reproduce both the timescale and luminosity of the early emission in SN 2013ge. Finally, the spectra of the first component of SN 2013ge are similar to those of the rapidly declining SN 2002bj.