Discovery of SN 2009nz Associated with GRB 091127

TL;DR

This paper reports the discovery of a supernova, SN 2009nz, associated with GRB 091127, based on multi-wavelength observations, showing the supernova's light curve and spectral properties, and confirming its connection to the gamma-ray burst.

Contribution

First identification and detailed analysis of SN 2009nz as the supernova associated with GRB 091127, expanding understanding of GRB-SN connections.

Findings

SN 2009nz peaked at M_V=-19.0+/-0.2

SN 2009nz evolved faster than SN 1998bw

Little to no reddening in host galaxy along line-of-sight

Abstract

We report SMARTS, Gemini and Swift-UVOT observations of the optical transient (OT) associated with gamma-ray burst (GRB) 091127, at redshift 0.49, taken between 0.9 hr and 102 days following the Swift trigger. In our early-time observations, the OT fades in a manner consistent with previously observed GRB afterglows. However, after 9 days post-burst, the OT is observed to brighten for a period of ~2 weeks, after which the source resumes fading. A comparison of this late-time "bump" to SN 1998bw (the broad-lined Type Ic supernova associated with GRB 980425), and several other GRB supernovae (SNe), indicates that the most straightforward explanation is that GRB 091127 was accompanied by a contemporaneous SN (SN 2009nz) that peaked at a magnitude of M_V=-19.0+/-0.2. SN 2009nz is globally similar to other GRB supernovae, but evolves slightly faster than SN 1998bw and reaches a slightly dimmer peak magnitude. We also analyze the early-time UV-optical-IR spectral energy distribution of the afterglow of GRB 091127 and find that there is little to no reddening in the host galaxy along the line-of-slight to this burst.