Astrophysics - Cosmology and Extragalactic Astrophysics

On the nature of the hostless' short GRBs

A significant proportion (̃30 per cent) of the short-duration gamma-ray bursts (SGRBs) localized by Swift have no detected host galaxy coincident with the burst location to deep limits, and also no high-likelihood association with proximate galaxies …

Discovery and Redshift of an Optical Afterglow in 71 deg$^2$: iPTF13bxl and GRB 130702A

We report the discovery of the optical afterglow of the γ-ray burst (GRB) 130702A, identified upon searching 71 deg$^2$ surrounding the Fermi Gamma-ray Burst Monitor (GBM) localization. Discovered and characterized by the intermediate Palomar …

Keck Observations of 160 Gamma-Ray Burst Host Galaxies

We present a preliminary data release from our multi-year campaign at Keck Observatory to study the host galaxies of a large sample of Swift-era gamma-ray bursts via multi-color ground-based optical imaging and spectroscopy. With over 160 targets …

The Properties of the 2175 ̊A Extinction Feature Discovered in GRB Afterglows

The unequivocal, spectroscopic detection of the 2175 ̊A bump in extinction curves outside the Local Group is rare. To date, the properties of the bump have been examined in only two gamma-ray burst (GRB) afterglows (GRB 070802 and GRB 080607). In …

A Compact Degenerate Primary-star Progenitor of SN 2011fe

While a white dwarf (WD) is, from a theoretical perspective, the most plausible primary star of a Type Ia supernova (SN Ia), many other candidates have not been formally ruled out. Shock energy deposited in the envelope of any exploding primary …

Exclusion of a luminous red giant as a companion star to the progenitor of supernova SN 2011fe

Type Ia supernovae are thought to result from a thermonuclear explosion of an accreting white dwarf in a binary system, but little is known of the precise nature of the companion star and the physical properties of the progenitor system. There are …

Circumstellar Material in Type Ia Supernovae via Sodium Absorption Features

Type Ia supernovae are key tools for measuring distances on a cosmic scale. They are generally thought to be the thermonuclear explosion of an accreting white dwarf in a close binary system. The nature of the mass donor is still uncertain. In the …

Galaxy Zoo Supernovae

This paper presents the first results from a new citizen science project: Galaxy Zoo Supernovae. This proof-of-concept project uses members of the public to identify supernova candidates from the latest generation of wide-field imaging transient …

Progenitor Diagnostics for Stripped Core-collapse Supernovae: Measured Metallicities at Explosion Sites

Metallicity is expected to influence not only the lives of massive stars but also the outcome of their deaths as supernovae (SNe) and gamma-ray bursts (GRBs). However, there are surprisingly few direct measurements of the local metallicities of …

Casting Light on the `Anomalous'' Statistics of Mg II Absorbers Toward Gamma-ray Burst Afterglows: The Incidence of Weak Systems

We revisit echelle spectra (spectral resolution R ≈ 40,000) of eight gamma-ray burst (GRB) afterglows to obtain the incidence (dN/dz) of weak intervening Mg II systems at a mean redshift of langzrang = 1.5. We show that dN/dz of systems having …