Emily Levesque (CU Boulder)

Probing the Host Galaxies of Nearby Long-Duration GRBs

We present the latest results from our spectroscopic survey of long-duration gamma-ray burst (LGRB) host galaxies at z < 1, including the hosts of the five nearby GRBs with well-studied core-collapse supernova counterparts. We have determined a wide range of ISM properties for these events' host environments, and find that LGRB host galaxies follow a statistically robust mass-metallicity relation. From this, we conclude that LGRBs do exhibit a general trend toward lower-metallicityhost galaxies; however, we also detect several high-metallicity host environments in our sample. We also find no statistically significant correlation between hostmetallicity and gamma-ray energy release for the LGRBs in our samples, a result at odds with previous theoretical and observational predictions. Further studies of LGRB host galaxies, both nearby and at z > 1, will shed new light on the phenomenological connection between the general LGRB population and the properties of their natal environments and continue to unravel the complex role that metallicity plays in the evolution of these events' massive progenitors.