Research
I am currently a sixth-year graduate student at UC Berkeley, working mainly with Josh Bloom and the rest of the transient group. Most of my work during graduate school has revolved around the observational study of gamma-ray bursts and their afterglows. I have been involved with afterglow follow-up using the robotic telescopes KAIT and PAIRITEL as well as with spectroscopy on large-aperture telescopes Keck and Gemini. However, the focus of my thesis work will be on host-galaxy follow-up: searching for and cataloguing the properties of the galaxies in which GRBs have occurred. Since the average redshift of a gamma-ray burst is about z=2.0, this means looking at extremely distant and faint galaxies, observed at a time when the universe was about half its present age.
Some particular research questions I've been interested in:
- What is the origin of 'dark' gamma-ray bursts, GRBs without optical afterglow? Are their host galaxies fundamentally different from normal GRBs?
- Observationally, how can we constrain and inform the various theoretical models of "short" gamma-ray bursts?
- Can GRBs be used to trace star formation in places not well-probed by more traditional survey techniques, such as intergalactic space, dusty clouds, or highly underluminous galaxies?
- Are there rare classes of, or production channels for, GRBs beyond the simple two-class (short/long) model? How can we improve our understanding of these events?
- Do genuine long GRBs sometimes fail to produce supernovae?
- What is the origin and frequency of magnetar hyperflares?
Before coming to Berkeley, I worked on several other projects in radio astronomy, software, and galaxy cluster identification (see Previous Research).
Select list of publications:
- Perley, Cenko, Bloom et al. (2009): "The Host Galaxies of Swift Dark Gamma-Ray Bursts: Observational Constraints on Highly Obscured and Very High-Redshift GRBs"
(AJ, submitted)
Here we examine a subsample of our host observations with uniform, deep early optical afterglow coverage from the P60 robotic telescope. Almost every "dark" event has a detectable host, ruling out the high redshift scenario as a predominant cause of dark bursts. We instead favor host-galaxy dust extinction (up to 5-10 magnitudes in some cases) as the predominant cause of dark bursts.
- Perley, Metzger, Granot et al. (2009): "GRB 080503: Implications of a Naked Short Gamma-Ray Burst Dominated by Extended Emission"
(ApJ 696:1871 2009)
This bright short gamma-ray burst showed one of the faintest afterglows on record, suggesting it had exploded in a near-vaccuum, in accordance with predictions of short gamma-ray bursts being ejected from their host galaxies. At the same time, the puzzling nature of its gamma-ray light curve poses theoretical difficulties for some of the leading models.
- Prochaska, Sheffer, Perley et al. (2009): "The First Positive Detection of Molecular Gas in a GRB Host Galaxy"
(ApJ 691:27 2009)
A phenominal burst at a redshift of z=3 that fortuitously occurred while we were at Keck showed features that the community had been seeking for decades: molecular lines (in addition to hundreds of ionic lines). By combining
the Keck spectrum with optical and infrared afterglow follow-up we were also able to constrain the dust properties and report a secure detection of the locally ubiquitous 2175-Angstrum dust feature.
- Bloom, Perley, Li et al. (2008): "Observations of the Naked-Eye GRB 080319B: Implications of Nature's Brightest Explosion"
(ApJ 691:723 2009)
GRB 080319B is the brightest and most optically luminous gamma-ray burst ever observed and has perhaps the best early data-set to date of any gamma-ray burst. We followed the burst starting from 1 minute and until many months after the burst, interpreting its unusual light curve and discussing implications for the observability of GRBs in the distant universe.
- Perley, Li, Chornock et al. (2008): "GRB 071003: Broadband Follow-up Observations of a Very Bright Gamma-Ray Burst in a Galactic Halo"
(ApJ 688:470 2008)
One of the brightest bursts that year, this event displayed several puzzling features including a dramatic late-time rebrightening and, most curiously, almost no sign of absorption from its host galaxy. No host galaxy was identified at the burst location. This burst either occurred in an extremely small galaxy or in a halo, perhaps in a tidal tail.
- Perley, Bloom, Butler et al. (2008): "The Troublesome Broadband Evolution of GRB 061126: Does a Gray Burst Imply Gray Dust?"
(ApJ 672:449 2007)
This extremely bright gamma-ray burst had among the best early broad-band coverage for any event, with simultaneous, highly precise measurements from the UV (2000 Angstroms) to IR (20000 Angstroms) plus X-ray follow-up. Surprisingly, relative to the X-ray the optical band appears strongly extinguished, but hardly reddened at all, suggesting the possible need for "gray" dust. This burst is probably the best example to date of this phenomenon.
Many additional publications are available via ADS below.
