# Astrophysics

## Unraveling the dynamics and kinematics of GRB hosts with high resolution spectroscopy

In the last years the research on GRB host galaxies has proceeded to more detailed studies both using high resolution afterglow spectroscopy and spatially resolved spectra of nearby hosts. High resolution spectra give a detailed picture of the …

## Discovery of a Very Bright, Nearby Gravitational Microlensing Event

We report the serendipitous detection of a very bright, very nearby microlensing event. In late 2006 October, an otherwise unremarkable A0 star at a distance of åisebox-0.5ex 1 kpc (GSC 3656-1328) brightened achromatically by a factor of nearly 40 …

## Towards a real-time transient classification engine

Temporal sampling does more than add another axis to the vector of observables. Instead, under the recognition that how objects change (and move) in time speaks directly to the physics underlying astronomical phenomena, next-generation wide-field …

## Observations of the 599 Hz Accreting X-Ray Pulsar IGR J00291+5934 during the 2004 Outburst and in Quiescence

We report on optical and near-infrared observations obtained during and after the 2004 December discovery outburst of the X-ray transient and accretion-powered millisecond pulsar IGR J00291+5934. Our observations monitored the evolution of the …

## On the Nature of Velocity Fields in High-z Galaxies

We analyze the gas kinematics of damped Lyα systems (DLAs) hosting high-z gamma-ray bursts (GRBs) and those toward quasars (QSO-DLAs), focusing on three statistics: (1) Δv$_90$, the velocity interval encompassing 90% of the integrated optical depth, …

## The Troublesome Broadband Evolution of GRB 061126: Does a Gray Burst Imply Gray Dust?

We report on observations of a gamma-ray burst (GRB 061126) with an extremely bright (R ≈ 12 mag at peak) early-time optical afterglow. The optical afterglow is already fading as a power law 22 s after the trigger, with no detectable prompt …

## A Complete Catalog of Swift Gamma-Ray Burst Spectra and Durations: Demise of a Physical Origin for Pre-Swift High-Energy Correlations

We calculate durations and spectral parameters for 218 Swift bursts detected by the BAT instrument between and including gamma-ray bursts (GRBs) 041220 and 070509, including 77 events with measured redshifts. Incorporating prior knowledge into the …

## Near-Infrared Interferometric, Spectroscopic, and Photometric Monitoring of T Tauri Inner Disks

We present high angular resolution observations with the Keck Interferometer, high-dispersion spectroscopic observations with Keck/NIRSPEC, and near-IR photometric observations from PAIRITEL of a sample of 11 solar-type T Tauri stars in nine systems. …

## Missing Molecular Hydrogen and the Physical Conditions of GRB Host Galaxies

We examine the abundance of molecular hydrogen (H$_2$) in the spectra of gamma ray burst afterglows (GRBs). In nearby galaxies, H$_2$ traces the cold neutral medium (CNM) and dense molecular star-forming interstellar gas. Although H$_2$ is detected …

## Pulse Width Evolution of Late-Time X-Ray Flares in Gamma-Ray Bursts

We study the duration and variability of late-time X-ray flares following gamma-ray bursts (GRBs) observed by the narrow-field X-ray telescope (XRT) aboard the Swift spacecraft. These flares are thought to be indicative of late-time activity by the …