The Spectroscopic Variability of GRB 021004

Abstract

We present spectra of the optical transient (OT) associated with GRB 021004. The spectra show a blue continuum with superposed absorption features and one emission line. We confirm two intervening metal-line systems at z = 1.380 and z = 1.602 and one very strong absorption system at a redshift of z = 2.323. Ly_alpha emission is also seen at this redshift. While the spectrum of the OT overall cannot be simply described with a power law, the spectral index over the range 5500-8850 A is steep, F_nu ~ nu^(-0.96 +/- 0.03). Comparison of spectra from multiple epochs shows a distinct color evolution with the OT becoming redder with time over the first three days. This is the first clear example of color change in an OT detected spectroscopically.

13 pages, two figures, revised per referee's comments, accepted for publication in ApJ Letters

References in corpus (11)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• The Shape of Spectral Breaks in GRB Afterglows
• Detailed Analysis of Early to Late-Time Spectra of Supernova 1993J
• X-ray Destruction of Dust Along the Line of Sight to Gamma-Ray Bursts
• VLT spectroscopy of GRB 990510 and GRB 990712; probing the faint and bright end of the GRB host galaxy population
• Gamma-Ray Burst in a Molecular Cloud: Destruction of Dust and H2, and Emergent Spectrum
• Time-Dependent Photoionization in a Dusty Medium I: Code Description and General Results
• The redshift and the ordinary host galaxy of GRB 970228
• Optical follow-up of GRB 970508
• Time-Dependent Optical Spectroscopy of GRB 010222: Clues to the GRB Environment
• The Redshift of the Optical Transient Associated with GRB 010222

Cited by in corpus (32)

• GRB Energetics and the GRB Hubble Diagram: Promises and Limitations
• Photometry and Spectroscopy of GRB 030329 and Its Associated Supernova 2003dh: The First Two Months
• The detailed optical light curve of GRB 030329
• Ly-alpha and UV emission from high-redshift GRB hosts: To what extent do GRBs trace star formation?
• GRB 021004: A Possible Shell Nebula around a Wolf-Rayet Star Gamma-Ray Burst Progenitor
• Optical Photometry of GRB 021004: The First Month
• GRB 021004: a Massive Progenitor Star Surrounded by Shells
• Can Gamma-Ray Bursts Be Used to Measure Cosmology? A Further Analysis
• A flash in the dark: UVES/VLT high resolution spectroscopy of GRB afterglows
• Detailed optical and near-infrared polarimetry, spectroscopy and broadband photometry of the afterglow of GRB 091018: Polarisation evolution
• The unusual optical afterglow of the gamma-ray burst GRB 021004: Color changes and short-time-scale variability
• Overcoming the Circular Problem for γ-ray Bursts in Cosmological Global Fitting Analysis
• Energy Injection Episodes in Gamma Ray Bursts: The Light Curves and Polarization Properties of GRB 021004
• "Anomalous" Optical GRB Afterglows are Common: Two z~4 Bursts, GRB 060206 and 060210
• Spectroscopy of GRB 021004: a structured jet ploughing through a massive stellar wind
• Variable polarization in the optical afterglow of GRB 021004
• High Quality Early Time Light Curves of GRB 060206: Implications for Gamma Ray Burst Environments and Energetics
• Polarization and light curve variability: the "patchy shell" model
• On the Afterglow and Host Galaxy of GRB021004: A Comprehensive Study with the Hubble Space Telescope
• Intrinsic and dust-induced polarization in gamma-ray burst afterglows: the case of GRB 021004
• Broadband Modeling of GRB 021004
• Radio, millimeter and optical monitoring of GRB030329 afterglow: Constraining the double jet model
• Selection Effects on the Observed Redshift Dependence of GRB Jet Opening Angles
• Wind-Interaction Models for the Early Afterglows of Gamma-Ray Bursts: The Case of GRB 021004
• GRB 021004: Tomography of a gamma-ray burst progenitor and its host galaxy
• Is the Redshift Clustering of Long-Duration Gamma-Ray Bursts Significant?
• GRB 021211 as a Faint Analogue of GRB 990123: Exploring the Similarities and Differences in their Optical Afterglows
• SCUBA sub-millimeter observations of gamma-ray bursters IV. GRB 021004, 021211, 030115, 030226, 041006
• The variable X-ray light curve of GRB 050713A: the case of refreshed shocks
• Time resolved spectroscopy of GRB 021004 reveals a clumpy extended wind
• Massive star-formation rates of gamma-ray burst host galaxies: an unobscured view in X-rays
• The rest-frame ultraviolet spectra of GRBs from massive rapidly-rotating stellar progenitors