The spectroscopic variability of GRB 021004

T. Matheson, P. M. Garnavich, C. Foltz, S. West, G. Williams, E. Falco, M. L. Calkins, F. J. Castander, E. Gawiser, S. Jha, D. Bersier, K. Z. Stanek

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


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. Lyα 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 Å is steep, Fv ∝ v- 0.93±0.03. Comparison of spectra from multiple epochs shows a distinct color evolution with the OT becoming redder with time over the first 3 days. This is the first clear example of color change in an OT detected spectroscopically.

Original languageEnglish (US)
Pages (from-to)L5-L9
JournalAstrophysical Journal
Issue number1 II
StatePublished - Jan 1 2003


  • Galaxies: ISM
  • Galaxies: distances and redshifts
  • Gamma rays: bursts
  • Ultraviolet: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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