The correlation of spectral lag evolution with prompt optical emission in GRB 080319B

Michael Stamatikos, Tilan N. Ukwatta, Takanori Sakamoto, Kalvir S. Dhuga, Kenji Toma, Asaf Pe'er, Peter Mészáros, David L. Band, Jay P. Norris, Scott D. Barthelmy, Neil Gehrels

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

2 Citations (Scopus)


We report on observations of correlated behavior between the prompt γ-ray and optical emission from GRB 080319B, which confirm that (i) they occurred within the same astrophysical source region and (ii) their respective radiation mechanisms were dynamically coupled. Our results, based upon a new cross-correlation function (CCF) methodology for determining the time-resolved spectral lag, are summarized as follows. First, the evolution in the arrival offset of prompt γ-ray photon counts between Swift-BAT 15-25 keV and 50-100 keV energy bands (intrinsic γ-ray spectral lag) appears to be anti-correlated with the arrival offset between prompt 15-350 keV γ-rays and the optical emission observed by TORTORA (extrinsic optical/γ-ray spectral lag), thus effectively partitioning the burst into two main episodes at ∼ T + 28 ± 2 sec. Second, the rise and decline of prompt optical emission at ∼ T +10 ± 1 sec and ∼ T + 50 ± 1 sec, respectively, both coincide with discontinuities in the hard to soft evolution of the photon index for a power law fit to 15-150 keV Swift-BAT data at ∼ T + 8±2 sec and ∼ T + 48±1 sec. These spectral energy changes also coincide with intervals whose time-resolved spectral lag values are consistent with zero, at ∼ T +12 ± 2 sec and ∼ T + 50 ± 2 sec. These results, which are robust across heuristic permutations of Swift-BAT energy channels and varying temporal bin resolution, have also been corroborated via independent analysis of Konus-Wind data. This potential discovery may provide the first observational evidence for an implicit connection between spectral lags and GRB emission mechanisms in the context of canonical fireball phenomenology. Future work includes exploring a subset of bursts with prompt optical emission to probe the unique or ubiquitous nature of this result.

Original languageEnglish
Title of host publicationGamma-Ray Burst - 6th Huntsville Symposium
Number of pages6
Publication statusPublished - 2009
Event6th Huntsville Symposium on Gamma-Ray Bursts - Huntsville, AL, United States
Duration: 2008 Oct 202008 Oct 23

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


Conference6th Huntsville Symposium on Gamma-Ray Bursts
Country/TerritoryUnited States
CityHuntsville, AL


  • Gamma rays: bursts
  • Radiation mechanisms: non-thermal
  • Temporal analysis


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