Observations of the intense and ultra-long burst GRB041219a with the Germanium Spectrometer on INTEGRAL

Abstract

GRB041219a is the brightest burst localised by INTEGRAL. The intense burst occurred about ~250s after the precursor and the long delay enabled optical and near infrared telescopes to observe the prompt emission. We present comprehensive results of the temporal and spectral analyses, including line and afterglow searches using the spectrometer, SPI, aboard INTEGRAL, BAT on Swift and ASM on RXTE. We avail of multi-wavelength data to generate broadband spectra of GRB041219a and afterglow. Spectra for the burst and sub-intervals were fit by the Band model and also by the quasithermal model. The high resolution Germanium spectrometer data were searched for emission and absorption features and for gamma-ray afterglow. The overall burst and sub-intervals are well fit by the Band model. The photon index below the break energy shows a marked change after the quiescent time interval. In addition the spectra are well described by a black body component with a power law. The burst was detected by BAT and ASM during the long quiescent interval in SPI indicating the central engine might not be dormant but that the emission occurs in different bands. No significant emission or absorption features were found and limits of 900 eV and 120 eV are set on the most significant features. No gamma-ray afterglow was detected from the end of the prompt phase to ~12 hours post-burst. Broadband spectra of the prompt emission were generated in 7 time intervals using gamma-ray, x-ray, optical and near-infrared data and these were compared to the high-redshift burst GRB050904. The optical and gamma-ray emission are correlated in GRB041219a. The spectral lag was determined using data from the BAT and it changes throughout the burst. A number of pseudo-redshifts were evaluated and large dispersion in values was found.