Abstract. The imaging Compton telescope COMPTEL aboard NASA's Compton Gamma-Ray Observatory has opened the MeV gamma-ray band as a new window to astronomy. COMPTEL provided the first complete all-sky survey in the energy range 0.75 to 30 MeV. The catalogue, presented here, is largely restricted to published results. It contains firm as well as marginal detections of continuum and line emitting sources and presents upper limits for various types of objects. The numbers of the most significant detections are 32 for steady sources and 31 for gammaray bursters. Among the continuum sources, detected so far, are spin-down pulsars, stellar black-hole candidates, supernova remnants, interstellar clouds, nuclei of active galaxies, gamma-ray bursters, and the Sun during solar flares. Line detections have been made in the light of the 1.809 MeV 26 Al line, the 1.157 MeV 44 Ti line, the 847 and 1238 keV 56 Co lines, and the neutron capture line at 2.223 MeV. For the identification of galactic sources, a modelling of the diffuse galactic emission is essential. Such a modelling at this time does not yet exist at the required degree of accuracy. Therefore, a second COMPTEL source catalogue will be produced after a detailed and accurate modelling of the diffuse interstellar emission has become possible.

GRB 990123 was the first burst from which simultaneous optical, X-ray and gammaray emission was detected; its afterglow has been followed by an extensive set of radio, optical and X-ray observations. We have studied the gamma-ray burst itself as observed by the CGRO detectors. We find that gamma-ray fluxes are not correlated with the simultaneous optical observations, and the gamma-ray spectra cannot be extrapolated simply to the optical fluxes. The burst is well fit by the standard four-parameter GRB function, with the exception that excess emission compared to this function is observed below ∼ 15 keV during some time intervals. The burst is characterized by the typical hard-to-soft and hardness-intensity correlation spectral evolution patterns. The energy of the peak of the νf ν spectrum, E p , reaches an unusually high value during the first intensity spike, 1470 ± 110 keV, and then falls to ∼300 keV during the tail of the burst. The high-energy spectrum above ∼ 1 MeV is consistent with a power law with a photon index of about −3. By fluence, GRB 990123 is brighter than all but 0.4% of the GRBs observed with BATSE, clearly placing it on the −3/2 power-law portion of the intensity distribution. However, the redshift measured for the afterglow is inconsistent with the Euclidean interpretation of the −3/2 power-law. Using the redshift value of ≥ 1.61 and assuming isotropic emission, the gamma-ray fluence exceeds 10 54 ergs.

No abstract

Context. GRB 041219a is the brightest burst localised by INTEGRAL. The peak flux of 43 ph cm −2 s −1 (1.84 × 10 −5 erg cm −2 s −1 , 20 keV-8 MeV, 1 s integration) is greater than that for ∼98% of all bursts and the T 90 duration of ∼186 s (∼20 keV-8 MeV) is longer than all but a small number of bursts. The intense burst occurred about ∼250 s after the precursor and the long delay enabled optical and near infrared telescopes to observe the prompt emission. Aims. 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 Rossi X-ray Timing Explorer. We avail of multi-wavelength data to generate broadband spectra of GRB 041219a and afterglow. Methods. 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 γ-ray afterglow. Results. 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 γ-ray afterglow was detected from the end of the prompt phase to ∼12 h post-burst. Broadband spectra of the prompt emission were generated in 7 time intervals using γ-ray, X-ray, optical and near-infrared data and these were compared to the high-redshift burst GRB 050904. The optical and γ-ray emission are correlated in GRB 041219a. We estimate isotropic radiated energy (E iso ) to be ∼5 × 10 52 erg. 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.

No abstract