Gamma-ray Counterpart Research Articles

Non-diffusive propagation of ultra high energy cosmic rays

We report the results of 3D simulations of non-diffusive propagation of Ultra High Energy Cosmic Rays (UHECR) ( E > 10 20 eV) through the intergalactic and extended halo media. We quantify the expected angular and temporal correlations between the events and the sources, and the temporal delay between protons and gamma-ray counterparts with a common origin for both halo and extragalactic origins. It is shown that the proposed UHECR-supergalactic plane source associations require either extremely high values of the halo magnetic field over as much as 100 kpc length scale or a very large correlation length for the IGM, even for the largest possible values of the intergalactic magnetic field. It can be stated that the UHECR seem to point to the sources even more strongly than previously believed. The simulations also show that the calculated time delays between UHE protons and gamma-ray counterparts do not match the claimed GRB-UHECR associations for either cosmological or extended halo distance scales.

Extrapolations of BATSE Gamma‐Ray Burst Spectra to the Optical‐Ultraviolet Band

Many gamma-ray burst counterpart searches are being conducted in the optical-UV band. To both predict detectability and understand the meaning of any detections or upper limits, we extrapolate gamma-ray spectra from 54 bright gamma-ray bursts to optical-UV energies. We assume optical emission is concurrent with gamma-ray emission and do not consider quiescent or fading counterparts. We find that the spectrum must be steeper (greater flux at low energy) than a simple extrapolation of the gamma-ray spectrum for more than one simultaneous optical flash to be observable per year by current searches.

Directions for Future X-Ray, Optical, and Radio Follow-up Observations of Gamma-Ray Burst Counterparts

We review the current state of X-ray, optical, and radio follow-up observations of gamma-ray burst (GRB) error boxes. We show that despite the lack of an identified burst counterpart, the time and flux domain within which such objects can exist has been severely constrained. A clear direction for future follow-up efforts is identified. In the radio, searches must extend below 3 mJy and begin within 3 days of burst detection. In the optical, deep imaging (>12 mag) within 10 hr of burst detection will be needed to improve significantly upon the time and flux domain already searched for GRB counterparts. At X-ray energies, deep exposures within 19 days of burst detection are needed to explore new regions in the time/flux domain. Significant progress in each of these regimes can be expected within the next year from current follow-up efforts.

Search for gamma-ray bursts with energies above 1 TEV

Some models of gamma-ray bursts suggest that their spectrum may extend into the energy range above 10 GeV, i.e. above energies accessible with CGRO. Data taken with the HEGRA extensive air shower array are used to search for very high energetic gamma-ray burst counterparts above 1 TeV. First results from the search for BATSE correlated and BATSE independent bursts are presented.

Results from GROCSE, a real-time search for the Optical Counterparts of Gamma-Ray bursts

The GROCSE Collaboration (Gamma-Ray Optical Counterpart Search Experiment) has been operating a rapid response camera since January 1994 in an attempt to capture optical images of GRB events. This detector has a response time of 15 seconds and a limiting magnitude of 8. A second generation detector is now under construction which is expected to eventually reach mv ≃ 15 with a 5 second exposure.

The first search for a gamma-ray burst quiescent counterpart in the extreme ultraviolet with EUVE

The opening of the extreme ultraviolet window by the Extreme Ultraviolet Explorer (EUVE) satellite has provided the unique opportunity to perform the first search for a quiescent gamma-ray burst counterpart at these wavelengths. Such emission might be expected if some bursts are related to nearby hot neutron stars or neutron stars with accretion disks, among other objects. We report here on a 40 ks observation on the 1992 March 25 gamma-ray burst error box, determined by triangulation with the Third Interplanetary Network. No quiescent 40-190 A Extreme Ultraviolet (EUV) source was identified using the Deep Survey instrument, and a 3 sigma upper limit of 2.9 x 10(exp -14) erg/sq cm/s was obtained. Similarly, upper limits to the 140-380 and 280-760 A fluxes were obtained with the medium- and long-wavelength spectrometers; they are 1.1 x 10(exp -12) and 5.0 x 10(exp -13) erg/sq cm/s, respectively. We discuss the constraints which these limits impose on thermally radiating quiescent counterparts.

Comets, X-ray bursts, and gamma-ray bursts

The proposal, revived by Tremaine and Zytkow (1985), that accretion of comets by neutron stars may be the origin of gamma-ray bursts is considered. This mechanism has difficulty accounting for the observed gamma-ray spectrum and optical counterparts of the bursts. The survival of comets near supernovae is investigated. Ablation rates and the thermal structure of an ablating surface layer are calculated. In some circumstances, mechanical disruption will erode a comet more rapidly than evaporation. The accretion of comets by neutron stars may produce a class of X-ray burst sources with novel properties.

Candidates for a gamma-ray burster optical counterpart

view Abstract Citations (48) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Candidates for a gamma-ray burster optical counterpart. Schaefer, B. E. ; Seitzer, P. ; Bradt, H. V. Abstract The small size of the 1928 optical error box for the 1978 November 19 gamma-ray burster (GRB) allows for a very deep search for the quiescent optical counterpart. A CCD camera on the Cerro Tololo Inter-American Observatory 4 m telescope has been used to search this field to a m(B) fainter than 25.0. Several objects in the 1928 error box, are found, including one which varies by over 1 mag on a time scale of under a day. This variable object corresponds in position to object A of Pedersen et al. (1982). Since it is confirmed that their object B has disappeared, there are two faint variables is the field. It is currently unclear which one (if either) of the variables is the true GRB counterpart. Astrometry and U, B, V, and r photometry for eight nearby comparison stars are also reported. Publication: The Astrophysical Journal Pub Date: July 1983 DOI: 10.1086/184068 Bibcode: 1983ApJ...270L..49S Keywords: Gamma Ray Astronomy; Gamma Ray Bursts; Visual Observation; Astrometry; Errors; Reference Stars; Stellar Spectrophotometry; Variable Stars; Astronomy full text sources ADS | data products SIMBAD (12)