Mathematics – Logic
Scientific paper
Oct 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998phdt..........m&link_type=abstract
Thesis (PHD). GEORGE MASON UNIVERSITY , Source DAI-B 59/04, p. 1695, Oct 1998, 157 pages.
Mathematics
Logic
6
Time Series, Gravitational Lensing, Dark Matter, Gamma Ray Burst, Cosmology, Statistical Analysis
Scientific paper
If Gamma-Ray Bursts (GRBs) are cosmological in origin, different signatures are expected to be found in the available \batse catalog and time series. Cross-correlation with extragalactic objects and gravitational lensing by intervening objects are some examples of these particular features. A new statistical method to perform 2-D angular cross-correlations between GRB positions and different catalogs of extragalactic objects has been implemented. For the best located 74 3B GRBs, a 2.5-σ level association with rich, nearby Abell clusters is found. If all the cluster are taken into account, a 3.5-σ association is found for the best located 27 3B bursts. Another 2.5-σ excess is found between soft GRBs and the whole Abell catalog. On the other hand, excesses of the order of ~ 3.5-4-σ are found between the best located 10 to 380 bursts and the nearest, intrinsically brightest radio quiet quasars. However, the correlations appears to be due to statistical fluctuations and the excesses are only suggestive of a physical association. A fully automated search among 1,235 4B bursts has been carried out to look for statistical similarities in the GRB time series. No two GRBs are found to be identical to within the statistical limits of the data, regardless of their position on the sky. GRBs that appear statistically similar in one energy channel are either dissimilar in other energy channels or too dim for a significant statistical comparison. One consequence of the search for statistical similarities is that no gravitational lensing of GRBs by foreground galaxies have been found. Given this null result, and assuming no GRB rate density or luminosity evolution, and that QSO images are distorted by the same galaxy field, a conservative upper limit to the redshift is derived, zmax ~ 4.22 at a 2-σ confidence level, for an Einstein-de Sitter universe and bursts with P > 1 photon cm-2 s-1. The gravitational lensing rates have been computed for different Friedmann-Robertson-Walker universes and GRB number density models, and assuming a monoluminous population of GRBs. >From the absence of lensed bursts, we have deduced that bursts should have z1.0 < 4.55 in a (ΩM,&OmegaΛ)=(0,1) universe where the GRB number density is assumed to evolve with cosmic time, or otherwise, this universe would be rejected. The cosmological abundance of dark compact objects (COs) in the universe has been studied by means of gravitational lensing of GRBs. An Ω = 0.15 nearly filled with COs with MCO ~ 106.5 Msolar has been ruled out at ~ 90.0 - 92.0 % confidence level, given that no lensing by such masses has been found. A comparison of peak counts for 60 bright bursts simultaneously detected by \batse and Ulysses was performed, and no evident discrepancies in the amplitudes have been detected. Although nearly no lenses are expected in the sample, an Einstein-de Sitter universe with Mco ~ 10-12.5- 10-9.0 Msolar and Ωco >= 0.9 has been weakly ruled out. Since \batse has not detected spectral lines, which might be created by gravitational lensing events by COs with masses between 10-16 Msolar and 10-13 Msolar, very loose constraints have been imposed on the CO density, rejecting Ωco >= 0.2 if zmax ~ 1, or Ωco >= 0.1 if zmax~ 2.
No associations
LandOfFree
Statistical and Time Analyses of Gamma-Ray Bursts does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Statistical and Time Analyses of Gamma-Ray Bursts, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Statistical and Time Analyses of Gamma-Ray Bursts will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1100621