Those of you who have read "Galileo Was Wrong" know about a puzzling observation concerning the isotropic distribution of Gamma Ray Bursts:
"No longer could astronomers hope that the Copernican dilemma would disappear with improved data. The data were in hand, and their implication inescapable: we are at the center of a spherically symmetric distribution of gamma-ray-burst sources, and this distribution has an outer edge. Beyond this edge the density of burst sources decreases to insignificance."---Jonathan Katz, The Biggest Bangs, p. 111.
Well, you can kiss that argument goodbye.
And so yet another Copernican dilemma returns front and center, just in time for "The Principle".
UPDATE 12/8: A letter to the editor submitted to Astronomy and Astrophysics in January of 2013 suggests that the Copernican challenge for GRB's is even much, much greater than this.......
"We observe that the dipolar and quadripolar moments of the selected subsamples of FREDs are found more than two standard deviations outside those of random isotropically generated samples. The most probable degree of contamination by Galactic sources for the FRED GRBs of the Swift catalog detected until February 2011 that do not have a known redshift is about 21 out of 77 sources, which represents roughly 27%. Furthermore, we observe that by removing from this sample those bursts that have any type of indirect redshift indicator and multiple peaks, the most probable contamination increases to 34% (17 out of 49 sources).
Conclusions. It is probable that a high degree of contamination by Galactic sources occurs among the single-peak FREDs observed by Swift. Accordingly we encourage additional studies on these type of events to determine the nature of what could be an exotic type of Galactic source."
They write: "using a flat ΛCDM cosmology with h = 0.71 and ΩΛ = 0.73, implying [the GRB has a] luminosity distance of 1.8 Gpc for z = 0.34."
ReplyDeleteThat may be relatively close for a GRB, but that's just one GRB.
Not "relatively close". Impossibly close, if the resolution of the Copernican dilemma holds (which, we now know, it doesn't).
ReplyDeleteBut it is not just one:
“We therefore consider it unlikely that GRB 070610 arises from a background (i.e., extragalactic) event. The spatial and temporal coincidence.....suggest that these are strongly related. If so, the event is of Galactic origin.”-- “GRB 070610: A Curious Galactic Transient” M. M. Kasliwal,1 S. B. Cenko,2 et al, Astrophysical Journal 2008, http://iopscience.iop.org/0004-637X/678/2/1127/fulltext
Also:
"“History is repeating itself. Only 30 years ago, astronomers referred to all bursts of gamma-ray radiation as GRBs........However, fissures are already developing. Recently, hypergiant flares from magnetars in our own Galaxy and nearby galaxies have been found to contaminate the SHB sample. The Galactic rate of the hypergiant flares is likely.....much larger than the estimated Galactic SHB rate...” --“GRB 070610: A Curious Galactic Transient” M. M. Kasliwal,1 S. B. Cenko,2 et al, Astrophysical Journal 2008, http://iopscience.iop.org/0004-637X/678/2/1127/fulltext
Interesting
Deletethanks for the links