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This page is an addendum to the GCN Circular 6155 (D. Denisenko, O. Terekhov) published on 2007 Feb. 27 and the extended version of the paper submitted to Astronomy Letters (Pis'ma v Astronomicheskiy Zhurnal). It contains the color images and animations which cannot be inserted to the printed version of journal, but are essential for illustrating the discovery. |
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As a result of the systematic search for the archival plates taken at the Palomar and Siding Spring observatories in the course of all sky survey, several cosmic gamma-ray bursts were selected whose error boxes were covered (entirely or in part) within a day after the event. Inside the error circle of bright long GRB 920925C an optical transient of magnitude 17.8 is found on the plate taken 6 hours after the burst. The position of an object falls inside the IPN annulus. Four suspect objects were found in the error box of another bright GRB 920903B on the plate taken 16 days after the burst, one of them being consistent with IPN annulus. Two of these objects are probably galactic variable stars, the other two - plate defects. |
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Comment: This page contains the description of GRB afterglow search program and list of the events studied. The article is divided in three parts. You can find the data related to GRB 920925C and GRB 920903B at the separate pages: |
There are also 47 bursts localized with the WATCH instrument onboard GRANAT observatory in 1990-1994 (Sazonov et al., 1998). WATCH error circles are much smaller than those by BATSE (3-sigma radii ranging from 0.19 to 1.54 deg, or from 0.28 to 1.56 deg including systematic errors).
2667 POSS-II plates cover the northern hemisphere six times on average (two times each in IR, R and B). However, since the adjacent plates overlap each other by about 2 deg (plate centers are separated by 5 degree in declination and right ascension), about 40% of sky (central 3x3 square degree) were only covered one time in each band, about 50% - two times and about 10% at the plate edges - three or even four times.
1788 DSS South plates cover the southern hemisphere four times on average (two times each in R and B). There are also 606 Anglo-Australian Red plates.
The plots below show the distribution of DSS plates taken in the northern celestial hemisphere at Palomar observatory (USA) and in the southern skies at Siding Spring observatory (Australia).
Next plots show the distribution of gamma-ray bursts localized by BATSE and WATCH.
Thus, one would expect about 10 BATSE error boxes to have been serendipitously covered by DSS plates within a day after the burst, and one WATCH error box with a probability about 25%.
Dates of burst triggers, their positions and error radii were taken from 5B catalogue and from WATCH catalogue. Information on DSS plate exposure start times and their centers was taken from NOFS site. A code was written to search for the coincidences in time and position in the sky. The following table lists the results of the search.
Listed below are bursts whose localizations fall within 6 degree from the centers of plates taken within 24 hours after the GRB. Dtime in the sixth column equals to the time of plate exposure start minus burst trigger time, Elong is the distance in degrees between the center of BATSE error circle and the plate center, and Error is one-sigma statistical localization radius.
-------------------------------------------------------------------- Trig# YYMMDD Sec RA GRB Decl Dtime Elong Error Flux -------------------------------------------------------------------- 755 910904 56090.16 354.15 -17.09 0.941 2.77 7.03 0.19 1458 920302 884.08 115.28 -58.92 -0.600 5.71 2.08 0.68 1458 920302 884.08 115.28 -58.92 0.420 5.50 2.08 0.68 2530 930914 10151.58 34.26 34.29 1.233 5.73 1.53 9.96 2600 931023 15230.36 4.19 74.17 0.964 5.46 1.07 2.25 2600 931023 15230.36 4.19 74.17 1.034 4.87 1.07 2.25 3144 940830 41839.28 1.76 -6.29 1.166 3.60 11.11 0.32 3903 951111 77568.43 31.41 69.55 0.262 5.40 5.73 0.64 3903 951111 77568.43 31.41 69.55 4.272 1.68 5.73 0.64 6219 970503 20769.35 170.66 70.18 -0.000 5.69 9.54 0.02 6219 970503 20769.35 170.66 70.18 2.990 5.75 9.54 0.02 7283 981227 67496.42 112.39 38.38 0.519 4.00 6.76 0.19 --------------------------------------------------------------------
------------------------------------------------------------------------- YYMMDD Sec RA GRB Decl Plate Date Dtime Elong Error ------------------------------------------------------------------------- 920925 81984 330.80 25.48 SJ04837 2448891.700 0.251 0.31 0.39 -------------------------------------------------------------------------And by unbelievable luck, this GRB is the third longest among all WATCH bursts with the measured duration. It is also the third brightest in 8-20 keV energy range, while it has the tenth largest fluence in 20-60 keV band. In the error circle of this burst we found an optical transient which is discussed in detail separately.
Extending the range of Dtime to one month gives another bright burst.
------------------------------------------------------------------------- YYMMDD Sec RA GRB Decl Plate Date Dtime Elong Error ------------------------------------------------------------------------- 920903 84541 301.54 22.59 SF04812 2448885.640 16.162 2.90 0.30 -------------------------------------------------------------------------This event will be discussed later in another chapter.
Denis Denisenko denis@hea.iki.rssi.ru