{
  "bibcode": "2017GCN.21029....1M",
  "body": "E. Mazaeva (IKI), A. Pozanenko (IKI), R. Inasaridze (AbAO), I. Reva \n(Fesenkov Astrophysical Institute), A. Kusakin (Fesenkov Astrophysical \nInstitute), A. Volnova (IKI),  V. Ayvazian  (AbAO),  O. Kvaratskhelia \n(AbAO), G. Inasaridze (AbAO), I. Molotov (KIAM), report on behalf of \nlarger GRB follow-up collaboration:\n\nWe observed the field of the SWIFT trigger 748858 (Siegel, et al., GCN \n21011) with AS-32 (0.7m) telescope of Abastumani Observatory and with \nZeiss-1000 1-m telescope of Tien Shan Astronomical Observatory. In each \nobservation we fully cover both BAT error circles, initial (Siegel  et \nal., GCN 21011) and ground-calculated error circle (Sakamoto  et al., \nGCN 21017). Within  ground-calculated error circle we do not find any \nnew source in comparison with SDSS catalog.  Within  XRT error circle of \nthe source reported in GCN 21017 (Sakamoto  et al.) we find the source \nwhich is already mentioned by (Butler et al., GCN 21026). The source \ncoincides with the star  of J131924.35+153001.6 and has the brightness \nof R =19.53 +/- 0.04 according to  SDSS DR9 and Lupton gri -> R \ntransformations.\n\nLimiting magnitudes as well as the brightness of the star \nJ131924.35+153001.6 for each observation are presented below.\n\nDate        UT start   t-T0      Filter Exp.   XRT    Err UpLim (3 sigma)\n                       (mid, days)       (s)\n\n2017-04-19 17:03:29    0.39918   CR     33*60  19.35  0.06 22.2\n2017-04-19 17:37:14    0.42414   R      21*180 19.47  0.05 22.0\n\nPhotometry is based on nearby SDSS DR9 stars (Lupton transformations)\nJ131940.43+152853.2    15.63\nJ131934.46+152944.3    15.44\nJ131930.90+152831.0    16.02\nJ131927.38+153041.9    16.17\nJ131911.74+152820.9    15.72\nJ131859.43+153017.2    16.72\nJ131859.61+152435.2    16.63",
  "circularId": 21029,
  "createdOn": 1492805777000,
  "email": "apozanen@iki.rssi.ru",
  "subject": "Swift Trigger 748858: AbAO and TSHAO optical observations",
  "submitter": "Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>"
}