{
  "bibcode": "2018GCN.22489....1B",
  "body": "S. D. Barthelmy (GSFC), J.D. Gropp (PSU), J. A. Kennea (PSU),\nA. Y. Lien (GSFC/UMBC), A. Melandri (INAF-OAB),\nK. L. Page (U Leicester), B. Sbarufatti (PSU), M. H. Siegel (PSU) and\nA. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 19:11:31 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated MAXI J1820+070 (trigger=814259).  Swift slewed immediately to the source. \nThe BAT on-board calculated location is \nRA, Dec 275.089, +7.181 which is \n   RA(J2000) = 18h 20m 21s\n   Dec(J2000) = +07d 10' 51\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a multi-peaked\nstructure that lasts beyond currently available data (T0+400 s).  \nThe peak count rate was ~800 counts/sec (15-350 keV), at ~-2 sec \nafter the trigger. \n\nThe XRT began observing the field at 19:13:54.3 UT, 143.0 seconds after\nthe BAT trigger. XRT found a bright X-ray source located at RA, Dec\n275.0898, 7.1831 which is equivalent to:\n   RA(J2000)  = +18h 20m 21.55s\n   Dec(J2000) = +07d 10' 59.2\"\nwith an uncertainty of 4.9 arcseconds (radius, 90% containment). This\nposition is 10 arcseconds from MAXI J1820+070, although we believe this\nis the same source. Assuming a typical GRB power-law spectrum \n(NH=3e21 cm^-2, gamma=2), the catalogue entry for this object \nis equivalent to a 0.2-10 keV flux of 9.3e-13 erg cm^-2 s^-1; \nthe flux in the 2.5 s XRT image was 3.32e-09 erg cm^-2 s^-1. No\nevent data are yet available to determine the column density using\nX-ray spectroscopy. \n\nUVOT took a finding chart exposure of 250 seconds with the U filter \nstarting  308 seconds after the BAT trigger. The source is  detected\nat a magnitude of 12.28 +/- 0.04.  No correction has been  made for\nthe expected extinction corresponding to E(B-V) of  0.23.",
  "circularId": 22489,
  "createdOn": 1521056335000,
  "email": "kennea@swift.psu.edu",
  "subject": "Swift Trigger on MAXI J1820+070",
  "submitter": "Jamie A. Kennea at PSU/Swift-XRT  <kennea@swift.psu.edu>"
}