Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 22489

Swift Trigger on MAXI J1820+070
2018-03-14T19:38:55Z (6 years ago)
Jamie A. Kennea at PSU/Swift-XRT <>
S. D. Barthelmy (GSFC), J.D. Gropp (PSU), J. A. Kennea (PSU),
A. Y. Lien (GSFC/UMBC), A. Melandri (INAF-OAB),
K. L. Page (U Leicester), B. Sbarufatti (PSU), M. H. Siegel (PSU) and
A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 19:11:31 UT, the Swift Burst Alert Telescope (BAT) triggered and
located MAXI J1820+070 (trigger=814259).  Swift slewed immediately to the source. 
The BAT on-board calculated location is 
RA, Dec 275.089, +7.181 which is 
   RA(J2000) = 18h 20m 21s
   Dec(J2000) = +07d 10' 51"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure that lasts beyond currently available data (T0+400 s).  
The peak count rate was ~800 counts/sec (15-350 keV), at ~-2 sec 
after the trigger. 

The XRT began observing the field at 19:13:54.3 UT, 143.0 seconds after
the BAT trigger. XRT found a bright X-ray source located at RA, Dec
275.0898, 7.1831 which is equivalent to:
   RA(J2000)  = +18h 20m 21.55s
   Dec(J2000) = +07d 10' 59.2"
with an uncertainty of 4.9 arcseconds (radius, 90% containment). This
position is 10 arcseconds from MAXI J1820+070, although we believe this
is the same source. Assuming a typical GRB power-law spectrum 
(NH=3e21 cm^-2, gamma=2), the catalogue entry for this object 
is equivalent to a 0.2-10 keV flux of 9.3e-13 erg cm^-2 s^-1; 
the flux in the 2.5 s XRT image was 3.32e-09 erg cm^-2 s^-1. No
event data are yet available to determine the column density using
X-ray spectroscopy. 

UVOT took a finding chart exposure of 250 seconds with the U filter 
starting  308 seconds after the BAT trigger. The source is  detected
at a magnitude of 12.28 +/- 0.04.  No correction has been  made for
the expected extinction corresponding to E(B-V) of  0.23.
Looking for U.S. government information and services? Visit