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GCN Circular 17464

Subject
GRB 150213B: Swift detection of a burst with an optical afterglow
Date
2015-02-13T22:47:24Z (9 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
C. Pagani (U Leicester), S. D. Barthelmy (GSFC),
N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL),
F. E. Marshall (NASA/GSFC), C. J. Mountford (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL) and
B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:

At 22:31:30 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150213B (trigger=631051).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 253.425, +34.179 which is 
   RA(J2000)  =  16h 53m 42s
   Dec(J2000) = +34d 10' 43"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty). As is typical for image triggers (64 sec),
the realtime TDRSS light curve does not show anything significant. 

The XRT began observing the field at 22:33:54.1 UT, 143.3 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 253.4532, 34.1886 which is equivalent to:
   RA(J2000)  = +16h 53m 48.77s
   Dec(J2000) = +34d 11' 19.0"
with an uncertainty of 5.0 arcseconds (radius, 90% containment). This
location is 90 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

The initial flux in the 2.5 s image was 2.84e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 152 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	16:53:48.65 = 253.45271
  DEC(J2000) = +34:11:19.4  =  34.18872
with a 90%-confidence error radius of about 0.63 arc sec. This position is 1.5
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.46 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.02. 

Burst Advocate for this burst is C. Pagani (cp232 AT star.le.ac.uk). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
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