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GCN Circular 17413

Subject
GRB 150206A: Swift detection of a burst with an optical afterglow
Date
2015-02-06T15:05:06Z (9 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
L. M. Z. Hagen (PSU), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), C. Gronwall (PSU), M.E. Gropp (PSU),
J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 14:30:02 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150206A (trigger=630019).  Swift did not immediately slew
due to observing constraint.  The BAT on-board calculated location is 
RA, Dec 10.088, -63.182, which is 
   RA(J2000)  =  00h 40m 21s
   Dec(J2000) = -63d 10' 53"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a weak beginning
with a strong increase starting at ~T+70 sec.  The duration is 
about 150 sec.  The peak count rate was ~8000 counts/sec (15-350 keV),
at ~97 sec after the trigger. 

The XRT began observing the field at 14:37:57.3 UT, 474.5 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 10.0774, -63.1852 which is equivalent to:
   RA(J2000)  = +00h 40m 18.58s
   Dec(J2000) = -63d 11' 06.7"
with an uncertainty of 5.1 arcseconds (radius, 90% containment). This
location is 20 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 2.35e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of  94 seconds with the White filter
starting 483 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	00:40:17.66 =  10.07358
  DEC(J2000) = -63:10:55.6  = -63.18211
with a 90%-confidence error radius of about 0.78 arc sec. This position is 12.7
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.62 with a 1-sigma error of about  0.16. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.02. 

Burst Advocate for this burst is L. M. Z. Hagen (lea.zernow.hagen AT gmail.com). 
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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