[vsnet-grb-info 6772] Swift-BAT triggered on the flare star Algol

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8371
SUBJECT: Swift-BAT triggered on the flare star Algol
DATE:    08/10/13 21:42:36 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

L. Vetere (PSU), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), D. N. Burrows (PSU),
P.A. Curran (MSSL-UCL), N. Gehrels (NASA/GSFC),
C. Guidorzi (INAF-OAB), S. T. Holland (CRESST/USRA/GSFC),
E. A. Hoversten (PSU), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (MSSL),
D. M. Palmer (LANL), J. L. Racusin (PSU), T. Sakamoto (NASA/UMBC) and
H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:

At 21:19:00 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a flare from Algol (trigger=331592).  Swift slewed immediately
to the location.  The BAT on-board calculated location is 
RA, Dec 47.029, +40.951, which is 
   RA(J2000)  =  03h 08m 07s
   Dec(J2000) = +40d 57' 05"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is typical for image triggers,
the TDRSS BAT light curve does not show anything significant. 

The XRT began observing the field at 21:21:07.4 UT, 126.6 seconds after
the BAT trigger. XRT found a very bright X-ray source located at RA, Dec
47.0437, +40.9542 which is equivalent to:
   RA(J2000)  = 03h 08m 10.48s
   Dec(J2000) = +40d 57' 15.1"
with an uncertainty of 6.2 arcseconds (radius, 90% containment). This position
is 6.6 arcseconds from Algol.  The prompt raw spectrum shows evidence for 
a bright Fe line.  Due to the optical brightness of Algol the XRT data suffer
from severe optical loading and care must be exercised in analyzing these 
data. 

Because Algol is a 2nd magnitude star it is too bright to be observed
with UVOT.  No data will be taken.