[vsnet-grb-info 6367] Trigger 317205: Swift detection of an outburst from XTE J1701-407

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7985
SUBJECT: Trigger 317205: Swift detection of an outburst from XTE J1701-407
DATE:    08/07/17 14:00:01 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester),
D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), C. Gronwall (PSU),
C. Guidorzi (INAF-OAB), S. T. Holland (CRESST/USRA/GSFC),
J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA),
V. Mangano (INAF-IASFPA), C. B. Markwardt (CRESST/GSFC/UMD),
F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),
C. Pagani (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL),
D. Perez (U Leicester), M. Perri (ASDC), P. Romano (INAF-IASFPA),
B. Sbarufatti (INAF-IASFPA), R. L. C. Starling (U Leicester),
G. Stratta (ASDC), M. C. Stroh (PSU), T. N. Ukwatta (GSFC/GWU),
D. E. Vanden Berk (PSU), L. Vetere (PSU) and H. Ziaeepour (UCL-MSSL)
report on behalf of the Swift Team:

At 13:29:59 UT, the Swift Burst Alert Telescope (BAT) triggered on an outburst 
from XTE J1701-407 (trigger=317205).  Swift slewed immediately to the location. 
The BAT on-board calculated location is 
RA, Dec 255.461, -40.868 which is 
   RA(J2000) = 17h 01m 51s
   Dec(J2000) = -40d 52' 03"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a broad peak starting 
at T-20 sec with some increased activity superimposed between T+0 and T+20 sec. 
Then there was a broad plateau extending to at least T+60 sec, when the 
spacecraft began to slew. The peak count rate was ~1500 counts/sec (15-350 keV),
at ~0 sec after the trigger.  The position of this transient is consistent
with XTE J1701-407, which was recently reported active (ATEL #1569, #1572). 

The XRT began observing the field at 13:31:36.9 UT, 97.2 seconds after
the BAT trigger. XRT found a bright, fading X-ray source 
located at RA, Dec 255.4352, -40.8576 which is equivalent to:
   RA(J2000)  = 17h 01m 44.4s
   Dec(J2000) = -40d 51' 27.3"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 79 arcseconds from the BAT onboard position, within the BAT
error circle and 3.8 arcseconds from the previously reported XRT position
for XTE J1701-407 (ATEL #1572). The initial flux in the 2.5 s image was 
1.08e-08 erg cm^-2 s^-1 (0.2-10 keV). 

UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm)
filter starting 106 seconds after the BAT trigger. No afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The 3-sigma upper limit for a new source is about 19.5 mag. 
No correction has been made for the large, but uncertain extinction expected.