GRB 151107A

A. Y. Lien (GSFC/UMBC), S. B. Cenko (GSFC), N. Gehrels (NASA/GSFC) and
K. L. Page (U Leicester) report on behalf of the Swift Team:

At 17:19:36 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 151107A (trigger=662757).  Swift could not
slew to the burst due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 217.139, -59.680 which is 
   RA(J2000) = 14h 28m 33s
   Dec(J2000) = -59d 40' 46"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual for an image trigger,
the immediately-available BAT lightcurve shows no obvious activity. 

Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 15:26 UT on 2015 December 12. There will thus be no XRT
or UVOT data for this trigger before this time. 

We note that this location is within a degree of the Galactic plane,
so this may be a Galactic transient.  Further determination of the
nature of the source will require the full downlinked dataset. 

Burst Advocate for this burst is A. Y. Lien (amy.y.lien AT nasa.gov). 
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.)

D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias

E. Gorbovskoy, V. Lipunov,    N.Tyurina, V.Kornilov, P.Balanutsa, A.Kuznetsov, 
D.Kuvshinov, D. Vlasenko, E.Popova
Lomonosov Moscow State University, Sternberg Astronomical Institute

K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk
Irkutsk State University

A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov
Blagoveschensk Educational State University, Blagoveschensk

V.Krushinski, I.Zalozhnih
Ural Federal University, Kourovka

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)

MASTER-SAAO  robotic telescope (MASTER-Net: http://observ.pereplet.ru), 
located in SAAO, received Swift  GRB 151107A at the sunset, when the Sun 
altitude was -3.4 degrees, GRB altitude was 18.4 degrees.

MASTER-SAAO was pointed to the  GRB151107A 1750 sec after notice time 
and 2141 sec after trigger time at 2015-11-07 17:55:20 UT (Sun Altitude: 
-10.34, Alert altitude: 14.75). On our images (180s exposure)  we haven`t 
found optical transient  within SWIFT error-box (ra=14 28 33 dec=-59 40 46 
r=0.05). The 5-sigma upper limit has been about 17.2mag. There is  a 
bright star near the BAT coordinates. GRB is setting.

The best single image was started at  	2015-11-07 18:49:45 	(exp 180) 
m_lim = 18.3 mag.
The message may be cited.

S. D. Barthelmy (GSFC),  J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 151107A (trigger #662757)
( Lien et al., GCN Circ. 18564
Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 217.139, -59.680 deg which is
  RA(J2000)  =  14h 28m 33.4s
  Dec(J2000) = -59d -40' -46.9"
with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows no obvious structure. The event starts
before the beginning of captured data at T-239 sec and extends out past the
end of collected event data at T+910 sec when the source location left the FoV
when the spacecraft slewed to a new target.

This burst occurred during the period of recovering the thermal control system
(Barthelmy et al., GCN Circ. 18562
Loading...
 
 ). The CZT bias voltage has been reduced
to -150v (instead of the normal -200v) and as such the energy scale is not fully
calibrated. Therefore, an accurate spectral analysis is unavailable.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/662757/BA/

H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), and D. M. Palmer (LANL) report on behalf of 
the Swift-BAT team:

We perform further investigation regarding the uncertainty of the source nature 
of GRB151107A (Lien et al., GCN Circ. 18564
Loading...
 
 ) due to its proximity to the 
Galactic plane (within 1 deg) and the featureless light curve.

Using analysis from the BAT transient monitor (Krimm et al., 2013), there is 
no significant emission in the 15-50 keV band at ~ 4000 s before and ~ 6000 s
after the event data (signal-to-noise ratio < 1.8 sigma). The source was out of 
the field of view for the immediate time outside the event data range due to
pre-planned telescope slews. A search in the daily mosaic images at the burst 
location shows a 4-sigma detection on Nov. 7 (12.5 mCrab) and 1.6 sigma on 
Nov. 8 (which corresponds to a 1-sigma upper limit of ~ 5 mCrab).

This flux level and time profile are consistent with a GRB, and appear dimmer 
and shorter than a usual accreting binary source during outburst. However, 
we cannot rule out other possible Galactic transients, such as thermonuclear 
bursts or flaring stars.

In addition, we note that within 20.3 arcsec of the revised BAT position is the 
bright M2/M3 type star designated HD 126577. It is possible that the BAT 
detections correspond to a flaring episode from HD 126577, although this 
star is not known for such episodes.