GRB 151205B

F. E. Marshall (NASA/GSFC), P. D'Avanzo (INAF-OAB), C. Gronwall (PSU),
L. M. Z. Hagen (PSU), H. A. Krimm (CRESST/GSFC/USRA),
A. Melandri (INAF-OAB), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Swift Team:

At 21:43:14 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 151205B (trigger=666378).  Swift could not slew immediately
to the burst due to an observing contraint. 
The BAT on-board calculated location is 
RA, Dec 41.158, -43.481 which is 
   RA(J2000) = 02h 44m 38s
   Dec(J2000) = -43d 28' 49"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 5 sec.  The peak count rate
was ~1800 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Due to an observing constraint, Swift will not slew until T0+50.6
minutes. There will be no XRT or UVOT data until this time. 

Burst Advocate for this burst is F. E. Marshall (marshall AT milkyway.gsfc.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.)

J.A. Kennea (PSU), G. Tagliaferri (INAF-OAB), S. Campana (INAF-OAB),
P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester) and D.N. Burrows
(PSU) report on behalf of the Swift-XRT team:

The XRT began observing the field of GRB 151205B at 22:35:21.5 UT,
3127.1 seconds after the BAT trigger. No source was detected in 245 s
of promptly downlinked data. We are waiting for the full dataset to
detect and localise the XRT counterpart.

L. M. Z. Hagen (PSU) reports on behalf of the Swift/UVOT team:

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 3131 seconds after the BAT trigger (Marshall et al., GCN Circ.
18659
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 ). No credible afterglow candidate has been found in the initial
data products. The 2.7'x2.7' sub-image covers 25% of the BAT error circle.
The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region
for the list of sources generated on-board covers 100% of the BAT error
circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to
E(B-V) of 0.02.

[GCN OPS NOTE(20jan16): Per author's request, the burst name in the
Subject-line was changed from "A" to "B".]

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

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

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.Senik
Kislovodsk Solar Station of the Pulkovo Observatory

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov
Blagoveschensk Educational State University, Blagoveschensk
21:43:14.53

V.Krushinski, I.Zalozhnih,  A. Popov
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)

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

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in SAAO was pointed to the  GRB151205B (Marshall et. al. GCN 
18659
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 ) 28 sec after notice time and 63 sec after trigger time at 21:44:18 
UT in two polarisations. On our first (10s exposure)  set we haven`t found 
optical transient  within SWIFT error-box (ra=02 44 38 dec=-43 28 50 
r=0.050000).
The 5-sigma upper limit has been about 17.0 mag.

We obtain a following early upper limits at a single an coadd images

T_start  T-Ts  T-Tm  Expt. Mlimit  Coadd
--------|----|-----|-----|-------|-------|
21:44:18   63    68    10    17.0   1
21:44:18   63   115    60    18.7   3
21:44:18   63   501   680    20.6  10
21:44:51   96   106    20    17.8   1
21:45:32  137   152    30    18.1   1
21:46:21  187   207    40    18.3   1
21:47:21  246   271    50    18.7   1
21:48:31  316   346    60    19.0   1
21:49:51  396   436    80    19.3   1
21:51:47  513   563   100    19.6   1
21:53:45  630   695   130    19.9   1
21:56:13  778   858   160    20.0   1
...

Ts - is exposure start time
Tm - is exposure middle time
T  - is trigger time

The message may be cited.

T. N. Ukwatta (LANL), 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), F. E. Marshall (NASA/GSFC),D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), (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 15120B (trigger #666378)
(Marshall, et al., GCN Circ. 18659
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 ).  The BAT ground-calculated position is
RA, Dec = 41.190, -43.461 deg which is
    RA(J2000)  =  02h 44m 45.6s
    Dec(J2000) = -43d 27' 39.8"
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 96%.

The mask-weighted light curve shows a single peak starting at T-2 sec
with total duration of ~5 seconds. The spacecraft slewed away from the
burst location at about T+350 seconds. T90 (15-350 keV) is 1.4 +- 0.2 sec
(estimated error including systematics).

The time-averaged spectrum from T-0.2 to T+1.3 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.74 +- 0.33.  The fluence in the 15-150 keV band is 7.7 +- 1.6 x 10^-8erg/cm2.
The 1-sec peak photon flux measured from T+0.25 sec in the 15-150 keV band
is 0.7 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/666378/BA/

P. D'Avanzo, A. Melandri (INAF-OAB), V. D'Elia (ASDC), A. D'Ai
(INAF-IASFPA), L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti
(INAF-OAB/PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester),
C. Pagani (U. Leicester), A. Maselli  (INAF-IASFPA), F. E. Marshall
(NASA/GSFC) and P.A. Evans (U. Leicester) report on behalf of the
Swift-XRT team:

We have analysed 3.3 ks of Photon Counting (PC) mode XRT data for the
Swift/BAT-detected burst GRB 151205B (Marshall et al. GCN Circ. 18659
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 ),
collected between T0+3.1 ks and T0+68.9 ks. 

The first set of observations consists of 1.0 ks of data collected 
between T0+3.1 ks and T0+5.7 ks. 
No X-ray sources have been detected inside or close to the Swift/BAT
error region. The 3-sigma upper limit in the field is 7.7e-3 ct  s^-1,
corresponding to a 0.3-10 keV observed flux of 2.7e-13 erg cm^-2 s^-1
(assuming a typical GRB spectrum).

The second set of observations consists of 2.3 ks data collected 
between T0+39.8 ks and T0+68.9 ks. 
No X-ray sources have been detected inside or close to the Swift/BAT
error region. The 3-sigma upper limit in the field is 3.7e-3 ct  s^-1,
corresponding to a 0.3-10 keV observed flux of 1.3e-13 erg cm^-2 s^-1
(assuming a typical GRB spectrum).


The results of the XRT-team automatic analysis of the XRT observations,
including a position specific upper limit calculator, are available at
http://www.swift.ac.uk/ToO_GRBs/00666378.

This circular is an official product of the Swift-XRT team.

R. Yates (MPE Garching) , D. A. Kann (TLS Tautenburg), C. Delvaux, and J.
Greiner (both MPE Garching) report on behalf of the GROND team:

We observed the field of GRB 151205B (Swift trigger 666378; Marshall et
al., GCN #18659
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 ) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla
Observatory (Chile).

Observations started at 01:21 UT on 06/12/2015, 3hrs 38 mins after the GRB
trigger, and continued for several hours. We obtained a second epoch in
the following night.

We stacked the four deepest images of the first night (exposure times 7920
s in g'r'i'z' and 6600 s in JHK). They were performed at an average seeing
of 0".77 and an average airmass of 1.04. The observations of the second
night (exposure times 5760 s in g'r'i'z' and 5400 s in JHK) were obtained
at 0".62 seeing and airmass 1.04.

As there is no XRT detection for this GRB (Kennea et al., GCN #18661
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 ;
D'Avanzo et al., GCN #18672
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 ), we performed image subtraction. We note that
the g'r'i'z' images do not cover about 25% of the revised BAT error circle
(Ukwatta et al., GCN #18670
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 ) to the north and east. The JHK images cover
both the flight and the revised BAT error circle completely.

No significantly variable sources are detected in any band. The formal
upper limits (all in AB system) of our images, centered at 0.1939 days
after the GRB, are:

g' > 26.5 mag,
r' > 26.5 mag,
i' > 25.6 mag,
z' > 25.0 mag,
J > 22.7 mag,
H > 22.2 mag, and
K > 21.3 mag.

The given limits are derived based on calibrating the images against GROND
zero points and 2MASS field stars and are not corrected for the Galactic
foreground extinction corresponding to a reddening of E_(B-V)= 0.02 in the
direction of the burst (Schlegel et al. 1998).