GRB 161105A

K. L. Page (U Leicester), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL)
and M. H. Siegel (PSU) report on behalf of the Swift Team:

At 04:53:02 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 161105A (trigger=720697).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 120.163, -44.780 which is 
   RA(J2000) = 08h 00m 39s
   Dec(J2000) = -44d 46' 46"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 140 sec.  The peak count rate
was ~2500 counts/sec (15-350 keV), at ~8 sec after the trigger. 

The XRT began observing the field at 04:54:10.1 UT, 67.8 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source with an enhanced position: RA, Dec 120.1839,
-44.7753 which is equivalent to:
   RA(J2000)  = 08h 00m 44.14s
   Dec(J2000) = -44d 46' 31.1"
with an uncertainty of 2.6 arcseconds (radius, 90% containment). This
location is 56 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.  We
cannot determine whether the source is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 4.15
x 10^21 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 3.12e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 586 seconds after the BAT trigger. No credible 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 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
XRT 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
0.32. 

Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). 
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.)

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

R. Rebolo, M. Serra Ricart, N. Lodieu, G. Israelian
The Instituto de Astrofisica de Canarias

R.Podesta, C.Lopez, F.Podesta
Observatorio Astronomico Felix Aguilar (OAFA), San Juan Univerdity,

H. Levato, C. Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

D.Buckley, S. Potter,
South African Astronomical Observatory

O.Gres, K.Ivanov, J.Rabinovich, N.M.Budnev,
Irkutsk State University

A. Tlatov, V.Senik, D. Dormidontov, A.Parkhomenko
Kislovodsk Solar Station of the Pulkovo Observatory

V.Yurkov, Yu.Sergienko, A.Gabovich
Blagoveschensk Educational State University, Blagoveschensk


MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in IAC was pointed to the  GRB161105A  27 sec after notice time 
and 42 sec after trigger time at 2016-11-05 04:53:44 UT. On our first (10s 
exposure)  set we haven`t found optical transient  within SWIFT error-box 
(ra=120.163 dec=-44.7794 r=0.05) (Page et al., GCN 20131
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 ).
The 5-sigma upper limit has been about  16.4 mag (polaroid, 
unfiltered).

The observations made on zenit distance = 75 degrees, galaxy latitude b = 
-7 degree. The moon (25 % bright part) below the horizon (The altitude of 
the Moon is  -80 degree ).
The sun  altitude  is -32.4 degree.
The object can be observed till sunrise at 2016-11-05 07:20:31

Maximal coadded limit ~19.5 m. No OT found.

The message may be cited.

J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 2913 s of XRT Photon Counting mode data and 6 UVOT
images for GRB 161105A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 120.18375, -44.77529 which is equivalent
to:

RA (J2000): 08h 00m 44.10s
Dec (J2000): -44d 46' 31.0"

with an uncertainty of 1.7 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
D. M. Palmer (LANL), K. L. Page (U Leicester),
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 161105A (trigger #720697)
(Page  et al. GCN Circ. 20131
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 ).  The BAT ground-calculated position is
RA, Dec = 120.198, -44.763 deg which is
  RA(J2000)  =  08h 00m 47.5s
  Dec(J2000) = -44d 45' 47.6"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 85%.

The mask-weighted light curve shows a multi-peaked structure that starts
at ~T-90 s and ends at ~T+160 s. There are roughly two main pulses
in the structure. The first one contains two obvious peaks at ~T0 and ~T+10s,
and the second one peaks at ~T+50 s. T90 (15-350 keV) is 177.3 +- 25.8 sec
(estimated error including systematics).

The time-averaged spectrum from T-88.00 to T+164.81 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.02 +- 0.24,
and Epeak of 159.1 +- 135.3 keV (chi squared 55.64 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 6.1 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+0.63 sec in the 15-150 keV band is
1.4 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.35 +- 0.06 (chi squared 61.67 for 57 d.o.f.).  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/720697/BA/

T.G.R. Roegiers (PSU), L.M. McCauley (PSU), A.P. Beardmore (U.
Leicester), P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester), P.
D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), J.A.
Kennea (PSU) and K.L. Page report on behalf of the Swift-XRT team:

We have analysed 5.0 ks of XRT data for GRB 161105A (Page et al. GCN
Circ. 20131
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 ), from 560 s to 23.3 ks after the  BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Osborne et al. (GCN Circ. 20135
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 ).

The light curve can be modelled with an initial power-law decay with an
index of alpha=4.6 (+/-1.2), followed by a break at T+909 s to an alpha
of 0.86 (+0.14, -0.15).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.90 (+0.28, -0.15). The
best-fitting absorption column is  consistent with the Galactic value
of 4.1 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum  is 4.1 x 10^-11 (5.8 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     4.1 (+/-1.1) x 10^21 cm^-2
Galactic foreground: 4.1 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.90 (+0.28, -0.15)

If the light curve continues to decay with a power-law decay index of
0.86, the count rate at T+24 hours will be 4.5 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.8 x
10^-13 (2.6 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00720697.

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

Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP),
Boer, M., Laugier, R. (CNRS-ARTEMIS),
Gendre B. (UVI - Etelman Obs.) report:

We imaged the field of GRB 161105A detected by SWIFT
(trigger 720697) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 27.4s after the GRB trigger
(14.8s after the notice). The elevation of the field increased from
31 degrees above horizon and weather conditions
were excellent.

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We do not detect any OT (in the XRT error box provided by
Page et al. GCNC 20131) with a limiting magnitude of:

t0+27.4s to t0+87.4s : Rlim = 16.5

Due to technical problems the second image was taken only
743 seconds after the GRB:

t0+743.2s to t0+833.2s : Rlim = 19.8

No more candidate were found in the next images taken
until 2000 seconds after the GRB at the same limiting
magnitude.

Magnitudes were estimated with the nearby NOMAD1 stars
and are not corrected for galactic dust extinction.

M. H. Siegel (PSU) and K. L. Page (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 161105A
586 s after the BAT trigger (Page et al., GCN Circ. 20131
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 ).
No optical afterglow consistent with the XRT position
(Osborne et al. GCN Circ. 20135
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 )
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white (fc)         586          735          147         >20.44
white              586         5286          549         >21.11
v                 1046         7179          274         >18.86
b                  841         5081          274         >20.07
u                  816         1652           86         >18.62
uvw1               792        11242          713         >19.91
uvm2               767         7384          293         >19.12
uvw2              1022         6974          290         >19.24

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.33 in the direction of the burst
(Schlegel et al. 1998).