GRB 160705B

J. K. Cannizzo (NASA/UMBC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), C. Gronwall (PSU), J. A. Kennea (PSU),
C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester) and T. N. Ukwatta (LANL) report on behalf of
the Swift Team:

At 21:02:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160705B (trigger=703176).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 168.086, +46.721 which is 
   RA(J2000)  =  11h 12m 21s
   Dec(J2000) = +46d 43' 17"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows some weak emission
from T_0 to about T+40 (this is a 64-sec image trigger, and as such
there is seldom anything see in the raw real-time TDRSS telemetry). 
The duration of about 40 sec.  The peak count rate
was ~600 counts/sec (15-350 keV), at ~3 sec after the trigger. 

The XRT began observing the field at 21:04:27.7 UT, 140.3 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 168.10943,
46.70085 which is equivalent to:
   RA(J2000)  = 11h 12m 26.26s
   Dec(J2000) = +46d 42' 03.1"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 92 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. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (1.19 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 2.7
(+2.18/-1.93) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 9.31e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 148 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
0.01. 

Burst Advocate for this burst is J. K. Cannizzo (cannizzo 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.)

C. Guidorzi (U. Ferrara), C.G. Mundell (U. Bath), S. Kobayashi, I.A. 
Steele (LJMU), A. Gomboc (U. Nova Gorica) on behalf of a large 
collaboration report:

The 2-m Liverpool Telescope began observing Swift GRB 160705B (Cannizzo 
et al., GCN 19657
Loading...
 
 ) on July 05, 21:05:14 UT (3.1 minutes after the burst 
trigger). Inside the XRT error circle we find an uncatalogued source 
which is not present in the SDSS at the following position:

RA(J2000)=  11:12:26.27
Dec(J2000)= +46:42:01.2

with an uncertainty of 0.5 arcsec and r~21 mag (AB) @ 36 minutes post GRB.

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

Using 2204 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 160705B, 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 = 168.10944, +46.69990 which is equivalent
to:

RA (J2000): 11h 12m 26.27s
Dec (J2000): +46d 41' 59.6"

with an uncertainty of 1.6 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.

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

We have analysed 6.3 ks of XRT data for GRB 160705B (Cannizzo et al.
GCN Circ. 19657
Loading...
 
 ), from 130 s to 23.8 ks after the  BAT trigger. The
data comprise 132 s in Windowed Timing (WT) mode (the first 9 s were
taken while Swift was slewing) with the remainder in Photon Counting
(PC) mode. The enhanced XRT position for this burst was given by
Osborne et al. (GCN Circ. 19659
Loading...
 
 ).

The light curve can be modelled with an initial power-law decay with an
index of alpha=3.81 (+0.14, -0.13), followed by a break at T+563 s to
an alpha of 0.60 (+0.12, -0.13).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.66 (+0.14, -0.13). The
best-fitting absorption column is  10.0 (+2.5, -2.4) x 10^20 cm^-2, in
excess of the Galactic value of 1.2 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.15 (+0.23, -0.21)
and a best-fitting absorption column of 8.1 (+5.2, -4.5) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.1 x 10^-11 (3.8 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     8.1 (+5.2, -4.5) x 10^20 cm^-2
Galactic foreground: 1.2 x 10^20 cm^-2
Excess significance: 2.5 sigma
Photon index:	     2.15 (+0.23, -0.21)

If the light curve continues to decay with a power-law decay index of
0.60, the count rate at T+24 hours will be 0.012 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.5 x
10^-13 (4.4 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/00703176.

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

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. K. Cannizzo (NASA/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (GSFC/UMBC), 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 downlinks,
we report further analysis of BAT GRB 160705B (trigger #703176)
(Cannizzo, et al., GCN Circ. 19657
Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 168.107, 46.707 deg, which is 
   RA(J2000)  =  11h 12m 25.7s 
   Dec(J2000) = +46d 42' 24.8" 
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 73%.
 
The mask-weighted light curve shows possible emission from before T-239 sec
(the beginning of the data), with the peak starting at ~T-30 sec, peaking
at ~T+10 sec, and ending at ~T+90 sec.
T90 (15-350 keV) is 54.4 +- 12.4 sec (estimated error including systematics).
 
The time-averaged spectrum from T-15.09 to T+54.70 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.79 +- 0.27.  The fluence in the 15-150 keV band is 7.3 +- 1.1 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+26.04 sec in the 15-150 keV band
is 0.5 +- 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/703176/BA/

Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC),
William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J.
Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara
(GSFC/STScI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico
Ramirez-Ruiz (UCSC), Jos�� A. de Diego (UNAM), Leonid Georgiev (UNAM),
Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Neil Gehrels (GSFC),
Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and
Vicki Toy (UMD) report:

We observed the field of GRB 160705B (Cannizzo et al., GCN 19657
Loading...
 
 ) with
the Reionization and Transients Infrared Camera (RATIR; www.ratir.org)
on the 1.5m Harold Johnson Telescope at the Observatorio Astron��mico
Nacional on Sierra San Pedro M��rtir from 2016/07 6.17 to 2016/07 6.21
UTC (7.04 to 8.05 hours after the BAT trigger), obtaining a total of
0.66 hours exposure in the r and i bands and 0.30 hours exposure in the
Z, Y, J, and H bands.

We detect two sources within the enhanced Swift-XRT error circle
(Osborne et al., GCN 19659
Loading...
 
 ). The brighter source is an uncataloged source
at 11:12:26.20 +46:42:01.2 (J2000, +/- 0.5 arcsec) with the following
detections and 3-sigma upper limit:

r = 22.89 +/- 0.15
i = 22.12 +/- 0.09
Z = 22.34 +/- 0.33
Y = 21.73 +/- 0.32
J > 21.54
H = 20.98 +/- 0.34

The fainter source is a cataloged SDSS source at 11:12:26.42 +46:41:59.6
(J2000, +/- 0.5 arcsec) with the following detections and 3-sigma upper
limits:

r = 23.39 +/- 0.24
i = 22.61 +/- 0.14
Z = 22.10 +/- 0.26
Y > 21.87
J > 21.54
H > 21.04

These magnitudes are in the AB system, are in comparison with the SDSS
DR9 and 2MASS catalogs, and are not corrected for Galactic extinction in
the direction of the GRB.

We note that Guidorzi et al. (GCN 19658
Loading...
 
 ) report an uncataloged source
with r of about 21 at 36 minutes after the burst trigger. Their source
is only 0.7 arcsec from our brighter uncataloged source and so we
postulate that these correspond to the afterglow of the GRB. The
afterglow has faded by about 2 magnitudes between their observations at
36 minutes and ours at 7.54 hours, which corresponds to a temporal index
of about -0.6.

We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.

S.W.K. Emery (UCL-MSSL) and J. K. Cannizzo (NASA/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160705B
149 s after the BAT trigger (Cannizzo et al., GCN Circ. 19657
Loading...
 
 ).
No optical afterglow consistent with the XRT position (Osborne et al. GCN Circ. 19659
Loading...
 
 )
or the LT and RATIR position (Guidorzi et al. GCN 19658
Loading...
 
 ; Watson et al. GCN Circ. 19663
Loading...
 
 )
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 first
finding chart (FC) exposure and subsequent exposures are:

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

white_FC           149          298          147         >20.6
u_FC               307          557          246         >19.9
white             4780         6415          393         >21.0
v                 5191        11327         1082         >19.9
b                 6011         6210          197         >20.1
w1               12239        12529          285         >20.0
m2               11333        12232          886         >20.7
w2                6421         6603          179         >19.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).

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 160705B detected by SWIFT
(trigger 703176) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 92s after the GRB trigger
(18s after the notice). The elevation of the field decreased from
36 degrees above horizon and weather conditions
were poor.

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 with a limiting magnitude of:
t0+92s to t0+152s : Rlim = 15.5

The second image is 30.0s exposure in tracking mode:
t0+190s to t0+250s : Rlim = 16.6

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.

K. P. Mooley, T. D. Staley, R. P. Fender (Oxford), G. E. Anderson 
(Curtin), T. Cantwell (Manchester), C. Rumsey, D. Titterington, S. H. 
Carey, J. Hickish, Y. C. Perrott, N. Razavi-Ghods, P. Scott (Cambridge), 
K. Grainge, A. Scaife (Manchester)

The AMI Large Array robotically triggered on the Swift alert for GRB 
160705B (Cannizzo et al., GCN 19657
Loading...
 
 ) as part of the 4pisky program, and 
subsequent follow up observations were obtained up to 10 days 
post-burst. Our observations at 15 GHz on 2016 Jul 05.89, Jul 06.73, Jul 
08.74, and Jul 12.72 (UT) do not reveal any radio source at the XRT 
location (Osborne et al., GCN 19659
Loading...
 
 ), with 3sigma upper limits of 177 
uJy, 102 uJy, 132 uJy, and 213 uJy respectively.

We thank the AMI staff for scheduling these observations. The AMI-GRB 
database is a log of all GRB follow up observations with the AMI, and is 
available at http://4pisky.org/ami-grb/.