GRB 161007A

V. D'Elia (ASDC), L. M. Z. Hagen (PSU), J. A. Kennea (PSU),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU) and
B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:

At 21:25:43 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 161007A (trigger=716127).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 103.390, +23.289 which is 
   RA(J2000) = 06h 53m 34s
   Dec(J2000) = +23d 17' 20"
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 60 sec.  The peak count rate
was ~600 counts/sec (15-350 keV), at ~30 sec after the trigger. 

The XRT began observing the field at 21:27:47.8 UT, 124.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 103.40706, 23.30639 which
is equivalent to:
   RA(J2000)  = 06h 53m 37.69s
   Dec(J2000) = +23d 18' 23.0"
with an uncertainty of 4.3 arcseconds (radius, 90% containment). This
location is 84 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. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

The initial flux in the 2.5 s image was 1.56e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 133 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
0.12. 

Burst Advocate for this burst is V. D'Elia (delia AT asdc.asi.it). 
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.)

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

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

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

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

V.Krushinsky, I.Zalozhnih,  A. Popov
Ural Federal University, Yekaterinburg, Kourovka


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

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

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

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Tunka was pointed to the  GRB161007A 38 sec after notice time 
and 114 sec after trigger time at 2016-10-07 21:27:42 UT in two 
polarizations. On our first (20s exposure)  set we haven`t found optical 
transient  within SWIFT error-box (ra=06 53 33 dec=+23 17 20 r=0.050000).
The 5-sigma upper limit has been about 17.0 mag.
The observations made on zenit distance = 33 degrees, galaxy latitude b = 
11 degree. The moon (38 % bright part) below the horizon (The altitude of 
the Moon is -56 degree ).



MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Kislovodsk was pointed to the  GRB161007A 33 sec after notice 
time and 109 sec after trigger time at 2016-10-07 21:27:36 UT in two 
polarizations.. On our first (20s exposure)  set we haven`t found optical 
transient  within SWIFT error-box.
The 5-sigma upper limit has been about 17.0 mag.
The observations made on zenit distance = 68 degrees, galaxy latitude b = 
11 degree. The moon (38 % bright part) below the horizon (The altitude of 
the Moon is -28 degree ).


The message may be cited.

P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:

Using  promptly downlinked XRT event data for GRB 161007A, we find an
enhanced XRT position of the afterglow: RA, Dec: 103.4092, 23.3068
which is equivalent to:
   RA (J2000)  = 06 53 38.21
   Dec (J2000) = +23 18 24.6
with an uncertainty of 2.1 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/716127.

Position enhancement is is described by Goad et al. (2007, A&A, 476,
1401) and Evans et al. (2009, MNRAS, 397, 1177).

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

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

Using 2452 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 161007A, 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 = 103.40903, +23.30704 which is equivalent
to:

RA (J2000): 06h 53m 38.17s
Dec (J2000): +23d 18' 25.4"

with an uncertainty of 2.2 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.

A. de Ugarte Postigo (IAA-CSIC), D. A. Kann (TLS Tautenburg), 
L. Izzo, C. C. Thoene (both IAA-CSIC), N. Castro-Rodriguez, and 
G. Gomez Velarde (GRANTECAN/IAC/Universidad de La Laguna) 
report:

We observed the field of GRB 161007A (Swift 716127, D'Elia et al., 
GCN #20008
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 ), with the 10.4m GTC on La Palma, Canary Islands, 
Spain. We obtained four 30 sec images in the Sloan i' band at an 
airmass of 1.8. The midtime of our observations was 0.2228 days 
after the GRB trigger.

At the UVOT-enhanced Swift XRT position (Goad et al., GCN #20013
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 ), 
we detect a source at the edge of the error circle, at:

RA (J2000) =     06:53:38.10
Dec. (J2000) = +23:18:24.6

For this source, we measure:

i��� (Vega) = 22.23 +/- 0.15 

The photometric calibration was done by comparing to USNOB-1.0 
stars in the I-band filter, therefore this is only a preliminary value.
 
No statement can be made about fading. We note that the X-ray 
spectrum of this GRB's afterglows shows evidence for excess 
absorption, therefore this may be a dark GRB, with this source being 
its host galaxy. The source looks extended in our image, which has a 
seeing of 1.2".

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

We have analysed 7.4 ks of XRT data for GRB 161007A (D'Elia et al. GCN
Circ. 20008
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 ), from 114 s to 24.7 ks after the  BAT trigger. The data
comprise 228 s in Windowed Timing (WT) mode (the first 8 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 Goad et al.
(GCN Circ. 20010
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 ).

The late-time light curve (from T0+5.0 ks) can be modelled with a
power-law decay with a decay index of alpha=0.8 (+/-0.4).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.69 (+/-0.09). The
best-fitting absorption column is  7.5 (+/-0.5) x 10^21 cm^-2, in
excess of the Galactic value of 1.7 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.65 (+0.25, -0.23)
and a best-fitting absorption column of 5.5 (+1.9, -1.6) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 5.1 x 10^-11 (7.0 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     5.5 (+1.9, -1.6) x 10^21 cm^-2
Galactic foreground: 1.7 x 10^21 cm^-2
Excess significance: 4.0 sigma
Photon index:	     1.65 (+0.25, -0.23)

If the light curve continues to decay with a power-law decay index of
0.8, the count rate at T+24 hours will be 3.1 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x
10^-13 (2.2 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/00716127.

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

L. M. Z. Hagen (PSU) and V. D'Elia (ASDC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 161007A
133 s after the BAT trigger (D'Elia et al., GCN Circ. 20008
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 ). No
optical afterglow consistent with the XRT position (Goad et al., GCN
Circ. 20013
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 ) or the possible GTC optical counterpart (de Ugarte
Postigo et al., GCN Circ. 20014
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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 early
exposures are:

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

white              133         1716          411         >20.79
v                  621         1593          116         >18.39
b                  547         1691          116         >19.26
u                  291         1666          343         >19.73
uvw1               671         1642          116         >18.69
uvm2               646         1617          116         >18.81
uvw2               596         1735          129         >19.04


The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.12 in the direction of the burst
(Schlegel et al. 1998).

M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
V. D'Elia (ASDC), 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 161007A (trigger #716127)
(D'Elia, et al., GCN Circ. 20008
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 ).  The BAT ground-calculated position is
RA, Dec = 103.408, 23.289 deg which is
    RA(J2000)  =  06h 53m 37.9s
    Dec(J2000) = +23d 17' 18.8"
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 87%.

The mask-weighted light curve shows a peak starting from T+20 sec,
peaking at T+40 sec and ending at T+100 sec.  There is a hint of an
extended emission up to T+250 sec.  T90 (15-350 keV) is 201.7 +- 40.3 sec
(estimated error including systematics).
  
The time-averaged spectrum from T+18.2 to T+105.4 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.46 +- 0.18.  The fluence in the 15-150 keV band is 1.3 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+33.81 sec in the 15-150 keV band
is 0.4 +- 0.1 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/716127/BA/

E. Mazaeva (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), A. Volnova 
(IKI), I. Korobtsev (ISTP)  report on behalf of larger GRB follow-up 
collaboration:

We observed the field of the the GRB 161007A (D'Elia et al., GCN 20008
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 ) 
with  AZT-33IK telescope of Sayan observatory (Mondy) starting on 
October, 07 (UT) 21:51:45. We obtained several images in R-filter. 
Within XRT error circle (Goad et al., GCN 20013
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 ) we do not detected any 
source. Preliminary photometry  of the field  is following

Date        UT start   t-T0      Filter Exp.   OT   UpLim (3 sigma)
                       (mid, days)       (s)

2016-10-07  21:51:45   0.03025   R      35*60  n/d  21.5

Photometry is based on nearby USNO-B1.0 stars
USNO-B1         R2
1133-0144160    15.67
1133-0144193    15.95
1133-0144230    14.48

E. Mazaeva (IKI), R. Inasaridze (AbAO), A. Pozanenko (IKI), A. Volnova 
(IKI),  V. Ayvazian  (AbAO), V. Zhuzhunadze,  (AbAO),  O.Kvaratskhelia 
(AbAO), G. Inasaridze (AbAO),  I. Molotov (KIAM), report on behalf of 
larger GRB follow-up collaboration:

We observed the field of the GRB 161007A (D'Elia et al., GCN 20008
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 ) with 
AS-32 (0.7m) telescope of Abastumani Observatory  on October, 07 (UT) 
22:14:13. We obtained several unfiltered images of the field. Within XRT 
error circle (Goad et al., GCN 20013
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 ) we do not detected optical 
afterglow candidate (de Ugarte Postigo et al., GCN 20014
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 ). Preliminary 
photometry  of the field  is following

Date        UT start   t-T0      Filter Exp.   OT   UpLim (3 sigma)
                       (mid, days)       (s)

2016-10-07  22:14:13   0.05758   CR     37*60  n/d  22.4

Photometry is based on nearby USNO-B1.0 stars
USNO-B.1_id R2
1133-0144160    15.67
1133-0144193    15.95
1133-0144230    14.48
1133-0144267    15.92
1133-0144281    15.23

K. E. Heintz (Univ. of Iceland and DARK/NBI), D. Malesani (DARK/NBI and DTU Space), A. de Ugarte Postigo (IAA-CSIC and DARK/NBI), T. Pursimo (NOT), T. Kruehler (MPE Garching), J. Telting (NOT) and J. P. U. Fynbo (DARK/NBI) report on behalf of a larger collaboration:

We observed the field of GRB 161007A (D'Elia et al., GCN 20008
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 ) using the ALFOSC camera mounted at the 2.56m Nordic Optical Telescope (NOT). Observations started at 04:39:59 UT on 2016-10-09 (i.e., 31 hr after the trigger) and 6x300 s SDSS i-band frames were obtained under excellent seeing (0.6-0.7").

In our stacked i-band image, we clearly detect the object reported by de Ugarte Postigo et al. (GCN 20014
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 ). We confirm that this source is extended.

No significant variability is measured with respect to the GTC images (taken 5.3 hr after the GRB) down to ~0.2 mag. The extension, the lack of variability, and the low chance probability association for such a bright object all indicate that this is the host galaxy of GRB 161007A.

K. P. Mooley (Hintze Fellow, Oxford), T. D. Staley, R. P. Fender 
(Oxford), G. E. Anderson (Curtin), T. Cantwell (Manchester), 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 
161007A (D'Elia et al., GCN 20008
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 ) 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 Oct 08.05, Oct 09.25, Oct 
11.25 and Oct 15.25 (UT) do not reveal any radio source at the XRT 
location (Goad et al., GCN 20013
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 ), with 3sigma upper limits of 372 uJy, 
273 uJy, 333 uJy and 222 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/.