GRB 120816A

K. L. Page (U Leicester), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), N. Gehrels (NASA/GSFC),
C. Guidorzi (U Ferrara), S. T. Holland (STScI), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (NASA/GSFC),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL) and
R. L. C. Starling (U Leicester) report on behalf of the Swift Team:

At 19:18:34 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 120816A (trigger=531223).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 282.126, -6.979, which is 
   RA(J2000) = 18h 48m 30s
   Dec(J2000) = -06d 58' 43"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single peak
with a duration of about 5 sec.  The peak count rate
was ~800 counts/sec (15-350 keV), at ~2 sec after the trigger. 

The XRT began observing the field at 19:20:47.3 UT, 132.6 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 282.14430, -6.93753 which is equivalent
to:
   RA(J2000)  = 18h 48m 34.63s
   Dec(J2000) = -06d 56' 15.1"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 162 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 (3.73 x
10^21 cm^-2, Kalberla et al. 2005), with an excess column of 4.4
(+3.28/-2.78) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 134 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 none of
the XRT error circle. The 8'x8' region for the list of sources generated
on-board covers 0.00% of the XRT error circle. Because of the density of
catalogued stars, further analysis is required to report an upper limit for any
afterglow in the region. No correction has been made for the large, but
uncertain extinction expected. 

Burst Advocate for this burst is K. L. Page (kpa AT star.le.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.)

W. Zheng (U Mich), W. Rujopakarn (Steward), T. Guver (Sabanci
University), report on behalf of the ROTSE collaboration:

ROTSE-IIId, located at the Turkish National Observatory at Bakirlitepe,
Turkey, automatically responded to GRB 120816A (Swift trigger 531223;
Page et al., GCN 13654
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 ). An automated response took the first image at
19:23:18.6 UT, 285 s after the burst, under fair conditions. We took 10
5-sec, 10 20-sec and 50 60-sec exposures. These unfiltered images are
calibrated relative to USNO A2.0 (R). Imaging is on going.

Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma Swift/BAT error circle or the XRT error circle; however, we are
limited as the field is severely crowded. Individual images have
limiting magnitudes ranging from 13.9-15.1; we set the following
specific limits.

start UT end UT t_exp(s) mlim Coadd?
----------------------------------------------------
19:23:18.6   19:23:23.6         5     13.9      N
19:23:45.6   19:23:50.6         5     14.2      N
19:24:13.1   19:24:18.1         5     14.3      N
19:25:34.5   19:25:54.5        20     14.8      N
19:35:05.4   19:40:22.7       600     15.1      Y

Klotz A. (IRAP-CNRS-OMP), Gendre B. (ASDC/INAF-OAR),
Boer M. (UNS-CNRS-OCA), Atteia J.L. (IRAP-CNRS-OMP) report:

We imaged the field of GRB 120816A detected by SWIFT
(trigger 531223) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 526s after the GRB trigger
(delay due to the beginning of the night).
The elevation of the field increased from
36 degrees above horizon and weather conditions
were good.

We co-added a series of exposures but we do not
detect any OT at the XRT position (Page et al.
GCNC 13654):

 From t0+526s to t0+942s, R > 16.5

Galactic coordinates are lon= 26.384d lat= -2.527d
and the galactic extinction in R band is about 3 magnitudes
(estimated from D. Schlegel et al. 1998ApJ...500..525S).
Although the field is very dense, there are no star brighter
than 18th mag in the XRT error box.

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

This message may be cited.

Arne Rau and Gottfried Kanbach (both MPE Garching) report on behalf of 
the OPTIMA-Burst Team:

"We observed the location of GRB 120816A (Page et al. GCN #13654
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 ) with 
OPTIMA-Burst (Kanbach et al. 2008, Astrophys. and Sp. Sci. Lib. Vol. 
351, 153) currently mounted at the 1.3m telescope at Skinakas 
Observatory, University of Crete. Observations started at 19:22:44 UT 
(249 sec after the burst) with unfiltered 20s exposures using the 
field-viewing CCD camera. Within the updated XRT error circle we find a 
fading source located at:

RA(J2000) = 18:48:34.4
Dec(J2000) = -06:56:16

with an approximate uncertainty of 1" in both coordinates.

We measure the following magnitudes:

T0+         white
--------------
249s        ~17.8
4844s    >19.1

calibrated against the R=15.2mag reference star USNO-B1.0 0830-0537586."

M. Jelínek, J. C. Tello, J. Gorosabel and A. J. Castro-Tirado (IAA-CSIC
Granada), on behalf of a larger collaboration, report:

"Following the detection of GRB 120816A (Page et al. GCNC 13654), the
BOOTES-2/TELMA 0.6m telescope (+COLORES) in southern Spain started to
observe the field about one hour after the GRB, as soon as the night
started, obtaining a series of unfiltered images. In particular, a
combination of 15x60s frames gathered around 20:24:35UT (i.e. T0+66min)
provides a limit of R > 18 at the position of the reported optical
counterpart (Rau and Kanbach GCNC 13657)."

This message can be quoted.

S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
C. B. Markwardt (GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL),
T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU),
J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-60 to T+192 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 120816A (trigger #531223)
(Page, et al., GCN Circ. 13654
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 ).  The BAT ground-calculated position is
RA, Dec = 282.133, -6.981 deg, which is 
   RA(J2000)  =  18h 48m 32.0s 
   Dec(J2000) = -06d 58' 51.6" 
with an uncertainty of 2.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 9%.
 
The mask-weighted light curve shows a single peak starting at ~T+0 sec,
peaking at ~T+1 sec, and ending at ~T+8 sec.  T90 (15-350 keV) is
7.6 +- 3.1 sec (estimated error including systematics).
 
The time-averaged spectrum from T-1.97 to T+6.66 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.54 +- 0.40.  The fluence in the 15-150 keV band is 4.3 +- 1.0 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.82 sec in the 15-150 keV band
is 2.1 +- 0.5 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/531223/BA/

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

Using 2433 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 120816A, 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 = 282.14298, -6.93791 which is equivalent
to:

RA (J2000): 18h 48m 34.31s
Dec (J2000): -06d 56' 16.5"

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.

K. L. Page (U Leicester) reports on behalf of the Swift-XRT team:

We have analysed 5.6 ks of XRT data for GRB 120816A (Page  et al. GCN
Circ. 13654
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 ), from 136 s to 12.5 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 13660).

The light curve can be modelled with  a power-law decay with a decay
index of alpha=0.94 (+0.08, -0.07).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.10 (+0.26, -0.25). The
best-fitting absorption column is  6.4 (+1.5, -1.4) x 10^21 cm^-2, in
excess of the Galactic value of 3.7 x 10^21 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.8 x 10^-11 (9.5 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     6.4 (+1.5, -1.4) x 10^21 cm^-2
Galactic foreground: 3.7 x 10^21 cm^-2
Excess significance: 3.2 sigma
Photon index:	     2.10 (+0.26, -0.25)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00531223.

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

U.Quadri, L.Strabla and R.Girelli A.Quadri report:

We imaged the field of GRB 120816A detected 
by SWIFT(trigger 531223) with the robotic 
telescope of (IAU station 565) Bassano Bresciano 
Observatory, Italy.

The observations started 26.7 min. after the 
GRB trigger,with our schmidt telescope 
D=320 mm F/D=3.1.

Weather conditions were discrete.

We co-added 4 series of 30 x 120s exposures.

We did not appear any optical counterpart 
in the error box of the XRTcandidate
(Page et al.GCNC 13654).

Start       End       Vlim
27.6min     278min    17.7

Magnitudes were estimated with the USNO-B1 cat. 

The message may be cited.

A. Ivanov, V. Ivanov, V. Lysenko (Kuban State University), A. Pozanenko 
(IKI)

We observed the field of the Swift GRB 120816A (Page  et al., GCN 13654
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 ) 
with 20-inch telescope of Kuban State University Astrophysical Observatory 
on August 16 starting on (UT) 19:34:49. We took several series of 40 s and 
60 s exposures using R filter. In a stacked image we do not detect any new 
source in the enhanced XRT error circle (Osborne et al., GCN 13660
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 ), in 
particular we do not detect the OT candidate  (Rau et al., GCN 13657
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 ). A 
preliminary photometry is based on the nearby USNO-B1.0 (R2) stars:

 Start,         T0+         Filter, Exposure,    OT,   uplim (3 sigma)
  (UT)         (mid, d)             (s)
19:34:49   0.0115      R       40               n/d    16.0
19:36:01   0.0221      R     830               n/d    17.9
19:36:01   0.0539      R   3530               n/d    18.1

S. Immler (NASA/CRESST/GSFC) and K. L. Page (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT observed the field of GRB 120815A starting 117 s
after the BAT trigger (Page et al., 2012, GCNC 13654). We detect
an uncatalogued source inside the enhanced XRT error circle
(Osborne et al., 2012, GCNC 13660) with preliminary coordinates

   RA (J2000.0) = 18:48:34.5 = 282.14359 (deg)
  Dec (J2000.0) = -06:56:16.4 = -6.93788 (deg)

and an estimated uncertainty of 0.6 arcsec (radius, 90% confidence,
statistical + systematic). The UVOT detection is consistent with
the optical afterglow reported by Rau et al. (2012, GCNC 13657).
Source magnitudes and 3-sigma upper limits at this location are
given below (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373).

Filter       TSTART   TSTOP    Exp Time      Mag  Err
-----------------------------------------------------
white          134      284         147      18.5  0.2
white          573     6306         598      19.9  0.2
    v          117     6716         500     >19.0
    b          548    11345        1174     >19.6
    u          293     7286         672     >21.1
 uvw1          672     7126         490     >21.1
 uvm2          647     6921         490     >19.5
 uvw2          599     6511         490     >19.8
-----------------------------------------------------

The quoted magnitudes and upper limits have not been corrected for
the Galactic extinction along the line of sight to this burst of
E_{B-V} = 0.703 mag.