GRB 130822A

D. Kocevski (NASA/GSFC/ORAU), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), S. T. Holland (STScI), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (UCL-MSSL),
V. Mangano (PSU), F. E. Marshall (NASA/GSFC), C. Pagani (U Leicester),
K. L. Page (U Leicester), J. L. Racusin (NASA/GSFC),
B. Sbarufatti (INAF-OAB/PSU), R. L. C. Starling (U Leicester) and
G. Tagliaferri (INAF-OAB) report on behalf of the Swift Team:

At 15:54:17 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 130822A (trigger=567163).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 27.940, -3.219 which is 
   RA(J2000) = 01h 51m 46s
   Dec(J2000) = -03d 13' 08"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single peak
structure with a duration of about 0.1 sec.  The peak count rate
was ~3700 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 15:55:30.7 UT, 73.5 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 27.9218, -3.2085 which
is equivalent to:
   RA(J2000)  = 01h 51m 41.22s
   Dec(J2000) = -03d 12' 30.6"
with an uncertainty of 3.1 arcseconds (radius, 90% containment). This
location is 75 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 2.76
x 10^20 cm^-2 (Kalberla et al. 2005). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
294 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 19.2 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 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.03. 

Burst Advocate for this burst is D. Kocevski (daniel.kocevski AT 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.)

D. Xu (DARK/NBI), D.-Y. Ren, C. Cao, S.-M. Hu (SDU) report:

We observed the field of GRB 130822A (Kocevski et al., GCN 15112
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 )
using the 1m telescope located in Weihai, Shandong, China.
Observations started at 17:05:49 UT on 2013-08-22 (i.e., 1.19 hr after
the BAT trigger) and 3x500s SDSS r'-band frames were obtained in a
cloudy weather.

No optical source is detected within the XRT error circle (Kocevski et
al., GCN 15112
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 ) in the stacked image down to r'>~20 mag, calibrated
with SDSS field.

T. N. Ukwatta (MSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
D. Kocevski (NASA/GSFC/ORAU), H. A. Krimm (GSFC/USRA),
A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC),
(i.e. the Swift-BAT team):
  
Using the data set from T-60 to T+123 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 130822A (trigger #567163)
(Kocevski, et al., GCN Circ. 15112
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 ).  The BAT ground-calculated position is
RA, Dec = 27.931, -3.193 deg which is
    RA(J2000)  =  01h 51m 43.4s
    Dec(J2000) = -03d 11' 34.0"
with an uncertainty of 2.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 92%.
  
The mask-weighted light curve shows a single peak.  T90 (15-350 keV) is
0.04 +- 0.01 sec (estimated error including systematics).
  
The time-averaged spectrum from T-0.004 to T+0.044 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.64 +- 0.29.  The fluence in the 15-150 keV band is 1.3 +- 0.3 x 10^-08 erg/cm2.
The 1-sec peak photon flux measured from T-0.48 sec in the 15-150 keV band is
0.3 +- 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/567163/BA/

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

Using 465 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 130822A, 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 = 27.92181, -3.20865 which is equivalent
to:

RA (J2000): 01h 51m 41.23s
Dec (J2000): -03d 12' 31.1"

with an uncertainty of 2.6 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.

A. A. Breeveld (UCL-MSSL) and D. Kocevski (NASA/GSFC/ORAU) report on 
behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 130822A 81 
s after the BAT trigger (Kocevski et al., GCN Circ. 15112
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 ).
No optical afterglow consistent with the XRT position (Beardmore et al. 
GCN Circ. 15117
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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 first finding 
chart (FC) exposure and subsequent exposures are:

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

white_FC            81          231          147         >20.8
u_FC               295          544          246         >20.7
white               81         1543          392         >21.4
v                  624         1420           97         >19.3
b                  550         1170           58         >20.1
u                  295         1145          265         >20.9
w1                 674         1470           97         >19.7
w2                 600          620           19         >19.4

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.03 in the direction of the 
burst (Schlegel et al. 1998).

K. Wiersema (Leicester), A. Levan (Warwick), D. Malesani (DARK) report on behalf of
a larger collaboration:

We observed the position of short GRB 130822A (Kocevski et al., GCN 15112
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 ) using the 4.2m William Herschel
Telescope with the ACAM instrument and a Sloan r filter. We do not identify a source in or near the refined
XRT error circle (Beardmore et al., GCN 15117
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 ) in a dataset of 20x50 seconds exposures (0.365 days after burst),
taken under poor weather conditions. An upper limit of r=21.9 is found at the XRT position.
We note the presence of a moderately bright galaxy (r=18.15) offset approximately 22" from the GRB location 
and with a photometric redshift of z=0.1. If associated with would correspond to an offset of 40 kpc.

A. Melandri (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), J.A. Kennea
(PSU), V. Mangano (PSU), M.C. Stroh (PSU), K.L. Page (U. Leicester), C.
Pagani (U. Leicester), A.P. Beardmore (U. Leicester), P. D'Avanzo
(INAF-OAB) and D. Kocevski report on behalf of the Swift-XRT team:

We have analysed 7.2 ks of XRT data for GRB 130822A (Kocevski  et al.
GCN Circ. 15112
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 ),  from 85 s to 41.0 ks after the  BAT trigger. The
data are entirely in Photon Counting (PC) mode. The enhanced XRT
position for this burst was given by Beardmore et al. (GCN. Circ
15117). The source is fading with alpha >0.5.


If the light curve continues to decay with a power-law decay index of ,
the count rate at T+24 hours will be 2.8 x 10^-5 count s^-1

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00567163.

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

S. B. Cenko (NASA / GSFC), D. A. Perley (Caltech), A. Cucchiara (UCSC), W.
Fong (CfA), and A. J. Levan (U. Warwick) report on behalf of a larger
collaboration:

We have imaged the location of the X-ray afterglow (Beardmore et al., GCN
15117
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 ) of the short GRB 130822A (Kocevski et al., GCN 15112
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 ) with the
Gemini Multi-Object Spectrograph on the 8 m Gemini North telescope.  We
obtained a total integration of 600 s in the i' filter beginning at 12:56
UT on 23 August 2013 (0.88 d after the Swift trigger).  We detect no
sources within the enhanced XRT error circle.  Using nearby point sources
from SDSS for calibration, we calculate an upper limit of i' > 24.5 mag at
this time.

W. Fong, B. A. Zauderer and E. Berger (Harvard) report:

"We observed the field of the short-duration GRB 130822A (Kocevski et
al., GCN 15112
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 ) with the Karl G. Jansky Very Large Array (VLA)
beginning on 2013 Aug 23.33 UT (15.9 hr post-burst) at a mean
frequency of 5.8 GHz. In 1 hour of observations, we do not detect any
radio source within or around the XRT position (Beardmore et al., GCN
15117
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 ). We therefore place a 3-sigma limit of ~30 microJy on the radio
afterglow of GRB 130822A at 15.9 hr after the burst.

We thank the VLA staff for quickly executing these observations."

J. Norris (BSU), S. D. Barthelmy (GSFC), T. Sakamoto (AGU), N. Gehrels (GSFC)

We report the spectral lag analysis for GRB 130822A (Kocevski, et al., GCN Circ. 15112
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 ) 
based on the BAT data.  Using 1-ms binned light curve, the spectral lag for the 15-25 keV 
to 50-100 keV bands is 2.6 (+3.5/-3.2) ms.  Since the lag value is consistent with zero, we 
believe this burst belongs to a short burst category.  There is no evidence for extended 
emission.

A. Volnova (IKI), R.Inasaridze (AAO), O. Kvaratskhelia (AAO), V.
Ayvazian(AAO), Yu. Krugly (IA KhNU), I. Slyusarev (IA KhNU), I. Molotov 
(KIAM), V. Linkov (ISON), A. Pozanenko (IKI)  report on behalf
of  larger GRB follow-up collaboration:

We observed the field of Swift GRB 130822A (Kocevski et al., GCN 15112
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 ) 
on Aug., 22 with AS-32 (0.7m) telescope of Abastumani Observatory, 
SANTEL-400AN (0.4m) telescope of ISON-Kislovodsk observatory, and AZT-8 
(0.7m) telescope of Institute of Astronomy, Kharkiv National University. 
We obtained several unfiltered frames with exposures of 120 s (AS-32), 
100 s and 60 s (SANTEL-400AN), and several frames with filter R with 
exposure of 120 s (AZT-8).  Within the enhanced XRT circle (Beardmore et 
al., GCN 15117
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 ) we did not detect any source on stacked images.

The details of the photometry are the following:

Telescope t_start, UT  filter exptime,s    t-t0, mid, days    uplim

AZT-8     21:39:21     R      55*120       0.28000            20.6
S-400     22:31:37     None   23*100       0.30332            19.3
AS-32     23:46:59     None   40*120       0.36513            21.9

The photometry is based on SDSS stars, R mag (R mag obtained via
transformations ugriz in BVRI (Lupton, 2005):

SDSS id             R      R_err
J015202.75-031421.9 12.80  0.012
J015134.64-031348.8 13.95  0.013
J015148.69-030854.9 14.62  0.013

K. Wiersema (Leicester), A. Levan (Warwick),  S. B.  Cenko (NASA/GSFC) 
and N. Tanvir (Leicester) report on behalf of a larger collaboration:

We acquired spectroscopy of two galaxies close to the afterglow position
of short GRB 130822A (Kocevski et al. GCN 15112
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 ), these galaxies have low chance
coincidence probability values (note that there are no sources found within the
XRT error circle, Cenko et al. GCN 15121
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 ).
These two galaxies, hereafter named G1 and G2, are located at approximate
positions (SDSS DR10):

G1
RA:   01:51:42.66
Dec: -03:12:25.48

G2
RA:   01:51:41.09
Dec: -03:11:07.47

A finder chart showing the locations of these galaxies (Gemini i' band; 
Cenko et al. GCN 15121
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 ) can be found here:
http://www.star.le.ac.uk/~kw113/G1G2.png

We acquired spectroscopy with ACAM on the William Herschel Telescope
(directly following the photometry observations reported in Wiersema
et al. GCN 15119
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 ) and GMOS on Gemini-North (starting at 13:35 UT on
2 September 2013). In both cases the slit was aligned such that both
galaxies were covered simultaneously by the slit. The ACAM spectrum
covers the range 3500-9400, the Gemini spectrum the range 3850-6730 A.

Galaxy G1 shows strong absorption complexes (G band, Mg b triplet, Fe 4668,
Ca II) as well as a single, weak, emission line (H beta), at a common redshift z=0.154.
Galaxy G2 shows stronger emission lines of H alpha and H beta, as well as absorption
complexes (G band, Na I, Mg b triplet) at a common redshift z=0.045.
At these redshifts, the offset from the afterglow to galaxy G1 is 58 kiloparsec,
and to G2 72 kiloparsec.
If the brighter, but somewhat further offset, galaxy G2 is the host galaxy, it would
place GRB 130822A within the Advanced LIGO / Virgo horizon.