GRB 121017A

A. A. Breeveld (MSSL-UCL) and D. Grupe (PSU) report on behalf of the 
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 121017A 
1142 s after the BAT trigger (Grupe et al., GCN Circ. 13875
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 ).
No optical afterglow consistent with the XRT position (Goad et al. GCN 
Circ. 13879
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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          1142         1291          147         >21.1
white             1142         1442          167         >21.2
v                 1298         1492           39         >18.5
b                 1397         1417           19         >19.1
u                 1373         1392           19         >18.6
w1                1347         1367           19         >18.1
w2                1448         1468           19         >18.1

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.44 in the direction of the 
burst (Schlegel et al. 1998).

J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U.
Leicester), V. D'Elia (ASDC), A. Maselli  (INAF-IASFPA), V. Mangano
(INAF-IASFPA), J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU)
and D. Grupe report on behalf of the Swift-XRT team:

We have analysed 8.0 ks of XRT data for GRB 121017A (Grupe  et al. GCN
Circ. 13875
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 ), from 1.1 ks to 30.0 ks after the	BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Goad et al. (GCN. Circ 13879).

The light curve can be modelled with  a power-law decay with a decay
index of alpha=0.93 (+/-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 (+0.28, -0.27). The
best-fitting absorption column is  6.0 (+1.7, -1.4) x 10^21 cm^-2, in
excess of the Galactic value of 2.2 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 4.6 x 10^-11 (9.1 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     6.0 (+1.7, -1.4) x 10^21 cm^-2
Galactic foreground: 2.2 x 10^21 cm^-2
Excess significance: 4.4 sigma
Photon index:	     2.10 (+0.28, -0.27)

If the light curve continues to decay with a power-law decay index of
0.93, the count rate at T+24 hours will be 9.5 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.4 x
10^-13 (8.7 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/00536172.

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

D. A. Kann (MPE/Universe Cluster), M. Nardini (Milano-Bicocca), and J.
Greiner (MPE) report on behalf of the GROND team:

We observed the field of GRB 121017A (Swift trigger 536172, Grupe et al.,
GCN # 13875) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla
Observatory (Chile).

Observations started on October 17, 2012, at 23:50 UT, 4.45 hr after the
GRB trigger. They were performed at an average seeing of 1" (in r') and at
an average airmass of 1.3.

We do not detect any sources in the enhanced XRT error circle (Goad et
al., GCN # 13879), in agreement with earlier reports of optical
observations (Jelínek et al., GCN # 13876, Volnova et al., GCN # 13877,
Gorosabel & Mottola, GCN # 13878). There is a star at the eastern edge of
the error circle but this affects only a small part of it.

Based on 284 s of total exposures in g'r'i'z' (mean time 0.18978 days
after the trigger) and 480 s in JHK (mean time 0.19003 days after the
trigger) we estimate preliminary AB magnitudes (upper limits are 3 sigma)
of

g' > 23.2,

r' > 23.2,

i' > 22.4,

z' > 22.2,

J  > 19.8,

H  > 19.4 and

K  > 19.3.

Given magnitudes are calibrated against GROND zeropoints in the optical as
well as 2MASS field stars in the NIR and are not corrected for the high
Galactic foreground reddening of E_(B-V) = 0.44 mag (Schlegel et al.
1998).

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. Grupe (PSU), H. A. Krimm (GSFC/USRA), 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-61 to T+242 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 121017A (trigger #536172)
(Grupe, et al., GCN Circ. 13875
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 ).  The BAT ground-calculated position is
RA, Dec = 288.820, -1.602 deg, which is 
   RA(J2000)  =  19h 15m 16.8s 
   Dec(J2000) = -01d 36' 07.3" 
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 35%.
 
The mask-weighted light curve a single peak starting at ~T-3 sec, peaking 
at ~T+1 sec, and ending at ~T+5 sec.  T90 (15-350 keV) is 4.2 +- 0.5 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-2.72 to T+2.53 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.74 +- 0.17.  The fluence in the 15-150 keV band is 6.6 +- 0.7 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.31 sec in the 15-150 keV band
is 3.3 +- 0.4 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/536172/BA/

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

Using 388 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 121017A, 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 = 288.83026, -1.60418 which is equivalent
to:

RA (J2000): 19h 15m 19.26s
Dec (J2000): -01d 36' 15.0"

with an uncertainty of 2.0 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.

J. Gorosabel (IAA-CSIC, Granada), S. Mottola (DLR, Berlin), report on
behalf of a larger collaboration:

"We imaged the field of the Swift GRB 121017A (Grupe et al., GCN Circ.
13875
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 ) with the 1.23m Calar Alto telescope. The observations were carried
out in the R-band on Oct. 17.85440--17.86153 UT (1.11--1.29 hours post
burst) with a total exposure time of 2x300s. No optical source brighter
than R~20 was found within the XRT error circle."

A. A. Volnova (SAI MSU, IKI RAS), A. S. Moskvitin (SAO RAS) on behalf
of larger collaboration, reports

We observed the field of GRB 121017A (Grupe et al., GCN Circ. 13875
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 )
with the 1-m Zeiss-1000 telescope of SAO RAS
in Rc band. The weather conditions were good, airmass = 5 - 6, seeing
= 2.6". Observations were started since 9.5 minutes
after the BAT trigger, middle time t-t0 = 0.01407 days.

We do not detect any object in the XRT error circle down to a limiting
magnitude 18.8 as well as Jelínek et al. (GCN Circ. 13876
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 ).

GRB 121017A: BOOTES-2/TELMA observations

M. Jelínek, A. J. Castro-Tirado, J. Gorosabel (IAA-CSIC Granada), S. Guziy
(Nikolaev Univ.), O. Rabaza (Univ. de Granada),
on behalf of a larger collaboration, report:

"Following the detection of GRB 121017A by Swift (Grupe et al. GCN Circ.
13875
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 ) the 0.6m TELMA robotic telescope (+ COLORES) in Málaga (Spain)
started to take images (unfiltered) about 3 min postburst (19:26:10 UT),
following the initial BAT position. There is no optical counterpart within
the Swift/X-ray error box down to R = 18.5 for a 153s combined exposure (5
min post burst). Further exposures in i'-band (22:05 UT, 1200s on the
aggregate) set a limit of 19.5 (35 min post burst). We note the
considerable extinction (A_v = 1.4) towards this direction 6 deg below the
Galactic Plane. Observations are ongoing."

[GCN OPS NOTE(17oct12): Per author's request, OR was added to the author list.]

D. Grupe (PSU), B. N. Barlow (PSU), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC),
E. A. Helder (PSU), S. T. Holland (STScI), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (NASA/GSFC),
F. E. Marshall (NASA/GSFC), C. J. Mountford (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU) and
C. A. Swenson (PSU) report on behalf of the Swift Team:

At 19:23:28 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 121017A (trigger=536172).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 288.816, -1.595 which is 
   RA(J2000)  =  19h 15m 16s
   Dec(J2000) = -01d 35' 43"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows at least two peaks 
with a duration of about 10 sec (possibly longer).  The peak count rate 
was ~2500 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 19:25:03.3 UT, 95.2 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 288.8302, -1.6042 which
is equivalent to:
   RA(J2000)  = 19h 15m 19.25s
   Dec(J2000) = -01d 36' 15.1"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 60 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 (2.22 x
10^21 cm^-2, Kalberla et al. 2005), with an excess column of 3
(+2.89/-2.40) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 1141 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. There is no new source down to a limit of
about 19th mag. The 8'x8' region for the list of sources generated on-board covers
100% 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 expected extinction corresponding
to E(B-V) of 0.44. 

XRT and UVOT detections were delayed due to entry into the SAA shortly
after the initial trigger. 

Burst Advocate for this burst is D. Grupe (grupe AT astro.psu.edu). 
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.)