GRB 171115A

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

We observed the field of GRB 171115A (Sbarufatti, et al., GCN 22124
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 ) 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 2017/11 16.08 to 2017/11 16.15 UTC (7.14 to
8.66 hours after the BAT trigger), obtaining a total of 1.07 hours exposure
in the r and i bands and 0.38 hours exposure in the Z, Y, J, and H bands.

For a source within the Swift-XRT error circle (Beardmore, et al., GCN
22125
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 ), in comparison with the USNO-B1 and 2MASS catalogs, we obtain the
following upper limits (3-sigma):

 r > 23.05
 i > 23.19
 Z > 21.86
 Y > 21.66
 J > 21.13
 H > 20.71

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

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

K. Morita, R. Itoh, K. L. Murata, T. Yoshii, Y. Tachibana, S. Harita, T.
Ozawa, H. Mamiya, K. Shiraishi, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:

We searched for the optical counterpart of GRB 171115A (B. Sbarufatti et
al., GCN Circular #22124
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 ) with the optical three color (g', Rc, and Ic) CCD
cameras attached to the MITSuME 50 cm telescope of Okayama Astrophysical
Observatory, Japan.

The observation started on 2017-11-16 08:59:56 UT. We did not find any new
point source within enhanced XRT circle (A.P. Beardmoreet al., GCN Circular
#22125
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 ) in all three bands.

We obtained following limits for the magnitudes.

T0+[hour]    MID-UT      T-EXP[sec]    g'       Rc        Ic
-------------------------------------------------------------------------------------------------------
~14.15       09:52:13.20     5100     >18.1     >17.5     >17.8
-------------------------------------------------------------------------------------------------------

T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration.

K. Morita, R. Itoh, K. L. Murata, T. Yoshii, Y. Tachibana, S. Harita, T.
Ozawa, H. Mamiya, K. Shiraishi, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:

We searched for the optical counterpart of GRB 171115A (B. Sbarufatti et
al., GCN Circular #22124
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 ) with the optical three color (g', Rc, and Ic) CCD
cameras attached to the MITSuME 50 cm telescope of Akeno Observatory,
Yamanashi, Japan.

The observation started on 2017-11-16 08:54:06 UT. We did not find any new
point source within enhanced XRT circle (A.P. Beardmoreet al., GCN Circular
#22125
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 ) in all three bands.

We obtained following limits for the magnitudes.

T0+[hour]    MID-UT      T-EXP[sec]    g'       Rc        Ic
-------------------------------------------------------------------------------------------------------
~14.05       09:14:00.87     2220     >19.6     >18.6     >18.1
-------------------------------------------------------------------------------------------------------

T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration.

T. Sakamoto (AGU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), B. Sbarufatti (PSU)
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 171115A (trigger #790053)
(Sbarufatti et al., GCN Circ. 22124
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 ).  The BAT ground-calculated position is
RA, Dec = 278.392, 9.118 deg which is
  RA(J2000)  =  18h 33m 34.2s
  Dec(J2000) = +09d 07' 06.4"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a weak pulse that starts at ~T-7 s,
peaks at ~T-1 s, and ends at ~T+35 s. T90 (15-350 keV) is 38.2 +- 3.4 sec
(estimated error including systematics).

The time-averaged spectrum from T-7.38 to T+34.78 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.76 +- 0.18.  The fluence in the 15-150 keV band is 6.9 +- 0.8 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-2.32 sec in the 15-150 keV band
is 0.6 +- 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/790053/BA/

J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), P. D'Avanzo
(INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), D.N. Burrows
(PSU), A. Tohuvavohu (PSU), S. J. LaPorte (PSU), A.P. Beardmore (U.
Leicester) and B. Sbarufatti report on behalf of the Swift-XRT team:

We have analysed 7.5 ks of XRT data for GRB 171115A (Sbarufatti et al.
GCN Circ. 22124
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 ), from 62 s to 18.4 ks after the  BAT trigger. The data
comprise 35 s in Windowed Timing (WT) mode (the first 6 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 Beardmore
et al. (GCN Circ. 22125
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 ).

The light curve can be modelled with an initial power-law decay with an
index of alpha=3.81 (+0.26, -0.23), followed by a break at T+289 s to
an alpha of 0.46 (+0.10, -0.11).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.92 (+0.33, -0.23). The
best-fitting absorption column is  3.3 (+1.7, -0.3) x 10^21 cm^-2,
consistent with the Galactic value of 3.0 x 10^21 cm^-2 (Willingale et
al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum  is 4.0 x 10^-11 (5.7 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     3.3 (+1.7, -0.3) x 10^21 cm^-2
Galactic foreground: 3.0 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.92 (+0.33, -0.23)

If the light curve continues to decay with a power-law decay index of
0.46, the count rate at T+24 hours will be 6.4 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.5 x
10^-13 (3.6 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/00790053.

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

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

Using 434 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 171115A, 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 = 278.38820, +9.12510 which is equivalent
to:

RA (J2000): 18h 33m 33.17s
Dec (J2000): +09d 07' 30.4"

with an uncertainty of 2.1 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.

B. Sbarufatti (PSU), D. N. Burrows (PSU), A. Deich (PSU),
J.D. Gropp (PSU), J. A. Kennea (PSU), H. A. Krimm (NSF/USRA),
S. J. LaPorte (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (PSU) report
on behalf of the Swift Team:

At 18:51:20 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 171115A (trigger=790053).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 278.413, +9.128 which is 
   RA(J2000) = 18h 33m 39s
   Dec(J2000) = +09d 07' 42"
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 50 sec.  The peak count rate
was ~1000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 18:52:30.0 UT, 69.2 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
278.3885, 9.1250 which is equivalent to:
   RA(J2000)  = 18h 33m 33.23s
   Dec(J2000) = +09d 07' 29.9"
with an uncertainty of 2.3 arcseconds (radius, 90% containment). This
location is 87 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 consistent with the Galactic value of 2.97
x 10^21 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 7.83e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White 
filter  starting 76 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 0.23. 

Burst Advocate for this burst is B. Sbarufatti (bxs60 AT 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.)