GRB 171007A

J. K. Cannizzo (NASA/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (NASA/UMBC), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of
the Swift Team:

At 11:57:38 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 171007A (trigger=777215).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 135.544, +42.849, which is 
   RA(J2000)   = 09h 02m 10s
   Dec(J2000) = +42d 50' 57"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows several peaks
with a total duration of about 25 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~3 sec after the trigger. 

The XRT began observing the field at 11:58:47.2 UT, 68.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
135.6006, 42.8195 which is equivalent to:
   RA(J2000)  = 09h 02m 24.15s
   Dec(J2000) = +42d 49' 10.3"
with an uncertainty of 2.3 arcseconds (radius, 90% containment). This
location is 183 arcseconds from the BAT onboard position, at the edge of 
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 2.05
x 10^20 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 6.22e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 77 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
0.02. 

Burst Advocate for this burst is J. K. Cannizzo (cannizzo AT milkyway.gsfc.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.)

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 171007A (Cannizzo, et al., GCN 21976
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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 2017/10 7.50 to 2017/10 7.52 UTC (3 minutes to
0.57 hours after the BAT trigger), obtaining a total of 0.31 hours exposure
in the r and i bands and 0.14 hours exposure in the Z, Y, J, and H bands.

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

 r > 22.05
 i > 21.94
 Z > 21.24
 Y > 21.02
 J > 20.65
 H > 20.34

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.

V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), J.A.
Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), P.A.
Evans (U. Leicester), S.L. Gibson (U. Leicester), J.P. Osborne (U.
Leicester) and J.K. Cannizzo report on behalf of the Swift-XRT team:

We have analysed 6.1 ks of XRT data for GRB 171007A (Cannizzo et al.
GCN Circ. 21976
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 ), from 62 s to 12.7 ks after the  BAT trigger. The data
comprise 107 s in Windowed Timing (WT) mode (the first 5 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The best available XRT position  (using the promptly downlinked
event data, the XRT-UVOT alignment and matching UVOT field sources to
the USNO-B1 catalogue) is RA, Dec = 135.6008, 42.8193 which is
equivalent to:

RA (J2000): 09 02 24.19
Dec(J2000): +42 49 09.5

with an uncertainty of 2.3 arcsec (radius, 90% confidence).

The light curve can be modelled with a power-law decay with a decay
index of alpha=3.56 (+0.21, -0.18).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.38 (+0.19, -0.18). The
best-fitting absorption column is  1.2 (+0.9, -0.7) x 10^21 cm^-2, in
excess of the Galactic value of 2.1 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.7 x 10^-11 (5.2 x 10^-11) erg
cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Total column:	     1.2 (+0.9, -0.7) x 10^21 cm^-2
Galactic foreground: 2.1 x 10^20 cm^-2
Excess significance: 2.4 sigma
Photon index:	     1.38 (+0.19, -0.18)

If the light curve continues to decay with a power-law decay index of
3.56, the count rate at T+24 hours will be 1.1 x 10^-10 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.2 x
10^-21 (5.7 x 10^-21) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00777215.

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 1637 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 171007A, 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 = 135.60048, +42.81920 which is equivalent
to:

RA (J2000): 09h 02m 24.11s
Dec (J2000): +42d 49' 09.1"

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.

Elisabetta Bissaldi (Politecnico & INFN Bari)
reports on behalf of the Fermi GBM Team:

"At 11:57:39.90 UT on 07 October 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 171007A (trigger 529070264 / 171007498),
which was also detected by the Swift-BAT (Cannizzo et al. 2017, GCN 21976
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 ).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 50 degrees.

The GBM light curve consists of single peak
with a duration (T90) of about 3.5 s (50-300 keV).
The time-averaged spectrum from T0-1.4 s to T0+2.1 s is
adequately fit by a simple power law function with
index -1.31 +/- 0.07.

The event fluence (10-1000 keV) in this time interval is
(6.1 +/- 0.7)E-07 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-1 s in the 10-1000 keV band
is 1.5 +/- 0.2 ph/s/cm^2.


The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

S. D. Barthelmy (GSFC), J. K. Cannizzo (NASA/UMBC),
J. R. Cummings (CPI), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
J. P. Norris (BSU), 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 171007A (trigger #777215)
(Cannizzo et al., GCN Circ. 21976
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 ).  The BAT ground-calculated position is
RA, Dec = 135.635, 42.930 deg which is
  RA(J2000)  =  09h 02m 32.5s
  Dec(J2000) = +42d 55' 47.4"
with an uncertainty of 3.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a short spike that start at ~ T-0.1 s and
ends at ~ T+2.9 s. There is some weak emission lasting till ~T+80 s.
T90 (15-350 keV) is 105 +- 45 sec (estimated error including systematics).

The time-averaged spectrum from T-0.08 to T+107.92 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.38 +- 0.52.  The fluence in the 15-150 keV band is 2.9 +- 1.1 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.92 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.

Although the burst is weak and the short spike is ~ 3 s, the structure of the burst
shows similarity to those of short GRBs with extended emission. We thus perform
further analysis on the short spike and the tail emission. The spectrum of the short
spike from T-0.08 to T+2.92 sec is best fit by a simple power-law model, with
power-law index of 0.83 +- 0.35 and fluence (15-150 keV) of 1.0 +- 0.2 x 10^-7 erg/cm2.
The spectrum of the tail emission from T+2.92 to T+107.92 sec is best fit by a simple
power-law model, with power-law index of 1.67 +- 0.73 and fluence (15-150 keV) of
1.8 +- 1.0 x 10^-7 erg/cm2. These values are consistent with those of short GRBs with
extended emission (Lien & Sakamoto et al. 2016).

The lag analysis is unconstrained due to the weakness of this burst.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/777215/BA/

F. E. Marshall (NASA/GSFC) and J. K. Cannizzo (NASA/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 171007A
77 s after the BAT trigger (Cannizzo et al., GCN Circ. 21976
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 ).
No optical afterglow consistent with the enhanced XRT position
(Beardmore et al. GCN Circ. 21979
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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            77          227          147         >20.7
u_FC               291          540          246         >20.4
white               77         6966          805         >21.7
v                  620         7377          529         >19.5
b                  546         6761          510         >20.8
u                  291         6556          559         >20.7
w1                 669         6351          333         >20.3
m2                 644         7572          480         >19.9
w2                 596         7172          529         >20.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).