GRB 170629A

A. Cholden-Brown (PSU), A. A. Breeveld (UCL-MSSL),
S. W. K Emery (UCL-MSSL), J. A. Kennea (PSU),
N. P. M. Kuin (UCL-MSSL), A. Y. Lien (GSFC/UMBC),
P. T. O'Brien (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 12:53:33 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 170629A (trigger=759159).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 130.016, -46.587 which is 
   RA(J2000) = 08h 40m 04s
   Dec(J2000) = -46d 35' 11"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve is incomplete at this
time due to lost telemetry, but was still rising at 8 sec after 
the trigger with a count rate of ~1500 counts/sec. 

The XRT began observing the field at 12:54:56.0 UT, 82.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 129.98653, -46.57155 which
is equivalent to:
   RA(J2000)  = 08h 39m 56.77s
   Dec(J2000) = -46d 34' 17.6"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 91 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. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

The initial flux in the 2.5 s image was 5.16e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of  90 seconds with the UVW2 filter
 starting  86 seconds after the BAT trigger. No credible afterglow 
candidate has been  found in the initial data products. Analysis is
complicated because of a nearby bright star (b Vel). Full  results
will have to await the full dataset. 

Burst Advocate for this burst is A. Cholden-Brown (aaronb AT swift.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.)

R. Hamburg (UAH), E. Bissaldi (Politecnico & INFN Bari), and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 12:53:31.63 UT on 29 June 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 170629A (trigger 520433616 / 170629537),
which was also detected by the Swift/BAT
(Cholden-Brown et al. 2017, GCN 21283
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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 24
degrees.

The GBM light curve consists of a single emission episode
with a duration (T90) of about 28 s (50-300 keV).
The time-averaged spectrum from T0-0.00 s to T0+12.29 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.1 +/- 0.1 and
the cutoff energy, parameterized as Epeak, is 126 +/- 10 keV.

The event fluence (10-1000 keV) in this time interval is
(3.3 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+8.70 s in the 10-1000 keV band
is 6.0 +/- 0.3 ph/s/cm^2.

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

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

Using 75 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 170629A, 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 = 129.98383, -46.57073 which is equivalent
to:

RA (J2000): 08h 39m 56.12s
Dec (J2000): -46d 34' 14.6"

with an uncertainty of 2.8 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. R. Cummings (CPI), S. D. Barthelmy (GSFC),
A. Cholden-Brown (PSU), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
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 170629A (trigger #759159)
(Cholden-Brown et al., GCN Circ. 21283
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 ).  The BAT ground-calculated position is
RA, Dec = 129.963, -46.585 deg which is 
  RA(J2000)  =  08h 39m 51.0s 
  Dec(J2000) = -46d 35' 06.3" 
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 17%.

The mask-weighted light curve shows a multi-peaked structure that starts 
at ~ T-1 s and ends at ~T+40 s. There are roughly two overlapping 
pulses with peaks at ~ T+1 s and ~ T+5 s, respectively.  The burst location 
went out of the FOV at around T+240 s. T90 (15-350 keV) is 34.4 +- 12.7 sec 
(estimated error including systematics).

The time-averaged spectrum from T-1.21 to T+39.32 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.66 +- 0.12.  The fluence in the 15-150 keV band is 2.6 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+4.96 sec in the 15-150 keV band
is 4.1 +- 0.6 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/759159/BA/

A. Cholden-Brown (PSU) reports on behalf of the Swift-XRT team:

We have analysed 2.0 ks of XRT data for GRB 170629A (Cholden-Brown et
al. GCN Circ. 21283
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 ), from 97 s to 5.9 ks after the  BAT trigger. The
data comprise 140 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Evans et al. (GCN Circ. 21286
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 ).

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.72 (+0.09, -0.12).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.8 (+0.6, -0.3). The
best-fitting absorption column is  1.11 (+0.79, -0.20) x 10^22 cm^-2,
consistent with the Galactic value of 9.1 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 5.3 x 10^-11 (8.5 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.11 (+0.79, -0.20) x 10^22 cm^-2
Galactic foreground: 9.1 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.8 (+0.6, -0.3)

If the light curve continues to decay with a power-law decay index of
0.72, the count rate at T+24 hours will be 0.014 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.2 x
10^-13 (1.2 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00759159.

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