GRB 160216A

E. Troja (NASA/GSFC/UMCP), S. D. Barthelmy (GSFC),
D. N. Burrows (PSU), S. B. Cenko (GSFC), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), F. E. Marshall (NASA/GSFC),
L. M. McCauley (PSU), T. G. R. Roegiers (PSU),
B. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf
of the Swift Team:

At 19:10:31 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160216A (trigger=673978).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 311.706, -71.555 which is 
   RA(J2000)  =  20h 46m 49s
   Dec(J2000) = -71d 33' 17"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows several bright peaks
with a duration of about 30 sec.  The peak count rate
was ~7000 counts/sec (15-350 keV), at ~3 sec after the trigger. 

The XRT began observing the field at 19:12:05.3 UT, 93.9 seconds after
the BAT trigger. The position determined from promptly downlinked data
differs significantly from the on-board position, suggesting that the
XRT may have centroided on a cosmic ray; the initial XRT position
notice should be treated with caution. Using promptly downlinked data
we find a fading, uncatalogued X-ray source located at RA, Dec
311.68630, -71.54787 which is equivalent to:
   RA(J2000)  = 20h 46m 44.71s
   Dec(J2000) = -71d 32' 52.3"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 34 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 (4.50 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 1.1
(+0.67/-0.50) x 10^22 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 100 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
0.05. 

Burst Advocate for this burst is E. Troja (eleonora.troja 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.)

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

Using 400 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 160216A, 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 = 311.68414, -71.54837 which is equivalent
to:

RA (J2000): 20h 46m 44.19s
Dec (J2000): -71d 32' 54.1"

with an uncertainty of 1.8 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.

N. P. M. Kuin (UCL-MSSL) and E. Troja (NASA/GSFC/UMCP) report
on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160216A
101 s after the BAT trigger (Troja et al., GCN Circ. 19014
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 ).  No optical
afterglow consistent with the XRT position (Beardmore et al. GCN Circ.
19015
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 ) has been 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           101          251          147         >19.8
u_FC               314          564          246         >19.1
white              101         5921          541         >20.6
v                 4695         6301          364         >19.0
b                 4079         5716          393         >19.9
u                  314         5510          442         >19.3
w1                5105         5305          197         >19.4
m2                4900         5099          197         >19.7
w2                4490         6126          393         >20.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).

A. D'Ai (INAF-IASFPA), A. Maselli  (INAF-IASFPA), A. Melandri
(INAF-OAB), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N.
Burrows (PSU), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester),
P.A. Evans (U. Leicester) and E. Troja report on behalf of the
Swift-XRT team:

We have analysed 7.5 ks of XRT data for GRB 160216A (Troja et al. GCN
Circ. 19014
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 ), from 81 s to 34.6 ks after the  BAT trigger. The data
comprise 36 s in Windowed Timing (WT) mode (the first 8 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. 19015
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 ).

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.996 (+0.026, -0.025).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.90 (+0.18, -0.17). The
best-fitting absorption column is  5.4 (+1.2, -1.0) x 10^21 cm^-2, in
excess of the Galactic value of 4.5 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 4.4 x 10^-11 (6.8 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     5.4 (+1.2, -1.0) x 10^21 cm^-2
Galactic foreground: 4.5 x 10^20 cm^-2
Excess significance: 7.8 sigma
Photon index:	     1.90 (+0.18, -0.17)

If the light curve continues to decay with a power-law decay index of
0.996, the count rate at T+24 hours will be 0.010 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.4 x
10^-13 (6.9 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/00673978.

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

A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks,
P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko,
and T. Cline on behalf of the Konus-Wind team, report:

The long-duration GRB 160216A (Swift-BAT trigger #673978:
Troja et al., GCN Circ. 19014
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 )
triggered Konus-Wind at T0=69030.129 s UT (19:10:30.129).

The burst light curve shows a double-peaked structure
started at ~T0-0.3 s with a total duration (80-1400 keV) of ~3.6 s.
The emission is seen up to ~4 MeV.

As observed by Konus-Wind, the burst
had a fluence of 3.05(-0.35,+0.39)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+2.864 s,
of 2.62(-0.70,+0.71)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.66 (-0.31,+0.36)
and Ep = 140 (-18,+25) keV (chi2 = 91/87 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -3.0
(chi2 = 91/86 dof)

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB160216_T69030/

Another long-duration GRB 160216B was detected by Konus-Wind
in the same trigger record at ~T0+150 s. This second burst was
also detected by Fermi-GBM, trigger #477342778.The KW ecliptic
latitude response for GRB 160216B is consistent with the GBM
localization and inconsistent with the BAT localization
of GRB 160216A.

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.

S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU),
E. Troja (NASA/GSFC/UMCP), 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 downlinks,
we report further analysis of BAT GRB 160216A (trigger #673978)
(Troja, et al., GCN Circ. 19014
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 ).  The BAT ground-calculated position is
RA, Dec = 311.679, -71.550 deg, which is 
   RA(J2000)  =  20h 46m 43.0s 
   Dec(J2000) = -71d 33' 01.0" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 48%.
 
The mask-weighted light curve shows a small peak starting at ~T-0.3 sec,
then two large peaks at ~T+0.6 s and ~T+3.2 sec, and ending at ~T+20 sec.
T90 (15-350 keV) is 11.0 +- 1.0 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.30 to T+11.70 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.48 +- 0.08.  The fluence in the 15-150 keV band is 2.0 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.70 sec in the 15-150 keV band
is 7.3 +- 0.5 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/673978/BA/