GRB 050716

J. Gorosabel, A.J. Castro-Tirado (IAA-CSIC, Granada), R. Lopez (Univ. of
 Barcelona), G. Andreuzzi (TNG, La Palma), A. de Ugarte Postigo, S. Guziy,
 M. Jelinek (IAA-CSIC, Granada), O. Bogdanov (Nikolaev State Univ.),
 report:

 "We have observed the field of GRB 050716 (Rol et al., GCN Circ. 3623
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 )
with the 3.5m TNG telescope on June 17.231-17.242 UT in the J-band (Texp =
15 min). The afterglow candidate reported by Tanvir et al. (GCN Circ. 3632
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 )
is not detected in our final combined image, which has a 3 sigma limiting
magnitude of J~22."

 This message can be cited.

N. Tanvir, K. Lowe, T. Gledhill (U. of Hertfordshire), A. Levan,
E. Rol, P. O'Brien, N. Bannister (U. of Leicester), T. Carroll (JACH),
C. Guidorzi, A. Gomboc, A. Monfardini, I. Steele, C. Mundell,
C. Mottram, M. Bode R. Smith, D. Carter (Liverpool JMU) report:

We imaged the Swift/XRT error circle of GRB 050716 (GCN 3623
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 /3624)
with UKIRT/UFTI starting about 56 minutes post-burst.

Just outside the XRT error circle we find a fading point source
at position (astrometry relative to nearby 2MASS star):

   22 34 20.73   +38 41 03.6  (J2000)

Provisional photometry indicates that this source declines from K~17.8
to K~18.3 between two integrations separated by about 30 mins, making it
very likely to be the afterglow of GRB 050716.

Interestingly, it also appears to be red with J-K~2.5.  A reanalysis
of the very early FT-N data (GCN 3625
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 ), however, shows excess flux in
R and I at the source position which, although not a clear detection
(due to the faintness and proximity of nearby USNO star), suggests
that the source is probably reddened rather than at very high
redshift.

Images can be found at:

  http://star-www.herts.ac.uk/~nrt/050716.html

Further observations are planned.
This message may be cited.

K. McGowan (MSSL), E. Rol (U. Leicester), J. Nousek (PSU),
F. Marshall, N. Gehrels (GSFC) report on behalf of the
Swift UVOT team:

Using summed images from Swift/UVOT of the field of
GRB 050716 (Rol et al., GCN 3623
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 ), taken from 99
seconds after the BAT trigger, no new source is detected
within the XRT error circle (Hurkett et al., GCN 3630
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 ) in
any of the six filters down to the following 3-sigma
magnitude upper limits:

Filter   Exposure (s)  T_mid (s)   3-sig limit
V        178            487        19.1
B        979           3121        21.1
U        978           2660        20.7
UVW1     178           2200        19.7
UVM2      88            545        19.5
UVW2     755           3468        20.8

where T_mid is the mid-point of the summed observation.

We caution that the instrument is not yet fully
calibrated and that the magnitude limits presented here
may need to be refined.

C. Hurkett, E. Rol, K. Page (U. Leicester), D. Burrows (PSU), J. Norris
(GSFC), K. Hurley (Berkeley) and N. Gehrels (GSFC) report for the Swift
XRT team:

We have analysed the XRT data for GRB 050716 (GCN 3623
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 , Rol et al) taken
104 seconds after the trigger. PSF fitting of the candidate afterglow in
the photon counting (PC) mode observations yields a refined position of
(J2000)

RA 22:34:20.5
Dec +38:40:57.1

with an uncertainty of 6 arcseconds (90% containment). This position is
less than 1 arcsecond from the position reported in GCN 3624
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  (Kennea et
al).

XRT observations began in Windowed Timing (WT) mode 104 seconds after the
trigger and show a decline with a power-law decay index of 1.68
+/- 0.04 with flares at approximately 177 and 386 seconds.
The decay index appears to stay the same at least until 6000 seconds after
the trigger.

The spectrum between 104 and 517 seconds after the trigger (WT data) has
an average photon index of 1.32 (+/-0.04), with the absorption fixed at
its Galactic value of 1.1e21 cm^-2. There is no evidence at the present
time for excess absorption. The mean unabsorbed flux in WT mode at 230s
(logarithmic mean time) is 7.02 (+0.27/-0.24) x 1e-10 erg/cm^2/s in the
0.5-10.0 keV energy range

S. Barthelmy (GSFC), L. Barbier (GSFC), J. Cummings (GSFC/NRC),
E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (GSFC/UMD),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), J. Tueller (GSFC),
M. Chester (PSU),  L. Angelini (GSFC/JHU)
on behalf of the Swift-BAT team:

Using the full data set from the recent telemetry downlink, we report
further analysis of Swift-BAT Trigger #146227 (E. Rol, et al., GCN 3623
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 ).
The ground-analysis position is RA,Dec 338.607, 38.682 (J2000) with an
uncertainty of 3 arcmin (radius, 90%, stat+sys).  T90 is 69 +/-1 sec.
The burst had a slow rise and slow decay with two broad peaks centered
at T+12 and T+44 seconds.  Fitting a cutoff power law over the full interval
from T-14 to T+76 seconds, the photon index is 0.79  +/- 0.26, Epeak is
104 +29 -15 keV and the Norm at 1 keV is 0.34 +0.38 -.19  with a fluence
of 8.3 +1.3 -0.6 X 10^-6 erg/cm^2 in the 15-350 keV band (90% c.l.).
The peak flux in a 1-sec wide window starting at T+12.2 seconds
is 2.23 +/- 0.41 ph/cm^2/sec (15-350 keV).

Z.Y. Lin(NCU), K.Y. Huang, W.H. Ip (NCU), Y. Urata(RIKEN),
Y. Qiu (BAO), Y.Q. Lou (THCA) on behalf of EAFON report:

"We have imaged the GRB 050716 X-ray afterglow position (Rol et
al. GCN 3623
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 ; J. Kennea et al.  3264) with B and R band using Lulin
1-m telescope. The observation was started at 14:30 (0.079 days after
the burst) after rising the field. These images show no optical
counterpart brighter than B=21.6 and R=21.3. These 3-sigma limiting
magnitudes are derived from the USNO-B1.0 catalogue.

This message may be cited."

E.Sonoda,S.Maeno,Y.Tokunaga,Myamauchi
(University of Miyazaki)


We have observed the field covering the error circle
of GRB 050716 (GCN 3623
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 ,3624
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 ;Swift BAT Trigger time is
12:36:04 UT) with the unfiltered CCD camera on the
30-cm telescope at University of Miyazaki. The observation was started
14:28:47 UT on July.16. We have compared with the USNO A2.0 catalog.
Preliminary analysis shows there is no new source brighter than 16.8 mag.

K. Torii (Osaka U.) reports on behalf of the ART collaboration:

 The error region of GRB 050716 (Rol et al. GCN 3623
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 ) was observed by
the Automated Response Telescope. The observation started at 2005 July
16 12:38:26 UT (142 s after the trigger) and BVRcIc frames of 60s
integration were acquired.

 We do not detect an optical counterpart of the X-ray afterglow (GCN
3623
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 , 3624
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 ) and derive its 3-sigma upper limit relative to
USNO-B1.0 magnitude as follows.

================================
Start(UT) Filter Mag   Exposure
--------------------------------
12:55:06  Ic     >16.5 60s x27
--------------------------------

C. Guidorzi, A. Gomboc, A. Monfardini, I. A. Steele, C.J. Mottram,
C.G. Mundell, R.J. Smith, D. Carter, M.F. Bode (Liverpool JMU),
E. Rol, P. O'Brien, N. Bannister (Leicester) report:
  
"The 2-m Faulkes North Telescope followed up robotically the GRB050716
detected by SWIFT (Rol et al. GCN 3623
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 ) 3.8 min after the GRB trigger
time. The automatic "detection mode" procedure did not detect any obvious
candidate up to about R=19.8 from 3 10-s images (mean epoch of 4.3 min
after the GRB), with FOV of 4.6'x4.6' centred on the BAT in-flight
location.
 
The limiting magnitude is automatically calculated with respect to the
USNOB1.0 'R2' values of the field objects.
 
Further observations are ongoing.
This message can be cited"

J. Kennea, D. Burrows (PSU), E.Rol, C. Hurkett, K. Page (U. Leicester) and 
N. Gehrels (GSFC) report for the Swift/XRT Team:

In GCN 3623
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  we reported an incorrect sign on the declination of the XRT 
position for GRB050716. The corrected position is:

RA:    22h 34m 20.4s (J2000),
Dec:  +38d 40' 56.7" (J2000).

With an estimated uncertainty of 6 arcseconds radius (90% containment).

E. Rol, C. Hurkett, K. Page (U. Leicester), S. Barthelmy, L. Barbier,
A. Parsons (GSFC), J. Cummings (NRC, GSFC), D. Palmer (LANL),
D. Burrows, J. Kennea (PSU), K. McGowan (MSSL), N. Gehrels (GSFC),
report for the Swift team:


At 12:36:04 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 050716 (trigger=146227).  The BAT on-board calculated
location is RA,Dec 338.598d {+22h 34m 23s}, +38.696d {+38d 41' 46"}
(J2000), with an uncertainty of 4 arcmin (radius, including estimated
systematic uncertainty; 90% containment).  The BAT light curve showed
a multi-peak structure with a duration of at least 40 seconds.  The
15-350 keV peak count rate was ~1300 counts/sec, measured by BAT at
~10 seconds after the trigger.

The spacecraft slewed immediately and the XRT began observing the
burst at 12:37:40 UT (96 seconds after the BAT trigger). The XRT found
a bright, uncatalogued X-ray source. The on board calculated position
is:

RA:     22h 34m 20.4s (J2000),
Dec:   -38d 40' 56.7" (J2000).

This position is 60.6 arcseconds from the BAT position.  The estimated
uncertainty is 6 arcseconds radius (90% containment).


The Swift Ultra Violet/Optical Telescope (UVOT) observations began at
12:37:43 UT, 99 seconds after the BAT trigger. The first data taken
after the spacecraft settled was a 100 sec exposure using the V filter
with the midpoint of the observation at 149 sec after the BAT
trigger. Based on comparisons to the DSS, we detect no new source at
the XRT position.