GRB 060413

M. Kuwahara (TUS/RIKEN), M. Tashiro, Y. Urata, K. Abe, K. Onda,
N. Kodaka, K. Masuno (Saitama-U), F. Usui (ISAS/JAXA), T. Tamagawa
(RIKEN) on behalf of the WIDGET collaboration report: 

"We have observed the entire error region of the Swift GRB 060413
(Pagani et al., GCN 4957
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 , 4959
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 ) with the very wide-field camera,
WIDGET, located at Akeno, Japan.  WIDGET has continuously monitored
the Swift Field-of-View with repeat of unfiltered 5-second exposures
between 26 seconds before and 335 seconds after the burst. The 1-sigma
limiting magnitude of each frame derived by the Tycho-2 catalog was
around V=10 mag. There was no significant emission from the X-ray
afterglow position up to the limiting magnitudes." 

This message may be cited.

A. J. Blustin (UCL-MSSL), C. Pagani (PSU), J. Kennea (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began taking data on the field of GRB060413 at
2006-04-13T18:42:28, 124 s after the BAT trigger (Pagani et al.,
GCN 4957
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 ). No afterglow candidate was detected at the refined
XRT position (Pagani et al., GCN 4959
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 ) in summed images from
any of the filters down to the following three-sigma upper
limits.

Filter  T_range(s)  Exp(s) 3sig_UL

V       230-11744   1960   19.96
B       707-24977   2014   20.90
U       683-24287   2262   20.80
UVW1    660-23374   2118   20.14
UVM2    635-12648   1378   20.23
UVW2    735-7623    388    19.74
White   124-19078   1220   20.74

These upper limits are uncorrected for the estimated Galactic
reddening of E_{B-V} = 1.95 mag (Schlegel et al. 1998); we
estimate the V-band extinction A_v to be 6.24 magnitudes in this
direction.

S.D. Vergani, P. D'Avanzo, E. Molinari, P. Romano, G. Chincarini, F.M. Zerbi,
S. Covino, V. Testa, G. Tosti, F. Vitali, L.A. Antonelli, P. Conconi, G. 
Cutispoto, G. Malaspina, L. Nicastro, E. Palazzi, E. Meurs, P. Goldoni, 
report on behalf of the REM/ROSS team:

We imaged the field of GRB 060413 (Pagani et al., GCN4957
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 ) with the 
robotic 60-cm REM telescope located at La Silla (Chile). Observations 
were performed in the near infrared (J, H, K, z bands) starting on 2006 
Apr 14th at 07:58:12.5 UT and ending at 08:38:34.3 UT (approximately 13
hours after the burst). Observations in each filter lasted 300 s. Inside 
the XRT error circle (Pagani et al., GCN4959
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 ), we find a single source, 
which is visible also in the 2MASS survey. Its magnitudes are consistent 
with the 2MASS values.

The 3-sigma limiting magnitudes are:
K=14.7
H=15.2

This message is citeable.

[GCN OPS NOTE(14apr06): Per author's request, Romano was added to the author list.]

L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC),
 E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (BYU-Idaho),
 H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), C. Pagani (PSU),
 D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC),
 G. Sato (ISAS), J. Tueller (GSFC)
 on behalf of the Swift-BAT team:
 
 Using the data set from T-239 to T+510 sec from recent telemetry downlinks,
 we report further analysis of BAT GRB 060413 (trigger #205096)
 (Pagani, et al., GCN 4957
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 ).  The BAT ground-calculated position is RA,Dec =
 291.288,+13.746 deg {19h 25m 9.2s,+13d 44' 45.5"} (J2000) +- 1.9 arcmin,
 (radius, sys+stat, 90% containment).  The partial coding was 100%.
  
 The mask-weighted lightcurve shows a slow rise starting at ~T+20
 to a cusp-like double peak, then followed by a slow decay
 ending at ~T+220 sec.  T90 (15-350 keV) is 150 +- 10 sec
 (estimated error including systematics).
  
 The time-averaged spectrum from T+29.6 to T+257.1 is best fit by 
 a simple power-law model.  The power law index of the time-averaged
 spectrum is 1.67 +- 0.08.  The fluence in the 15-150 keV band is
 3.6 +- 0.1 x 10-06 erg/cm2.  The 1-sec peak photon flux measured
 from T+90.16 sec in the 15-150 keV band is 0.9 +- 0.1 ph/cm2/sec.
 All the quoted errors are at the 90% confidence level.

J.French, G.Melady, L.Hanlon, B.McBreen, S.McBreen (University College
Dublin, Ireland), P.Meintjes, M.Hoffman, H.Calitz (University of the
Free State, South Africa), N.Smith (Cork Institute of Technology,Ireland),
M.Jelinek, A. de Ugarte Postigo, A.J. Castro-Tirado (IAA, Granada),
R.Hudec (ASU AV CR Ondrejov) and P.Kubanek (ASU AV CR Ondrejov & ISDC,
Versoix)

reports

under control of RTS2, and using JIBARO astrometry package, Watcher
telescope, located at Boyden Observatory, South Africa, observed XRT
location of GRB 060413 (GCN 4958
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 ). Observation at UBVR filters started
at high airmass at 23:10 UT, e.g. 4 h 13 m after GRB. Preliminary
analysis of single 60 seconds R exposure doesn't shown any new object
down to 16.5 magnitude.

Observation is continuing. Watcher telescope is currently in
commissioning phase.

This message can be quoted.

C. Pagani, D. Morris, J. Racusin, J. Kennea and D. N. Burrows (PSU)  
report on behalf of the Swift XRT team:

We have analysed the first orbit of Swift XRT data on the BAT GRB 060413 
(Pagani, et al., GCN 4957
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 ) with a total exposure of 1700 seconds.

The refined XRT position is:

RA(J2000):   19 25 07.7
Dec(J2000): +13 45 27.3

This position is 192 arcseconds from the BAT position 
and 4 arcsec from the XRT position given in GCN 4957
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 . 
We estimate an uncertainty of 3.6 arcseconds radius (90% containment).

The 0.2-10 keV light curve starts in Windowed Timing (WT) mode
119 seconds after the BAT trigger (T0) and then switches into Photon Counting 
(PC) at T0+305. 
The XRT data show a steep power law decay with slope of -3.5 +/- 0.2
followed by a flare centered at T0+646 seconds with a peak count rate of 
6 counts/s.

The X-ray spectrum covering the time period from T+119s to T+1840s is
well fit by an absorbed power-law with a photon index of 1.9+/-0.1 and a
column density of 2.30e22 cm-2, which is higher than the Galactic value 
in the direction of the source (1.20e22 cm-2). However, the NH measurement of 
this galactic plane line of sight is likely to be underestimated.
The unabsorbed 0.3-10 keV flux is 4.8e-09 erg/cm**2/s.

Due to the flare in the light curve the predicted XRT count rate is uncertain.  
Extrapolating the late part of the lightcurve of the first orbit we estimate 
the XRT count rate to be about 0.0006 cps at T+24 hr, corresponding to an 
unabsorbed 0.3-10 keV flux of about 1.6E-13 erg/cm2/s

This circular is an official product of the Swift XRT Team.

GRB 060413: No Optical Afterglow in Swift/UVOT TDRSS Data

Padi Boyd (GRFC), R. E. Weigand (GSFC), Stephen T. Holland (GSFC/USRA)
and Alex Blustin (MSSL) report on behalf of the Swift/UVOT team:

      UVOT took a finding chart exposure of GRB 060413 (Pagani et
al. 2006, GCN Circular 4957
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 ).  The exposure length was 400 seconds
with the V filter starting 960 seconds after the BAT trigger.  No
afterglow candidate has been found in the initial data products.  The
2.7'x2.7' sub-image covers the entire XRT error circle.  The 3-sigma
upper limit inside the XRT error circle is 19.2 mag.  We note that
this GRB occurred at a Galactic latitude of -1.04 degrees and the
estimated Galactic reddening along this line of sight is E_{B-V} =
1.95 mag (Schlegel et al. 1998).

C. Pagani (PSU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
J. R. Cummings (NASA/ORAU), A. D. Falcone (PSU),
S. D. Hunsberger (PSU), J. A. Kennea (PSU), D. M. Palmer (LANL) and
P. Romano (INAF-OAB) report on behalf of the Swift Team:

BAT detected a GRB at 18:40:24. The BAT in-flight position is
RA, Dec 291.300d, +13.808d (J2000). There were no immediate
notices because the TDRSS link was down at the time. No 
information is available about the light curve until the
full data arrive in about an hour. 

XRT began observing at 18:42:19UT, 115 seconds after the BAT trigger. 
XRT centroided on a bright, fading, uncatalogued X-ray point source at the
following coordinates:  

RA(J2000):   19 25 07.5 
Dec(J2000): +13 45 26.4 

with an estimated uncertainty of 5 arcsec radius (90% containment). 
This position is 194 arcseconds from the BAT position. The estimated flux 
from this burst is 1.0E-8 erg/s/cm^2 (0.2-10 keV). Note that the flux in 
the GCN XRT position notice was underestimated by a factor of 10. 

The UVOT took a V finding chart. Only raw data (no coordinates) are
available at  this time. Further results will be available following
the full data download.