GRB 050416B

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

At 22:35:54.11 UT Swift-BAT triggered on burst GRB 050416b (trigger=114797).
The BAT flight position is RA,Dec=133.853,+11.173 (J2000).  We note this
is 17 deg from the Moon, hence the s/c did not slew because of the Moon
observing constraint.  The burst was 53 deg off the BAT bore sight.
The lightcurve shows a narrow peak with a total burst duration of ~5 sec
(T90=~3sec in 15-350 keV).

S. Piranomonte, A. Melandri, L.A. Antonelli, S. Covino, F.M. Zerbi,
G. Chincarini, M. Rodono', G. Tosti, P. Conconi, G. Cutispoto, E.
Molinari, L. Nicastro, E. Palazzi, E. Meurs, P. Goldoni, on behalf of
the REM/ROSS Team report:


"The REM telescope at the La Silla Observatory (ESO) is observing the
field of GRB 050416B (BAT Trigger #114797).

Observations started just after the sunset in La Silla on Apr. 17
00:01:17 UT about 1.1hr after the burst.

Preliminary analysis of the first frames reveal no new sources in the
BAT error circle (Hullinger et al., GCN 3279
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 ) approximately down to the 2MASS
limit in the J, H and Ks bands.

Observations and further analyses are going on.


This message may be cited."



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E. Berger, J. Mulchaey (Carnegie Observatories), N. Morrell, and W.  
Krzeminski (LCO) report:

"We imaged the BAT error circle of GRB 050416b (GCN 3279
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 ) with the Swope
40-inch telescope (r-band) and the du Pont 100-inch telescope (I-band) at
LCO starting on 2005, April 17.001 and 17.002 UT, respectively (86 and 114
min after the burst).  We also obtained a 5-minute image with IMACS on the
Magellan/Baade telescope in R-band.  A comparison to DSS reveals no new
sources to the depth of the survey in any of our images."

E. Berger, J. Mulchaey (Carnegie Observatories), N. Morrell, and W.  
Krzeminski (LCO) report:

"We imaged the BAT error circle of GRB 050416b (GCN 3279
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 ) with the Swope
40-inch telescope (r-band) and the du Pont 100-inch telescope (I-band) at
LCO starting on 2005, April 17.001 and 17.002 UT, respectively (86 and 114
min after the burst).  We also obtained a 5-minute image with IMACS on the
Magellan/Baade telescope in R-band.  A comparison to DSS reveals no new
sources to the depth of the survey in any of our images."

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

At 22:35:54.1 UT Swift-BAT detected GRB 050416b (trigger=114797)
(GCN Circ 3279
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 , Hullinger et al.).  The refined BAT ground position
is (RA,Dec) = 133.854,  11.182, [deg; J2000] +- 3 arcmin, (95%
containment).  The partial coding fraction was 16%. 
 
The moon is moving towards the position of the GRB, and Swift will not 
be able to observe for several days because of the spacecraft moon 
angle constraint. 

The BAT mask weighted light curve shows a FRED-like structure.   
T90 (15-350 keV) is (5.4 +- 0.9) seconds (estimated error including 
systematics).

The time-averaged spectrum is well fitted in a simple power-law 
model.  The photon index is 1.5 +- 0.2.  The fluence in the 15-350 
keV band is (2.1 +- 0.3) x 10^-6 erg/cm2.   The peak photon flux in 
the 15-350 band is (7.9 +- 0.7) ph/cm2/s.  The quoted errors are at 
the 90% confidence level.

M. Jelinek, A. de Ugarte Postigo (IAA-CSIC Granada),
P. Kubanek (ASU-CAS Ondrejov), T. J. Mateo Sanguino
(Univ. de Huelva), S. Castillo, J. Gorosabel, S.Guziy 
and A. J. Castro-Tirado (IAA-CSIC),

report:

"Following the detection by SWIFT/BAT of GRB 050416B
(Hullinger et al., GCN 3279
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 ), the 0.6m BOOTES-IR
telescope at IAA's Observatorio de Sierra Nevada
responded automatically at 23:13 UT (i.e. 38 minutes
after the event). Although we are still testing the                    
telescope during the commissioning phase, and the                    
near-IR camera is not yet installed, an optical camera                    
was available. A co-addition of first 20 R-band images                    
taken at that particular instrument reveals no optical                    
counterpart in the SWIFT/BAT error box down to R = 19.                    
The instrument sensitivity was highly compromised due                    
to the presence of the nearby moon. Additional info on                    
BOOTES-IR can be found at www.iaa.csic.es/BOOTES-IR.html."

This message can be quoted.

J. A. Kennea, C. P. Hurkett, D. N. Burrows (PSU), V. Mangano 
(IASF/Palermo), T. Sakamoto (GSFC/NRC), N. Gehrels (NASA/GSFC) report on 
behalf of the Swift XRT team:

The Swift BAT instrument detected a GRB at 22:35:54 UT on 16th April 2005 
(GCN Circ 3279
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 ). Due to the close proximity of this burst to the moon, the 
observatory did not executed an automated slew at that time. This burst 
became visible to Swift Narrow Field Instruments at 12:48:00 UT on 20th 
April 2005, and was observed by Swift-XRT as a pre-planned target. From 
ground processed data we find a uncatalogued X-ray source within the BAT 
error circle, located at:

RA(J2000) = 08:55:35.2,
Dec(J2000) = +11:10:32.

We estimate an uncertainty of about 5 arcseconds radius (90% containment). 
This position is 152 arcseconds from the BAT position reported in GCN 
3284
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 . This source should be considered a tentative afterglow candidate, we 
are currently performing further observations to determine if the source 
is fading.

The Swift BAT instrument detected a GRB at 22:35:54 UT on 16th April 2005 
(Hullinger et al., GCN 3279
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 ). Due to the close proximity of this burst to 
the moon, the observatory did not execute an automated slew at that time. 
This burst became visible to Swift Narrow Field Instruments at 12:48:00 UT 
on 20th April 2005 (i.e. 86.3 hours after the trigger), and was observed by 
Swift-XRT as a pre-planned target on 20th April, 22nd April, and 1st May 
2005.  Five uncataloged sources are detected within the BAT error 
circle(Sato et al., GCN Circ 3284
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 ), but none of them is fading. The source 
previously indicated as a tentative afterglow candidate in GCN 3295
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  (Kennea 
et al.) is stable within errors.  Thus we cannot identify any afterglow for 
this GRB. We estimate 3 sigma upper limits of 2E-14, 1.7E-14, and 1.5E-14 
erg/cm2/s for the flux of the GRB afterglow in the first, second and third 
observations, respectively.

V. La Parola, V. Mangano (INAF-IASF/Palermo), J. A. Kennea, D. N. Burrows 
(PSU), T. Sakamoto (GSFC), C. P. Hurkett (U. Leicester) and N. Gehrels 
(GSFC) report on behalf of the Swift XRT team:

The Swift BAT instrument detected a GRB at 22:35:54 UT on 16th April 2005
(Hullinger et al., GCN 3279
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 ). Due to the close proximity of this burst to
the moon, the observatory did not execute an automated slew at that time.
This burst became visible to Swift Narrow Field Instruments at 12:48:00 UT
on 20th April 2005 (i.e. 86.3 hours after the trigger), and was observed by
Swift-XRT as a pre-planned target on 20th April, 22nd April, and 1st May
2005.  Five uncataloged sources are detected within the BAT error
circle(Sato et al., GCN Circ 3284
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 ), but none of them is fading. The source
previously indicated as a tentative afterglow candidate in GCN 3295
Loading...
 
  (Kennea
et al.) is stable within errors.  Thus we cannot identify any afterglow for
this GRB. We estimate 3 sigma upper limits of 2E-14, 1.7E-14, and 1.5E-14
erg/cm2/s for the flux of the GRB afterglow in the first, second and third
observations, respectively.