Gamma-ray Burst 050418

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE


TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 18 Apr 05 11:03:19 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     114893,   Seg_Num: 0
GRB_RA:           44.341d {+02h 57m 22s} (J2000),
                  44.402d {+02h 57m 37s} (current),
                  43.766d {+02h 55m 04s} (1950)
GRB_DEC:         -18.538d {-18d 32' 15"} (J2000),
                 -18.517d {-18d 31' 00"} (current),
                 -18.738d {-18d 44' 15"} (1950)
GRB_ERROR:       4.00 [arcmin radius, statistical only]
GRB_INTEN:       6973 [cnts]    Peak=533 [cnts/sec]
TRIGGER_DUR:     1.024 [sec]
TRIGGER_INDEX:   148     E_range: 25-100 keV
BKG_INTEN:       35835 [cnts]
BKG_TIME:        39616.00 SOD {11:00:16.00} UT
BKG_DUR:         8 [sec]
GRB_DATE:        13478 TJD;   108 DOY;   05/04/18
GRB_TIME:        39634.62 SOD {11:00:34.62} UT
GRB_PHI:         -133.76 [deg]
GRB_THETA:        39.42 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     39.63 [sigma]
IMAGE_SIGNIF:    18.00 [sigma]
MERIT_PARAMS:     +1  +0  +0  +4  +2 +15 -100  +0 -82  +1 
SUN_POSTN:        26.49d {+01h 45m 58s}  +10.95d {+10d 56' 44"}
SUN_DIST:         34.35 [deg]
MOON_POSTN:      142.69d {+09h 30m 46s}  +19.76d {+19d 45' 34"}
MOON_DIST:       103.65 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      203.11,-59.83 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       35.38,-33.73 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.

red DSS finding chart ps-file

GCN/SWIFT NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 18 Apr 05 11:04:10 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     114893,   Seg_Num: 0
GRB_RA:           44.341d {+02h 57m 22s} (J2000),
                  44.402d {+02h 57m 37s} (current),
                  43.766d {+02h 55m 04s} (1950)
GRB_DEC:         -18.538d {-18d 32' 15"} (J2000),
                 -18.517d {-18d 31' 00"} (current),
                 -18.738d {-18d 44' 15"} (1950)
GRB_DATE:        13478 TJD;   108 DOY;   05/04/18
GRB_TIME:        39634.62 SOD {11:00:34.62} UT
TRIGGER_INDEX:   148
GRB_PHI:         -133.76 [deg]
GRB_THETA:        39.42 [deg]
DELTA_TIME:      65484.00 [sec]
LC_URL:          sw00114893000msb.lc
SUN_POSTN:        26.49d {+01h 45m 58s}  +10.95d {+10d 56' 44"}
SUN_DIST:         34.35 [deg]
MOON_POSTN:      142.69d {+09h 30m 46s}  +19.76d {+19d 45' 34"}
MOON_DIST:       103.65 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      203.11,-59.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       35.38,-33.73 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:        This does not match any source in the ground catalog.

GCN notice #3288
L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (GSFC/UMD), K. Hurley (UC Berkeley), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), F. Marshall (GSFC), 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 11:00:34.6 UT Swift-BAT triggered on burst GRB 050418 (trigger=114893). The BAT flight position is RA,Dec=44.341,-18.538 (J2000). We note this is 34 deg from the Sun, hence the s/c did not slew because of the Sun observing constraint. The burst was 39 deg off the BAT boresight. The lightcurve shows a main peak of duration 15-20 seconds, followed by apparent peaks at up to 70-80 seconds after the trigger. The peak count rate measured by BAT was 4500 counts/sec in the 15-350 keV band.
GCN notice #3289
T. Mitani (ISAS), L. Barbier (GSFC), 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), G. Sato (ISAS), M. Suzuki (Saitama), J. Tueller (GSFC), on behalf of the Swift/BAT team:
At 11:00:34.6 UT Swift-BAT detected GRB 050418 (trigger=114893) (GCN Circ 3288, Barbier et al.). The refined BAT ground position is (RA,Dec) = 44.346, -18.538, [deg; J2000] +- 3 arcmin, (95% containment). The partial coding was 48 %.
The BAT mask-weighted light curve shows an initial triangular peak (~12 s rise, ~8 s fall time) followed by a quartet of softer peaks from 50 to 80 seconds after the maximum of the first peak, with the last and brightest of the four being as intense as the initial peak in 15-50 keV, but less than a quarter the height in 50-100 keV. T90 (15-350 keV) is (83 +- 5) seconds (estimated error including systematics).
The photon index of the time-averaged spectrum is 1.7 +- 0.1. The fluence in the 15-350 keV band are (8.6 +- 0.4) x 10^-6 erg/cm2. The 1-s peak photon flux measured from T0+0.75 second in the 15-350 band is (5.0 +- 0.3) ph/cm2/s. All the quoted errors are at the 90% confidence level.

GCN notice #3292
B. Monard and A. Price report on behalf of the AAVSO International High Energy Network on optical observations of the field of GRB050418 (Sakamoto et al,; GCN #3288).
Observations by Monard do not reveal ay new source compared with the POSS-II red plates down to an unfiltered limiting magnitude of 16 at an observation midpoint time of 16:50 (UT). As previously reported in GCN #3288, the field was relatively close to the Sun therefore close to the horizon.
Details of the observation are below.

Name: Berto Monard
email: bmonard@mweb.co.za
Site: Bronberg Observatory
Location: -25 =BA 54' 48", 28=BA 26' 44"E
Elevation: 1590m
Scope: LX200 12"
ScopeFocalRatio: f/3.7
CCDVendor: SBIG, ST-7XME
CCDPixelScale: about 1.8 arcsec /pixel
CCDFOV: 21 arcmin (E/W) x 14 arcmin (N/S)
Object: 050418
ObsDate: 050418
ObsMidPointTime: 16 50 UT
Exposure per frame: 28 sec
NumberOfFrames: 33
Filters: none
Processing: dark/flat
Seeing: good (about 3 arcsec)
LimitingMag: 16CR for stack of 13 images
Sky: partly cloudy / 1/2 moon / target field close to horizon
afterglowmag: NA
Report: the observed star field was centered on 02h 57m 22s -18d 32' 15"
(2000). The obtained deep image was compared visually to a DSS-2 red image
centered on the above coordinates.

No new object showed in the quoted error box down to a magnitude of 16CR.
Note: The actual observation period was very short due to the circumstances and no further observations were possible.

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Jochen Greiner, last update: 18-Apr-2005 [Disclaimer]