Gamma-ray Burst 000416

On April 16, 2000 at 14:32:54 UT a burst was detected in WFC n.2, which was only marginally detected in the GRBM. It therefore was classified as a X-ray rich GRB. However, BATSE detected it in continuous data mode with 1.024-s temporal resolution. If this event is a GRB, it ranks in the lower ~2% (10%) of the BATSE flux/fluence distribution.

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN notice #635 = BeppoSAX mail n. 00/07
  On April 16 at 14:32:54 UT a burst was detected in WFC n.2 with a peak flux of about 2 Crab in the 2-26 keV range. The burst lasted about 25 s. Preliminary position is:

  R.A.= 258.76
  Decl.= -71.56
  

  with an error radius of 4'.
  We name the source 1SAXJ1715.0-7134.
  A marginal detection of the burst in the GRBM (40-700 keV) would lead to classify the event as an X-Ray rich GRB, although we could not exclude a type I X-ray burster on the basis of the WFC hardness ratio. A fast TOO observation was technically feasible but we could not perform it because of budget reduction of BeppoSAX operations (see GCN #634).
• GCN notice #637 = BeppoSAX mail n. 00/08
  The refined position of 1SAXJ1715.0-7134, the source associated to the burst detected by BeppoSAX WFC2 on April 16 at 14:32:54 UT, is:

  R.A.= 258.861
  Decl.= -71.607
  (equinox 2000)
  

  with an error radius of 2'.
  Further analysis to establish the nature of the transient are in progress.
• GCN notice #638
  Bradley E. Schaefer (Yale) reports:
  I have taken images of the improved (2' radius) error box for GRB000416 (Gandolfi, BeppoSAX mail 00/08) in the B, R, J, and K bands with the Yale 1-m telescope on Cerro Tololo. Images started at UT 05:18 on 18 April. At this time, the only comparison is with the Digital Sky Survey, even though my images go considerably deeper. My images do not show any optical transient in this comparison. Further observations or radio images might yet reveal a counterpart.
• GCN notice #639
  R. M. Kippen (University of Alabama in Huntsville) and P. M. Woods (Universities Space Research Association) report on behalf of the CGRO-BATSE team:
  The fast x-ray transient (possible gamma-ray burst) 1SAXJ1715.0-7134 observed with BeppoSAX-WFC on April 16.60618 UT (Piro et al., GCN 635) was detected with BATSE, having significant flux in the 20-100 keV energy range. The event did not activate the BATSE on-board trigger system (currently operating in the >100 keV energy range), but was recorded in continuous data mode with 1.024-s temporal resolution. Furthermore, the BATSE location is consistent with that of the WFC. The event consisted of a single weak pulse lasting about 8 seconds. The peak flux was 0.14 (-/+ 0.04) ph/cm2/s (50-300 keV; 1.024 s), with a total fluence of 2.9 (-/+ 0.3) E-7 erg/cm2 (>20 keV). The spectrum is consistent with a single power-law model with photon index -2.7 (-/+ 0.2). About 1% of BATSE gamma-ray bursts have such soft spectra. If this event is a gamma-ray burst, it ranks in the lower ~2% (10%) of the BATSE flux/fluence distribution.
• GCN notice #640
  Paul Price, Tim Axelrod and Brian Schmidt report
  that we have imaged the error-circle of GRB000416 / 1SAXJ1715.0-7134 with the 50-inch telescope at Mount Stromlo Observatory. Exposure details are:

  Date            Exp Time        Limiting Mag.
  April 18.47     3 x 300s        R_M ~ 19.5
  April 18.70     6 x 300s        R_M ~ 20.7
  

  where R_M refers to the MACHO red passband.
  We see no new variable candidates within the error circle, either from comparison of both epochs with the DSS, or from subtraction of the two epochs.