HETE Burst U11475

Burst U11475 summary

  • Trigger time is
    • UTC=20040228_001325
    • GRB=GRB040228+805
  • Triggering instrument was Fregate
  • Trigger timescale was 0.16 seconds
  • Trigger detected in 30-400 keV band

Evaluation GRB040228B

HETE detected three bursts on February 28. The first two were
triggers H3066 and H3067: both were quite hard, and there was
no signal from either in the WXM. The third burst was seen in
the WXM shortly after H3067 and was localizable.

IPN observations confirm that H3066 and H3067 came from well
outside the WXM FOV; it is likely that these two are the same
burst, so we have designated both to be GRB040228A. The soft
pulse has been given the HETE untriggered burst number 11475
and is designated GRB040228B.

Download ASCII table of Fregate Band A, B, C lightcurves here.

The color of trigger U11475, defined by the ratio of total counts in Fregate band C (30-400 keV) to band A (7-40 keV) vs. band B (7-80 keV) to band A, overlaid on a the color-color plot of all localized bursts detected to date. Note the separation of XRFs, XRRs, and GRBs.

The signal to noise in Fregate band C (30-400 keV) of trigger U11475 in relation to the S/N of band C of other localized HETE triggers. We find empirically that most XRFs are faint and soft: the fact that localized bursts require a minimum S/N in the 2-25 keV band means that the band C S/N should be low. We find a cutoff in the band C S/N of 6.5 delineates the XRF/non-XRF population with high reliability.

Link to Jochen Greiner's web page on

Skymap for HETE trigger U11475