HETE Burst H2275

Burst H2275 summary

  • Trigger time is
    • UTC=20020819_145735
    • GRB=GRB020819+53855
  • Triggering instrument was Fregate
  • Trigger timescale was 0.16 seconds
  • Trigger detected in 30-400 keV band


Evaluation



Bright GRB.



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

The color of trigger H2275, 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 H2275 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.

An automated fit of a cutoff power-law spectrum has been performed for H2275. The fit of the model to the data is shown below; the calculated values of Epeak and the burst fluence (30-400 keV) are: 

	Epeak    = 116.47 keV
	Fluence  = 1.188e-05 erg/cm^2
	Duration = 23.200 seconds

CAUTION:

These results are computed by an automatic script. Please visually inspect the XSPEC summary plot to judge the quality of the results.

Please note that this value of Epeak results from a fit to FREGATE data (8-400 keV) only -- a more reliable joint fit to FREGATE and WXM data is not yet automated. As such, this Epeak estimate is likely to be biased high, especially for soft events, such as XRFs. In our experience, the inclusion of WXM data can lower the value of E_peak substantially. The above Epeak value should thus be viewed as a preliminary estimate.

Click here for an explanation of the method. 

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1508
SUBJECT: GRB020819(=H2275): A Long Burst Localized by the HETE WXM and SXC
DATE:    02/08/19 22:50:50 GMT
FROM:    George Ricker at MIT  

GRB020819(=H2275): A Long Burst Localized by the HETE WXM and SXC

R. Vanderspek, J. Villasenor, J.G. Jernigan, G. Monnelly, J. Doty, G. 
Crew, N. Butler, T. Cline, A. Levine, F. Martel, E. Morgan, G. 
Prigozhin, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, 
on behalf of the HETE Optical-SXC and HETE Operations Teams;

G. Ricker, J-L Atteia, N. Kawai, D. Lamb, and S. Woosley on behalf of 
the HETE Science Team;

Y. Shirasaki, C. Graziani, M. Matsuoka, T. Tamagawa, K. Torii, T. 
Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, T. Tavenner, and T. 
Donaghy, on behalf of the HETE WXM Team;

M. Boer, J-F Olive, J-P Dezalay, and K. Hurley on behalf of the HETE 
FREGATE Team;

write:

At 14:57:35.82 UTC (53855.82 s UT) on 19 Aug 2002, the HETE FREGATE, 
WXM, and SXC instruments detected event H2275, a moderately bright, 
long GRB. In the FREGATE 8-40 keV band, the burst had a duration of 
~20 seconds, and a peak brightness of ~5x Crab. A GCN Burst Alert 
Notice was disseminated 55s after the burst. No real-time optical 
camera aspect was generated at the time of the burst; thus, no WXM 
real-time localization could be disseminated.  Ground analysis of the 
optical camera data, and of the WXM data for the burst, produced a 
refined location which was reported in a GCN Position Notice issued 
98 minutes after the burst. The WXM location can be expressed as a 
90% confidence circle that is 7 arcminutes in radius and is centered 
at

WXM:    RA = 23h 27m 07s, Dec = +6o 21' 50" (J2000).

Ground analysis of the SXC data for the burst also produced a refined 
location, which was reported in a GCN Position Notice issued 176 
minutes after the burst.  The SXC location can be expressed as a 90% 
confidence circle that is 130 arcseconds in radius and is centered at

SXC:    RA = 23h 27m 24s, Dec = +6o 16' 08" (J2000).

We note that the SXC error circle (reported at 17:54:08 UTC) lies 
almost fully within the subsequently-reported IPN annulus (Hurley et 
al, GCN1507, issued at 19:30:40 UTC). Also, the catalogued X-ray 
source 1RXS J232705.9+062419 lies within the WXM error box, but is 
not within the SXC error box.

Further information (including a light curve and the error boxes) for 
GRB020819 is provided at the following URL:

http://space.mit.edu/HETE/Bursts/

This message is citable.

The sky map for GRB020819 (H2275). Shown are the error circles from the WXM, the SXC, and the annulus calculated by the IPN using HETE and Ulysses data. To date (0h UT 2002 August 20), no counterpart to GRB020819 has been found.