The need for rapid and accurate gamma-ray burst locations has long been recognized as the fundamental key to solving the gamma-ray burst (GRB) counterpart problem. However, its realization has been technically difficult to achieve. For the past four years the BACODINE system has been attempting to solve this problem by providing roughly-determined (accurate to ~4 deg, at best) BATSE burst locations in near real-time (typically a few seconds) to a network of dedicated optical/radio counterpart searchers. The BACODINE system sacrifices location accuracy in favor of speed in its use of small amounts of data, automated background estimation and simplified location algorithm. Unfortunately, BACODINE locations are too imprecise to allow for the sensitive observations now known to be required to detect faint GRB afterglows.

To facilitate more sensitive counterpart searches on somewhat longer timescales we have developed the BATSE Rapid Burst Response (RBR) system, that takes the opposite approach from BACODINE: better location accuracy at the cost of longer delay. This is accomplished using more data, human background estimation and a more detailed location algorithm (LOCBURST). The improved BATSE RBR locations have a typical accuracy of ~2 deg (68% containment radius), with a post-burst delay of ~10-30 minutes. The RBR system operates in parallel with normal BACODINE processing and the locations from both systems are distributed via the same, well-established, GCN/BACODINE network.

SYSTEM OPERATION

The following diagram illustrates the operation of the BATSE RBR system from the detection of a burst by BATSE on-board software to the computation and dissemation of the burst location through the Gamma-Ray Coordinates Network (GCN). While data downloading and location dissemenation are automated, human operators are a valuable part of the procedure for estimation of source/ background time-intervals and efficient rejection of non-GRB triggers.

LOCATION ERRORS

While the BATSE RBR system uses the same LOCBURST algorithm employed for all "best-and-final" BATSE burst locations, it cannot make use of the full BATSE dataset (most burst data are stored in memory and are thus not available in the real-time telemetry at the time of a burst). We have therefore independently assessed the location errors from the BATSE RBR system. As a comparison sample, we use 70 of the most recent bursts located to single annuli by BATSE/Ulysses IPN timing analysis. The shortest angular separation rho between BATSE locations and IPN annuli yields a statistical estimate of the total BATSE location error (a combination of measured statistical error and an unknown systematic contribution).

The following figure shows the cumulative distribution of BATSE-RBR/IPN separations. The procedure has been repeated for the BACODINE locations and the official BATSE locations from the 4B catalog. It is evident that the BATSE RBR locations are consistent with the 4B locations, whereas they are significantly more accurate (factor of ~3, on average) than BACODINE.

Through Monte Carlo simulations, we have found that a constant systematic error of ~2 deg is required in addition to the measured statistical errors to explain the BATSE RBR/IPN distribution. The following table shows the fraction of BATSE RBR bursts expected as a function of total location error (assuming 2 deg systematic error).

A more detailed analysis of the BATSE-RBR location errors is explained in a paper presented at the 4th Huntsville GRB symposium. Follow THIS LINK to read a web-version of the paper, or go back to the RBR home page and select "publications" to download a printable version.

This link to GCN lists all recent BATSE triggers (updated in real-time). Triggers indicated by type=LOCBURST have been localized by the BATSE RBR system. Burst location coordinates and (in many cases) BATSE lightcurves can be downloaded from this site.

Notable bursts detected with the BATSE RBR system.

Burst lightcurves and location "finding" maps for notable bursts are provided below in viewable GIF and printable PS formats.

Some of these events were scanned by the Proportional Counter Array (PCA; 2-10 keV) instrument on the Rossi X-ray Timing Explorer (RXTE) in an attempt to detect fading x-ray afterglow emission. Links to current GCN notices for these bursts are provided.

The remaining events are notable for other reasons, as indicated.

Burst	Trigger	Sky-Map		Lightcurve		Comments
GRB_000307	8022	GIF	PS	GIF	PS	Detected by Konus, Ulysses, and NEAR
GRB_000210	n/a	GIF	PS	GIF	PS	Untriggered burst detected by SAX-WFC, Konus, Ulysses, and Chandra.
GRB_000115	7954	GIF	PS	GIF	PS	Fading x-ray source detectected by RXTE-PCA!! (See GCN Notice). Detected by Konus and NEAR.
GRB_991216	7906	GIF	PS	GIF	PS	Very large BATSE burst. Fading x-ray source detectected by RXTE-PCA!! (See GCN Notice). Optical transient discovered!! Detected by Ulysses and NEAR.
GRB_991127	7884	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_991115	7858	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_991014	7803	GIF	PS	GIF	PS	Detected by SAX & Ulysses.
GRB_990915	7766	GIF	PS	GIF	PS	Detected by COMPTEL & Ulysses.
GRB_990806	7701	GIF	PS	GIF	PS	Detected by SAX-WFC, NFI; scanned by XTE-PCA.
GRB_990728	7678	GIF	PS	GIF	PS	Detected by COMPTEL.
GRB_990625	7619	GIF	PS	GIF	PS	Detected by SAX-WFC.
GRB_990615	7607	GIF	PS	GIF	PS	Location scanned by RXTE-PCA; Detected by Ulysses.
GRB_990518	7575	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_990510	7560	GIF	PS	GIF	PS	Detected by SAX-WFC.
GRB_990506	7549	GIF	PS	GIF	PS	Fading x-ray source detectected by RXTE-PCA!! (See GCN Notice).Detected by Ulysses.
GRB_990505	7548	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_990425	7530	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_990424b	7529	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_990424a	7527	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_990403	7503	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_990323	7491	GIF	PS	GIF	PS	Detected by Ulysses, NEAR.
GRB_990316	7475	GIF	PS	GIF	PS	Imaged in optical, detected by Ulysses.
GRB_990311	7464	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_990308	7457	GIF	PS	GIF	PS	Detected by RXTE-ASM, Ulysses.
GRB_990304	7446	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_990123	7343	GIF	PS	GIF	PS	Detected by SAX, COMPTEL.
GRB_990111	7319	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_981223	7277	GIF	PS	GIF	PS	Location scanned by RXTE-PCA (See GCN Notice).Detected by Ulysses.
GRB_981205	7250	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_981130	7240	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_980923	7113	GIF	PS	GIF	PS	Very bright; location scanned by RXTE-PCA (See GCN Notice).
GRB_980810	6985	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_980706	6904	GIF	PS	GIF	PS	Location scanned by RXTE-PCA; detected by COMPTEL and Ulysses. (See GCN Notice)
GRB_980703	6891	GIF	PS	GIF	PS	Detected by RXTE-ASM, BeppoSAX-NFI, and Ulysses. Optical transient detected.
GRB_980611	6816	GIF	PS	GIF	PS	Location scanned by RXTE-PCA (See GCN Notice); detected by Ulysses
GRB_980519	6764	GIF	PS	GIF	PS	Localized by SAX-WFC, SAX-NFI; optical transient detected; detected by Ulysses
GRB_980425	6707	GIF	PS	GIF	PS	Localized by SAX-WFC, SAX-NFI; possible optical transient
GRB_980401	6672	GIF	PS	GIF	PS	Detected by Ulysses
GRB_980329	6665	GIF	PS	GIF	PS	Localized by COMPTEL, SAX-WFC, SAX-NFI, Ulysses (see IAUC).
GRB_980326	6660	GIF	PS	GIF	PS	Localized by SAX-WFC; detected by Ulysses; optical transient detected (see IAUC).
GRB_980306	6630	GIF	PS	GIF	PS	Detected by Ulysses
GRB_980208	6593	GIF	PS	GIF	PS	Location scanned by RXTE-PCA (See GCN Notice); detected by Ulysses
GRB_980203	6587	GIF	PS	GIF	PS	Location scanned by RXTE-PCA (See GCN Notice); detected by Ulysses
GRB_980125	6581	GIF	PS	GIF	PS	Location scanned by RXTE-PCA (See GCN Notice); detected by Ulysses
GRB_980124	6576	GIF	PS	GIF	PS	Detected by CGRO-COMPTEL and Ulysses
GRB_980109	6564	GIF	PS	GIF	PS	Detected by SAX-WFC
GRB_971227	6546	GIF	PS	GIF	PS	Detected by SAX-WFC, SAX-NFI (see IAUC).
GRB_971214	6533	GIF	PS	GIF	PS	Detected by RXTE-ASM, SAX-WFC, SAX-NFI, and Ulysses (see IAUC).
GRB_971212	6531	GIF	PS	GIF	PS	The 2000th GRB detected by BATSE!
GRB_971210	6528	GIF	PS	GIF	PS	Detected by Ulysses.
GRB_971209	6527	GIF	PS	GIF	PS	Location scanned by RXTE-PCA (See GCN Notice); detected by Ulysses
GRB_971208	6526	GIF	PS	GIF	PS	The longest, smoothest single GRB episode ever observed by BATSE (see IAUC); also detected by Ulysses.
GRB_971113	6476	GIF	PS	GIF	PS	Location scanned by RXTE-PCA (See GCN Notice)
GRB_970925	6397	GIF	PS	GIF	PS	Location scanned by RXTE-PCA (See GCN Notice); detected by Ulysses
GRB_970807	6329	GIF	PS	n/a	n/a	Location scanned by RXTE-PCA (See GCN Notice); detected by Ulysses
GRB_970704	6293	GIF	PS	n/a	n/a	Location scanned by RXTE-PCA (See GCN Notice); detected by Ulysses
GRB_970616	6274	GIF	PS	n/a	n/a	Location scanned by RXTE-PCA (See GCN Notice); detected by Ulysses
GRB_970603	6251	GIF	PS	n/a	n/a	Location scanned by RXTE-PCA (See GCN Notice); detected by Ulysses

Gamma-Ray Burst Astronomy and Instrumentation

Compton Gamma Ray Observatory
BATSE (Burst and Transient Source Experiment)
BATSE Home Page at MSFC
GCN/BACODINE
COMPTEL (Compton Telescope)
COMPTEL Gamma-Ray Burst Page
EGRET (Energetic Gamma-Ray Experiment Telescope)
OSSE (Oriented Scintillation Spectrometer Experiment)

HETE - High-Energy Transient Experiment

HETE at MIT
HETE at LANL
BeppoSAX Science Data Center
Rossi XTE Guest Observer Facility
TGRS
ASCA
CATSAT
MILAGRO
INTEGRAL
SiliconGLAST
Detector development at NRL

Related Places

NASA
Marshall Space Flight Center
Space Sciences Laboratory
Gamma-Ray Astronomy
Goddard Space Flight Center
Laboratory for High-Energy Astrophysics
The University of Alabama in Huntsville
Center for Space Plasma, Aeronomic and Astrophysics Research
Physics Department

Information Resources

High-Energy Astrophysics Science Archive Research Center
Astrophysics Data System Abstracts Service
LANL Astrophysics Preprint Server
Astrophysical Journal Electronic Edition
Nature
Astronomy Picture of the Day

Scientific Organizations

AAS - American Astronomical Society
High-Energy Astrophysics Division
SPIE - The International Society for Optical Engineering
APS - The American Physical Society
SigmaXi - The Scientific Research Society

Journal Publications (including IAU Circulars)

The following is a list of journal publications related to the BATSE Rapid Burst Response Effort. Postscript versions of some papers may be downloaded by selecting the word "postscript". Select the paper title to read the full abstract and author list.

1. RXTE Observations of GRB Afterglows, Marshall, F. E., et al., 1998. Nucl. Phys. B 69, 640-645
2. GRB 980326 & GRB 980329, Briggs et al., 1997. IAU Circ. 6856
3. GRB 971227, Woods et al., 1997. IAU Circ. 6798
4. GRB 971214, Kippen et al., 1997. IAU Circ. 6789
5. GRB 971208, Connaughton et al., 1997. IAU Circ. 6785
6. GRB 970616, Connaughton et al., 1997. IAU Circ. 6683
7. GRB 970616, Marshall et al., 1997. IAU Circ. 6683

Conference Presentations (including proceedings articles)

The following is a list of conference presentations related to the BATSE Rapid Burst Response effort. Postscript versions of some articles may be downloaded by selecting the word "postscript". Select the article title to read the full abstract and author list.

1. Conference on Cosmic Explosions (College Park, MD, October, 1999)
   1. Detection of Decaying X-Ray Afterglow of GRB 990506 with RXTE/PCA, Takeshima, T., et al., 1999.
   
   
2. 4th Huntsville Gamma Ray Burst Symposium (Huntsville, AL, September, 1997)
   1. The BATSE Rapid Burst Response System, Kippen et al., 1997. [HTML version] or [PS version]
   2. RXTE Quick Response Observations of Afterglows from GRBs, Takeshima et al., 1997.

3. 190th Meeting of the AAS (Winston-Salem, NC, June, 1997)
   1. Rapid Follow-Up Gamma-Ray Burst Locations from BATSE, Kippen et al. 1995. Bull. Am. Astr. Soc. 29(2), 849.