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Evidence for TeV Emission from GRB 970417a.
The Astrophysical Journal
|April 19, 2000
Summary
Milagrito detected a potential very high energy gamma-ray signal from a gamma-ray burst (GRB) event, GRB 970417a. While other GRBs showed no significant signals, this finding warrants further investigation into TeV gamma-ray bursts.
Area of Science:
- High-energy astrophysics
- Gamma-ray astronomy
- Cosmic ray physics
Background:
- The Milagrito detector observed the northern sky for very high energy gamma rays.
- Gamma-ray bursts (GRBs) are intense, brief flashes of gamma radiation from space.
- Searching for TeV gamma-ray counterparts to GRBs is crucial for understanding their emission mechanisms.
Purpose of the Study:
- To search for TeV gamma-ray counterparts to GRBs detected by the Burst and Transient Source Experiment (BATSE).
- To analyze data from the Milagrito detector for coincident events with observed GRBs.
Main Methods:
- Milagrito monitored the northern sky from February 1997 to May 1998.
- Data analysis focused on identifying excesses of gamma-ray events coincident in time and location with BATSE-detected GRBs.
- Statistical methods were used to assess the significance of any observed excesses.
Main Results:
- BATSE detected 54 GRBs within Milagrito's field of view during the observation period.
- A statistically significant excess of events (chance probability 2.8x10^-5) was observed coincident with GRB 970417a.
- No significant TeV gamma-ray signals were detected from the other 53 GRBs.
Conclusions:
- The observed excess from GRB 970417a suggests a potential TeV counterpart, requiring further study.
- The lack of significant signals from other GRBs provides constraints on TeV emission from these events.
- This study highlights the capability of ground-based detectors in searching for transient high-energy phenomena.
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