finding untriggered gamma-ray transients in the fermi gbm data · • 1-day poisson probability...
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sGRB ver 103a of 2017 June 5 run on 2017-09-20 22:07:53T0 = 527647422.176000 = 2017-09-21 00:43:37.176000
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sGRB ver 103a of 2017 June 5 run on 2017-09-20 22:07:53T0 = 527647422.176000 = 2017-09-21 00:43:37.176000
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Finding untriggered gamma-ray transients in the Fermi GBM dataC. M. Hui, M. S. Briggs, P. Veres, R. Hamburg
•GCN notice type Fermi-GBM SubThreshold now available.https://gcn.gsfc.nasa.gov/fermi_gbm_subthreshold.html
•Time delay for notice range from 0.5 to 6 hours, due to telemetry schedule.•List of candidates from older data (2013 and on) are available.http://gammaray.nsstc.nasa.gov/gbm/science/sgrb_search.html
•Available with the GCN notice:‣Localization FITS file‣Contour sky map ‣Lightcurve
GRB 170921C [Zhang et al. GCN 21919] • Insight-HXMT 12σ detection coincident with
Fermi-GBM subthreshold transient 527647422.• T90 is 1.2s, energy range ~200-800 keV.Fermi-GBM transient 527647422 info:• High reliability candidate• 3 detectors >4σ• 2.8s long
Fermi-GBM 527647422 localization map Fermi-GBM 527647422 Insight-HXMT lightcurve
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sGRB ver 60b of 2016-02-10 run on 2016-02-14 13:32:28E range: 93 to 494 keV T0 = 2014-06-06 10:58:13.625000
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sGRB ver 60b of 2016-02-10 run on 2016-02-14 13:32:28E range: 93 to 494 keV T0 = 2014-06-06 10:58:13.625000
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sGRB ver 60b of 2016-02-10 run on 2016-02-14 13:32:28E range: 93 to 494 keV T0 = 2014-06-06 10:58:13.625000
Algr: 3: P01 of F0061: glg_tte_b0_140606386_v00
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• 318 short, hard candidates found in 46 months in previous study.➡~80 per year, twice the rate of GBM triggered
short GRBs.
• Looks for signals in 2 NaI detectors with 2.5σ and 1.25σ excess above background in the continuous time-tagged events (2μs resolution, 128 energy channels).
• The 2 signal detectors must have valid geometry for a point source.• 18 timescales: 64ms to 31s.
• Only candidates <2.8s are reported at the moment.• 4 energy ranges optimized for short GRBs.
• 27—539 keV; 50—539 keV; 102—539 keV; 102—985 keV• 1-day Poisson probability calculated for each event,
threshold for short candidate notice is 1e-5.• Expected rate of notice ~70/month,
higher during active periods of galactic transients.
Short, Not Soft, Not Trigger 318 Events
Galactic Coordinates
Galactic coordinates
INTEGRAL Anti-Coincidence Shield (ACS) lightcurve
Swift GRB 140606A• Fermi-GBM did not trigger due to low peak flux • Found in 0.25s time binning• 93 - 494 keV energy range
• Archival candidates starting 2013 are available:http://gammaray.nsstc.nasa.gov/gbm/science/sgrb_search.html
Fermi-GBM 423745096.56