gbm team dc2 effort

GBM Team DC2 EffortCharles Meegan Giselher LichtiNarayana BhatMichael BriggsValerie ConnaughtonRoland DiehlGerald FishmanJochen GreinerR. Marc KippenAndreas von KienlinChryssa KouveliotouWilliam PaciesasRobert PreeceHelmut SteinleRobert WilsonColleen Wilson-Hodge

Modeling:Nicola OmedeiFrancesco LongoJay NorrisFelix Ryde

Simulations:Nicola OmodeiDavid Band

Analysis:Nicola OmodeiJohann Cohen-Tanugi

GLAST Burst Monitor

12 NaI Detectors 0.5 x 5in 8 keV – 1 MeV2 BGO Detectors 5 x 5in 150 keV – 30 MeV

GBM Triggering

• 2 NaI detectors > 4.5 sigma above background 50—300 keV, various timescales.

• Expect >200 triggered GRB’s per year.

• In DC2 we have 64 GRB’s in 55 days! We apply a fluence threshold to avoid those that would not have triggered GBM.

GBM Trigger Threshold

LAT GRBs per year

Data Types

• Continuous: CTIME (0.256 sec, 8 channels) and CSPEC ( 8.192 sec, 128 channels). In flight, temporal resolution increased on triggering.

• Triggered: TTE photon lists (2 microsec, 128 channels) for 300 sec after trigger + 500k buffered pre-trigger events.

• Triggered: TRIGDAT. Immediate and calculated information (location, intensity, backgrounds, Maximum detector rates).

• Housekeeping + Diagnostic.

Burst Localization• Use relative rates in detectors of different orientations.• On board: 15 degrees accuracy using table and

comparing rates expected for zenith pointing and “average” spectrum. Enough for LAT repoint.

• On ground: 3 degrees using grid search. Immediate (automated) + Refined.

• Statistical (intensity-dependent) and systematic errors.• In DC2: move true location after generating data… as

if we had a ground location. Incorporate both statistical and systematic error.

GBM On-Board localization

For bright bursts error willBe dominated by systematics:Burst spectrum, S/C elevation.

GRB characteristic distributions

Typical GRB spectrum characterized at BATSE energies by the Band parameterization α, β, A, Epeak or some similar function where the physical meaning of these parameters is not specified.

GRB Durations

In DC2: No measure of duration given, just the trigger time (Warning!).

GBM Intensities

In Flight and In DC2: Calculated Information will be Standard Intensity which is the source-angle adjusted sum of peak 50—300 keV Counts in brightest 2 NaI detectors expressed as Rates.

DC2 GBM Data Generation

• IDL programs read spectral parameters at 16 ms resolution output from GLEAM.

• Calculate response to burst at this location. Proceed only with viewable detectors.

• Generate counts in each detector.• Superimpose on typical background file.• Many approximations !!!• Calculate peak intensity, statistical burst location error, and

move true location accordingly.• Write data files -- as close as possible to Level 1 Data

Products defined in ICD (but no TRIGDAT).

DC2 Data Products1 each per viewable detector per burst:• CSPEC: GLG_CSPEC_N6_BN050718002_V01.FIT • CTIME: GLG_CTIME_N6_BN050718002_V01.FIT• TTE: GLG_TTE_N6_BN050718002_V01.FIT• Background: GLG_BCK_N6_BN050718002_V01.BAK• Response: GLG_CSPEC_N6_BN050718002_V01.RSP1 each per viewable detector per day:• Daily CTIME: GLG_CTIME_N6_050718_V01.FIT• Daily CSPEC : GLG_CSPEC_N6_050718_V01.FIT1 per burst:• Notice to replace TRIGDAT in DC2: GLG_NOTICE_050718002.TXT.

Notice is an ascii file giving TJD, trigger time, burst location, 1 sigma statistical error in burst location, standard intensity (flux), 2 closest NaI detectors, closest BGO detector.