GLAST BURST MONITOR
1
GLAST BURST MONITOR Narayana P. Bhat 1 , Valerie Connaughton 1 , Andreas von Kienlin 3 , Michael S. Briggs 1 , Charles A. Meegan 2 , Roland Diehl 3 , Gerald J. Fishman 2 , Jochen Greiner 3 , Marc Kippen 4 , Chryssa Kouveliotou 2,5 , Giselher G. Lichti 3 ,William S. Paciesas 1 , Robert D. Preece 1 , Volker Schönfelder 3 and Robert B. Wilson 2 . 1. The University of Alabama in Huntsville 2. NASA/Marshall Space Flight Center 3. Max-Planck-Institut für extraterrestrische Physik 4. Los Alamos National Laboratory 5. Universities Space Research Association The Gamma Ray Large Area Space Telescope (GLAST) mission is a follow-up on the successful EGRET experiment onboard the CGRO. It will provide a high-sensitivity survey of the sky in high-energy -rays, and will perform detailed observations of selected persistent and transient sources. There are two experiments onboard GLAST - a Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM). The primary mission of the GBM instrument is to support the LAT in observing -ray bursts (GRB's) by providing low-energy measurements with high time resolution and rapid burst locations over a large (> 8 sr) field of view. The GBM will complement the LAT measurements by observing GRBs in the energy range 10 keV to 30 MeV, the region of the prominent spectral turnover of GRB's. An important objective of GBM is to compute the locations of GRB sources on-board the spacecraft and quickly communicate them to the LAT and to the ground to allow rapid follow-up observations at space- and ground- based observatories. This information may be used to re-point the spacecraft towards particularly interesting burst sources that occurred outside the LAT field of view.The GBM consists of 14 uncollimated scintillation detectors coupled to phototubes to measure -ray energies and arrival times. Two different detector types are used to obtain spectral information over a wide energy range: 12 NaI detectors (10 keV to 1 MeV), and 2 BGO detectors (150 keV to 30 MeV). The detectors are distributed around the GLAST spacecraft to provide a large unobstructed field of view. The 12 NaI detectors are mounted with different orientations to provide directional information for use in locating GRB sources. ABSTRACT Introduction Introduction G am m a Ray Bursts(G RB’s), regarded asastrophysicalm ysteries, are energetically com parable to supernovae (assum ing significant beam ing). G RB energy spectra have been m easured from ~ 2 keV to 18 GeV with no evidence forspectralcut-offathigh energies. The G RB energy spectra w hen plotted in F units, m ake itclear thatthe peak ofenergy outputduring the burstisindeed at ray energies. G RB940217 show ed em ission of GeV photonsin prom ptasw ell asextended em ission phases. The distincthigherenergy com ponentin G RB941017, for e.g., require extended energy range studies. The high energy com ponentofG RB’scould be related to relativistic electronseitherthrough synchrotron em ission ortheirinteraction w ith the surrounding cloud. There are a significantnum berof“X -ray rich” G RB’s(w ith -rays above 20 keV) asw ellas“X -ray flashes”. H ence itisim portantto study the G RB spectra overan extended energy range in orderto understand the em ission m echanism s. • The goalofthe G LA ST BurstM onitor(GBM )isto enhance the science return ofthe G LA ST m ission in the study ofgam m a-ray burstsby providing low -energy contextm easurem entsw ith high tim e resolution (2 s ); • GBM w illprovide spectra forburstsfrom 10 keV to 30 MeV , connecting LA T high-energy m easurem entswith m ore fam iliarenergy dom ain; • LA T w illprovide ground-breaking new G RB observations, butw ithoutG BM itw ould be difficultto evaluate them in the contextofpriorobservations& currentknow ledge; The Role ofG LA ST BurstM onitor The Role ofG LA ST BurstM onitor LAT FoV GBM FoV • G BM w illprovide a w ide sky coverage (8 sr )-- enabling autonom ous re-pointrequests forinteresting brightbursts thatoccuroutside LA T field-of-view (FoV ) forhigh-energy afterglow studies (an im portantquestion from EGRET) • GBM w illalso provide im proved burstlocationsto the ground forfollow -up studiesatotherwavelengths. Im proved G BM +LA T w ide-band spectralsensitivity Com parelow -energy vs. high-energy tem poralvariability Continuity w ith currentG R B know ledge-base (G RO -BA TSE) • GBM w illprovide rapid G RB tim ing & location triggersw ith a field ofview > LA T field ofview Im prove LA T sensitivity and response tim e forw eak bursts Re-pointG LA ST/LA T atparticularly interesting burstsfor afterglow observations Provide rapid locationsforground/space follow -up observations& IPN tim ing Trigger S/C GBM LAT Classification,Location, H ardness, InitialFlux Flux, Fluence, H ardness (Running U pdates) Parameters Science Re-pointCandidate S/C Re-point Decision M ode Change ? Im m ediateTriggerSignal < 2 s Begin R/T dow nlink Continue R/T, 5 -10 m in. GBM LAT GBM /LAT S/C Inform ation packet Re-pointrequest < 5 ms 2 to ~ 60 s G BM Burst A le rts G BM Burst A le rts Instrum entFunctionalDiagram Simulated GBM and LAT response to time- integrated flux from bright GRB 940217 Spectral model parameters from C GRO wide-band fit 1 NaI (14 º) and 1 BGO (30 º) + LA T in understanding the ProspectsofG BM + LA T in understanding the ProspectsofG BM + LA T in understanding the H igh Energy H igh Energy - - ray Em ission from ray Em ission from G RB’s G RB’s H igh energy em ission from H igh energy em ission from G RB’s G RB’s isgenerally consistentw ith isgenerally consistentw ith Relativistic Shock M odel. H ow everthereare notableexceptions Relativistic Shock M odel. H ow everthereare notableexceptions e.g. e.g. G RB 941017 w hich show ed G RB 941017 w hich show ed multi multi - - MeV MeV com ponentwith com ponentwith flatterspectralslope flatterspectralslope ( ( - - 1, > 200 1, > 200 MeV MeV ), ), a slow erdecay tim e and a a slow erdecay tim e and a higher higher fluence fluence com pared those ofthe low erenergy com ponent. com pared those ofthe low erenergy com ponent. GBM Detectors GBM Detectors Characteristics – 5-inch diam eter, 0.5 inch thick [N aI( Tl Tl)] – O ne 5-inch diam eter PM T per D etector. – Placem entto m axim ize FoV – Thin beryllium entrance w indow – Energy range:~10 keV to 1 MeV M ajor Purposes – Provide low -energy spectral coverage in the typicalG RB energy regim e over a w ide FoV – Provide burstlocationsover a w ide FoV Characteristics – 5-inch diam eter, 5-inch thick – H igh-Z (B G O ), high-density – T w o 5-inch diam eter PM Tsper D etector. – Energy range:~150 keV to 30 MeV M ajor Purpose – Provide high-energy spectral coverage to overlap LA T range over a w ide FoV 12 Sodium Iodide (N aI) Scintillation D etectors 2 Bism uth G erm anate(BG O ) Scintillation D etectors Location and orientation ofG BM Location and orientation ofG BM detectorsin the spacecraft detectorsin the spacecraft P aram eter R eq u irem en t G oal C u rren t C ap ab ility E nergy range 10 keV – 25 MeV 5 keV – 30 MeV ~10 keV – 30 MeV E nergy resolution < 23.5% FWHM (10 keV – 25 MeV) < 7% ~12% FWHM @ 511 keV Tim e resolution 10 s 2 s 2 s O n-board G RB locations W ith in 2 s 15º w ithin 1 s <15º;1.8 s R apid ground G RB locations 5º accuracy (1 radius) w ithin 5 s 3º w ithin 1 s TBD by analysis (scattering influenced) FinalG RB locations 3º accuracy (1 radius) w ithin 1 day (no stated goal) TB D by analysis (scattering influenced) G R B sensitivity (on ground) 0.5 photons cm -2 s -1 (peak flux,50–300 keV ) 0.3 photons cm -2 s -1 (peak flux,50–300 keV ) 0.35 photons cm -2 s -1 (peak flux,50–300 keV ) G R B on-board trigger sensitivity 1.0 photons cm -2 s -1 (peak flux,50–300 keV ) 0.75 photons cm -2 s -1 (peak flux,50–300 keV ) 0.76 photons cm -2 s -1 (peak flux,50–300 keV F ield ofview 8 sr 10 sr 8.8 sr Dead-time < 10 s/count <3 s/count ~2.5 s/count G B M D esign C apabilities G B M D esign C apabilities G B M D esign C apabilities BurstSpectra GBM can provide tim e resolved energy spectra of GBM can provide tim e resolved energy spectra of G R B’s G R B’s in in the range 10 the range 10 keV keV – – 30 30 MeV MeV . . o o to explore the possible relation betw een to explore the possible relation betw een keV keV - - MeV MeV - - GeV GeV em issions em issions o o to explore ifthose to explore ifthose G RB’s G RB’s detected by the LA T form a detected by the LA T form a separate class separate class + + detection ofhigh energy em ission alone isnotadequate detection ofhigh energy em ission alone isnotadequate forsuch classification forsuch classification o o additionalbenefitofa continuation ofthe BA TSE archive additionalbenefitofa continuation ofthe BA TSE archive GBM can m easure thetem poralbehavior& distribution ofspect GBM can m easure thetem poralbehavior& distribution ofspect ral ral param eters: param eters: E E p , , etc etc . . Possible relation betw een Possible relation betw een E E p p and high energy em ission. and high energy em ission. GBM + LA T can m easure the G RB spectra spanning 8 decadesin GBM + LA T can m easure the G RB spectra spanning 8 decadesin in in - - ray energy (10 ray energy (10 keV keV – – 300 300 GeV GeV ) ) o o O ne can detectpossible high energy cut O ne can detectpossible high energy cut - - offin G R B spectra offin G R B spectra GBM can also m easure energy resolved lightcurvesso thaton GBM can also m easure energy resolved lightcurvesso thaton e can e can look forpossible tim e delaysbetw een them . look forpossible tim e delaysbetw een them . o o 128 channelspectra every 8 128 channelspectra every 8 s s o o 4 channelspectra every 0.256 4 channelspectra every 0.256 s s and and o o ~ 15 ~ 15 s s ofPre ofPre - - burstdata ofTim e Tagged Events(TTE)w ith 2 burstdata ofTim e Tagged Events(TTE)w ith 2 s s tim e resolution. tim e resolution. o o D uring the burstTTE data isavailable for> 300 D uring the burstTTE data isavailable for> 300 s s ata peak rate ata peak rate of350 kH z. of350 kH z. BurstLight-curves O ne w ould expect~150 G R B triggers/yearofw hich ~ 50 O ne w ould expect~150 G R B triggers/yearofw hich ~ 50 - - 100 100 triggersare expected to be detected by LA T triggersare expected to be detected by LA T Priorlocation provided by G BM w ould enable LA T to detect Priorlocation provided by G BM w ould enable LA T to detect w eaker w eaker G RB’s G RB’s by lim iting the search area w hich, in turn, reduces by lim iting the search area w hich, in turn, reduces the background. the background. BurstTriggers U niversity ofA labam a U niversity ofA labam a in H untsville in H untsville NASA NASA M arshallSpace FlightC enter M arshallSpace FlightC enter M ax M ax- Planck Planck- Institut Institut für für extraterrestrische extraterrestrische Physik Physik N ationalS pace Science & Technology C enter M ichaelBriggs W illiam Paciesas RobertPreece Narayana Bhat V alerie C onnaughton C harles M eegan (PI) G erald Fishm an C hryssa Kouveliotou RobertW ilson C olleen W ilson-H odge G iselherLichti(C o-PI) A ndreas von Kienlin V olkerSchönfelder Roland D iehl Jochen G reiner On-board processing, flight software, systems engineering, analysis software, and management Detectors, power supplies, calibration and analysis software Los A lam os Los A lam os N ationalLaboratory N ationalLaboratory Detector Response M arc Kippen
-
Upload
drake-vincent -
Category
Documents
-
view
30 -
download
3
description
G. LAST. urst. B. onitor. M. GLAST BURST MONITOR. - PowerPoint PPT Presentation
Transcript of GLAST BURST MONITOR
GLAST BURST MONITORGLAST BURST MONITOR
Narayana P. Bhat1, Valerie Connaughton1, Andreas von Kienlin3, Michael S. Briggs1, Charles A. Meegan2, Roland Diehl3, Gerald J. Fishman2, Jochen Greiner3, Marc Kippen4, Chryssa Kouveliotou2,5, Giselher G. Lichti3,William S. Paciesas1, Robert D. Preece1, Volker Schönfelder3 and Robert B. Wilson2.
1. The University of Alabama in Huntsville 2. NASA/Marshall Space Flight Center3. Max-Planck-Institut für extraterrestrische Physik 4. Los Alamos National Laboratory5. Universities Space Research Association
The Gamma Ray Large Area Space Telescope (GLAST) mission is a follow-up on the successful EGRET experiment onboard the CGRO. It will provide a high-sensitivity survey of the sky in high-energy -rays, and will perform detailed observations of selected persistent and transient sources. There are two experiments onboard GLAST - a Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM). The primary mission of the GBM instrument is to support the LAT in observing -ray bursts (GRB's) by providing low-energy measurements with high time resolution and rapid burst locations over a large (> 8 sr) field of view. The GBM will complement the LAT measurements by observing GRBs in the energy range 10 keV to 30 MeV, the region of the prominent spectral turnover of GRB's. An important objective of GBM is to compute the locations of GRB sources on-board the spacecraft and quickly communicate them to the LAT and to the ground to allow rapid follow-up observations at space- and ground-based observatories. This information may be used to re-point the spacecraft towards particularly interesting burst sources that occurred outside the LAT field of view.The GBM consists of 14 uncollimated scintillation detectors coupled to phototubes to measure -ray energies and arrival times. Two different detector types are used to obtain spectral information over a wide energy range: 12 NaI detectors (10 keV to 1 MeV), and 2 BGO detectors (150 keV to 30 MeV). The detectors are distributed around the GLAST spacecraft to provide a large unobstructed field of view. The 12 NaI detectors are mounted with different orientations to provide directional information for use in locating GRB sources.
ABSTRACT
IntroductionIntroduction Gamma Ray Bursts (GRB’s), regarded as astrophysical mysteries,
are energetically comparable to supernovae (assuming significantbeaming).
GRB energy spectra have been measured from ~ 2 keV to 18 GeVwith no evidence for spectral cut-off at high energies.
The GRB energy spectra when plotted in Funits, make it clear that the peak of energy output during the burst is indeed at ray energies.
GRB940217 showed emission of GeV photons in prompt as wellas extended emission phases. The distinct higher energy component in GRB941017, for e.g., require extended energy range studies.
The high energy component of GRB’s could be related to relativistic electrons either through synchrotron emission or their interactionwith the surrounding cloud.
There are a significant number of “X-ray rich” GRB’s (with -raysabove 20 keV) as well as “X-ray flashes”.
Hence it is important to study the GRB spectra over an extended energy range in order to understand the emission mechanisms.
• The goal of the GLAST Burst Monitor (GBM) is toenhance the science return of the GLAST mission in the study of gamma-ray bursts by providing low-energy context measurements with high time resolution (2s);
• GBM will provide spectra for bursts from 10 keV to 30 MeV, connecting LAT high-energy measurements with more familiar energy domain;
• LAT will provide ground-breaking new GRB
observations, but without GBM it would be difficult to
evaluate them in the context of prior observations &
current knowledge;
The Role of GLAST Burst MonitorThe Role of GLAST Burst Monitor
LAT Fo V
GBM Fo V
• GBM will provide a wide sky coverage (8 sr) --enabling autonomous re-point requests for interesting bright bursts that occur outside LAT field-of-view (FoV) for high-energy afterglow studies (an important question from EGRET)
• GBM will also provide improved burst locations to the ground for follow-up studies at other wavelengths.
Improved GBM+LAT wide-band spectral sensitivity
Compare low-energy vs. high-energy temporal variability
Continuity with current GRB knowledge-base (GRO-BATSE)
• GBM will provide rapid GRB timing & location triggers with a field of view > LAT field of view
Improve LAT sensitivity and response time for weak bursts
Re-point GLAST/LAT at particularly interesting bursts for afterglow observations
Provide rapid locations for ground/space follow-up observations & IPN timing
Trigger
S/CGBM LAT
Classification, Location, Hardness, Initial Flux
Flux, Fluence, Hardness(Running Updates)
Parameters
Science Re-point Candidate
S/C Re-point Decision
Mode Change?
Immediate Trigger Signal
< 2 s Begin R/T downlink
Continue R/T,5 - 10 min.
GBM LATGBM/LATS/C
Information packet
Re-point request
< 5ms
2 to ~ 60 s
GBM Burst AlertsGBM Burst Alerts
Instrument Functional Diagram
Simulated GBM and LAT response to time-integrated flux from bright GRB 940217
Spectral model parameters from CGRO wide-band fit
1 NaI (14 º) and 1 BGO (30 º)
Prospects of GBM + LAT in understanding the High Energy -ray Emission from GRB’s
Prospects of GBM + LAT in understanding the Prospects of GBM + LAT in understanding the High Energy High Energy --ray Emission from ray Emission from GRB’sGRB’s
High energy emission from High energy emission from GRB’s GRB’s is generally consistent with is generally consistent with Relativistic Shock Model. However there are notable exceptions Relativistic Shock Model. However there are notable exceptions e.g.e.g. GRB 941017 which showed GRB 941017 which showed multimulti--MeVMeV component with component with flatter spectral slope flatter spectral slope ((--1, >200 1, >200 MeVMeV),), a slower decay time and a a slower decay time and a higher higher fluence fluence compared those of the lower energy component.compared those of the lower energy component.
GBM DetectorsGBM Detectors
Characteristics– 5-inch diameter, 0.5 inch thick
[NaI (TlTl)]– One 5-inch diameter PMT per
Detector.– Placement to maximize FoV– Thin beryllium entrance window– Energy range: ~10 keV to 1 MeV
Major Purposes– Provide low-energy spectral
coverage in the typical GRB energy regime over a wide FoV
– Provide burst locations over a wide FoV
Characteristics
– 5-inch diameter, 5-inch thick
– High-Z (BGO), high-density
– Two 5-inch diameter PMTs per Detector.
– Energy range: ~150 keV to 30 MeV
Major Purpose
– Provide high-energy spectral coverage to overlap LAT range over a wide FoV
12 Sodium Iodide (NaI)Scintillation Detectors
2 Bismuth Germanate (BGO)Scintillation Detectors
Location and orientation of GBM Location and orientation of GBM detectors in the spacecraftdetectors in the spacecraft
Param eter Requirem ent G oal Current Capability Energy range 10 keV – 25 M eV 5 keV – 30 M eV ~10 keV – 30 M eV
Energy resolution < 23.5% FW H M
(10 keV – 25 M eV)
< 7% ~12% FW H M @ 511 keV
T im e resolution 10 s 2 s 2 s
O n-board G R B locations
W ith in 2 s 15º w ith in 1 s <15º; 1.8 s
R apid ground G R B locations
5º accuracy (1 radius) w ith in 5 s
3º w ith in 1 s TBD by analysis (scattering influenced)
F inal G R B locations
3º accuracy (1 radius) w ith in 1 day
(no stated goal) TBD by analysis
(scattering influenced)
G R B sensitivity
(on ground)
0.5 photons cm -2 s -1
(peak flux, 50–300 keV )
0 .3 photons cm -2 s -1 (peak flux, 50–300 keV )
0 .35 photons cm -2 s -1 (peak flux, 50–300 keV )
G R B on-board trigger sensitivity
1.0 photons cm -2 s -1 (peak flux, 50–300 keV )
0 .75 photons cm -2 s -1 (peak flux, 50–300 keV )
0 .76 photons cm -2 s -1 (peak flux, 50–300 keV
F ie ld of view 8 sr 10 sr 8 .8 sr
D ead-tim e < 10 s/count <3 s/count ~2.5 s/count
G BM Design CapabilitiesG BM Design CapabilitiesG BM Design Capabilities
Burst Spectra
GBM can provide time resolved energy spectra of GBM can provide time resolved energy spectra of GRB’s GRB’s in in the range 10 the range 10 keVkeV –– 30 30 MeVMeV. . oo to explore the possible relation between to explore the possible relation between keVkeV--MeVMeV--GeVGeV
emissionsemissionsoo to explore if those to explore if those GRB’s GRB’s detected by the LAT form a detected by the LAT form a
separate classseparate class++ detection of high energy emission alone is not adequate detection of high energy emission alone is not adequate
for such classification for such classification oo additional benefit of a continuation of the BATSE archiveadditional benefit of a continuation of the BATSE archive
GBM can measure the temporal behavior & distribution of spectGBM can measure the temporal behavior & distribution of spectralralparameters: parameters: EEpp, , etcetc. .
Possible relation between Possible relation between EEp p and high energy emission.and high energy emission. GBM + LAT can measure the GRB spectra spanning 8 decades inGBM + LAT can measure the GRB spectra spanning 8 decades in
in in --ray energy (10 ray energy (10 keVkeV –– 300 300 GeVGeV) ) oo One can detect possible high energy cutOne can detect possible high energy cut--off in GRB spectraoff in GRB spectra
GBM can also measure energy resolved light curves so that onGBM can also measure energy resolved light curves so that one cane canlook for possible time delays between them. look for possible time delays between them. oo 128 channel spectra every 8 128 channel spectra every 8 ssoo 4 channel spectra every 0.256 4 channel spectra every 0.256 ss andandoo ~ 15 ~ 15 ss of Preof Pre--burst data of Time Tagged Events (TTE) with 2 burst data of Time Tagged Events (TTE) with 2 ss
time resolution.time resolution.oo During the burst TTE data is available for > 300 During the burst TTE data is available for > 300 ss at a peak rateat a peak rate
of 350 kHz.of 350 kHz.
Burst Light-curves
One would expect ~150 GRB triggers/year of which ~ 50One would expect ~150 GRB triggers/year of which ~ 50--100100triggers are expected to be detected by LATtriggers are expected to be detected by LAT
Prior location provided by GBM would enable LAT to detect Prior location provided by GBM would enable LAT to detect weaker weaker GRB’s GRB’s by limiting the search area which, in turn, reducesby limiting the search area which, in turn, reducesthe background.the background.
Burst Triggers
University of AlabamaUniversity of Alabamain Huntsvillein Huntsville
NASANASAMarshall Space Flight CenterMarshall Space Flight Center
MaxMax--PlanckPlanck--InstitutInstitut für für extraterrestrischeextraterrestrische PhysikPhysik
National Space Science & Technology Center
Michael BriggsWilliam PaciesasRobert PreeceNarayana BhatValerie Connaughton
Charles Meegan (PI)Gerald FishmanChryssa KouveliotouRobert WilsonColleen Wilson-Hodge
GiselherLichti (Co-PI)Andreas von KienlinVolker SchönfelderRoland DiehlJochenGreiner
On-board processing, flight software, systems engineering, analysis software, and management
Detectors, power supplies, calibration and analysis software
Los AlamosLos AlamosNational LaboratoryNational Laboratory
Detector Response
Marc Kippen
