Can we constrain GRB shock parameters using the Gamma Ray Large
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SABER workshop Mar 15, 2006 Can we constrain GRB shock parameters using the Gamma Ray Large Area Space Telescope? Eduardo do Couto e Silva SLAC/KIPAC SABER Workshop – Mar 15, 2006 E. do Couto e Silva SLAC/KIPAC SABER workshop Mar 15, 2006 The Main Questions Is there any connection between the SABER program and the GRB science with GLAST? • Can we create an environment similar to that of the shock dissipation phase in GRBs? see poster (Stochastic wake field particle acceleration in Gamma-Ray Bursts, Baribiellini et al) • Can we quantify the relative importance of magnetic fields during the shock dissipation phase in GRBs? E. do Couto e Silva SLAC/KIPAC SABER workshop Mar 15, 2006 Outline Overview of the GLAST Observatory • two high energy gamma ray telescopes Introduction to Gamma Ray Bursts (GRB) • focus mostly high energy emissions (> GeV) Can we measure shock parameters related to Gamma Ray Bursts? • phenomenological approach within the fireball scenario List expectations for this Workshop E. do Couto e Silva SLAC/KIPAC SABER workshop Mar 15, 2006 GLAST Observatory : Overview GLAST will measure the direction, energy and arrival time of celestial g rays Principal Investigator: Peter Michelson LAT will record gamma-rays in the energy range ~ 20 MeV to >300 GeV Orbit 565 km, circular GBM will provide correlative observations of transient events in the energy range ~10 keV – 25 MeV Observing modes All sky survey Pointed observations Re-pointing Capabilities Autonomous Rapid slew speed (75° in < 10 minutes) E. do Couto e Silva SLAC/KIPAC Inclination 28.5o Lifetime 5 years (min) Will follow on the measurements by its predecessor (EGRET) with unprecedented capabilities Launch Date Sep 2007 Launch Vehicle Delta 2920H-10 Launch Site Kennedy Space Center SABER workshop Mar 15, 2006 GLAST Burst Monitor: Overview NaI and BGO counters exposed to the entire sky Principal Investigator: Charles Meegan NaI crystals (12) low-energy spectral coverage ~10 keV to ~1 MeV rough burst locations BGO crystals (2) high-energy spectral coverage ~150 keV to ~30 MeV GBM 10 keV to ~ 25 MeV Correlative observations of transient phenomena E. do Couto e Silva SLAC/KIPAC Spectral Measurements measures spectra for bursts connects with LAT measurements Afterglows in Gamma Ray Bursts Wide Sky Coverage (8 sr) autonomous repoint for exceptionally bright bursts that occur outside LAT field of view Connections to the Ground Network of Telescopes burst alerts to the LAT and ground telescopes within seconds SABER workshop Mar 15, 2006 Large Area Telescope: Overview Principal Investigator: Peter Michelson The LAT is a pair-conversion telescope of 16 towers surrounded by plastic scintillators g Silicon Microstrip Tracker ~ 80 m2 of silicon 8.8 x 105 readout channels Strip pitch = 228 µm xy layers interleaved with W converters ~1.5 X0 Calorimeter Hodoscopic array Array of 1536 CsI(Tl) crystals in 8 layers ~8.5 X0 Anti-Coincidence Detector 89 scintillator tiles Segmented design E. do Couto e Silva SLAC/KIPAC Silicon Microstrip Tracker Measures g direction g identification Calorimeter Measures g energy Shower imaging e+ e– LAT 3000 kg, 650 W (allocation) 1.8 m 1.8 m 1.0 m 20 MeV – 300 GeV Currently there is no other telescope covering this energy range Anti-Coincidence Detector Rejects background of charged cosmic rays segmentation removes selfveto effects at high energy SABER workshop Mar 15, 2006 LAT Integration @ SLAC Calorimeter module Tracker module LAT Integration & Test Team Anti Coincidence Detector being integrated with 16 towers E. do Couto e Silva SLAC/KIPAC SABER workshop Mar 15, 2006 LAT Data from Tests at SLAC From A. Borgland Muon candidates Most of the 500 Hz of triggers recorded are muons Photon Candidates? ~20% of cosmic ray showers are not muons E. do Couto e Silva SLAC/KIPAC SABER workshop Mar 15, 2006 3rd Comparison of Instrument Performance EGRET Catalog LAT Simulation EGRET LAT E > 100 MeV E > 100 MeV Pointing 1991-2001 All sky 2007 - ? 5 yr operation requirement 10 yr operation goal Improvement Energy 30 MeV - 30 GeV Peak effective area 1500 cm² Field of view Sensitivity (1yr) 0.5 sr ~ 10-7 g cm-2 s-1 Localization (bright source) Deadtime E. do Couto e Silva SLAC/KIPAC 15 ’ 100 ms 20 MeV - 300 GeV > 8000 cm² >5 > 2.0 sr >4 < 6 10-9 g cm-2 s-1 > 20 < 0.5 ’ > 30 < 30 ms > 1000 Large area Low instrumental background SABER workshop Mar 15, 2006 All Sky Monitoring with Improved Sensitivity All-sky survey: sensitivity after O(1) day to detect the weakest EGRET sources at (5s) level ! 100 sec Fraction of the g ray sky 100 sec observed within 2 min - GRB940217 (100sec) - PKS 1622-287 flare - 3C279 flare - Vela Pulsar 1 orbit ~ 90 min - Crab Pulsar - 3EG 2020+40 (SNR g Cygni?) zenith-pointed - 3EG 1835+59 - 3C279 lowest 5s detection - 3EG 1911-2000 (AGN) - Mrk 421 - Weakest 5s EGRET source 1 day 1~day EGRET Flux rocking” all-sky scan: alternating orbits point above/below the orbit plane E. do Couto e Silva SLAC/KIPAC SABER workshop Mar 15, 2006 Some GRB Experimental Facts Intensity, location, rate • Typical fluences • Cosmological distances • 1 /Myrs/galaxy 940217 (Hurley 1994) Energy Spectrum • Non-thermal emission z~1 Rate 10-4 to -7 ergs cm-2 up to g rays (3 GeV) Temporal properties • Rapid flux variations • miliseconds Range of burst durations few seconds to hours E. do Couto e Silva SLAC/KIPAC Transients are hard to catch! SABER workshop Mar 15, 2006 Delayed High Energy Emission in GRB940217 LAT • Large effective Area (can probe smaller fluxes) • Extends spectral coverage to higher energies GBM will cover down to few keV E. do Couto e Silva SLAC/KIPAC GRB 940217 (Hurley 1994) SABER workshop Mar 15, 2006 Fireball Model Kobayashi, Piran & Sari 1999 z=43 E=1052 ergs h=50 R =3×1010 cm UInt to UKin External Shock Plethora of models • Shells HOT HOT COLD Reverse Forward Relativistic or Newtonian • External Medium COLD thin or thick • Shocks Ukin to UISM ISM or wind like E. do Couto e Silva SLAC/KIPAC shock Fireball shock ISM ISM SABER workshop Mar 15, 2006 Shock Plasma Parameters Can we use GLAST measurements to help constrain these parameters? Fraction of Magnetic Energy Density behind the shock • eB ~ 1 to 10-5 Fraction of Thermal Electron Energy Density behind the shock • ee ~ 1 to 10-5 Ratio of peaks in Spectral Energy Density (GLAST + X ray Detector) Ratio of peaks in Spectral Energy Density (GLAST + X ray Detector) Energy distribution of accelerated electrons • p (power law index) ~ 2 to 3 Are p, eB ee time Fits from Spectral Energy Density (GLAST + X ray Detector) independent? (Paitanescu and Kumar 2001) E. do Couto e Silva SLAC/KIPAC SABER workshop Mar 15, 2006 High Energy Emission Models Leptonic Models No definitive answer yet… Hard to model IC Hadronic models (Pe’er Waxman 2005) • • • Shocks: Internal/ External? KN regime HE EM cascades Large t from e+- Proton Synchrotron Forward/ Reverse? Meszaros & Zhang 2001 IC Synchroton E. do Couto e Silva SLAC/KIPAC pp, pn , pg SABER workshop Mar 15, 2006 Mechanisms for High Energy Emission Meszaros & Zhang 2001 Inverse Compton scattering of low energy photons off energetic electrons • most likely the answer to GRB940217? • requires small eB • denser medium helps to increase the flux Proton-synchroton radiation • maybe too faint for a GLAST detection • if detected may provide hints that the medium density is constant • requires large eB • very interesting because it may connect UHECR with GRBs E. do Couto e Silva SLAC/KIPAC SABER workshop Mar 15, 2006 Which model should we choose? Region I • Proton synchroton hard with GLAST large eB Region II • Inverse Compton good for GLAST denser medium helps Typical from afterglows (Painatescu & Kumar 2001) (Painatescu & Kumar 2002) small eB :internal shocks Region III • Electron synchroton not in GLAST range E. do Couto e Silva SLAC/KIPAC Zhang && Meszaros 2001 Zhang Meszaros 2001 SABER workshop Mar 15, 2006 We need DATA ! Region I Zhang & Meszaros 2001 z = 0.1 z=1 • Proton synchroton hard with GLAST large eB Region II • Inverse Compton good for GLAST denser medium helps Region III • Electron synchroton maybe hard with GLAST E. do Couto e Silva SLAC/KIPAC eB = 10-4 ee = 0.5 GRB 940217 (Hurley 1994) SABER workshop Mar 15, 2006 Back to the Main Questions Is there any connection between the SABER program and the physics interests of GLAST? • Can we simulate in the laboratory an environment similar to that of the shock dissipation phase in GRBs? • Can we quantify the relative importance of magnetic fields during the shock dissipation phase in GRBs? • A deeper question: Are B fields generated locally or at the central engine? E. do Couto e Silva SLAC/KIPAC back up slides Page Number SABER workshop Mar 15, 2006 Gamma Ray Bursts: GBM and LAT GBM • Huge field of view (8sr) • Measure spectra for bursts from 10 keV to 30 MeV LAT • Wide field of view (>2sr) • Extends spectral coverage to higher energies GLAST Can be re-pointed to catch exceptionally bright bursts that occur outside the LAT field of view GLAST all-sky monitoring will be follow transient phenomena to a wide range of time scales from ~ 30 µs (GRB, solar flares) to hours or longer (AGN) E. do Couto e Silva SLAC/KIPAC + Simulated GBM and LAT response to timeintegrated flux from bright GRB 940217 Spectral model parameters from CGRO wide-band fit 1 NaI (14 º) and 1 BGO (30 º) NaI BGO LAT SABER workshop Mar 15, 2006 GLAST/LAT performance Thin Thick Intrinsic resolution of the tracker Slide from N. Omodei Energy Resolution: ~10% (~5% off-axis) PSF (68%) at 100 MeV ~ 5o PSF (68%) at 10 GeV ~ 0.1o Field Of View: 2.4 sr Point Source sens. (>100 MeV): 3x10-9 cm-2 s-1 Thin converters (3%) Thin Thick Full Tkr E. do Couto e Silva SLAC/KIPAC Thick converters (18%) No converters F.o.V.: 2.4 sr SABER workshop Mar 15, 2006 High Energy Emission in GRB 941017 Compare data from EGRET and BATSE: high-energy component has different time behavior than sub–MeV component! Low Energy < 3 MeV Epeak ~ 0.5 MeV Duration ~ 100s Where is the high-energy peak? Is there a cut-off? internal or external shocks? High Energy > 3 MeV dN/dE ~ E-1 Duration ~ 200s hadrons or electrons? Is the spectral index timedependent ? How common is this GRB ? -18 to 14 s 14 to 47 s high energy component start to develop 47 to 80 s 80 to 113 s 113 to 211 s BASTE-LAD Gonzalez et al 2003 E. do Couto e Silva SLAC/KIPAC Need GLAST data!! EGRET-TASC SABER workshop Mar 15, 2006 Modeling High Energy Emission for GRB941017 Two models used • External shock (Pe’er &Waxmann 2004) e- accelerated in FS IC scatter g from RS SSA is important • Internal Shock (Granot & Guetta 2003) e- in FS IC scatter g whlle RS is going on SSC from RS (depends on spectal index) eB ~ 10-7 Dt = 10-5 E. do Couto e Silva SLAC/KIPAC High Energy data constrains Total energy, Lorentz factor and ambient density Pe’er & Waxman 2004 E = 3 × 1054 ergs, n = 0.10 cm-3, G i = 300, eB,r = 10-1, eB,f= 10-6, z = 0.10 E = 1 × 1055 ergs, n = 0.10 cm-3, G i = 200, eB,r = 10-3, eB,f= 10-5, z = 0.10 E = 1 × 1054 ergs, n = 0.03 cm-3, G i = 220, eB,r = 0.2, eB,f= 10-6, z = 0.06 E = 3 × 1052 ergs, n = 0.10 cm-3, G i = 1500, eB,r = 10-7, eB,f= 10-7, z = 0.15 Flux between 100 and 200 s after the burst Data from Gonzalez et al 2003 GRB941017 GBM LAT Dt = 10-5 SABER workshop Mar 15, 2006 Multiwavelength Observations to Constrain Models Model • Prompt emission from internal shocks in relativistic wind Pe’er & Wazman 2004 • Spectra as high as 10 GeV Flux has a strong dependence on G Measure cut-offs with GLAST! Ratio of peaks in kev/GeV can be used to constrain ratio of eB / ee LAT + GBM? Swift + GLAST? Caveat: • single shell collisions E. do Couto e Silva SLAC/KIPAC 100 keV eB = 0.33 eB = 0.01 eB = 0.0001 1 GeV l’ < 10 G = 600 Dt = 10-4 SABER workshop Mar 15, 2006 Can we constrain p and G from GRB940217? Guetta & Granot 2003 Model • Prompt emission from internal shocks • G = 600 G = 350 G = 200 300 keV 1 GeV in relativistic wind SSC dominates above 100 MeV Power law index > 2 GLAST can constrain p 30 MeV Parameters • • G= 600, Dt = 0.1 ms, Ep = 200 KeV Should we expect variability smaller that 0.1 ms? E. do Couto e Silva SLAC/KIPAC Dt = 10 ms Dt = 1 ms Dt = 0.1 ms SABER workshop Mar 15, 2006 GBM Performance The GLAST Burst Monitor for GLAST, A. von Kienlin et al., in Proc of the SPIE-Conference, Glasgow 2004 •compare count rates for 2 of the modules GBM NaI Location • 6 in the equatorial plane • 4 at 45o • 2 at 20o GBM BGO Location • 2 in opposite sides of the spacecaft GBM Trigger same as BATSE GBM Trigger Sensitivity •< 1 ph cm-2s-1 BATSE: 0.2 ph cm-2s-1 (5s) GBM Burst Localization •< 15o within 1.8s (on board) can be used as a LAT trigger if outside LAT FOV •possible to repoint to catch delayed emissions •< 5o within 5s (ground) E. do Couto e Silva SLAC/KIPAC < 3o within 1 day (ground) SABER workshop Mar 15, 2006 GLAST and GRBs Full sky survey every 3 hours Number of Bursts • GBM ~ 200 bursts/yr • > 60 bursts within FoV of the LAT 1 burst/month ~ 100 photons Alert and Localization • Alert to GCN ~ 10 s • GBM < 150 initially, update 50 • LAT > 10 arcmin depending on the burst Downlink and Communications • near real-time (TDRSS) • full science data ~ 6-8 times a day Downlink and Communications • Intense burst: GLAST can repoint keep LAT in the FoV Dwell time: 5 hr (adjustable) E. do Couto e Silva SLAC/KIPAC Slide from N. Omodei (GLAST GRB SWG) SABER workshop Mar 15, 2006 GLAST and SWIFT era • Swift can point for follow on observations. Precise measurements of the position will be given by Swift! GLAST will frequently scan the position of the bursts hours after the Swift alerts • • Slide from N. Omodei (GLAST GRB SWG) GLAST can provide alerts to GRBs monitoring for High energy emission. In these cases, we will have a broad spectral coverage of the GRB spectrum (from 0.1 keV to hundreds of GeV > 9 decades!!). Swift is seeing 100 bursts per yr: ~ 20/yr will be in the LAT FoV ~2020 GBM LAT 2007 XRT BAT 2005 E. do Couto e Silva SLAC/KIPAC 0.1 keV 10 keV 100 KeV 1 MeV 30 MeV 300 GeV SABER workshop Mar 15, 2006 Duration of GRBs 160 (e.g stellar mass BH accreting from a massive disk, rotating NS driving Poynting flux) 120 NUMBER OF BURSTS If there is a compact object at the inner engine, the source must also be active for a long time Long Compact Mergers? (ISM) Collapsar Model ? (wind) 1 cm-3 103-4 cm-3 80 40 0 0.01 E. do Couto e Silva SLAC/KIPAC Short 0.1 1 10 DURATION, SECONDS 100 1000 SABER workshop Mar 15, 2006 X ray Flares Giant X-ray Flare • 500 times higher amplitude GRB050502b Falcone 2005 E. do Couto e Silva SLAC/KIPAC Can we detect IC from X ray flares?
