GRB 090323 and GRB 090328 Two long high-energy GRBs detected by Fermi Elisabetta Bissaldi on behalf of the Fermi GBM and LAT collaborations Max-Planck-Institut für extraterrestrische Physik (MPE - Garching) • Member of the Fermi GBM Team

Outline Overview of the two bursts: Main infos GBM detection GRB 090323 GRB 090328 Open issues and conclusions Main infos GBM detection ARR and LAT detection Background issues Time interval selection Spectral analysis Time-integrated Time-resolved LAT long-lived emission

GRB 090323 PRELIMINARY NaI 9 and NaI 11 50-300 keV Main infos: GBM Trigger time: 00:02:42.63 UT on March 23, 2009 Triggered detectors: NaI 9 and NaI 11 Also seed in detectors NaI 6, 7, 8 and 10 Detected in BGO 1 up to 1.5 MeV Autonomous repointing maneuver sent from GBM to LAT LAT detection gives an improved localization Follow-up by Swift in the X-ray and optical Follow up by ground-based telescopes Redshift measurement  z = 3.6 (Chornock et al., 2009)

GBM detectors First quick-look data analysis of the NaI detectors (50-300 keV band) Temporal resolution: Blue line: 1 s resolution 70 s, covering ~8 s pre-burst and ~60 s post-burst. Black line: 8 s resolution n0 n1 n2 n3 n4 n5 n6 n7 n8 n9 na nb

Autonomous Repoint Request (ARR) Actual orbit due to ARR Planned orbit The high energy emission detected by the LAT was made possible by the ARR sent from GBM Otherwise GRB would have been out of FOV! GRB 090323 LAT 6 hour automated science processing 5

GBM orientation evolution NaI 6 In GBM, the effect of the ARR is particularly visible after T0+60 s, where the detectors orientation changes with incredible rapidity, making the spectral analysis a delicate issue Actual orbit NaI 7 angle (deg) NaI 9 ARR NaI 11 Time since T0 (sec)

NaI background subtraction 8 – 900 keV 8 – 900 keV

Time interval selection 8 – 900 keV For each time interval, because of the slewing due to the ARR, we need to select the best NaI detector combination! T90 ~140 s Fluence = (1.23 ± 0.02)E-04 erg/cm2 1-sec Peak Flux = 12.3 ± 0.4 ph/s/cm2

Spectral results interval c 8 – 900 keV GBM only Band fit Energy (keV) Time resolved analysis Epeak = 536 +25-24 keV alpha = -0.80 ± 0.02 beta = -2.8 +0.2-0.4

Band parameter evolution 8 – 900 keV Epeak alpha beta

GRB 090323 LAT afterglow LAT detections During GBM time: ~25 events PRELIMINARY PRELIMINARY Binsize: 60 s 15 deg ROI blue line: GRB within 98deg of Earth limb black line: (SAA) 50MeV-300GeV transient class binsize: 50 s LAT detections During GBM time: ~25 events Next 10 minutes: ~60 events Extended emission (up to 1.7 ks): ~80 events

GRB 090328 NaI 6 and NaI 7 50-300 keV PRELIMINARY Main facts: GBM Trigger time: 09:36:46.51 UT on March 28, 2009 Triggered detectors: NaI 6 and NaI 7 ARR LAT detection gives an improved localization Follow-up by Swift in the X-ray and optical Follow-up by ground-based telescopes Redshift measurement: z = 0.736 (Cenko et al., 2009) Radio afterglow detected with the VLA at 8.46 GHz (Frail et al. 2009)

Time interval selection 8 – 900 keV T90~60s Fluence = (5.2 ± 0.7)E-05 erg/cm2 1-sec Peak Flux = 22.6 ± 0.8 ph/s/cm2

Interval c GBM only Band fit 101 100 10-1 10-2 10-3 10-4 10-5 Epeak = 479 ± 58 keV alpha = -1.08 +0.04-0.03 beta = -2.26 +0.18-0.3 Energy (keV)

Band parameter evolution

GRB 090328 LAT afterglow LAT high-energy detection PRELIMINARY PRELIMINARY 50MeV-300GeV transient class binsize: 50 s Binsize: 60 s 15 deg ROI blue line: GRB within 98deg of Earth limb black line: (SAA) LAT high-energy detection During GBM time: ~18 events Next 1.5 ks: ~100 events Extended emission (6.8 ks): ~60 events

Conclusions Fermi analysis of two long bursts ~150 s and ~60 s in GBM Detected to much longer time in the LAT ARR enabled the detections of the extended emission …Papers coming soon!

Backup slides

BGO detector BGO 1 0.15-0.40 MeV 0.40-0.85 MeV 0.85-1.5 MeV 1.5-3 MeV

090323 GBM+LAT Band fit Epeak = 482 ±18 keV Alpha = -0.74 ± 0.02 Beta = -2.7 +0.09-0.12

GBM+LAT Band+PL fit Epeak = 508 ± 33 alpha = -1.086 ± 0.020 beta = -2.53 ± 0.15 G = -1. 2 ± 0.5

GBM+LAT Band+PL nFn GBM+LAT Band fit Epeak = 488 ± 31 alpha = -1.078 ± 0.021 beta = -2.36 ± 0.0 Energy (keV) Energy (keV)

Fluence interval: 8-1000 keV GBM T90 calculation Fluence interval: 8-1000 keV T50 ~ 56 s T90 ~ 135 s Fluence = (1.23 ± 0.02)E-04 erg/cm2 1-sec Peak Flux = 12.3 ± 0.4 ph/s/cm2 Time since T0 (sec)

Fluence interval: 8-1000 keV GBM T90 calculation Fluence interval: 8-1000 keV T50 ~ 19 s T90 ~ 61 s Fluence = (5.2 ± 0.7)E-05 erg/cm2 1-sec Peak Flux = 22.6 ± 0.8 ph/s/cm2 Time since T0 (sec)

NaI trigger detectors combined 7-10 keV 10-22 keV 22-44 keV 44-95 keV 300-500 keV 500-800 keV 800-1000 keV 95-300 keV NaI 9 + NaI 11

BGO detector BGO 1 0.15-0.40 MeV 0.40-0.85 MeV 0.85-1.5 MeV 1.5-3 MeV

GBM detectors NaI 6 + NaI 7 BGO 1 7-10 keV 10-22 keV 22-44 keV 0.15-0.40 MeV 0.40-0.85 MeV 0.85-1.5 MeV 1.5-3 MeV 5.5-10 MeV 10-20 MeV 20-30 MeV 3.0-5.5 MeV NaI 6 + NaI 7 BGO 1