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GRB 091024 and ultra-long GRBs

GRB 091024 and ultra-long GRBs. Francisco Virgili , LJMU June 22, 2012 GRBs 2012 Liverpool. C. Mundell , A. Melandri , C. Guidorzi , R. Margutti , A. Gomboc , S . Kobayashi, V . Pal’shin , etc…. Outline. GRB 091024 case study Observations Analysis Temporal Spectral (limited)

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GRB 091024 and ultra-long GRBs

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  1. GRB 091024 and ultra-long GRBs Francisco Virgili, LJMU June 22, 2012 GRBs 2012 Liverpool C. Mundell, A. Melandri, C. Guidorzi, R. Margutti, A. Gomboc, S. Kobayashi, V. Pal’shin, etc…

  2. Outline • GRB 091024 case study • Observations • Analysis • Temporal • Spectral (limited) • Energetics • Interpretation • Other ultra-long GRBs

  3. High-energy emission GBM bg subtracted lc Gruber+ 2011

  4. High-energy emission XRT starting at ~T0+53 min Evans+ 2009 BAT emission up to ~T0+483 s

  5. (Part of) What we do… x 2

  6. Optical Emission FTN LT KAIT Super-LOTIS SRO Gemini FTN LT KAIT Super-LOTIS SRO Gemini

  7. Temporal • 3 optical peaks (451 +/- 18 s; 2222 +214 s 5081 +306 s) • No correlation to gamma-ray peaks (~ 0s, 600s, 950 s) • Steep rise/fall of 1st peak

  8. Power spectrum analysis • Calculate fractional signal power density (fpd) for various time slices of the KW and BAT lc. • Find a variety of timescales, specifically 2 short timescales (0.5 and 1 s) and 2 long timescales (7 and 14s) R. Margutti+ 2008 (arxiv:0809.0189)

  9. PDS: Time slices • Same analysis as full signal but on three different regimes of the BAT lightcurve: -200:250 s 250:800 s 800:1200 s • Short var in 1st and 3rd emission episode • Longer timescales in period of quiescence

  10. PDS: Energy dependant • Vary over energy channels • Softest energy range has no short timescale component • Hardest scales show clear peak at low variability timescales

  11. Analysis: Spectral • Limited spectral information: • 1st episode: BAT+GBM • 2nd and 3rd: GBM only • Waiting on KW spectra (ideally GBM+KW) • All segments fit with CPL • 1st: α= -0.89, Ep=461 keV • -0.89, 522 keV (joint) • 2nd: -1.2, 311 keV • 3rd: -1.58, 388 keV • -1.57, 275 keV • -1.49, 472 keV Gruber+ 2011

  12. z and energetics • z=1.092 • Energetics: • Total Eiso: 6-8e53 erg • Most (2e53 erg) in last emission episode • Time-resolved: Most in very last peak • Amati: Consistent (Amati+ 2008)

  13. Other wavelengths? 1 100 100 Extend analysis from Mundell+ 2007, Melandri+ 2009 No radio data (sadly)…but if we did…

  14. Other Ultra-long GRBs • Table from V. Pal’shin • Also add GRB 110709B (B.B. Zhang’s talk), GRB 111209 (FTN obs)

  15. Summary and Future Work • Long-lived central engine activity (~500-600s in RF) • Similar variability timescales at early and late times • No correlation of gamma and optical emission • Different emission regions • Indicative of RS peak followed by FS emission in optical LC • Rise/fall slopes of 1st peak

  16. Summary and Future work • Comprehensive/broadband study of prompt and any afterglow emission of ultra-long GRBs • KW sample has many bursts with good spectral/temporal coverage

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