GRB 091024 and ultra-long GRBs

GRB 091024 and ultra-long GRBsFrancisco Virgili, LJMUJune 22, 2012GRBs 2012 LiverpoolC. Mundell, A. Melandri, C. Guidorzi, R. Margutti, A. Gomboc,S. Kobayashi, V. Palshin, etcOutlineGRB 091024 case studyObservationsAnalysisTemporalSpectral (limited)EnergeticsInterpretationOther ultra-long GRBs

High-energy emissionGBM bg subtracted lc

Gruber+ 2011High-energy emission

BAT emission up to ~T0+483 sXRT starting at ~T0+53 minEvans+ 2009(Part of) What we do

x 2Few words on our follow-up: Built telescopes, where they are, software, follow-up etc etc5Optical Emission

FTNLTKAITSuper-LOTISSROGemini

FTNLTKAITSuper-LOTISSROGeminiI (shifted to R), R; LT no polarization, just later time points6Temporal3 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 peakFirst peak: 1.83 rise, -2.376 fall7Power spectrum analysisCalculate 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)Gives indication of typical variability timescales, look at varience and rate of change of varience of count lightcurve8PDS: Time slicesSame analysis as full signal but on three different regimes of the BAT lightcurve:-200:250 s250:800 s800:1200 sShort var in 1st and 3rd emission episodeLonger timescales in period of quiescence Un-masked count rate lc, similar results with masked for beginning sectionUnlike naked eye burst 089PDS: Energy dependantVary over energy channelsSoftest energy range has no short timescale componentHardest scales show clear peak at low variability timescalesAnalysis: SpectralLimited spectral information:1st episode: BAT+GBM2nd and 3rd: GBM onlyWaiting on KW spectra (ideally GBM+KW)All segments fit with CPL1st: = -0.89, Ep=461 keV-0.89, 522 keV (joint)2nd: -1.2, 311 keV3rd: -1.58, 388 keV-1.57, 275 keV-1.49, 472 keV

Gruber+ 2011Tracking behavior, fits improved with time-dependent analysis of final peak, could only do one due to limited signal strength90, 50, 17011z and energeticsz=1.092

Energetics:Total Eiso: 6-8e53 ergMost (2e53 erg) in last emission episodeTime-resolved: Most in very last peakAmati: Consistent(Amati+ 2008)

Left three: 1st, 2nd, 3rd peaks (decreasing in Ep) then final either 3rd emission episode or last peak alone, both about same12Other wavelengths?No radio data (sadly)but if we didExtend analysis from Mundell+ 2007, Melandri+ 20091100100Talk about spread, radial profile; can constrain model parameters in this way, e.g. microphysical parameters, ambient medium density1513Other Ultra-long GRBsTable from V. PalshinAlso add GRB 110709B (B.B. Zhangs talk), GRB 111209 (FTN obs)

Ideally, collect this data and compare characteristics. Lots of different types of prompt emission, but sample is getting larger. No optical data for a lot,041219A? Only 500 sec, possibly xrf 14Summary and Future WorkLong-lived central engine activity (~500-600s in RF)Similar variability timescales at early and late timesNo correlation of gamma and optical emissionDifferent emission regionsIndicative of RS peak followed by FS emission in optical LCRise/fall slopes of 1st peakNo correlation gives hints as to something interesting? 15Summary and Future workComprehensive/broadband study of prompt and any afterglow emission of ultra-long GRBsKW sample has many bursts with good spectral/temporal coverage

Lead to constraints on models for late-time accretion and CE activity16

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