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a complete sample of long bright Swift GRBs: correlation studies

a complete sample of long bright Swift GRBs: correlation studies. Paolo D’Avanzo INAF-Osservatorio Astronomico di Brera. S. Campana (OAB) S. Covino (OAB) D. Fugazza (OAB) G. Ghirlanda (OAB). G. Ghisellini (OAB) A. Melandri (OAB) L. Nava (APC) R. Salvaterra (IASF-MI).

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a complete sample of long bright Swift GRBs: correlation studies

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  1. a complete sample of long bright Swift GRBs: correlation studies Paolo D’Avanzo INAF-Osservatorio Astronomico di Brera S. Campana (OAB) S. Covino (OAB) D. Fugazza (OAB) G. Ghirlanda (OAB) G. Ghisellini (OAB) A. Melandri (OAB) L. Nava (APC) R. Salvaterra (IASF-MI) B. Sbarufatti (OAB) G. Tagliaferri (OAB) S.D. Vergani (OAB)

  2. towards a complete sample Swift/BAT [180/540] • most of the GRBs lack of measured redshift due to: • observing conditions from ground • bad weather • high galactic extinction • late observations • ... • intrinsic biases • redshift desert • dark bursts • ... Salvaterra et al. 2012, ApJ

  3. towards a complete sample Swift/BAT [180/540] • Jakobsson et al. (2004) provides some criteria to select GRBs with favorable observing condition from ground: • XRT position with 12h • low Galactic extinction: AV<0.5 • declination: -70°<δ<+70° • distant from Sun: θ>55° Daniele Malesani talk Jakobsson [132/248] Salvaterra et al. 2012, ApJ

  4. towards a complete sample Swift/BAT [180/540] Jakobsson [132/248] Swift/BAT6 [55/58] BAT6: Jakobsson criteria + bright in the BAT band 6 times worst sensitivity with respect to BAT Salvaterra et al. 2012, ApJ

  5. BAT6 redshift distribution mean (median) z = 2.23 (2.14) Daniele Malesani talk Hjorth et al. 2012 in spite of the severe cut in photon flux the mean (median) redshift is 1.82 (1.62) and the distribution extend at least up to z=5.47 Salvaterra et al. 2012, ApJ

  6. complete sample: overview • highlights of some results obtained so far from our complete sample: • GRB luminosity function (Salvaterra et al. 2012, ApJ, 749, 68 ) • need of evolution? • prompt emission spectral correlations (Nava et al., 2012, MNRAS, 421, 1256) • complete vs incomplete samples • redshift evolution? • correlations of γand X-rays rest frame properties (D’Avanzo et al., 2012, MNRAS, in press) • relative contribution of prompt and afterglow • radiative efficiency • distribution of the X-ray absorptions (Campana et al. 2012, MNRAS, 421, 1697) • complete vs incomplete samples • dark bursts (Melandri et al. 2012, MNRAS, 421, 1265) • redshift and luminosity distributions • nature

  7. complete sample: overview • highlights of some results obtained so far from our complete sample: • GRB luminosity function (Salvaterra et al. 2012, ApJ, 749, 68 ) • need of evolution? • prompt emission spectral correlations (Nava et al., 2012, MNRAS, 421, 1256) • complete vs incomplete samples • redshift evolution? • correlations of γand X-rays rest frame properties (D’Avanzo et al., 2012, MNRAS, in press) • relative contribution of prompt and afterglow • radiative efficiency • distribution of the X-ray absorptions (Campana et al. 2012, MNRAS, 421, 1697) • complete vs incomplete samples • dark bursts (Melandri et al. 2012, MNRAS, 421, 1265) • redshift and luminosity distributions • nature Andrea Melandri talk on Friday

  8. GRB luminosity function

  9. jointly fit the BATSE logN-logP and the z-distribution of the complete sample grb luminosity function BATSE Salvaterra et al. 2012, ApJ

  10. no evolution model no evolution model provides a poor fit of the data (KS~5x10-5) Salvaterra et al. 2012, ApJ

  11. luminosity evolution model Salvaterra et al. 2012, ApJ

  12. density evolution model Salvaterra et al. 2012, ApJ

  13. density evolution model Salvaterra et al. 2012, ApJ

  14. prompt spectral correlations

  15. correlations are confirmed but 1 outlier is found (~2% see Nava et al. 2008) Amati & Yonetoku correlations Nava et al. 2012, MNRAS

  16. no evolution of the slope of the correlations is found evolution in redshift? Nava et al. 2012, MNRAS

  17. correlations of rest-frame gamma- and X-ray properties

  18. “Eiso-normalized” light curve D’Avanzo et al. 2012, MNRAS in press

  19. the 2-10 keV X-ray luminosity correlates linearly with Eiso “Eiso-normalized” light curve trf=5 min trf=1 h LX trf=11 h trf=24 h Eiso D’Avanzo et al. 2012, MNRAS in press

  20. 5 min strong correlations with scatters increasing and significances decreasing with time 1 h 1. LX∝Eiso1.0 σ=0.25 ÷ 0.48 2. LX ∝ Liso0.9 σ=0.34 ÷ 0.47 3. LX ∝ Ep1.6 σ=0.35 ÷ 0.43 LX 11 h 24 h hint for an additional component (afterglow) rising up at late times Eiso Liso Ep D’Avanzo et al. 2012, MNRAS in press

  21. prompt and afterglow contribution steep decay plateau/shallow decay normal decay D’Avanzo et al. 2012, MNRAS in press

  22. prompt and afterglow contribution steep decay plateau/shallow decay normal decay • At trf = 5 min the X-ray luminosity strongly correlates with Eiso and Liso -> LX is still dominated by the prompt emission and ~2/3 of the X-ray light curves are in the plateau/shallow decay phase. • - The plateau/shallow decay phase is likely dominated by the central engine activity (Zhang et al. 2006) • At later times (trf > 1 hr) almost all events show the normal decay (X-ray luminosity afterglow dominated). D’Avanzo et al. 2012, MNRAS in press

  23. GRB radiative efficiency EK,iso νX > νC (Panaitescu & Kumar 2002) LX,24h p~2.3 εe= 0.1 εB= 0.01 <Eiso/EK,iso>= 0.06 (σ=0.14) 6% of average radiative efficiency (Freedman & Waxmann 2001; Berger et al. 2003; Granot et al. 2006; Zhang et al. 2007; Berger 2007; Nakar 2007) D’Avanzo et al. 2012, MNRAS in press

  24. conclusions • This complete sample (90%) of bright long Swift GRBs allows for the first time to study the GRB population in an unbiased way • GRB luminosity function • strong evolution (luminosity and/or density) is required • GRBs (assuming no lum. evo.) peak at higher z with respect to stars • observed z-distribution does not allow to distinguish among evo. models • prompt emission spectral correlations • Amati & Yonetoku correlations are confirmed with 1 outlier (~2%) • no redshift evolution of the slope is found • correlations of γand X-rays rest frame properties • strong correlations withσincreasing and significances decreasing with time • plateau/shallow decay powered by central engine • similar radiative efficiency for GRB (average of 6% of the total EK) • 5 papers published + 2 in preparation more to come...

  25. “the missing badge mistery”

  26. Someone stole Stefano’s badge… …without the badge he cannot attend the social dinner

  27. we heard some rumors…

  28. we heard some rumors… …it seems that one of these guys might be the responsible

  29. HE

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