A complete sample of long bright swift grbs correlation studies
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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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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)

B. Sbarufatti (OAB) G. Tagliaferri (OAB)

S.D. Vergani (OAB)


Towards a complete sample

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


Towards a complete sample1

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


Towards a complete sample2

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


Bat 6 redshift distribution

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


Complete sample overview

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


  • Complete sample overview1

    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


    Grb luminosity function

    GRB luminosity function


    Grb luminosity function1

    jointly fit the BATSE logN-logP and the z-distribution of the complete sample

    grb luminosity function

    BATSE

    Salvaterra et al. 2012, ApJ


    No evolution model

    no evolution model

    no evolution model provides a poor fit of the data (KS~5x10-5)

    Salvaterra et al. 2012, ApJ


    Luminosity evolution model

    luminosity evolution model

    Salvaterra et al. 2012, ApJ


    Density evolution model

    density evolution model

    Salvaterra et al. 2012, ApJ


    Density evolution model1

    density evolution model

    Salvaterra et al. 2012, ApJ


    Prompt spectral correlations

    prompt spectral correlations


    Amati yonetoku correlations

    correlations are confirmed but 1 outlier is found (~2% see Nava et al. 2008)

    Amati & Yonetoku correlations

    Nava et al. 2012, MNRAS


    Evolution in redshift

    no evolution of the slope of the correlations is found

    evolution in redshift?

    Nava et al. 2012, MNRAS


    Correlations of rest frame gamma and x ray properties

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


    E iso normalized light curve

    “Eiso-normalized” light curve

    D’Avanzo et al. 2012, MNRAS in press


    E iso normalized light curve1

    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


    A complete sample of long bright swift grbs correlation studies

    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


    Prompt and afterglow contribution

    prompt and afterglow contribution

    steep decay

    plateau/shallow decay

    normal decay

    D’Avanzo et al. 2012, MNRAS in press


    Prompt and afterglow contribution1

    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


    Grb radiative efficiency

    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


    Conclusions

    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...


    The missing badge mistery

    “the missing badge mistery”


    Someone stole stefano s badge

    Someone stole Stefano’s badge…

    …without the badge he cannot attend the social dinner


    We heard some rumors

    we heard some rumors…


    We heard some rumors1

    we heard some rumors…

    …it seems that one of these guys might be the responsible


    A complete sample of long bright swift grbs correlation studies

    HE


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