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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
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 studies

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 studies

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 studies

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
BAT studies6 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 studies

  • 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 studies

    • 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 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 the complete sample

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

    Salvaterra et al. 2012, ApJ


    Luminosity evolution model
    luminosity evolution model the complete sample

    Salvaterra et al. 2012, ApJ


    Density evolution model
    density evolution model the complete sample

    Salvaterra et al. 2012, ApJ


    Density evolution model1
    density evolution model the complete sample

    Salvaterra et al. 2012, ApJ


    Prompt spectral correlations
    prompt spectral correlations the complete sample


    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 Nava et al. 2008)

    evolution in redshift?

    Nava et al. 2012, MNRAS



    E iso normalized light curve
    “E Nava et al. 2008)iso-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 Nava et al. 2008)

    “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


    5 min Nava et al. 2008)

    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 Nava et al. 2008)

    steep decay

    plateau/shallow decay

    normal decay

    D’Avanzo et al. 2012, MNRAS in press


    Prompt and afterglow contribution1
    prompt and afterglow contribution Nava et al. 2008)

    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 Nava et al. 2008)

    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 Nava et al. 2008)

    • 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...



    Someone stole stefano s badge
    Someone stole Stefano’s badge… Nava et al. 2008)

    …without the badge he cannot attend the social dinner


    We heard some rumors
    we heard some rumors… Nava et al. 2008)


    We heard some rumors1
    we heard some rumors… Nava et al. 2008)

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


    HE Nava et al. 2008)


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