grb 030328 : the burst before the burst

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Elisabetta Maiorano IASF/INAF, Sezione di Bologna & Dip. Astronomia, Università di Bologna GRB 030328: the burst before the Burst

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GRB 030328 : the burst before the Burst. Elisabetta Maiorano IASF/INAF, Sezione di Bologna & Dip. Astronomia, Università di Bologna. Collaborators. Evert Rol Nicola Masetti Eliana Palazzi Elena Pian Paul Vreeswijk Javier Gorosabel Antonio de Ugarte Postigo - PowerPoint PPT Presentation

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  • GRB 030328: the burst beforethe Burst Elisabetta Maiorano IASF/INAF, Sezione di Bologna &Dip. Astronomia, Universit di Bologna

  • CollaboratorsEvert RolNicola Masetti Eliana PalazziElena PianPaul VreeswijkJavier GorosabelAntonio de Ugarte Postigo

    On behalf of the GRACE collaboration

  • HEADLINES

    GRB030328: overview

    Prompt event

    Optical photometry

    Optical spectroscopy

    Optical polarimetry

    Broadband spectrum

    Discussion

    Conclusions

  • GRB030328Trigger: March 28.473 UT 2003 (by HETE-2)

    Coordinates (J2000): RA = 12h 10m 51s.00 DEC = -09 21 05.00 error circle = 52

    Optical Transient: obs ~ 1 hr after the GRB, R ~ 18 (Peterson & Price 2003)

    X-ray Transient: obs ~ 15 hr after the GRB (exp=94 ks), Chandra (Butler et al. 2003)

    Redshift: z = 1.52 (Martini et al. 2003; Rol et al. 2003)

    Host galaxy: obs ~ 1 yr after the GRB, R ~ 24.4 (Gorosabel et al. 2005)

  • Prompt event Prompt event light curve

    Duration (30-400 keV): ~ 100 s (T90)

    Total Fluence (30-400 keV): 3 x 10-5 ergs cm-2 Peak Flux (30-400 keV): 7.3 x 10-7 ergs cm-2 s-1

    (Villasenor et al. 2003; Butler et al. 2005)

    (7-40 keV) (7-80 keV)(30-400 keV)Hete-2

  • ObservationsBVRI Photometry (2.2m+WFI @ ESO)

    Spectroscopy (VLT+FORS1 @ ESO)

    Polarimetry (VLT+FORS1 @ ESO)

    X-ray Observations (ACIS-S @ CXO)

    Host galaxy Observations (2.2m+BUSCA @ CAHA)

  • WFI R-band imageThe Optical Transient is clearly detected

    Mid exp time = 29.272 UT(0.79 d after the trigger)

    R = 21.17 0.04NEField size: 2x2 arcmin(2.2m+WFI @ ESO)

  • BVRI light curvesI/10RBx100Vx10(Maiorano et al. in preparation)

  • VLT+FORS1 SpectrumSpectrum acquired 0.59 days after the GRB and corrected for the Galactic extinction E(B-V) = 0.047Significant lines explained assuming two systems at redshiftsz = 1.5223 0.0006 (GRB redshift) and z = 1.295

  • Polarimetry P = (2.4 0.6) %

    = (170 7) degrees

    5 different cycles of polarizationmeasurements were obtained, the percentage of linearpolarization P and the polarization angle do not vary across the 5 cycles.

    We thus summed the images on each angle to increase the S/N. t start = 0.13 dt end = 0.34 dV = 21.25 0.10(VLT+FORS1 @ ESO)

  • Host galaxy analysis(Gorosabel et al.)The restframe Spectral Energy Distribution of the host galaxy.The best-fit is obtained using a Starburst galaxy (green template).The red dashed line shows the fit obtained using a powerlaw with index = 1.25 0.54. Co-added C1+C2+C3+C4 image of the host galaxy obtained with 2.2m + BUSCA @ Calar Alto Telescope

  • Host galaxy analysis(Gorosabel et al.)The restframe Spectral Energy Distribution of the host galaxy from the UV band (left panel) to the Optical and Infrared bands (right panel).The best fit is obtained using a Starburst galaxy of age 15 Myr(green template). The red dashed line in the left panel indicates the fit obtained using a powerlaw with index = 1.25 0.54.

  • X-ray afterglow analysis (Butler et al.)0.5-5 keV spectrum is well fitted using an absorbed powerlaw with photon index = 2.0 0.2 NH = NH (Gal) = 1021 cm-2No X-ray emission linesThe X-ray afterglow decreases in brightness following a powerlawwith index x = 1.5 0.1 (ACIS-S @ CXO)

  • R-band light curve analysisabc = 1.070.05 = 1.50.11 = 0.80.12 = 1.60.2tb = 0.70.1 daysabc

  • Broadband spectrum (tsed = 0.78 d)opt = 0.5 0.1

    x = 1.0 0.2

    c = 1.7 x 10 16 Hz

    x-opt= 0.84 0.01

  • Closure Relations (1)(x=opt)x = 1.5 1.1

    1.5 opt Break

    No break x = opt = 3(p1)/4 = 1.2 ism = (1-3p)/4 = 1.7 wind

    1 = 3(p-1)/4 = 1.22 = p = 2.61 = 3(p-1)/4+1/2 = 1.7 2 = 3(p-1)/4+1 = 2.2=p/2 =(p-1)/2

    c > x p=2.6spherejetc < o p=1.6 = (p+6)/4 = 1.9 < 1sphere

    jet ismwind1 = 0.82 = 1.6

  • Closure Relations (2)(xopt)x = 1 = 3(p-1)/4 = 0.75 = (3p-1)/4 = 1.25

    1 = 3(p-1)/4 = 0.75 2 = 3(p-1)/4+3/4 = 1.5 1 = 3(p-1)/4+1/2 = 1.252 = 3(p-1)/4+1 = 1.75x=p/2spherejeto < c < x p = 2 opt = 0.5x = 1.5 c = 1.7 x 10 16 Hzopt = (p-1)/2 = 0.5o < c < xEiso~1.8x1053 erg jet=4.3E= 5x1050 ergismwindismwind

  • SummaryOptical and X-ray afterglow well detected

    Redshift: z = 1.522

    Polarization: P ~ 2.4%

    Host galaxy: Starburst

    Preferred regimes in fireball scenario: (1) isotropic expansion within a wind-shaped medium, p ~ 2.6 (2) jet collimated expansion within a homogeneous medium, p ~ 2

    more data (if any) are welcome