grb 030328 : the burst before the burst
DESCRIPTION
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 PresentationTRANSCRIPT
Elisabetta Maiorano IASF/INAF, Sezione di Bologna
&Dip. Astronomia, Università di
Bologna
GRB 030328: the burst before
the Burst
Collaborators
• Evert Rol• Nicola Masetti • Eliana Palazzi• Elena Pian• Paul Vreeswijk• Javier Gorosabel• Antonio de Ugarte Postigo
On behalf of the GRACE collaboration
HEADLINESHEADLINES
•GRB030328: overview
•Prompt event
•Optical photometry
•Optical spectroscopy
•Optical polarimetry
•Broadband spectrum
•Discussion
•Conclusions
GRB030328•Trigger: 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
Observations
•BVRI 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 image
The Optical Transient is clearly detected
Mid exp time = 29.272 UT(0.79 d after the trigger)
R = 21.17 ± 0.04
N
E
Field size: 2x2 arcmin(2.2m+WFI @ ESO)
BVRI light curves
I/10
R
Bx100
Vx10
(Maiorano et al. in preparation)
VLT+FORS1 Spectrum
Spectrum 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) %
θ = (170 ± 7) degrees
5 different cycles of polarizationmeasurements were obtained, the percentage of linearpolarization P and the polarization angle θ 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 β = 1.25 ± 0.54.
Co-added C1+C2+C3+C4 image of the host galaxy obtained with 2.2m + BUSCA @ Calar Alto Telescope
X-ray afterglow analysis (Butler et al.)
0.5-5 keV spectrum is well fitted using an absorbed powerlaw with photon index Γ = 2.0 ± 0.2 NH = NH (Gal) = 1021 cm-2
No X-ray emission lines
The X-ray afterglow decreases in brightness following a powerlawwith index αx = 1.5 ± 0.1
(ACIS-S @ CXO)
R-band light curve analysis
a b
c
α = 1.07±0.05
α = 1.5±0.1
α1 = 0.8±0.1α2 = 1.6±0.2tb = 0.7±0.1 days
a
b
c
Broadband spectrum (tsed = 0.78 d)
βopt = 0.5 ± 0.1
βx = 1.0 ± 0.2
νc = 1.7 x 10 16 Hz
βx-opt= 0.84 ± 0.01
Closure Relations (1)(βx=βopt)
αx = 1.5 1.1
1.5 αopt Break
No break
βx = βopt
α = 3(p1)/4 = 1.2 ismα = (1-3p)/4 = 1.7 wind
α1 = 3(p-1)/4 = 1.2α2 = p = 2.6α1 = 3(p-1)/4+1/2 = 1.7 α2 = 3(p-1)/4+1 = 2.2
β=p/2
β=(p-1)/2
νc > νx p=2.6
sphere
jet
νc < νo p=1.6 α = (p+6)/4 = 1.9 α < 1
sphere
jet
ism
wind
α1 = 0.8α2 = 1.6
Closure Relations (2)(βx≠βopt)
βx = 1
α = 3(p-1)/4 = 0.75 α = (3p-1)/4 = 1.25
α1 = 3(p-1)/4 = 0.75 α2 = 3(p-1)/4+3/4 = 1.5 α1 = 3(p-1)/4+1/2 = 1.25α2 = 3(p-1)/4+1 = 1.75
βx=p/2
sphere
jet
νo < νc < νx
p = 2
βopt = 0.5 αx = 1.5
νc = 1.7 x 10 16 Hz
βopt = (p-1)/2 = 0.5νo < νc < νx
Eiso~1.8x1053 erg
Θjet=4°.3
Eγ= 5x1050 erg
ism
wind
ismwind
Summary•Optical 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