e. pian – lngs, 13 sep 2005 elena pian - inaf, trieste astronomical observatory, italy lngs summer...
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E. Pian – LNGS, 13 Sep 2005
Elena Pian - INAF, Trieste Astronomical Observatory, Italy
LNGS Summer Institute 2005
GRB: Modern Status
E. Pian – LNGS, 13 Sep 2005
Outline
Connection between Supernovae and long GRBs / X-ray Flashes
Swift: early GRB counterparts
Short Gamma-Ray Bursts
E. Pian – LNGS, 13 Sep 2005
Bimodal distribution of GRBdurations
short
long
The progenitors of short bursts are still to be identified!!!
Binary neutron stars?
Kulkarni 2000
E. Pian – LNGS, 13 Sep 2005
GRB980425Supernova 1998bw (Type Ic)
z = 0.0085
E. Pian – LNGS, 13 Sep 2005
GRB030329/SN 2003dh
Si II 6355
Hjorth et al. 2003
z = 0.168
ESO VLT + FORS
Photospheric velocity
E. Pian – LNGS, 13 Sep 2005
GRB031202/SN2003lw
z = 0.105
ESO VLT FORS
Malesani et al. 2004
E. Pian – LNGS, 13 Sep 2005
z = 0.695
Galama et al. 2000
SN1998bw
E. Pian – LNGS, 13 Sep 2005
X-ray Flashes
E. Pian – LNGS, 13 Sep 2005
XRF030723
Fynbo et al. 2004
Tominaga et al. 2004
Soderberg et al. 2004
E. Pian – LNGS, 13 Sep 2005
Is there a unifying scheme for SNe and GRBs?
Four clear cases of SN-GRB association have been detected spectroscopically, all are Type Ic SNe. In all of these, the SN is very powerful (high luminosity, large kinetic energy), i.e. it is a “Hypernova” (Paczynski 1998; Iwamoto et al. 1998)
The rate of GRBs (taking into account collimation) corresponds to the relative rate of hypernovae with respect to the total number of Ic SNe (i.e. ~5%, Podsiadlowski et al. 2004)
SNe with hypernova characteristics have been detected, although they are not accompanied by a GRB (SNe 1997dq, 1997ef, 2002ap, 2004aw…); see also IPN survey
Do all hypernovae have jets and produce GRBs, so that only those aligned with the line of sight are detected?
Can we test this “unified scenario”?
E. Pian – LNGS, 13 Sep 2005
Signatures of asphericity in SN1998bw
• In nebular spectra of SN1998bw, Fe lines are broader than O lines
• A spherically symmetric explosion of a massive star would result in the opposite
[FeII] 5200A
[OI] 6300A
SN 1998bw
O
Fe
E. Pian – LNGS, 13 Sep 2005
0.7 s
1.5 s
2D explosion: KE=11foe, MBH(final)=5.9M, M(56Ni)=0.11M
Outflow
Inflow
Maeda et al. 2002
E. Pian – LNGS, 13 Sep 2005
56Fe
16O
Spherical
Aspherical
FeII] 5200A
[OI] 6300A
SN 1998bw
Aspherical explosion: confined nucleosynthesis
Orientation 15 deg
Maeda et al. 2002
E. Pian – LNGS, 13 Sep 2005
The bright Type Ic SN 2003jd
Courtesy: K. Kawabata
Discovered 25 Oct 2003; distance: 80 Mpc
E. Pian – LNGS, 13 Sep 2005
The bright Type Ic SN 2003jd
• SN 2003jd was as bright at peak as SN1998bw (Mv = -18.7)
• Early-time spectra had broad lines, similar to hypernova SN2002ap
• No GRB or XRF
E. Pian – LNGS, 13 Sep 2005
SN 2003jd:
The [O I] 6300A line shows a double peak, suggesting an explosion similar to SN1998bw but viewed ~70° from the axis
an aspherical SN viewed off-axis
Mazzali et al. 2005, Science 308, 1284
Observations:Subaru+FOCAS, at 330 daysKeck+LRIS, at 370 days
Subaru
E. Pian – LNGS, 13 Sep 2005
Mg I]
[Fe II] [O I]
[Ca II]
Subaru+FOCAS
Keck+LRIS
SN2003jd: an aspherical supernova viewed off-axis
Mazzali et al. 2005
E. Pian – LNGS, 13 Sep 2005
[O I] line:strong dependenceon viewingangle
Mazzali et al. 2005
[O I] nebularemission
E. Pian – LNGS, 13 Sep 2005
Was SN 2003jd also a GRB/HN?
• Radio and X-ray upper limits are not in contradiction with a GRB viewed off-axis X-ray
radio
Mazzali et al. 2005
E. Pian – LNGS, 13 Sep 2005
SwiftLaunched 20 Nov 2004
E. Pian – LNGS, 13 Sep 2005
Swift localization of GRBs
E. Pian – LNGS, 13 Sep 2005
Steep decline common
Gets shallower around here
Examples of Swift-XRT light curves
Nousek et al. 2005
E. Pian – LNGS, 13 Sep 2005
Maiorano et al. 2004
GRB990123
Corsi et al. 2004
WFC
PDS
MECS2-10 keV15-28 keV
E. Pian – LNGS, 13 Sep 2005
GRB990123 (z = 1.6)
Fruchter et al. 1999
E. Pian – LNGS, 13 Sep 2005
GRB041219a: Optical flash from internal shocks
Akerlof et al. 1999; Vestrand et al. 2005
RAPTORInternal shock
ROTSE-IReverse shock
E. Pian – LNGS, 13 Sep 2005
Optical Flashes
Guidorzi et al. 2005
E. Pian – LNGS, 13 Sep 2005
GRB050502a z = 3.793
Liverpool 2m telescope+ Robonet consortium
Forward shock in ISMIn variable densityEnvironment
Guidorzi et al. 2005
E. Pian – LNGS, 13 Sep 2005
BAT+XRT emission consistent with a single decay rate of 1.2±0.09
1 keV X-ray light curveGRB050509b (T90=0.04s)
Gehrels et al. 2005
E. Pian – LNGS, 13 Sep 2005
Comparison with other X-ray transients
E. Pian – LNGS, 13 Sep 2005
GRB050509b
Bloom et al. 2005
Host galaxy
E. Pian – LNGS, 13 Sep 2005
GRB050509b (z = 0.22) Upper limits on opticalFlux are inconsistentWith supernova
Hjorth et al. 2005
E. Pian – LNGS, 13 Sep 2005
t-4 ν-1
GRB050724 looks long to BAT (T90=153s), but would be short to BATSE (<1s)
GRB050724 (z = 0.257)
E. Pian – LNGS, 13 Sep 2005
Optical afterglow of the short GRB050724 (T = 0.25 s)
Berger et al. 2005
E. Pian – LNGS, 13 Sep 2005
Host Galaxy of the Short GRB050724 (z = 0.257)
Bloom et al. 2005
SFR < 0.03 Msun/yr
E. Pian – LNGS, 13 Sep 2005
Isotropic irradiated –ray energy vs redshift
GRB/SN
Short GRB
GRB050904z = 6.29
E. Pian – LNGS, 13 Sep 2005
ConclusionsThe nebular spectrum of the Type Ic energetic SN2003jd is differentfrom that of SN1998bw: it exhibits a double-peaked [O I] emission line,which suggests an aspherical geometry and an equatorial view. This is consistent with the lack of a detected GRB, and could support a unified scenario for SNe and GRBs
Are hypernovae the most aspherical SNe? Possibly, and this would be related to the presence of GRBs
In this picture, X-ray flashes may be off-axis GRBs or weaker explosions
Short GRBs have afterglows similar to those of long GRBs. They arePreferentially detected at lower redshifts, and in galaxies with scarceStar formation. The evidence that they are not associated with supernovaeis increasing. They are probably double neutron star mergers
Are hypernovae the only aspherical SNe Ic? No, normal Ic are polarized
Optical flashes probe the early emission mechanisms and circumburst medium
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