LNGS Summer Institute 2005
GRB: Modern Status
Elena Pian - INAF, Trieste Astronomical Observatory, Italy
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
long
Bimodal
distribution
of GRB
durations
short
The progenitors of
short bursts are still
to be identified!!!
Binary
neutron stars?
Kulkarni 2000
E. Pian – LNGS, 13 Sep 2005
GRB980425
Supernova 1998bw (Type Ic)
z = 0.0085
E. Pian – LNGS, 13 Sep 2005
GRB030329/SN 2003dh
z = 0.168
ESO VLT + FORS
Photospheric velocity
Si II 6355
Hjorth et al. 2003
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
SN1998bw
Galama et al. 2000
E. Pian – LNGS, 13 Sep 2005
X-ray Flashes
E. Pian – LNGS, 13 Sep 2005
XRF030723
Fynbo et al. 2004
Soderberg et al. 2004
Tominaga 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)
SNe with hypernova characteristics have been detected, although they are not
accompanied by a GRB (SNe 1997dq, 1997ef, 2002ap, 2004aw…); see also
IPN survey
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)
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
[FeII]
5200A
• A spherically symmetric
explosion of a massive star
would result in the opposite
[OI] 6300A
O
Fe
SN 1998bw
E. Pian – LNGS, 13 Sep 2005
2D explosion: KE=11foe, MBH(final)=5.9M, M(56Ni)=0.11M
0.7 s
Outflow
Inflow
1.5 s
Maeda et al. 2002
E. Pian – LNGS, 13 Sep 2005
Aspherical explosion:
confined nucleosynthesis
Spherical
FeII]
5200A
[OI] 6300A
SN 1998bw
56Fe
Aspherical
Orientation
15 deg
16O
E. Pian – LNGS, 13 Sep 2005
Maeda et al. 2002
The bright Type Ic SN 2003jd
Discovered 25 Oct 2003; distance: 80 Mpc
Courtesy: K. Kawabata
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:
an aspherical SN viewed off-axis
Observations:
Subaru+FOCAS, at 330 days
Keck+LRIS, at 370 days
Subaru
The [O I] 6300A line
shows a double peak,
suggesting an explosion
similar to SN1998bw but
viewed ~70° from the
axis
Mazzali et al. 2005, Science 308, 1284
E. Pian – LNGS, 13 Sep 2005
SN2003jd: an aspherical supernova viewed off-axis
Keck+LRIS
Subaru+FOCAS
Mg I]
[Ca II]
[Fe II]
[O I]
Mazzali et al. 2005
E. Pian – LNGS, 13 Sep 2005
[O I] nebular
emission
[O I] line:
strong
dependence
on viewing
angle
Mazzali et al. 2005
E. Pian – LNGS, 13 Sep 2005
Was SN 2003jd also a GRB/HN?
radio
• Radio and X-ray
upper limits are not
in contradiction
with a GRB viewed
off-axis
X-ray
Mazzali et al. 2005
E. Pian – LNGS, 13 Sep 2005
Swift
Launched 20 Nov 2004
E. Pian – LNGS, 13 Sep 2005
Swift localization of GRBs
E. Pian – LNGS, 13 Sep 2005
Examples of Swift-XRT light curves
Steep decline common
Gets shallower around here
Nousek et al. 2005
E. Pian – LNGS, 13 Sep 2005
GRB990123
WFC
MECS
2-10 keV
15-28 keV
PDS
Maiorano et al. 2004
Corsi et al. 2004
E. Pian – LNGS, 13 Sep 2005
GRB990123 (z = 1.6)
E. Pian – LNGS, 13 Sep 2005
Fruchter et al. 1999
GRB041219a: Optical flash from internal shocks
RAPTOR
Internal shock
ROTSE-I
Reverse shock
Akerlof et al. 1999; Vestrand
et al. 2005
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 ISM
In variable density
Environment
Guidorzi et al. 2005
E. Pian – LNGS, 13 Sep 2005
GRB050509b (T90=0.04s)
1 keV X-ray light curve
BAT+XRT emission consistent with a single decay rate of 1.2±0.09
Gehrels et al. 2005
E. Pian – LNGS, 13 Sep 2005
Comparison with other X-ray transients
E. Pian – LNGS, 13 Sep 2005
GRB050509b
Host galaxy
Bloom et al. 2005
E. Pian – LNGS, 13 Sep 2005
GRB050509b (z = 0.22)
Upper limits on optical
Flux are inconsistent
With supernova
Hjorth et al. 2005
E. Pian – LNGS, 13 Sep 2005
GRB050724 looks long to BAT (T90=153s), but would be short to BATSE (<1s)
GRB050724 (z = 0.257)
t-4 ν-1
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)
SFR < 0.03 Msun/yr
Bloom et al. 2005
E. Pian – LNGS, 13 Sep 2005
Isotropic irradiated –ray energy vs redshift
GRB/SN
Short GRB
GRB050904
z = 6.29
E. Pian – LNGS, 13 Sep 2005
Conclusions
The nebular spectrum of the Type Ic energetic SN2003jd is different
from 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 only aspherical SNe Ic? No, normal Ic are polarized
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 are
Preferentially detected at lower redshifts, and in galaxies with scarce
Star formation. The evidence that they are not associated with supernovae
is increasing. They are probably double neutron star mergers
Optical flashes probe the early emission mechanisms and circumburst
medium
E. Pian – LNGS, 13 Sep 2005