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