On the Gamma-Ray Burst and Connection

Li-Xin Li (MPA) March 2007 There are cumulative evidences suggesting that all long-duration GRBs arise from the death of massive stars and are accompanied by supernovae.

Spectroscopically confirmed GRB-SN:

GRB 980425 / SN 1998bw: z = 0.0085 GRB 030329 / SN 2003dh: z = 0.1687 GRB 031203 / SN 2003lw: z = 0.1055 GRB 060218 / SN 2006aj: z = 0.0335

A less direct way: observing the rebrightening and/or flattening ('red bump') in the late GRB afterglow GRB 980326, R-band lightcurve Bloom et al '99, Nature, 401, 453

The red bump is interpreted as the emergence of SN lightcurve (but alternative interpretation exists)

Zeh et al (2004) suggest that all long-duration GRBs are associated with SNe All of the four spectroscopically confirmed GRB-connected SNe are among a special class of Type Ic SNe, called the broad-lined SNe, which are characterized by smooth and featureless spectra.

They are also called 'hypernovae'. Short-duration GRBs are often found in inactive galaxies and have no evidence of association with SNe GRB 980425/SN 1998bw

The GRB: Detected by BATSE/BeppoSAX Single pulse, duration = 35 s redshift z = 0.0085 (host galaxy) 48 E  ,iso≈10 erg , E  , peak≈55 keV

The SN: Discovered in the error box of the GRB, 2.5 days after the GRB. It is one of the most unusual Type Ic SNe ever seen. It is very bright, and has very strong radio emission. (Galama et al 1998) 52 M SN , peak≈−18.65, E K≈5×10 erg

M ej≈10 Msun , M Nikel≈0.38−0.48 Msun GRB 030329/SN 2003dh

The GRB: Detected by HETE-2 Double pulses, duration = 23 s redshift z = 0.1687 (afterglow) 52 E  ,iso≈1.7×10 erg , E  , peak≈79 keV

The SN: Discovered 6 days after the GRB as a bump in the optical lightcurve, whose spectrum closely resembles that of SN 1998bw. (Hjorth et al 2003; Stanek et al 2003) 52 M SN , peak≈−18.79, E K≈4×10 erg

M ej≈8 Msun , M Nikel≈0.25−0.45 Msun GRB 031203/SN 2003lw

The GRB: Detected by INTEGRAL Single pulse, duration = 40 s redshift z = 0.1055 (host galaxy) 50 E  ,iso≈10 erg , E  , peak≈159 keV

Sazonov et al 2004, Nature, 430, 646 The SN: Discovered 10 days after the GRB. It is extremely luminous and has a spectrum closely resembling that of SN 1998bw. (Malesani et al 2004; Thomsen et al 2004) 52 M SN , peak≈−18.92, E K≈6×10 erg

M ej≈13 Msun , M Nikel≈0.45−0.65 Msun GRB 060218/SN 2006aj

The GRB: Detected by Swift Single pulse, duration = 2000 s redshift z = 0.0335 (afterglow/supernova) 49 E  ,iso≈6×10 erg , E  , peak≈4.9 keV

The SN: Discovered 3 days after the GRB. It is intrinsically less luminous than GRB-SNe, but more luminous than normal SNe Ibc. (Modjaz et al 2006; Pian et al 2006; Sollerman et al 2006) 51 M SN , peak≈−18.16, E K≈2×10 erg

M ej≈2 Msun , M Nikel≈0.2 Msun (Mazzali et al 2006) SN 1998bw SN 2003dh SN 2003lw SN 2006aj

SN 1994I Li 2006, MNRAS, 372, 1357

Pian et al 2006, Nature, 442, 1011

m=0.28, =0.72, H 0=73

It appears that SN 2006aj is closer to normal Type Ibc SNe than to GRB-SNe Correlation between the GRB Peak Energy and the SN Maximum Luminosity (Li 2006)

The Pearson linear correlation coefficient  x −x y − y r i i 0.997 = 2 2 =  xi−x  yi− y corresponding to P = 0.003 for zero correlation.

4.97 LSN , peak E , peak=90.2 keV   1043 erg / s 

 =0.28,  =0.72, H =72 m  0 Li 2006, MNRAS, 372, 1357 Correlation between the GRB Peak Energy and the SN Nickel Mass (Li 2006)

Approximately, the maximum luminosity of SNe powered by radioactive decays is proportional to the mass of Nickel generated in the SN ejecta.

Solid line:

log E , peak=3.133.51log M Nickel Dashed line:

log E , peak=3.744.97 log M Nickel

Pearson r = 0.95, corresponding to P = 0.05 for zero correlation. Li 2006, MNRAS, 372, 1357 Relation between the GRB Isotropic Energy and the SN Maximum Luminosity (Li 2006)

Short GRBs

Amati (2006):

0.49 E ,iso E =97 keV   , peak  1052 erg 

Hence we have

10 L E ≤0.86×1052 erg SN , peak  ,iso  1043 erg s−1 

Soft GRBs Are Mildly Relativistic

An analysis by Amati (2006; 45 GRBs) shows that the GRB peak spectral energy can be described by a log-normal distribution with mean of 350 keV.

GRB 980425: 55 keV GRB 030329: 79 keV GRB 031203: 159 keV GRB 060218: 4.9 keV GRB 030329

Softer GRB spectrum indicates larger jet angle and smaller Li 2006, MNRAS, 372, 1357 Lorentz factor: [Data from Bloom et al 2003; Berger

log  jet=3.84−1.17 log E , peak & Becker 2005; Grupe et al 2006; Racusin et al 2005; Amati 2006] It is generally thought that short GRBs are harder than long GRBs. Then, do short GRBs have larger Lorentz factors than long GRBs? Application of the GRB-SN Relation to SNe without GRBs (I)

45 SN 1994I in M51 (d = 8.4 Mpc): E peak=0.07 keV ; Eiso≤4×10 erg looks ~10 times fainter than GRB 980425

44 SN 1997ef: E peak=0.017 keV ; Eiso≤2.7×10 erg

44 SN 2002ap: E peak=0.016 keV ; Eiso≤2.3×10 erg

SN 2004aw: one of the most well observed Type Ic SNe, z=0.0163 (Taubenberger et al 2006). It is intrinsically slightly brighter than 1994 I, but fainter than 1998bw by 1.3mag. No GRB has been found. 46 E peak=0.12 keV ; Eiso≤1.4×10 erg Application of the GRB-SN Relation to SNe without GRBs (II)

Therefore, if normal SNe Ibc are accompanied by GRBs, the GRBs should be extremely underluminous in the gamma-ray band despite their close distances. Their peak spectral energy is expected to be in the soft X-ray and UV band.

A Possible Outlier: SN 2003jd in MCG-01-59-021 (z=0.01886)

SN 2003jd has been argued to be evidence of an aspherical explosion viewed from a direction near the equatorial plane (Mazalli et al 2005). Slightly less luminous than 1998bw but brighter than 2006aj. However, radio observation ~1.6 yr after the explosion has found no signature of GRB (Soderberg et al 2006). Application of the GRB-SN Relation to Cosmological GRBs

Applying the correlation to GRB 990123 at z=1.6 with an intrinsic peak spectral energy 2000keV (isotropic energy = 2.66e54 erg; one of the brightest GRBs), we get that the maximum luminosity of the SN is 1.87e43 erg/s, only 2 times brighter than SN 1998bw. GRB 060614 and GRB 060505: Exception for the GRB-SN Connection?

GRB 060614: z=0.125, T90=102s; GRB 060505: z=0.089, T90=4s.

No SN has been found, down to limits hundreds of times fainter than SN 1998bw, fainter than any Type Ic SN ever observed (Della Valle et al 2006; Fynbo et al 2006; Gal-Yam et al 2006; Gehrels et al 2006).

The existence of long GRBs without SNe poses a challenge to both the collapsar and the merging NS model, and opens the door on a new classification scheme for GRBs (See, Gal-Yam et al 2006; Gehrels et al 2006; King et al 2007).

However, GRB 060614 and its 'host' may be a chance superposition (P~1 percent; Cobb et al 2006). GRB 060505 could simply be a short burst (Ofek et al 2007). Summary

1. It appears that all long GRBs are associated with SNe (however, GRBs 060614 and GRB 060505)

2. The GRB peak spectral energy is correlated with the SN maximum luminosity

3. Normal Type Ibc SNe may be accompanied by bursts with spectra peaking in the soft X-ray and UV band

4. The results suggest that the critical parameter characterizing the GRB-SN connection is the large peak luminosity (or the large mass of Nickel).