The Empirical Grounds of the SN-GRB Connection. M. Della Valle INAF-Napoli ICRANet-Pescara

Transcription

1 The Empirical Grounds of the SN-GRB Connection M. Della Valle INAF-Napoli ICRANet-Pescara

2 Outline Supernova Taxonomy GRB-SN properties GRB-SN census GRB D / SN 2010bh Open questions

3 Supernova taxonomy thermonuclear < 8M H core-collapse > 8M Si I II IIL IIP IIn Ia He Ic Ib bright faint very bright High KE SNe-Ic Hypernovae GRB-SNe

4 Properties of GRB-SNe (broad-lined SNe-Ic) Lack of H and He in the ejecta: SNe-Ic Very broad features: large expansion velocity (0.1c) Very large luminosity: large 56 Ni mass ( ~ 0.5±0.2 M ) Energy (non-relativistic ejecta) ~ erg 10 larger than usual CC-SNe Explosions are aspherical (profiles of nebular lines O vs. Fe)

5 Interpreting spectra: position of elements Immediately after explosion SNe go into homologous expansion, i.e. vel is proportional to the radius: i) Relative positions of elements do not change ii) Inner elements move slower than the outer ones

6 Late time spectra of SN1998bw O Fe FWHM Fe lines broader than O lines [FeII] 5200A Observation [OI] 6300A Expansion Observer Never in Spherical Model Maeda et al. 2002

7 Spherical FeII] 5200A [OI] 6300A Observed Aspherical Orientation 15 deg II IIb Ib Ic 1%. 4% Maeda et al. 2002

8 SN 1998bw SN 1987A GRB-SNe are very energetic events = Maeda et al Aspherical explosion 2008 E ~ ergs E ~ ergs

9 GRB-SN Census GRB SN z Ref. GRB SN 1998bw Galama et al GRB SN 2002lt Della Valle et al GRB SN 2003dh 0.16 Hjorth et al Stanek et al GRB SN 2003lw 0.11 Malesani et al GRB SN 2006aj Campana et al GRB A SN 2005nc Della Valle et al GRB SN 2008D GRB SN 2008hw 0.53 GRB SN 2009nz 0.49 GRB D SN 2010bh 0.06 Soderberg et al Della Valle et al Cobb et al Chornoch et al Bufano et al. 2010

10 Local GRB-SNe (z<0.2) GRB SN z Ref. GRB SN 1998bw Galama et al GRB SN 2002lt Della Valle et al GRB SN 2003dh 0.16 Hjorth et al Stanek et al GRB SN 2003lw 0.11 Malesani et al GRB SN 2006aj Campana et al GRB A SN 2005nc Della Valle et al GRB SN 2008D GRB SN 2008hw 0.53 GRB SN 2009nz 0.49 GRB D SN 2010bh 0.06 Soderberg et al Della Valle et al Cobb et al Chornoch et al Bufano et al. 2010

11 Are GRB progenitors the same at different z? GRB SN z Ref. GRB SN 1998bw Galama et al GRB SN 2002lt Della Valle et al GRB SN 2003dh 0.16 Hjorth et al GRB SN 2003lw 0.11 Malesani et al GRB SN 2006aj Campana et al GRB A SN 2005nc Della Valle et al GRB SN 2008D GRB SN 2008hw 0.53 GRB SN 2009nz 0.49 GRB D SN 2010bh 0.06 Soderberg et al Della Valle et al Cobb et al Chornoch et al. 2010

12 up to z ~ 1 GRB GRB Della Valle et al Sahu et al Bjornsson et al GRB A Lazzati et al Della Valle et al Garnavich et al. 2003

13 These observations allow us to use the rebrightenings observed in the AGs as tracers of SNe. Rebrightenings are observed up to z ~ 1, then the Ca connection between GRBs and SNe can be confidently extended up to z ~ 1 (~8 Gyr) Della Valle et al. 2003

14 The newborn baby GRB D/SN 2010bh

15 INTENSIVE VLT FOLLOW-UP No evidence for He lines the progenitor was largely stripped of its He envelope Ic

16 Chornock et al The inferred expansion velocity at ~20d past maximum is a factor 2 larger than it was observed in 1998bw larger explosion energy (modelling > erg). This is too large for a slow magnetar central engine (c.f. GRB /2006aj) (see Fan et al. 2010)

17 Oversimplified Scheme for GRB-SN associations - an almost isotropic component carrying most energy erg and mass (~10M ) SN event 30,000 km/s -highly collimated component (4-10 for HL-GRBs) containing a tiny fraction of the mass (10-4/-5 M ) moving at G ~ x GRB line of sight SN ~25 for LL-GRBs line of sight SN + GRB

18 Messing up matters: GRB Low redshift: z = SN search? Short GRBs: T < 2 s Gehrels et al Long GRBs: T > 2 s Mangano et al s 50s 100s

19 Factor >100 Looking for a SN Late time: host galaxy contribution (no variation) Upper limit: M V > (3 ) Della Valle et al (see also Gal-Yam et al Fynbo et al. 2006)

20 Scenarios without Supernova Binary merging mechanisms similar to those proposed to power short GRBs (Gehrels et al. 2006)

21 Scenarios with Supernova -13.5

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24 SN 2008ha is the first faint, hydrogen deficient, low-energy core-collapse supernovae ever detected. Potential dark SN (GRB progenitor)?

25 Massive star evolution Zampieri et al. (2003) Nomoto et al. ( 2005) Smartt et al. (2008) GRB : SN with small explosion energy low expansion velocity most 56 Ni falls back into the BH small 56 Ni mass in the ejecta << 10-4/-5 M 56 Ni Dark Supernovae (see DV et al. 2006, Nomoto et al and Tominaga et al. 2007)

26 GRBs are very rare phenomena (compared to SN explosions) < 0.4-3% of all SNe-Ibc produce GRBs (Guetta & DV 2007) < 0.7 % (Soderberg et al. 2010) (< 99% c.l.) What causes some small fraction of SNe-Ibc to produce observable GRBs, while the majority do not?

27 Special conditions are requested to stars to be GRB progenitors: i) to be massive ~ M (Raskin et al. 2008) ii) H/He envelopes to be lost before the collapse of the core, i.e. the GRB progenitor is a WR star (Campana et al. 2006) iii) low metallicity and star forming environments (Fruchter et al. 2006, Modjaz et al. 2010) iv) high rotation (Yoon et Langer 2005; Campana et al. 2008) v) binarity (Smartt et al. 2008)

28 What produces the observed variety in long duration GRB phenomenology? i) HL-GRBs ( erg) + bright HN (GRB / 2003dh) ii) LL-GRBs ( erg) + faint HN (GRB /SN 2006aj) iii) LL-GRBs ( erg) + bright HN (GRB D/SN 2010bh) iv) vll-grb ( erg) + SN-Ibc (GRB /SN 2008D) v) HNe w/out GRBs (e.g. 2002ap) vi) GRBs w/out (bright?) SN (GRB ) Mass of the Progenitors + binarity Different Central Engines

29 All truths are easy to understand once they are discovered; the point is to discover them. (G. Galilei)