Long-GRBs and Hypernovae

Paolo A. Mazzali

Max-Planck Institut fϋr Astrophysik, Garching

Istituto Naz. di Astrofisica, Oss. Astron. Trieste

Astronomy Department and RESearch Centre for the Early Universe,

University of Tokyo

17.5.2006 Swift Meeting, Venice, 7.6.06 4

The Type Ic SN 1998bw

SN1998bw was a very bright

Type Ic SN, with very broad

absorption lines, indicative of

high-velocity ejecta (~0.1c),

and of

a very energetic explosion

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Type Ic SNe / Hypernovae

Broad lines

Large Kinetic Energy

“Hypernovae”

(only SN1998bw was associated with a GRB)

Narrow lines

“normal” KE (1 foe)

Normal SN Ic

Mazzali et al. 2002

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GRB/SN LCs are brightestOther broad-lined SNeIc w/o GRB are dimmer

Narrow-lined, non-GRB SNeIc are dimmest

Mazzali et al. 2002

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Light curves can be degenerate

if both M and E are allowed to vary

4/1

4/32/1

E

MLC

Iwamoto et al. 1998

SN 1998bw

LC

Determining the properties of SN 1998bw

17.5.2006 Swift Meeting, Venice, 7.6.06 9Iwamoto et al. 1998

SN 1998bw

Early-time spectra

Model CO138

ergKE 52105

17.5.2006 Swift Meeting, Venice, 7.6.06 10Mazzali et al. 2001

SN 1998bw

Late-time spectra

`Broad-line’ models

v~10,000 km/s

Fits FeII lines

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56Fe

16O

Spherical

Aspherical

FeII] 5200A

[OI] 6300A

Observed

Interpretation as an Aspherical explosion

Orientation 15 deg

Maeda et al. 2002

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SN2003dh: the nebular phase

The nebular spectrum shows a strong but narrow [O I]6300 line, like SN1998bw.

Model:

v = 5000 km/s

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A non-GRB HN: SN2002ap

KE = 4 foe

Mazzali et al.2002

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SN 2002ap: nebular models

Foley et al. 2003[O I] line is sharp: no asphericity?

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Non-GRB, broad lined SN Ic: 1997dq (= SN1997ef)

M(56Ni) = 0.15M⊙.

[OI] profile rounded: no asphericity?

(Mazzali et al. 2004)

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SN 83N 94I 02ap 97ef/dq 98bw

type Ib Ic Ic (Hypernovae)

MZAMS 15 15 21 34 40

MHe 4 4 6.6 13 16

MCO 2 2 4.5 11 14

MExpl 4 2.1 4.6 11.1 13.8

MRem 1.25 1.2 2.1 1.6 2.9

MEj 2.75 0.9 2.5 9.5 10.9

MHe 2.0 --- 0.1 --- ---

MCO 0.5 0.6 1.8 5.3 8

MIME(Si,S) 0.1 0.2 0.5 4 2

MNi 0.15 0.07 0.1 0.13 0.7

E51 1 1 5 19 50

GRB X X X X

Properties of Type Ib/c Super/Hypernovae

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?56MSMNiM

`bright’ branch:

Hypernovae

`faint’ branch:

SN1997D etc.

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?MSMKE

Again two branches

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Properties of GRB/HNe: Photospheric velocities

• Velocity also seems to be proportional to global properties: GRB/SNe have the highest velocities

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3 HNe/GRB

Same SN properties,

but very different

X-ray light curves

(and radio properties)

What is the diagnostic value?

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[OI] line profiles as tracers of Asphericity

• GRB/SNe show [O I] line narrower than [Fe II] lines aspherical explosions viewed near the axis of

energy injection (in agreement with presence of GRBs)• Lower energy, non-GRB/SNe do not share this.

• Are GRB/SNe the only aspherical SNe Ic?• No: normal SNe Ic are polarised• GRB/SNe may be the most aspherical SNe• What is the effect of the viewing angle?

looking for asphericity through late-time spectra: a Subaru-VLT campaign

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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 HN SN2002ap

• No GRB or XRF

Mazzali et al. (2005)

17.5.2006 Swift Meeting, Venice, 7.6.06 33

SN 2003jd:

• The [O I] 6300A line shows a double peak, suggesting an explosion similar to SN1998bw but viewed ~70° from the axis

(Subaru and Keck data, Mazzali et al. 2005)

an aspherical SN viewed off-axis

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What we see depends on where we look…

(von oben Gammablitz, von der Seite

Supernova?)

Mazzali et al. (2005)

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Was SN 2003jd also a GRB/HN?

• X-ray and Early Radio upper limits are not in contradiction with a GRB viewed off-axis

• Later Radio upper limits (Soderberg et al 2005) indicate no jet

Mazzali et al. 2005

17.5.2006 Swift Meeting, Venice, 7.6.06 41

FACTS• GRB/SNe (SNe Ic) are highly energetic (Eiso~50foe,

Etrue~10foe) and aspherical• Less energetic SNe Ic appear less aspherical• XRFs may be connected to less energetic SNe and

to off-axis events RADIO FACTS• HNe in GRBs (and XRFs) have radio • Off-axis HNe (and lower-E SNe Ic) show no radio… QUESTIONS1) Do all HNe make GRBs? (γ- and optical sample ≠)2) Where are the off-axis GRBs?3) What are the jet properties? (is there a jet at all)?

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SN2006aj: Bolometric Light Curve

SN2006aj was dimmer than other GRB/SNe (98bw, 03dh, 03lw)

Light curve similar to non-GRB broad-lined SN Ic 2002ap, but brighter

Estimate ~ 0.2M⊙ of 56Ni

Rapid LC evolution:

Mej3/E is small

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SN2006aj: Spectral modelling

Model similar to that used for SN2002ap, but with smaller Mej, KE, more 56Ni, less O.

O-dominated shell (~0.1Mʘ) at 20-25,000 km/s: shell ejection from progenitor?

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Evolution of photosheric velocity from spectral modelling

• SN2006aj never reached velocities as high as the GRB/SNe

• It is intermediate between non-GRB, broad-lined SNe Ic such as SN2002ap and SN1997ef, and GRB/SNe

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Light Curve model of SN2006aj

Explosion model gives a LC consistent with results of spectral fitting

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Placing SN2006aj in context

A neutron star-making SN

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Conclusions (for now….)

• SN 2006aj exploded as a CO core (a WR star) of ~3.2 Mʘ.

• The ejecta (~2Mʘ) consisted of O (~1.3Mʘ), and heavier elements (~ 0.5Mʘ), incl. ~ 0.2Mʘ of 56Ni.

• A NS (M ~ 1.4 Mʘ) was formed.

The progenitor of SN 2006aj was a small mass star (MZAMS ~ 20 Mʘ).

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Hypotheses, future checks

• Magnetar activity may have been responsible for the high energy transient

possible rebrightenings

• Asymmetries, orientation TBD when nebular spectra available (from July) – expect [O I] 6300,6363Å emission to be weak and broad

17.5.2006 Swift Meeting, Venice, 7.6.06 52

The Grand Scheme• Collapse of very massive (~35-50 M⊙), stripped

stars to Black hole makes GRB-HN (GRB can be very different, HN much less).

• Collapse of less massive star (~ 20 M⊙) to NS

can cause an XRF (via magnetic activity ?). • Some of these NS may later (when spin is lower)

harbour some short-hard GRBs (SGRs).• If system is a close binary (possibly necessary

for mass loss) it may end as a NS-NS merger and again produce a short-hard GRB.