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Gamma-Ray Bursts from Magnetar Birth. Brian Metzger NASA Einstein Fellow (Princeton University). In collaboration with. Dimitrios Giannios (Princeton) Todd Thompson (OSU) Niccolo Bucciantini (Nordita) Eliot Quataert (UC Berkeley) Jon Arons (Berkeley).

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gamma ray bursts from magnetar birth

Gamma-Ray Bursts from Magnetar Birth

Brian Metzger NASA Einstein Fellow (Princeton University)

In collaboration with

Dimitrios Giannios (Princeton)

Todd Thompson (OSU)

Niccolo Bucciantini (Nordita)

Eliot Quataert (UC Berkeley)

Jon Arons (Berkeley)

Metzger, Giannios, Thompson, Bucciantini & Quataert 2011

Prompt Activity of GRBs (Raleigh, NC 03/05/2011)

slide2

Constraints on the Central Engine

Canonical GRB Lightcurve

  • Energies - E~ 1049-52 ergs
  • Rapid Variability (down to ms) -
  • Duration - T ~10-100 seconds
  • Steep Decay Phase after GRB
  • Ultra-Relativistic, Collimated Outflow with  ~ 100-1000
  • Association w Energetic Core Collapse Supernovae
  • Late-Time Central Engine Activity (Plateau & Flaring)

from Nakar 07

NS

BH

versus

slide4

The Fates of Massive Stars (Heger et al. 2003)

Assumes supernova energy ~ 1051 ergs!

collapsar failed supernova model woosley 93
Collapsar “Failed Supernova” Model (Woosley 93)

(e.g. MacFadyen & Woosley 1999; Aloy et al. 2000; MacFadyen et al. 2001; Proga & Begelman 2003; Takiwaki et al. 2008; Barkov & Komissarov 2008; Nagataki et al. 2007; Lindler et al. 2010)

MacFadyen & Woosley 1999

Zhang, Woosley & Heger 2004

  • Energy -Accretion / Black Hole Spin
  • Duration -Stellar Envelope In-Fall
  • Hyper-Energetic SNe -Delayed Black Hole Formation

or Accretion Disk Winds

  • Late-Time Activity -Fall-Back Accretion
slide6

Core Collapse with Magnetic Fields & Rotation(e.g. LeBlanc & Wilson 1970; Bisnovatyi-Kogan 1971; Akiyama et al. 2003)

  • Collapsar Requirements:
  • Angular Momentum
  • Strong, Ordered Magnetic Field (e.g. Proga & Begelman 2003; McKinney 2006)

Neutron Star Mass

Time

slide7

Neutron Stars are Born Hot, Cool via -Emission: ~1053 ergs in KH ~ 10-100 s

Key Insight :(Thompson, Chang & Quataert 04)

  • Neutrinos Heat Proto-NS Atmosphere (e.g. e + n  p + e-)  Drives Thermal Wind Behind SN Shock(e.g. Qian & Woosley 96)

Before SN Explosion

After SN Explosion

Neutrino-Heated Wind

Burrows, Hayes, & Fryxell 1995

slide8

Evolutionary Wind Models(BDM et al. 2010)

NS Cooling

(Pons+99; Hudepohl+10)

3D Magnetosphere Geometry(e.g. Bucciantini et al. 2006; Spitkovsky 2006)

Calculate:

In terms of

Initial Rotation Period P0 , Dipole Field Strength Bdip & Obliquitydip

slide9

Example Solution

Max Lorentz Factor (Solid Line)

Jet Power (Dotted Line)

slide10

Jet Collimation via Stellar Confinement (Bucciantini et al. 2007, 08, 09; cf. Uzdensky & MacFadyen 07; Komissarov & Barkov 08)

Zooming Out

  • Assume Successful Supernova(35 M ZAMS Progenitor; Woosley & Heger 06)
  • Magnetar with Bdip= 31015G, P0=1 ms

Jet vs. Wind Power

Average jet power and mass-loading match those injected by central magnetar

slide11

Jet Breaks Out of Star

Max Lorentz Factor (Solid Line)

Jet Power (Dotted Line)

Wind becomes relativistic at t ~ 2 seconds;Jet breaks out of star at tbo ~ R/c ~ 10 seconds

slide12

GRB

Jet Breaks Out of Star

Max Lorentz Factor (Solid Line)

Jet Power (Dotted Line)

High Energy Emission (GRB) from t ~ 10 to ~100 s as Magnetization Increases from 0 ~  ~ 30 to ~ 103

slide13

GRB Emission - Still Elusive!

Relativistic Outflow ( >> 1)

Slide from B. Zhang

~ 107 cm

Central Engine

GRB / Flaring

Afterglow

What is jet’s composition? (kinetic or magnetic?)

Where is dissipation occurring? (photosphere? deceleration radius?)

How is radiation generated? (synchrotron, IC, hadronic?)

slide14

GRB Emission - Still Elusive!

Relativistic Outflow ( >> 1)

Photospheric IC

Slide from B. Zhang

~ 107 cm

Central Engine

GRB / Flaring

Afterglow

What is jet’s composition? (kinetic or magnetic?)

Where is dissipation occurring? (photosphere? deceleration radius?)

How is radiation generated? (synchrotron, IC, hadronic?)

slide15
Prompt Emission from Magnetic Dissipation(e.g. Spruit et al. 2001; Drenkahn & Spruit 2002; Giannios & Spruit 2006)

e.g. Coroniti 1990

Non-Axisymmetries  Small-Scale Field Reversals (e.g. striped wind with RL ~ 107 cm) Reconnection at speed vr ~ c

 Bulk Acceleration   r1/3& Electron Heating

slide16

Time-Averaged Light Curve

Metzger et al. 2010

Jet Break-Out

Optically-Thick

Optically-Thin

slide17

Time-Averaged Light Curve

Metzger et al. 2010

Jet Break-Out

Optically-Thick

Optically-Thin

Spectral Snapshots

IC Tail

Synch

t ~ 15 s

t ~ 30 s

E FE (1050 erg s-1)

Hot Electrons  IC Scattering (-rays) and Synchrotron (optical)

E (keV)

slide18

Parameter Study

3 1014 G < Bdip< 3 1016 G, 1 ms < P0 < 5 ms,  = 0, /2

GRB Energy (ergs)

solid = oblique, dotted = aligned

slide20

avg-L Correlation

avg  L1-1.5

Prediction: More Luminous / Energetic GRBs  Higher 

Ave Magnetization avg

Ave Wind Power (erg s-1)

slide21

avg-L Correlation

avg  L1-1.5

Prediction: More Luminous / Energetic GRBs  Higher 

Ave Magnetization avg

Assuming Magnetic Dissipation Model

Ave Wind Power (erg s-1)

Epeak Liso0.11 00.2 0.33

Agreement withEpeak  Eiso0.4(Amati+02)

and Epeak  Liso0.5(Yonetoku+04) Correlations

Ave Peak Energy Epeak

Epeak Liso0.5

Peak Isotropic Jet Luminosity (erg s-1)

slide22

End of the GRB = Neutrino Transparency

Ultra High- Outflow 

- Full Acceleration to ~  Difficult (e.g. Tchekovskoy et al. 2009)

- Reconnection Slow

- Internal Shocks Weak (e.g. Kennel & Coroniti 1984)

TGRB ~ T thin ~ 10 - 100 s

slide23

End of the GRB = Neutrino Transparency

Ultra High- Outflow 

- Full Acceleration to ~  Difficult (e.g. Tchekovskoy et al. 2009)

- Reconnection Slow

- Internal Shocks Weak (e.g. Kennel & Coroniti 1984)

Steep Decline Phase

TGRB ~ T thin ~ 10 - 100 s

slide24

GRB

Late-Time (Force-Free) Spin-Down

SD

slide25

GRB

X-ray Afterglow

Late-Time (Force-Free) Spin-Down

`Plateau’

Willingale et al. 2007

SD

e.g. Zhang & Meszaros 2001; Troja et al. 2007; Yu et al. 2009; Lyons et al. 2010

Time after trigger (s)

the diversity of magnetar birth
The Diversity of Magnetar Birth

Classical GRB E~1050-52 ergs, jet < 1,  ~ 102-103

Low Luminosity GRB

Bdip (G)

Thermal-Rich GRB (XRF?)E~1050 ergs, jet ~ 1,  < 10

Buried Jet

P0 (ms)

slide27

Recap - Constraints on the Central Engine

  • GRB Duration ~ 10 - 100 seconds& Steep Decay Phase

-Time until NS is transparent to neutrinos

  • Energies - EGRB ~ 1050-52 ergs

- Rotational energy lost in ~10-100 s (rad. efficiency ~30-50%)

  • Ultra-Relativistic Outflow with  ~ 100-1000

- Mass loading set by physics of neutrino heating (not fine-tuned).

  • Jet Collimation

- Exploding star confines and redirects magnetar wind into jet

  • Association with Energetic Core Collapse Supernovae

- Erot~ESN~1052 ergs - MHD-powered SN associated w magnetar birth.

  • Late-Time Central Engine Activity

- Residual rotational (plateau) or magnetic energy (flares)?

predictions and constraints
Predictions and Constraints
  • Max Energy - EGRB, Max ~ few 1052 ergs

- So far consistent with observations (but a few Fermi bursts are pushing this limit.)

- Precise measurements of EGRB hindered by uncertainties in application of beaming correction.

  • Supernova should always accompany GRB

- So far consistent with observations.

  •  increases monotonically during GRB and positively correlate with EGRB

- Testing will requires translating jet properties (e.g. power and magnetization) into gamma-ray light curves and spectra.

summary
Summary
  • Long duration GRBs originate from the deaths of massive stars, but whether the central engine is a BH or NS remains unsettled.
  • Almost all central engine models require rapid rotation and strong magnetic fields. Assessing BH vs. NS dichotomy must self-consistently address the effects of these ingredients on core collapse.
  • The power and mass-loading of the jet in the magnetar model can be calculated with some confidence, allowing the construction of a `first principles’ GRB model.
  • The magnetar model provides quantitative explanations for the energies, Lorentz factors, durations, and collimation of GRBs; the association with hypernova; and, potentially, the steep decay and late-time X-ray activity.
  • Magnetic dissipation is favored over internal shocks and the emission mechanism because it predicts a roughly constant spectral peak energy and reproduces the Amati-Yonetoku correlations