1 / 25

Collapsar Accretion and the Gamma-Ray Burst X-Ray Light Curve

Collapsar Accretion and the Gamma-Ray Burst X-Ray Light Curve. Chris Lindner Milos Milosavljevic , Sean M. Couch, Pawan Kumar. Gamma Ray Bursts. High Energy (foe) Highly Variable Two Types Short Duration – Associated with compact object mergers

Download Presentation

Collapsar Accretion and the Gamma-Ray Burst X-Ray Light Curve

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Collapsar Accretion and the Gamma-Ray Burst X-Ray LightCurve Chris Lindner MilosMilosavljevic, Sean M. Couch, Pawan Kumar

  2. Gamma Ray Bursts • High Energy (foe) • Highly Variable • Two Types • Short Duration – Associated with compact object mergers • Long Duration – Associated with Core-Collapse supernova • Observable in multiple wavelengths

  3. X-ray Light Curve Typically, long duration GRB exhibit 3 distinct phases in the first 103 s • Phase 0 – 101 s – Prompt Phase • Phase I – 102 s – Fast Decay • Phase II – 103 s – Plateau Phase X-ray flares often occur in fast decay and plateau phase The x-ray light curve for GRB 050315 from Vaughan et al. 2006

  4. The Collapsar model • Outer H layers stripped away off of a massive Wolf-Rayetprogenitor • Center of star collapses into a neutron star or black hole • Rotation causes a disk (torus) to form • Magnetic (?) Jets form and are able to push through the star • Luminosity is modulated by central object accretion rate http://www.tls-tautenburg.de/research/klose/GRB.review.html Simulation from MacFadyen

  5. The Collapsar model:Questions • Does the accretion history in the collapsarmodel actually mimic the variability in the X-ray light curve? • If so, what causes the joined, distinct phases? • Is there enough material to account for late time (> 103 -104 s) activity? • What is the source of viscosity in the accretion disk? MRI? • Will jets actually form? Why? • What causes X-ray flares? • What is the mechanism of explosion? Jets? Neutrinos? Both?

  6. Kumar, Narayan, & Johnson 2008 • Constructed an analytical model of collapsar accretion • Use 14 solar mass progenitor star from Woosley & Heger 2006 • Use a basic power law model for rotation profile • Used α-model viscosity (α=.1) • Compute onset of accretion shock (~102 s), a steep decline phase, and plateau phase

  7. Lindner, Milosavljevic, Couch, Kumar 2009 (Submitted to ApJ) • 2D Hydrodynamic (HD) simulation of collapsar model using FLASH AMR HD code • Start with same 14 Solar Mass Heger & Woosley model (16TI) WR – high rotation – low metalicity • Use an explicit shear viscosity (modified α model) • Set up a modified outflow inner boundary at (Rmin=5.0E7 to 2E8 cm) • Ran simulations for up to 1000 s

  8. Lindner, Milosavljevic, Couch, Kumar 2009 (Submitted to ApJ) • 2D Hydrodynamic (HD) simulation of collapsar model using FLASH AMR HD code • Start with same 14 Solar Mass Heger & Woosley model (16TI) WR – high rotation – low metalicity • Use an explicit shear viscosity (modified α model) • Set up a modified outflow inner boundary at (Rmin=5.0E7 to 2E8 cm) • Ran simulations for up to 1000 s

  9. Results: (play movies)

  10. Results: Mass Accretion

  11. Phase 0: Quasiradialaccretion

  12. Phase I: Funnel and Thick Disk Accretion

  13. Phase II: Funnel Outflow, Thick Disk Accretion

  14. Phase II: Funnel Outflow, Thick Disk Accretion

  15. Future Work • 2D MHD Simulations • 3D Simulations – X-ray Flares? • Jets and Neutrinos • Early Universe Progenitors

  16. Conclusions • The three initial phases of the GRB X-ray light curve fit well with the three phases of accretion history in the collapsar model • Phase 0: Quasiradial Accretion • Phase I: Funnel and Thick Disk Accretion • Phase II: Funnel Outflow, Thick Disk Accretion Future Work • 2D MHD Simulations • 3D Simulations – X-ray Flares? • Jets and Neutrinos • Early Universe Progenitors

  17. Pressure

  18. Pressure • Gravity

  19. Pressure • Gravity • Magnetic Fields

  20. Pressure • Gravity • Magnetic Fields • Radiation

  21. Basic Equations of Hydrodynamics Continuity of Mass: Momentum Continuity: Conservation of Energy: Poisson Equation:

  22. -Each grid point contains a full set of fluid variables -Hydrodynamic equations allow grid coordinates to ‘talk’ to each other

More Related