Gamma-ray binaries: hydrodynamics and high energy emission

Transcription

1 Gamma-ray binaries: hydrodynamics and high energy emission Astrid Lamberts University of Wisconsin-Milwaukee Collaborators: Guillaume Dubus (Grenoble, France) - Sébastien Fromang (CEA-Saclay, France) - Romain Teyssier (ETH-Zurich, Switserland) Midwest Relativity Meeting, October, 27, 2013 A. Lamberts Gamma-ray binaries MWRM / 14

2 Gamma-ray binaries : young pulsar + massive star PSR B (taken from Mirabel et al, 2006) colliding wind region similar to massive stars (Dubus, 2006) Particle acceleration at relativistic shock very high energy emission A handful of systems discovered so far (e.g LS 5039/PSR B1259/LSI ). A. Lamberts Gamma-ray binaries MWRM / 14

3 A wealth of observations SED of PSR B (Fermi Collab, 2011) LSI radio map (Dhawan et al., 2006) Energy peaks in gamma-ray band! Emission up to TeV Extended radio emssion, change with orbital phase A. Lamberts Gamma-ray binaries MWRM / 14

4 A wealth of observations How to explain emission? Emission from radio to γ : which are the emitting regions? where do modulations come from? Geometry of interaction region? (Impact of Be disk, instabilities) SED for PSR B (Fermi Collab, 2011) A. Lamberts Gamma-ray binaries MWRM / 14

5 Why is this important? Very interesting astrophysical conditions γ-ray binaries probe the wind at much shorter distances than pulsar wind nebulae Understanding of fundamental astrophysical processes : relativistic hydro, particle acceleration, associated non-thermal emission Complex to model Highly relativistic, (magneto) hydrodynamics Particle acceleration and non-thermal emission Complex, 3D geometry, different length scales Time evolution We need a good toolbox! A. Lamberts Gamma-ray binaries MWRM / 14

6 Hydrodynamical evolu0on : RAMSES with special rela0vity (Lamberts et al, 2013) Overall structure : Similar to colliding stellar winds (e.g. PiNard, 2009; Lamberts et al, ) Emission proper0es : Post- process simula0on with non- thermal par0cles injected at shock (Dubus, Lamberts, 2014, in prep). A. Lamberts Gamma-ray binaries MWRM / 14

7 (Very) brief introduction to RAMSES RAMSES (Teyssier, 2002) solves the Euler equations Based on finite volume method ideal for discontinuities Allows Adaptive Mesh Refinement (AMR) Local increase of resolution according to gradients well-suited for discontinuities AMR map and density map A. Lamberts Gamma-ray binaries MWRM / 14

8 (Special) relativistic hydro codes Necessary for : pulsar wind nebulae, gamma-ray bursts, active galactic nuclei jets, microquasar jets, γ-ray binaries e.g. GENSESIS (Aloy et al, 1999), PLUTO (Mignone et al, 2007), r-enzo (Wang et al, 2008), ATHENA (Beckwith et al, 2011)... different degrees of adaptive mesh refinement different physical features : magnetohydrodynamics, equations of state Lorentz factors Γ 10 while real flows may have Γ = 10 6 Methods still under development A. Lamberts Gamma-ray binaries MWRM / 14

9 Some equations HD U t + 3 i=1 F i x i = 0 U = ρ ρv i F i = 1 2 ρv 2 + P γ 1 ρv i ρv i v j + Pδ ij v i (E + P) RHD (c 1) D Γρ ργv i U = m i = E Γ 2 ρhv i Γ 2 ρh P, F i = ρhγ v i v j + Pδ ij ρhγ 2 v i RHD vs HD Similar structure but coupling through Lorentz factor Γ = 1 1 v 2 Additional constraint v<c, More complex Equation of State A. Lamberts Gamma-ray binaries MWRM / 14

10 Geometry of the colliding wind region 2D simulation (no orbital motion) with vp =.99 (Γ ' 7). Study of Kelvin-Helmholtz instability PULSAR STAR Density (with/ without KH) and mixing No significant difference with Newtonian case at this distance Relativistic effects impact position of discontinuities but scaling relations Kelvin-Helmholtz instability develops, what impact at large scale? why use relativistic simulations? A. Lamberts Gamma-ray binaries MWRM / 14

11 RHD Lorentz factor boosted emission STAR Doppler boosting (taken from Dubus, et al, 2010)/ Lorentz factor map Modulated emission in LS 5039 Geometrical effects dominate Absorption cannot explain X-ray modulation (Szostek et al, 2011) A. Lamberts Gamma-ray binaries MWRM / 14

12 Non-thermal emssion Model a distribution of particles Injection at shock with E particles = E magnetic = ɛe total at shock Follow particles along field lines including (Begelman, Li, 1992) Adiabatic losses (from code), synchrotron losses, anisotropic inverse compton losses because of companion star Determine emission in the shocked wind : inverse compton + synchrotron - pair creation Relativistic Doppler boosting and excentricity effects taken into account A. Lamberts Gamma-ray binaries MWRM / 14

13 Non-thermal emssion Emission maps : KeV, GeV, TeV, and spectrum Extended emission Two distinct populations Spectral energy distribution averaged over orbit compares well with observations A. Lamberts Gamma-ray binaries MWRM / 14

14 Conclusions : γ-ray binaries γ-ray binaries Close to the binary, γ-ray binaries show similar structure to stellar binaries with small relativistic effects RHD simulations provide Lorentz factor and exact shock structure necessary for emission Coupling between simulations and non thermal emission works well extened high-energy emission, agreement with observed SED More to come 3D model of LS 5039 (Dubus, Lamberts, 2014, in prep) lightcurves, spectra constrains on system orbital parameters and companion Suited for extension to other gamma-ray binaries (with Be disk), and other high energy systems (X-ray binaries, pulsar wind nebulae..) A. Lamberts Gamma-ray binaries MWRM / 14