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Inverse Compton Scattering in Be-XPBs

Inverse Compton Scattering in Be-XPBs. Brian van Soelen University of the Free State supervisor P.J. Meintjes. Outline. Modelling inverse Compton gamma-ray emission from Be-XPBs PSR B1259-63 Modelling Be stars Isotropic scattering Anisotropic scattering Solid angle System geometry.

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Inverse Compton Scattering in Be-XPBs

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  1. Inverse Compton Scattering in Be-XPBs Brian van Soelen University of the Free State supervisor P.J. Meintjes

  2. Outline • Modelling inverse Compton gamma-ray emission from Be-XPBs • PSR B1259-63 • Modelling • Be stars • Isotropic scattering • Anisotropic scattering • Solid angle • System geometry Aharonian et al., (2005) A&A, 442, 1 SA SKA 2010 Postgraduate Bursary Conference

  3. PSR B1259-63 • Detected pulsar • Be star & pulsar in a ~3.4 year orbit • Eccentricity e = 0.87 • Pulse period ~48 ms • SS 2883 is a Be star • Fast rotators ν≈ 0.7 νcritical • Have an equatorial circumstellar disc • Unpulsed emission detected: • Radio • TeV gamma-rays • X-rays periastron SA SKA 2010 Postgraduate Bursary Conference

  4. PSR B1259-63 • OB star & pulsar binaries • The interaction between the pulsar and the Be star winds results in a bow shock • Pressure balance between the pulsar wind and the Be star wind • Shock front randomizes the electrons into a power law distribution • Electrons cool through synchrotron and IC scattering. • Photons from the Be star are up-scattered to TeV gamma-rays Chernyakova et al. (2009) Taken from Gaensler & Slane (2006), ARA&A, 44, 17 SA SKA 2010 Postgraduate Bursary Conference

  5. The Circumstellar Disc • As the disc grows and shrinks there is a change in the size of the disc and the IR excess • We want the solution to be general, i.e. we can consider any size disc of any orientation, in each case the solid angle will change. • The solid angle will change during the orbital period, especially close to periastron X Persei SA SKA 2010 Postgraduate Bursary Conference

  6. Modelling: Be stars • Data • UBV (Westerlund & Garnier,1989) • JHK (2MASS) • 8.28 & 12.13 µm (MSX) • Pulsar becomes eclipsed at ~20 days before periastron • Binary seperation ~ 50 Rstar • Star • Star temperature: 25000K • log g: 3.5 • Disc • n: 2.37 • log X*: 7.87 • Rdisc: 50 Rstar (held) • Tdisc: 12500 K (held) • Theta: 5 ° (held) SA SKA 2010 Postgraduate Bursary Conference

  7. Modelling: Isotropic IC • Flux increase > 2 below a few GeV • The exception is for broad energy distribution • We expect that the anisotropic calculation will have a larger influence. Van Soelen & Meintjes (2010) SA SKA 2010 Postgraduate Bursary Conference

  8. Anisotropic IC scattering Need to speed up the calculations • Coded in Fortran, 64bit Intel compiler • To speed things up this is run on one of the 8 CPU node at the HPC at UFS • 26 x Dell 1950 Nodes with the following configuration: • 2 x Intel Xeon Quad Core CPUS (8 Cores Per node) • 8 - 16GB Memory • Upgrade • 17 x Super Micro nodes with the following configuration: • 4 x AMD Opteron 6174 12-Core CPUS (48 Cores per node) • Thanks to Albert van Eck Depends on the size of the solid angle Cerutti (2007) Master’s Dubus, Cerutti & Henri (2008), A&A, 477, 691 SA SKA 2010 Postgraduate Bursary Conference

  9. Modelling: Solid Angle • For integration over a sphere the solid angle is simple: • For integration over a disc it becomes more complicated SA SKA 2010 Postgraduate Bursary Conference

  10. Modelling: Solid Angle Taken from: Pomme et al. (2003) & John Keightley SA SKA 2010 Postgraduate Bursary Conference

  11. Modelling: Orbital System • We know all the parameters and angles in the orbital system, we need to convert this to a “disc” system. • We’ll consider a co-ordinate system (K), centred at the pulsar, and parallel to the lines of semi-minor and semi-major axis. • This will be converted into K’, the co-ordinate system based on the disc. SA SKA 2010 Postgraduate Bursary Conference

  12. Modelling: Anisotropic IC K system, based on orbit K’ system, based on disc SA SKA 2010 Postgraduate Bursary Conference

  13. Model: Photon contribution SA SKA 2010 Postgraduate Bursary Conference

  14. Model: Photon contribution • Constraints on the angles • Only a disc contribution • You are looking at the edge of disc where it is obscuring that star. • Use a disc constraints • Whole of the visible star • Rotated to co-ordinate system centred on star H ρ SA SKA 2010 Postgraduate Bursary Conference

  15. Model: Photon contribution • So do a bunch of geometry and you can solve for θ1,θ2 and θ3 • This gives the limits on θ which must be used to check where we are looking, i.e. disc or star • These constraints need to be included in nph(ε,θ,φ) SA SKA 2010 Postgraduate Bursary Conference

  16. Anisotropic IC scattering • With disc contribution added • Assuming face-on disc at periastron • Complicated geometry can be ignored. • Just increase α* • Viewing angle is correct, except that the TeV is eclipse at periastron by the circumstellar disc • Much larger influence than the isotropic case SA SKA 2010 Postgraduate Bursary Conference

  17. Anisotropic IC scattering • With disc contribution added • Assuming face-on disc at periastron • Complicated geometry can be ignored. • Just increase α* • Viewing angle is correct, except that the TeV is eclipse at periastron by the circumstellar disc • Much larger influence than the isotropic case SA SKA 2010 Postgraduate Bursary Conference

  18. Anisotropic IC scattering • There is an alternative model for PSR B1259-63 • Gamma-rays created via hadronic collisions in the disc • X-rays created via IC scattering • Unlike the isotropic case, in the effects of the disc are noticeable at lower energy levels. • Same photon spectrum, • p = 2.2 • γ = 100 - 200 SA SKA 2010 Postgraduate Bursary Conference

  19. Anisotropic IC scattering • The geometry results are being “double-checked” • Once that’s done it can be coded • Can be used to predict changes in the IC flux • Applicable to other systems, • LSI+61°303 • HESS J0632+057? • New ones? MeerKAT SKA SA SKA 2010 Postgraduate Bursary Conference

  20. SKA/MeerKAT • Searching for new binary systems. • Radio morphology • Jets? • Radio monitoring of known systems • LMC/SMC? PSR B1259-63 1.38 GHz (>0.2 mJy) 2.38 GHz (>0.12 mJy) SA SKA 2010 Postgraduate Bursary Conference

  21. Observations • Multi-wavelength campaign being organized for December’s periastron passage: • SS 2883 & circumstellar disc • SAAO 1.9m • SALT • SAAO 1m • Boyden 1.5m • IRSF • VISIR/VLT • X-ray , gamma-rays • XMM-Newton ? • Fermi ? optical spectroscopy optical photometry Near & mid-IR photometry SA SKA 2010 Postgraduate Bursary Conference

  22. Thank you Acknowledgements M.J. Coe, L.J. Townsend, E. Bartlette P. Charles, A. Rajoelimanana SKA Bursary Program Albert van Eck & HCP at the UFS References Aharonian et al., (2005) A&A, 442, 1 Aharonian et al. (2006) A&A, 460, 743 Aharonian et al. (2009) A&A, 507, 389 Blumenthal & Gould (1970) Rev. of Modern Physics, 42, 237 Chernyakova et al. (2009) MNRAS, 397, 2123 Cerutti (2007) Master’s Dubus, Cerutti & Henri (2008), A&A, 477, 691 Fargion et al. (1997) Z. Phys. C 74, 571 Gaensler & Slane (2006), ARA&A, 44, 17 Johnston et al. (1996) MNRAS, 279, 1026 Johnston et. al., (1999) MNRAS, 302, 277 Johnston et al., (2005) MNRAS, 358, 1069 Pomme_etal_2003NIMPA.505..286P Telting et al., (1998) MNRAS, 296, 785 Van Soelen & Meintjes (2010) MNRAS in press Waters (1986) A&A, 162, 121

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