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Les binaires gamma Un nouveau type de sources compactes de très haute énergie dans la Galaxie ?

Les binaires gamma Un nouveau type de sources compactes de très haute énergie dans la Galaxie ?. Guillaume Dubus. Very High Energy. HESS. Sky > 100 GeV New arrays Cherenkov Telescopes Spectacular increase in # of sources!. VHE sky 2005. LS I+61 303. +14 sources in Gal. Plane. close to

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Les binaires gamma Un nouveau type de sources compactes de très haute énergie dans la Galaxie ?

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  1. Les binaires gammaUn nouveau type de sources compactes de très haute énergie dans la Galaxie ? Guillaume Dubus GD - SF2A 2006

  2. Very High Energy HESS • Sky > 100 GeV • New arrays Cherenkov Telescopes • Spectacular increase in # of sources! GD - SF2A 2006

  3. VHE sky 2005 LS I+61 303 +14 sources in Gal. Plane close to 40 sources 4 3 GD - SF2A 2006

  4. Gamma-ray binaries: sources of VHE emission associated with binaries Aharonian et al. 2005, A&A, 442, 1 HESS MAGIC Aharonian et al., 2005, Science, 309, 746 Albert et al., 2006, Science GD - SF2A 2006

  5. Gamma-ray binaries: a new class of sources ? Aharonian et al. 2005, A&A, 442, 1 HESS MAGIC Aharonian et al., 2005, Science, 309, 746 Albert et al., 2006, Science GD - SF2A 2006

  6. All have massive companion + compact objectin eccentric orbit (4, 26, 1237 days) Copious source of seed photons in UV for IC Young pulsar in PSR B1259 Others: black hole or neutron star ? ESA Blondin mass transfer ? Blondin GD - SF2A 2006

  7. Gamma-ray binaries • Similarities • massive star (O, Be) e≠0 • TeV emission ~ 1033-34 erg/s • Low, ~ stable radio and X-ray emission (periodic radio outbursts in LS I+61 303 and PSR B1259-63) • Spectral energy distributions GD - SF2A 2006

  8. Similarities in SEDs GD - SF2A 2006

  9. Similarities in SEDs GD - SF2A 2006

  10. Similarities in SEDs GD - SF2A 2006

  11. Gamma-ray binaries Is there a common scenario ? Clue : PSR B1259-63 is a young 48 ms pulsar with dEspin/dt≈1036 erg/s Pulsar spindown powers a relativistic wind. VHE emission arises from containment of this relativistic wind (plerion): rotation-powered scenario GD - SF2A 2006

  12. In PSR B1259 there is no mass transfer: ram pressure of pulsar relativistic wind and stellar wind balance. • VHE emission due to particle acceleration at PW termination shock (small Crab  “binary plerion”) Maraschi & Treves 81, Tavani & Arons 97… GD - SF2A 2006

  13. Pulsar Wind Nebula emission • Proven mechanism (Crab) Proposed long ago for LS I+61 303 by Maraschi & Treves (1981) • Low steady emission • Radio pulse ? absorbed in strong stellar wind (tighter orbits in LS 5039, LS I+61 303) GD - SF2A 2006

  14. Apply to LS 5039 (LS I+61 303) • Take PSR B1259, put it in LS 5039 (LSI) • Pulsar spindown luminosity E (1036 erg/s) • ratio of wind magnetic/kinetic energy s(0.01) • mono-energetic e+e- in pulsar wind (gp=105) • Star wind parameters & orbit are constrained from optical data. GD - SF2A 2006

  15. Compact Pulsar Wind Nebula • Balance ram pressure of winds: shock close to pulsar • MHD shock conditions set B, flow speed, etc. • Acceleration to g-2 distribution gmax,min are set by jump conditions / radiative losses. • Inverse Compton (star photons) + synchrotron emission • Follow changes in flow conditions (B, v…) and particle distribution high E close to shock, low E further away stellar wind dM/dt=10-7 Msol/yr vw=2000 km/s GD - SF2A 2006

  16. MHD simulation of pulsar wind - ISM interaction ISM shocked pulsar wind material Pulsar wind Everything scales with RS Bucciantini et al. 2005 GD - SF2A 2006

  17. SED Pulsar wind parameters: 1036 erg/s, gw=105 and s=0.01 Break frequencies Emitted close to pulsar on timescale <10 ks Emitted far on timescale > Porb GD 2006, A&A in press (astro-ph/0605287) GD - SF2A 2006

  18. Evolution of particles in flow Electrons Emission GD - SF2A 2006

  19. There is a competition between three timescales Acceleration (gyrofrequency) Inverse Compton cooling on star photons (KleinNishina regime) Synchrotron cooling Model independent: pulsar wind only comes into play via B GD - SF2A 2006

  20. Qualitatively • High energy: synchrotron losses so steepening of electron distribution (flat X-rays, soft VHE spectra) • At lower energy, IC losses take over. Klein Nishina regime so hard VHE spectrum ~ injection spectrum. • Characteristic break frequencies See Moderski et al. 2005 GD - SF2A 2006

  21. Qualitatively • High energy: synchrotron losses so steepening of electron distribution (flat X-rays, soft VHE spectra) • At lower energy, IC losses take over. Klein Nishina regime so hard VHE spectrum ~ injection spectrum. • Characteristic break frequencies spectral change with orbit (simple pulsar model Bd) See Moderski et al. 2005 GD - SF2A 2006

  22. LS 5039: periastron Bd and d varies by ~2 only nsync varies (by ~2) most of the variability due to g-ray absorption GD - SF2A 2006

  23. LS 5039: apastron Bd and d varies by ~2 only nsync varies (by ~2) most of the variability due to g-ray absorption GD - SF2A 2006

  24. Gamma-ray opacity Gamma-rays of sufficient energy interact with ambient photon to create pairs g g  e+ e- Threshold Tight orbit + 1039 erg/s from star in UV = high opacity HESS! angle between photons LS 5039 orbit to scale GD - SF2A 2006

  25. Fraction of absorbed 30 GeV flux 10% 1% Observer at far right 50% 90% 99% Compact object orbit O6V star GD - SF2A 2006

  26. Fraction of absorbed 300 GeV flux GD - SF2A 2006

  27. Fraction of absorbed 3 TeV flux GD - SF2A 2006

  28. Fraction of absorbed 30 TeV flux GD - SF2A 2006

  29. LS 5039: Variation orbitale attendue 2004 data Max @ inferior conjunction Integrated flux GD, 2006, A&A, 451, 9 M. de Naurois à 14h GD - SF2A 2006

  30. TeV variation in LS I+61o303 Expected modulation due to absorption Albert et al. (MAGIC) 2006 • Max/min do not match + wide orbit wide so absorption moderate • Another reason for TeV flux variation in LS I+61 303: Be star companion: passage through dense equatorial wind will crush PWN (~like Earth magnetosphere during solar CME) Dubus 2006, A&A, 451,1 GD - SF2A 2006

  31. LS I+61o303 TeV modulation: passage through dense wind ? Apastron: diffuse polar wind, large shock distance, low B = VHE Periastron: dense equatorial wind, small shock distance, high B =noVHE 1036 erg/s, gw=105 and s=0.02 MAGIC periastron apastron Rs=3 (no absorption) GD 2006, A&A in press (astro-ph/0605287) GD - SF2A 2006

  32. Pulsar Wind Nebula emission • Proven mechanism (Crab) • Low steady emission (some variability), SEDs ok • Radio pulse absorbed in strong stellar wind • But LS 5039, LS I+61 303 have resolved radio emission ?! GD - SF2A 2006

  33. Massi et al. 2004 Paredes et al. 2000 Resolved radio emission • Resolved radio emission on scales of AU+ in LS 5039 and LS I+61 303 interpreted as microquasar jet. Confirmation of the long-held suspicion that small-scale analogues of AGN should also display VHE emission ?! GD - SF2A 2006

  34. Controversy: microquasar or pulsar ? Mirabel 2006 GD - SF2A 2006

  35. ~10 parsecs X-rays Radio Massi et al. 2004 Paredes et al. 2000 Resolved radio emission • Resolved radio emission on scales of AU+ in LS 5039 and LS I+61 303 interpreted as microquasar jet. • Butpulsars interacting w/ ISM have “comet” nebula the Mouse (Gaensler et al. 2004) GD - SF2A 2006

  36. ~10 parsecs X-rays Radio Aspect = cooling of advected particles in tail e.g. isolated pulsars + orbital change in geometry of interacting winds e.g. WR+O binary Dougherty et al., NRAO/AUI/NSF GD - SF2A 2006 http://vela.astro.ulg.ac.be/themes/stellar/massive/coll_e.html

  37. Large-scale emission: radio nebula Low E electrons last long; pulsar moves along its orbit so that flow direction changes with forb. LS 5039 i=60o scPorb denser “comet tail” GD - SF2A 2006

  38. Radio emission from comet tail VLBI observation Model 5 GHz emission Paredes et al. 2000 GD - SF2A 2006

  39. LS I+61o303 radio emission One-sided radio outflow model (5 GHz) only polar wind scPorb~100 AU with s =0.01 Longer Porb explains larger size vs LS 5039 GD - SF2A 2006

  40. PSR B1259-63 The spectral energy distribution, assuming same inputs as others (only orbit/star change) Resulting radio map close after periastron GD - SF2A 2006

  41. Conclusions: gamma-ray binaries as compact PWN • Interpretation as pulsar / stellar wind interaction explains similarities between VHE emitting binaries. • VHE emission occurs close to pulsar/star (gg absorption should modulate TeV flux in LS 5039). • Large scale emission can be explained by comet-like shocked material, radio morphology depends on orbit. GD - SF2A 2006

  42. Conclusions: gamma-ray binaries as compact PWN • Spectrum depends on magnetic field: pulsar wind physics on scales inaccessible before in a repeating environment. • Short-lived expected progenitors of HMXBs: about 30 in Galaxy Meurs & van den Heuvel 1989 Others in HESS galactic plane survey ? GD - SF2A 2006

  43. G359.95-0.04 SgrA* plerion ! ≈20” Chandra X-ray PWN are the new stars of the VHE sky GC source = plerion G359? Wang et al. 2006 Y. Gallant jeudi matin Established VHE emission from galactic compact objects • PlerionicSNR (e.g. Crab) • Binaries: compact plerions (*not* microquasars !) • Galactic Centre GD - SF2A 2006

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