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Associations of H.E.S.S. VHE  -ray sources with Pulsar Wind Nebulae

Associations of H.E.S.S. VHE  -ray sources with Pulsar Wind Nebulae. Yves Gallant (LPTA, U. Montpellier II, France) for the H.E.S.S. Collaboration “The Multi-Messenger Approach to High Energy Gamma-ray Sources” Barcelona, July 5, 2006. “Established” VHE Pulsar Wind Nebula

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Associations of H.E.S.S. VHE  -ray sources with Pulsar Wind Nebulae

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  1. Associations of H.E.S.S. VHE -ray sourceswith Pulsar Wind Nebulae Yves Gallant (LPTA, U. Montpellier II, France) for the H.E.S.S. Collaboration “The Multi-Messenger Approach to High Energy Gamma-ray Sources” Barcelona, July 5, 2006 • “Established” VHE Pulsar Wind Nebula • Crab Nebula, G0.9+0.1, MSH 15-52 • Vela X, Kookaburra (2), HESS J1825-137 • Association criteria, pulsar energetics • Other possible associations with PWNe • Summary and prospects

  2. H.E.S.S. spectrum (A&A, submitted): Spectral curvature, Consistent with IC expectations Radio, optical, X-rays synchrotron PWN emission mechanisms: the Crab Nebula • Assume leptonic model: synchrotron and Inverse Compton emission • Relativistic electrons and positrons created and accelerated by the pulsar Target photons : CMB, interstellar IR, stellar photons, synchrotron (SSC)…

  3. VHE plerion in the composite SNR G0.9+0.1 Radio (90cm), LaRosa et al. (2000) H.E.S.S. excess: A&A 432, L25 (2005) • radio shell and PWN (Helfand & Becker 1984); X-ray non-thermal plerion (e.g. Porquet, Decourchelle & Warwick 2003 with XMM-Newton) • H.E.S.S. excess compatible with point source at plerion position • spectrum compatible with IC and X-ray synchrotron => B = 6G

  4. “Composite” SNR: radio and X-ray shell nonthermal X-ray nebula young pulsar B1509-58 H.E.S.S. detection: A&A 435, L17 (2005) First angularly resolved PWN in VHE -rays Synchrotron emission  ne B2 whereas IC emission  ne nph, with nph  uniform Spatial distribution of high-energy e, independently of B-field variations Pulsar Wind Nebula in MSH 15-52(a.k.a. G 320.4-1.2)

  5. In composite Vela SNR (at 290 pc) Matches hard X-ray emission seen with ROSAT and ASCA, at position of (larger) radio nebula Vela X Nebula “crushed” by asymmetric reverse shock? (Blondin et al. 2001) Spectral curvature :  F peaks in VHE “VHE observations of inverse Compton scattering of the CMBR allow direct inference of the spatial and spectral distribution of non-thermal electrons” Detection of the Vela X plerionic nebula(A&A 448, L43, 2006) contours : X-rays (ROSAT)

  6. HESS J1420-609 : associated X-ray (K3) and radio plerion, and energetic PSR J1420-6048 HESS J1418-607 : associated X-ray and radio plerion (“Rabbit”), candidate pulsar Large, offset nebulae in both cases contours : radio (ATCA) • Target photon densities vary smoothly (except close to stars, e.g. PSR B1259-58) => VHE -ray observations reveal high-energy electron sources in the Galaxy • H.E.S.S. Galactic plane survey (extended to -60o in longitude in 2005) found new PWN associations Two new H.E.S.S. sources in the Kookaburra complex(A&A 2006, in press, astro-ph/0606311)

  7. Pulsar offset from source, but profile peaks near PSR position Much smaller, X-ray nebula trailing in the same direction VHE gamma-ray spectral index steepening away from pulsar! (first spectral variations) Consistent with energy losses of electrons (also X-ray size) HESS J1825-137 as the nebula of PSR B1823-13(A&A 2006, submitted)

  8. 7 (+1 : PSR B1259-63) “established” VHE -ray PWN associations • consistent MWL spectral model (synchrotron + IC), and • positional and morphological match to lower-energy counterpart, or • VHE morphological and spectral evidence for association with known pulsar (e.g. HESS J1825-137 with PSR B1823-13), and consistent MWL data Association Criteria • pulsar energy loss rate (”spindown luminosity”) derived from observed timing parameters: • pulsar distance D derived from radio dispersion measure DM • as a criterion for pulsar association with TeV source, estimate ratio / (4  D)2 vs F0.3-30 TeV(0.3 - 30 TeV : arbitrary energy range, but representative of H.E.S.S.; actual range depends on zenith angle and high-energy statistics) • Caveat: assumes short particle lifetime; if delayed energy release (from particles injected earlier in history), apparent efficiency increases • “Established” association efficiencies range from ~0.01% (Crab, Vela) through ~0.5% (MSH 15-52, Kookaburra) to 2.2% (HESS J1825-137) Pulsar Energetics

  9. PSR B1800-21 : D = 3.9 kpc Required efficiency : 2.4% Other possible counterpart: G8.7-0.1 PSR J1617-5055 : D = 6.8 kpc Required efficiency : 1.3% HESS J1804-216 HESS J1616-508 Possible associations of VHE sources with known pulsars Two sources from Galactic plane scan : ApJ 636, 777 (2006) Deeper X-ray and/or VHE observations needed to confirm associations…

  10. No obvious counterpart; most energetic pulsar in field, PSR J1301-6305, has ATNF pulsar catalogue: D = 15.8 kpc based on Taylor & Cordes (1993) Galactic ne model Latest model (“NE2001”, Cordes & Lazio 2003) yields D = 6.65 kpc!(factor > 5 in D2) (now use NE2001 distances throughout, but only such major discrepancy) Current implied efficiency in 0.3 - 30 TeV band : ~ 7% PSR J1301-6305 HESS J1303-631 : first H.E.S.S. unidentified sourceA&A 439, 1013 (2005) M. Beilicke / H.E.S.S. Coll.

  11. More data since ApJ (2006) paper:Increased significance of “tail” towards PSR J1702-4128 D = 4.8 kpc, => required efficiency : ~ 11%(for entire HESS source) Poster by S. Carrigan, forthe H.E.S.S. Collaboration Statistical analysis of pulsar catalogue and HESS sources: significant correlation New sources possibly associated with energetic pulsars: HESS J1809-193 HESS J1718-384 HESS J1702-420 Other possible assocations with known pulsars

  12. G0.9+0.1 : no pulsar detected, but consistent MWL plerion in shell HESS J1813-178 / SNR G12.82-0.02 could show evidence for a central X-ray plerion in XMM-Newton observations [talk by S. Funk] HESS J1634-472 may be associated with SNR G337.2+0.1, revealed by XMM-Newton as a probable Crab-like SNR [poster by J. Combi et al.] HESS J1834-087 appears associated with G23.3-0.3 (W41) but more centrally concentrated? plerionic counterpart in the radio? Associations with possible PWNe in composite SNRs

  13. 7 (+1) “established” associations of VHE -ray sources with PWNe : most numerous class of identified Galactic VHE -ray sources If Inverse Compton : target photons approximately known and uniform=> direct inference of electron spatial and spectral distribution Galactic survey in VHE -rays reveals high-energy electron sources in Galaxy Often large offset and physical size : several old PWNe, strongly affected by passage of asymmetric reverse shock? 6 additional “possible” associations of H.E.S.S. sources with energetic pulsars, but required efficiency and/or offset often large… In 3 additional probable associations with shell SNRs, the VHE -ray emission may be from an embedded plerionic component of the SNR (without a pulsar detection yet, e.g. G0.9+0.1) More MWL data on these objects needed to study possible associations VHE gamma-ray astronomy provides new, independent observational input into the physics of pulsar wind nebulae The fastest-growing class of identified Galactic -ray source? Summary and Prospects

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