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Locating PeV Cosmic-Ray Accelerators: Future Detectors in Multi-TeV Gamma-Ray Astronomy Adelaide, 6-8 December 2006

Josep M. Paredes. HE AND VHE EMISSION FROM X-RAY BINARIES. Locating PeV Cosmic-Ray Accelerators: Future Detectors in Multi-TeV Gamma-Ray Astronomy Adelaide, 6-8 December 2006. OUTLINE. X-ray binaries How many microquasars we know µqs as HE and VHE γ -ray sources:

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Locating PeV Cosmic-Ray Accelerators: Future Detectors in Multi-TeV Gamma-Ray Astronomy Adelaide, 6-8 December 2006

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  1. Josep M. Paredes HE AND VHE EMISSION FROM X-RAY BINARIES Locating PeV Cosmic-Ray Accelerators: Future Detectors in Multi-TeV Gamma-Ray Astronomy Adelaide, 6-8 December 2006

  2. OUTLINE • X-ray binaries • How many microquasars we know • µqs as HE and VHE γ-ray sources: Theoretical point of view Observational point of view 4. µqs, gamma-ray binaries,…….. 5. Summary

  3. Microquasars: X-ray binaries with relativistic jets XB: A binary system containing a compact object (NS or a stellar-mass BH) accreting matter from the companion star. The accreted matter forms an accretion disc, responsible for the X-ray emission. A total of 280 XB (Liu et al. 2000, 2001). HMXBs: (131) Optical companion with spectral type O or B. Mass transfer via decretion disc (Be stars) or via strong wind or Roche-lobe overflow. LMXBs:(149) Optical companion with spectral type later than B. Mass transfer via Roche-lobe overflow. 8 HMXBs 35 LMXBs 280 XB 43 (15%) REXBs At least 15 microquasars Maybe the majority of RXBs are microquasars (Fender 2001)

  4. MICROQUASARS IN OUR GALAXY High Energy Detections Name Mcomp Radio Jet INTEGRAL BATSE COMPTEL EGRETOthers (M) p/tappSize Note30-50 keV 40-100 keV 20-100 keV 160-430 keV 1-30 MeV >100 MeV (AU)(significance) (count/s) (significance) (mCrab) High Mass X-ray Binaries LSI+61303  p 0.4 10 700 Prec ? 7.12.4 ± 0.55.2 5.1 ± 2.1 yes?3EGJ0241+6103 MAGIC V4641 Sgr9.6 t 9.5  LS 50395.4 p 0.18 10 1000 Prec ? 8.01.7 ± 0.2 10.7 3.7 ± 1.8 yes? 3EGJ1824 1514 HESS SS 433 11±5? p 0.26 ~104 106Prec. 94.7 5.2 ± 0.2 21.7 0.0 ± 2.8  Hadronic, X-ray jet Cygnus X-110.1 p  ~40 4651 876.7 ±0.3 1186.8 924.5± 2.5 yes  Cygnus X-3 p 0.69 ~104 Radio outb. 1096 78.3 ± 0.3 197.8 15.5 ± 2.1  Low Mass X-ray Binaries Circinus X-1 t > 15 >104 99.1 0.6 ± 0.2 3.8 0.3 ± 2.6   XTE J1550-5649.4 t 2~103 X-ray jet 738 55.3±0.217.1 -2.3 ± 2.5   Scorpius X-1 1.4 p 0.68 ~40 2422 24.7 ± 0.3 460.6 9.9 ± 2.2   GRO J1655-407.02 t 1.1 8000 Prec?592.7 ± 0.240.6 23.4± 3.9   GX 339-4 5.8± 0.5 t  < 4000 306 46.7 ± 0.2 89.0 58.0 ± 3.5  1E 1740.7-2942 p  ~106 147.3 4.32 ± 0.03 92.461.2 ± 3.7   XTE J1748-288 > 4.5? t 1.3 > 104 -12.4   GRS 1758-258p  ~106 813 75.3± 0.174.3 38.0 ± 3.0 GRS 1915+10514± 4 t 1.21.7 ~10 104Prec?2556 123.4 ± 0.2 208.8 33.5 ± 2.7   The 3rd IBIS/ISGRI soft gamma-ray survey catalog(Bird et al. 2006, ApJ, in press, astro-ph/0611493) BATSE Earth Occultation Catalog, Deep Sample Results(Harmon et al. 2004, ApJS, 154, 585)

  5. Wind • Visible  radio • (free-free) • M • MULTIFREQUENCY EMISSION IN MICROQUASARS Adapted from Chaty (Ph.D. Thesis) • Compacts jets • Radio  IR •  X? •  gamma? • (synchrotron) • Donor star • IR  UV • (thermal) • Disc • + corona ? • X  IR • therm + non therm • Large scaleejection • Radio & X • gamma? • Interaction with environment • Dust ? • IR  mm • (thermal)

  6. BLACK HOLE STATES • Black holes display different X-ray spectral states: • Low/hard state (a.k.a. power-law state). Compact radio jet. • High/soft state (a.k.a. steep power-law state). No radio emission. • Intermediate and very high states  transitions. Transient radio emission. Fender 2001, ApSSS 276, 69

  7. High/Soft Low/Hard Corbel et al. 2000, A&A 359, 251 Grebenev et al. 1993, A&ASS 97, 281

  8. MQs as high-energy γ -ray sources Theoretical point of view Leptonic models: SSC Atoyan & Aharonian 1999, MNRAS 302, 253 Latham et al. 2005, AIP CP745, 323 EC Kaufman Bernadó et al. 2002, A&A 385, L10 Georganopoulos et al. 2002, A&A 388, L25 SSC+EC Bosch-Ramon et al. 2004 A&A 417, 1075 Synchrotron jet emission Markoff et al. 2003, A&A 397, 645 Hadronic models: Pion decay Romero et al. 2003, A&A 410, L1 Bosch-Ramon et al. 2005, A&A 432, 609

  9. Leptonic high energy models Synchrotron self Compton model • Non-thermal flares GRS1915+105(Atoyan & Aharonian 1999, MNRAS 302, 253) • Flares are caused by synchrotron radiation of relativistic e suffering radiative, adiabatic and energy-dependent escape losses in fast-expanding plasmoids(radio clouds) Rodríguez et al. 1995, ApJS 101, 173 • Continuous supply or in-situ acceleration of radio e

  10. After limiting, from the radio data, the basic parameter characterizing the expanding plasmoids, the emay be accelerated up to TeV energies, and the fluxes of synchrotron radiation could then extend beyond the X-ray region and the fluxes of the IC γ-rays to HE and VHE. BATSE 0.05 G 0.1G IR 0.2 G sub-mm Exponential cutoff energies: 20 TeV _____ 1 TeV _ _ _ _ 30 GeV _ . _ . _ B = 0.05 G GRS 1915+105 radio IC scattering or maybe even direct synchrotron emission from the jets could dominate the high-energy emission above an MeV or soAtoyan & Aharonian 1999, MNRAS 302, 253, and 2001

  11. External Compton Scattering - HMXB • Jet exposed to star, disk and corona photon fields. • Applied to Cygnus X-1(Romero, Kaufman Bernadó & Mirabel 2002, A&A 393, L61) • Corona (Klein-Nishina regime), disk and companion star (Thomson) • The Compton losses in the different regions will modify the injected electron spectrum, introducing a break in the power law at the energy at which the cooling time equals the escape time. Radiation absorbed in the local field trough pair creation Viewing angle of 30º Bulk Lorentz factorΓ=5 Up-scattering of star photons (A) disk (B) corona (C) The recurrent and relatively rapid variability could be explained by the precession of the jet, which results in a variable Doppler amplification

  12. Hadronic jet models for microquasars • Hadronic models (only) for gamma γ-ray emission: • Conical jet 1014 eV protons interacting with strong stellar wind protons, assuming efficient wind proton diffusion inside the jet. • Protons are injected in the base of the jet and evolve adiabaticaly. • Applied to explain gamma-ray emission from high mass microquasars (Romero et al. 2003, A&A 410, L1). • The γ-ray emission arises from the decay of neutral pions created in the inelastic collisions between relativistic protons ejected by the compact object and the ions in the stellar wind.

  13. The only requisites for the model are a windy high-mass stellar companion and the presence of multi-TeV protons in the jet. Spherically symmetric wind and circular orbit Romero,Torres, Kaufman, Mirabel 2003, A&A 410, L1 Interactions of hadronic beams with moving clouds in the context of accreting pulsars have been previously discussed in the literature by Aharonian & Atoyan (1996, Space Sci. Rev. 75, 357).

  14. Models from radio to VHE: • Released 1014 eV protons from the jet that diffuse through and interact with the ISM. • Computed the broadband spectrum of the emission coming out from the pp primary interactions (γ-rays produced by neutral pion decay) as well as the emission (synchrotron, bremsstrahlung and IC scattering) produced by the secondary particles produced by charged pion-decay. • All the respective energy losses have been taken unto account. • Applied to impulsive and permanent microquasar ejections. 1) 100 yr 2) 1000 yr, 3) 10000 yr dMQ/cloud=10pc Mcloud=105Msun Ljet=1037 erg/s Bosch-Ramon et al. 2005, A&A 432, 609

  15. MQs as high-energy γ -ray sources Observational point of view

  16. EGRET candidate: LS 5039 Orbital phase 0.2 LS 5039 could be related to the high energy gamma-ray source 3EG J1824-1514 VLBA, 5 GHz Jet parameters:  >0.15 ,  <81 TB = 9.4 x 107 K Equipartition: Ee= 5 x 1039 erg B = 0.2 G The photon spectral index is steeper than thea < 2values usually found for pulsars Merk et al.1996, A&ASS 120, 465 Lγ(>100 MeV)=41035erg·s1 It is the only simultaneousX-ray/radio source within the 3EG J1824-1514 statistical contours. Paredes et al. 2000, Science 288, 2340

  17. Radio, L0.1-100 GHz ~ 11031 erg/s Synchrotron Radiation e- e- e- g-ray, E > 100 MeV, Lg ~ 41035 erg/s Inverse Compton Scattering UV, E ~ 10 eV Lopt ~ 11039 erg/s e- ge ~ 103 X-ray L3-30 keV ~ 51034 erg/s O6.5V((f)) e- vjet 0.15c e- Proposed scenario

  18. 3EG J1812-1316 GRO J1817-15 3EG J1823-1314 3EG J1826-1302 3EG J1824-1514 µ-quasar LS 5039 GRO J1823-12 (l/b: 17.5/-0.5) Summary • complicated source region• possible counterparts: - 3 known -sources (unid. EGRET) (MeV emission: superposition ?) - micro quasar RX J1826.2-1450/LS 5039 (sug. counterpart of 3EG J1824-1514; Paredes et al. 2000) • work in progress Collmar 2003, Proc. 4th Agile Science Workshop

  19. Discovery of the TeV counterpart by HESS (Aharonian et al. 2005). Good position agreement with LS 5039. Good extrapolation of the EGRET spectrum.

  20. A black hole in LS 5039 ? Radial velocity curve of LS 5039 New spectroscopic observations of LS 5039 INT 2.5 m telescope (July 2002 and 2003) New orbital ephemeris!! P = 3.9060 ± 0.0002 d e = 0.35 ± 0.04 Periastron at phase 0.0 And assuming pseudo-synchronisation at periastron: i = 20.3˚ ± 4.0 Mcompact = 5.4 (+1.9-1.4) M Casares et al., 2005, MNRAS, 364, 899

  21. With the new orbital ephemerides →correlated TeV and X-ray orbital variability. HESS RXTE (Casares et al. 2005),

  22. 3.9 day orbital modulation in the TeV gamma-ray flux Aharonian et al. 2006, A&A, in press (astro-ph/0607192) VHE γ-rays can be absorbed by optical photons of energy hνε, when their scattering angle θ exceeds zero.

  23. We have enough information to build up a Spectral Energy Distribution that can be modeled to extract physical information(Paredes et al. 2006, A&A 451, 259).

  24. EGRET candidate: LSI+61303 The radio emitting X-ray binary LSI+61 303, since its discovery, has been proposed to be associated with the γ-ray source 2CG 135+01 (= 3EG J0241+6103) The broadband 1 keV-100 MeV spectrum remains uncertain (OSSE and COMPTEL observations were likely dominated by the QSO 0241+622 emission) Harrison et al. 2000, ApJ 528, 454 The EGRET angular resolution is sufficient to exclude the quasar QSO 0241+622as the source of γ-ray emission. Hartman et al. 1999, ApJS 123, 79 Strickman et al. 1998, ApJ 497, 419 Periodic emission Radio (P=26.496 d)↔ accretion at periastron passage Taylor&Gregory 1982, ApJ 255, 210 Optical and IRMendelson&Mazeh 1989, MNRAS 239, 733; Paredes et al. 1994 A&A 288, 519 X-raysParedes et al. 1997 A&A 320, L25 γ-rays ???

  25. 3EG J0241+6103 variability INTEGRAL variability Tavani et al. 1998, ApJ 497, L89 EGRET observations of 3EG J0241+6103 shows variability on short (days) and long (months) timescales Massi et al. 2005 (astro-ph/0410504) Hermsen et al. 2006 Rome, “keV to TeV connection”Workshop, 18 October 2006

  26. ChandraImage of LSI+61303 Chandra PSF 5” Obtained using the Chandra simulator Surface brightness distribution LSI+61303 PSF Flux changes on timescales of few hours. Factor of two variability Paredes et al. 2006

  27. MAGIC has observed LSI during 6 orbital cycles • A variable flux (probability of statistical fluctuation 310-5) detected • Marginal detections at phases 0.2-0.4 • Maximum flux detected at phase 0.6-0.7 with a 16% of the Crab Nebula flux • Strong orbital modulation  the emission is produced by the interplay of the two objects in the binary • No emission at periastron, two maxima in consecutive cycles at similar phases  hint of periodicity! Flux time variability Albert et al. 2006

  28. LS I +61 303: the film Albert et al. 2006 • The average emission has a maximum at phase 0.6. • Search for intra-night flux variations (observed in radio and x-rays) yields negative result • Marginal detections occur at lower phases. We need more observation time at periastron passage • Parts of the orbit not covered due to similarities between orbital period (26.5 days) and Moon period

  29. Radio 15 GHz /Ryle, simultaneous with MAGIC obs. The TeV flux maximum is detected at phases 0.5-0.6, overlapping with the X-ray outburst and the onset of the radio outburst. Concerning energetics, a relativistic power of several 1035 erg s-1 could explain the non thermal luminosity of the source from radio to VHE gamma-rays. This power can be extracted from accretion in a slow inhomogeneous wind along the orbit (Bednarek 2006, MNRAS 268, 579). This spectrum is consistent with that of EGRET for a spectral break between 10 and 100 GeV. The flux above 200 GeV corresponds to an isotropic luminosity of ~7 x 1033 erg s-1, at a distance of 2 kpc. The intrinsic luminosity of LS I +61 303 at its maximum is a factor ~6 higher than that of LS 5039, and a factor ~2 lower than the combined upper limit (<8.8 x 10 -12 cm-2 s-1 above 500 GeV) obtained by Whipple (Fegan et al. 2005, ApJ 624, 638). Spectrum for phases 0.4 and 0.7

  30. LSI+61303 VLBA images over full orbit ---------- 10 AU Orbital Phase New VLBI observations show a rotating jet-like structure Dhawan et al. 2006, VI MIcroquasars Workshop, Como, Setember 2006 3.6cm images ~3d apart. Beam 1.5x1.1mas 3x2.2 AU. Contours +_0.2mJy, increment sqrt(2).

  31. Mirabel 2006, (Perspective) Science 312, 1759 A possible scenario comes from the application of the pulsar wind nebulae formed with the interaction of a relativistic pulsar wind with the ISM but where the wind of the companion plays the role of the ISM. The stagnation point, where the pressure from the two winds is balanced, is within the binary system. Particles are accelerated at the termination shock and produce the non-thermal synchrotron emission(Dubus 2006, A&A 456, 801).

  32. UV photons from the companion star suffer inverse Compton scattering by the same population of non-thermal particles, leading to emission in the GeV-TeV energy range. Particles move downstream away from the pulsar at a speed v (initially ≈c/3). A cometary nebula of radio emitting particles is formed. It rotates with the orbital period of the binary system. We see this nebula projected(Dubus 2006, A&A 456, 801).

  33. PSR B1259-63 PSR B1259-63 / SS 2883 is a binary system containing a B2Ve donor and a 47.7 ms radio pulsar orbiting it every 3.4 years, in a very eccentric orbit with e=0.87. No radio pulses are observed when the NS is behind the circumstellar disk (free-free absorption). VHE gamma-rays are detected when the NS is close to periastron or crosses de disk (Aharonian et al. 2005).

  34. The VHE spectrum can be fit with a power-law and explained by IC scattering processes. The lightcurve shows significant variability and a puzzling behavior not predicted by previously available models (Aharonian et al. 2005).

  35. Detection of new VHE sources? • Three TeV sources (all HMXBs) discovered up to now: • LS 5039 O+BH? • LS I +61 303 Be+NS? • PSR B1259-63 Be+NS Since these sources are located in the Galactic plane, a sensitivity better by a factor X with respect to current instruments means detecting ~3X sources. • Binaries with short orbital periods, difficult for Be but likely for O donors, should be ‘on’ all the time, although strong variability due to absorption is an issue. Detectable in deep enough surveys. • Binaries with long orbital periods and high eccentricities should display an ‘on/off’ behavior, more with higher values. Detectable in long monitorings.

  36. but what about gamma-rays from Colliding winds of massive stars ? Binary pulsars? IC spectra of WR 147 Gamma-ray emission should be expected either through: Leptonic processes (IC) (Chen & White 1991, ApJ 366, 512) Relativistic bremsstrahlung (Pollock 1987, A&A 171, 135) Hadronic interactions of co-accelerated ions with the dense wind material (White & Chen 1992, ApJ 387, 81) A. Reimer et al. 2006, A&SS (astro-ph/0611647)

  37. Unidentified TeV source: TeV J2032 • SIGNIFICANCE + 6.1 by HEGRA • STEADY in flux over 4 years of data taking • EXTENDED with radius ~ (6.2  1.2  0.9) arcmin • HARD SPECTRUMwith index -1.9  0.1stat 0.3sys • INTEGRAL FLUX > 1 TeVat the level of ~ 5% Crab Aharonian et al. 2002, A&A 293, L37

  38. VLA, 20 cm Paredes et al. 2006, ApJ Letters, in press

  39. GMRT, 45cm At 10 kpc, these objects would present luminosities likely requiring the presence of a compact object, and thus pointing to an X-ray binary nature. (for a model of microquasars -X-ray binaries with jets- powering extended TeV hadronicemission, see Bosch-Ramon et al. (2005)).

  40. Summary • Microquasars are among the most interesting sources in the galaxy from the viewpoint of high-energy astrophysics. • Models predict that radio jets could be natural sites for the production of high energy photons via both Compton scattering and maybe direct synchrotron emission. • Leptonic and hadronic processes could be behind TeV emission. • Up to now, above ~ 500 keV, a handful of µqs have been detected: Cygnus X-1 at  1 MeV, GRO J1655-40 at ~1 MeV, GRS 1915+105 and Cygnus X-3 at TeV? LS 5039 and LSI+61303: 100 MeV - few TeV • More microquasars will be detected soon with the Cherenkov telescopes and GLAST. This will bring more constraints to the physics of these systems. • Multiwavelength (multi-particle) campaigns are of primary importance.

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