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Spectral states of NS and BH systems

This study explores the spectral states of neutron star (NS) and black hole (BH) systems, focusing on the "hard tails" observed in the brightest persistent sources and initial outbursts of transients. It examines the relative contributions of thermal and non-thermal components, investigates the correlation between timing and spectral properties, and aims to model the spectral properties to determine fundamental quantities. The study also explores the origins of quiescent emissions in NS and BH transients, investigates cyclotron resonant scattering in magnetized NS, and examines the spectra of magnetars, ultra-luminous X-ray sources, and non-thermal emissions from shell-like supernova remnants (SNRs). The ultimate goal is to better understand the physics of accretion and ejection processes in NS and BH systems. The study requires good sensitivity, spectral modeling capabilities, and the ability to handle high count rates.

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Spectral states of NS and BH systems

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  1. Cyg X-1 (Zdziarski 2000) Spectral states of NS and BH systems “hard tails” currently studied only in ~20 sources (brightest persistent sources and initial part of transients outbursts)

  2. Spectral states of NS and BH systems • Different relative contribution of two main components • thermal - accretion disk in NS/BH , boundary layer in NS, … • Non-thermal - Comptonization ? Jets ? • Probably driven by mass accretion rate • Timing and spectral properties intrinsically correlated • Best studied in transient systems Relevance: • physics of accretion / ejection can be investigated on short timescales within a single object  complements AGNs studies • Spectral modelling can give fundamental quantities (mass, spin, B, composition, etc..) but requires good knowledge of a) processes at work and b) geometry Immediate objectives: • More accurate spectral modeling of the bright sources • Enlarge sample of well studied sources going to fainter fluxes • Study variability (e.g. QPOs) at higher energies Main requirement: Good sensitivity over broadest range and with timing capability

  3. NS and BH transients in quiescence Origin of quiescent emissions: • ADAF? • NS cooling ? • Propeller ? • Radio PSR shock ?

  4. NS and BH transients in quiescence • Relevance: • Evidence for event horizon in black holes • Evolution of binary systems leading to recycled radio PSRs • Immediate objectives: • Origin of emission in quiescence • Difference between NS and BH • Is there a high-energy cut-off in the hard tails? • Main requirement: • Good sensitivity at high energy

  5. Cyclotron resonant scattering in magnetized NS

  6. Cyclotron resonant scattering in magnetized NS • Relevance: • Direct measure of magnetic field • Geometry of magnetic field and accretion flow • Immediate objectives: • More detailed study of known systems (e.g. line modeling is dependent on continuum spectrum) with phase-resolved spectr. • Enlarge sample thanks to increased sensitivity  correlations between spectral parameters • Main requirements: • Good sensitivity over broad energy range • Energy resolution • Possibility of handling high count rates (e.g. no pile-up, saturations, etc…)

  7. Magnetars • The highest magnetic fields in the Universe are observed in this class of isolated, slowly rotating neutron stars B=1014 – 1015 Gauss P = 5-12 s • Come in two “flavors” • Soft Gamma-ray Repeaters  hard X-rays in bursts and flares • Anomalous X-ray pulsars  persistent soft X-ray emission • Recent INTEGRAL results show that both AXPs and SGRs have persistent hard X-ray tails up to 100 keV • Dominates energy budget • Currents in the magnetosphere driven by variations in field geometry (twisted magnetosphere model)

  8. Gotz et al. 2006, A&A in press Magnetars 20-100 keV fluxes in the ~mCrab range at the limit of INTEGRAL capability Long (few Msec) exposures required It is fundamental to better study their spectral shape and establish presence of pulsations also at high E

  9. Ultra Luminous X-ray sources • Stellar mass black holes ? • - super-Eddington luminosity • - sub-Eddington + anisotropy • or • Intermediate mass black holes ?

  10. Non thermal emission from shell like SNRs • Old “paradigm” on SNR X-ray emission: • Shell like  thermal emission from heated ejecta and ISM • Center filled  non-thermal emission powered by young fast pulsar • Composite = combination of the two

  11. Non thermal emission from shell like SNRs • SN 1006 - first shell SNR with evidence for NON-THERMAL emission (Koyama et al. 1995) • Electrons accelerated up to 100 TeV energies emit in the keV range by synchrotron • Proof of CR origin in SNR (at least for electrons) Now seen in a few shell-like SNRs

  12. G347.3-0.5 - HESS @ TeV Non thermal emission from shell like SNRs Recently the non-thermal shell SNR have also been seen at TeV gamma-rays Inverse Compton from electrons ? or collisions of accelerated protons on ISM and/or molecular clouds

  13. 10 arcmin Simbol–X (multi-couches) Spectre 1 arcmin2 1000 photons - 100 ks Nucléosynthèse : à la recherche du 44Ti 44Ti : produit de la nucléosynthèse explosive Période 88 ans Raies (44Sc) à 68 et 78 keV Détecté (pour le moment) seulement dans CasA, par BeppoSAX et INTEGRAL

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