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Gamma-ray pulsars discovery by Fermi Space Observatory

Gamma-ray pulsars discovery by Fermi Space Observatory. Sergei Popov (SAI MSU). Plan. General intro Pulsar models Population synthesis Summary of discoveries. EGRET legacy. Just 6 pulsars: Crab Geminga Vela PSR B1055-52 PSR B1706-44 PSR B1951+32. (plus one by COMPTEL).

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Gamma-ray pulsars discovery by Fermi Space Observatory

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  1. Gamma-ray pulsars discovery by Fermi Space Observatory Sergei Popov(SAI MSU)

  2. Plan • General intro • Pulsar models • Population synthesis • Summary of discoveries

  3. EGRET legacy • Just 6 pulsars: • Crab • Geminga • Vela • PSR B1055-52 • PSR B1706-44 • PSR B1951+32 (plus one by COMPTEL) Nolan et al. 1996astro-ph/9607079

  4. Fermi PSR light curves The first catalogue of Fermi pulsars: arXiv:0910.1608

  5. Galactic map arXiv:0910.1608

  6. Luminosity vs Edot arXiv:0910.1608

  7. Spectra Geminga arXiv:0910.1608 arXiv: 1007.1142

  8. Light cylinder magnetic field vs. age Total of 46 pulsars 29 of which detected in radio (further divided between 8 mPSRs and 21 “classical” pulsars) and 17 selected in gamma-rays (i.e. 16 discovered by LAT + Geminga) Caraveo arXiv: 1009.2421

  9. Emission geometry D. Thomson, NASA/GSFC) From Encyclopedia article 'Gamma-ray astronomy' gsfc.nasa.gov

  10. Crab pulsar profile Now there are examplesthat radio and gammapulses can be both:at nearly the same positions andsignificantly shifted.Gamma – OG,Radio – TPC? Gamma pulse is shiftedrelative to the radio pulse arXiv: 1007.2183

  11. Several models • Polar cap (inner gap or space-charge limited flow) • Outer gap • Slot gap and TPC • Striped wind

  12. Inner gap (polar cap) model

  13. Outer gap model

  14. Slot gap and TPC model Dyks, Rudak 2003 Gonthier et al. 2004

  15. Polar vs. Slot (TPC) gap Harding arXiv:0710.3517

  16. In brief Fermi data favors outer gap

  17. Population synthesis of gamma-ray PSRs Ingredients • Geometry of radio and gamma beam • Period evolution • Magnetic field evolution • Initial spatial distribution • Initial velocity distribution • Radio and gamma spectra • Radio and gamma luminosity • Properties of gamma detectors • Radio surveys to compare with. Tasks • To test models • To make predictions for GLAST and AGILE (following Gonthier et al astro-ph/0312565)

  18. Beams 1. Radio beam 2. Gamma beam. Geometry of gamma-ray beam was adapted from the slot gap model (Muslimov, Harding 2003)

  19. Other properties • Pulsars are initially distributed in an exponential (in R and z) disc, following Paczynski (1990). • Birthrate is 1.38 per century • Velocity distribution from Arzoumanian, Chernoff and Cordes (2002). • Dispersion measure is calculated with the new model by Cordes and Lazio • Initial period distribution is taken to be flat from 0 to 150 ms. • Magnetic field decays with the time scale 2.8 Myrs (note, that it can be mimicked by the evolution of the inclination angle between spin and magnetic axis). The code is run till the number of detected (artificially) pulsars is 10 timeslarger than the number of really detected objects. Results are compared with nine surveys (including PMBPS)

  20. Drawbacks of the scenario • Simplified initial spatial distribution (no spiral arms) • Uncertainties in beaming at different energies • Uncertainties and manipulations with luminosity • Unknown correlations between parameters

  21. P-Pdot diagrams Detected Simulated

  22. Comparison of distributions Shaded – detected, plain - simulated

  23. Distributions on the sky

  24. Results for Fermi Crosses – radio-quiet Dots – radio-loud Examples of pulse profiles

  25. Predictions for Fermi and AGILE (prediction just for detection as a source, not as a pulsating sources!)

  26. Spatial distribution of gamma sources

  27. New population synthesis Outer gap model is prefered Watters, Romani arXiv: 1009.5305

  28. Another one Outer gap Takata et al. arXiv: 1010.5870

  29. The first Fermi catalogue 56 pulsating sources out from 1451 sources in total arXiv: 1002.2280

  30. Blind searches 24 PSRs found in blind searches. PSR J1957+5033 arXiv: 1007.2183 See details in arXiv: 1009.0748 and arXiv: 1006.2134

  31. Blind search Up to now few (3) are foundalso in radio, but it is not easy! arXiv: 1009.0748

  32. Pulsar timing PSR J1836+5925 18 months timing arXiv: 1007.2183

  33. Millisecond pulsars PSR J0218+4232 was probably detected by EGRET.With Fermi we now have 11+18 clearly detected in gamma mPSRs. Many “black widows”. No radio-quiet mPSR, yet. Plus, there are 8 gamma-sources coincident with globular clusters. More are coming.

  34. P-Pdot diagram 63 PSRs detected by Fermi arXiv: 1007.2183

  35. Bottom line • 63 clearly detected pulsating PSRs: ~20 radio selected (with 7 known from CGRO time) 24 – in blind searches (several detected also in radio) 27 - mPSRs • 18 mPSRs candidates from radio (non-pulsating in gamma) The outer gap models seems to bemore probable on the base of Fermi data. About radio pulsar populationsee Lorimer arXiv: 1008.1928

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