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

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Presentation on theme: "Gamma-ray pulsars discovery by Fermi Space Observatory Sergei Popov (SAI MSU)"— Presentation transcript:

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

2 Plan 1. General intro 2. Pulsar models 3. Population synthesis 4. Summary of discoveries

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

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 arXiv:0910.1608arXiv: 1007.1142 Geminga

8 Light cylinder magnetic field vs. age Caraveo arXiv: 1009.2421 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)

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

10 Crab pulsar profile arXiv: 1007.2183 Gamma pulse is shifted relative to the radio pulse Now there are examples that radio and gamma pulses can be both: at nearly the same positions and significantly shifted. Gamma – OG, Radio – TPC?

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 Gonthier et al. 2004 Dyks, Rudak 2003

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 (following Gonthier et al astro-ph/0312565) Ingredients 1.Geometry of radio and gamma beam 2.Period evolution 3.Magnetic field evolution 4.Initial spatial distribution 5.Initial velocity distribution 6.Radio and gamma spectra 7.Radio and gamma luminosity 8.Properties of gamma detectors 9.Radio surveys to compare with. Tasks 1.To test models 2.To make predictions for GLAST and AGILE

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 times larger 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 DetectedSimulated

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 Watters, Romani arXiv: 1009.5305 Outer gap model is prefered

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

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

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

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

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

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 arXiv: 1007.2183 63 PSRs detected by Fermi

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) About radio pulsar population see Lorimer arXiv: 1008.1928 The outer gap models seems to be more probable on the base of Fermi data.

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