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

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

EGRET legacy Just 6 pulsars: Crab Geminga Vela PSR B PSR B PSR B Nolan et al astro-ph/ (plus one by COMPTEL)

Fermi PSR light curves The first catalogue of Fermi pulsars: arXiv:

Galactic map arXiv:

Luminosity vs Edot arXiv:

Spectra arXiv: arXiv: Geminga

Light cylinder magnetic field vs. age Caraveo arXiv: 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)

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

Crab pulsar profile arXiv: 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?

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

Inner gap (polar cap) model

Outer gap model

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

Polar vs. Slot (TPC) gap Harding arXiv:

In brief Fermi data favors outer gap

Population synthesis of gamma-ray PSRs (following Gonthier et al astro-ph/ ) 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

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

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)

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

P-Pdot diagrams DetectedSimulated

Comparison of distributions Shaded – detected, plain - simulated

Distributions on the sky

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

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

Spatial distribution of gamma sources

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

Another one Takata et al. arXiv: Outer gap

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

Blind searches arXiv: PSR J PSRs found in blind searches. See details in arXiv: and arXiv:

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

Pulsar timing arXiv: PSR J months timing

Millisecond pulsars PSR J was probably detected by EGRET. With Fermi we now have 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.

P-Pdot diagram arXiv: PSRs detected by Fermi

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: The outer gap models seems to be more probable on the base of Fermi data.