Sergei Popov SAI MSU Plan General intro Pulsar models Population synthesis Summary of discoveries EGRET legacy Just 6 pulsars Crab Geminga Vela PSR B105552 PSR B170644 PSR B195132 ID: 376283
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Slide1
Gamma-ray pulsars discovery by Fermi Space Observatory
Sergei Popov(SAI MSU)Slide2
Plan
General intro
Pulsar models
Population synthesis
Summary of discoveriesSlide3
EGRET legacy
Just 6 pulsars:
Crab
Geminga
Vela
PSR B1055-52
PSR B1706-44
PSR B1951+32
Nolan et al. 1996astro-ph/9607079
(plus one by COMPTEL)Slide4
Fermi PSR light curves
The first catalogue of Fermi pulsars: arXiv:0910.1608Slide5
Galactic map
arXiv:0910.1608Slide6
Luminosity vs Edot
arXiv:0910.1608Slide7
Spectra
arXiv:0910.1608
arXiv: 1007.1142
GemingaSlide8
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) Slide9
Emission geometry
D. Thomson, NASA/GSFC
)
From Encyclopedia article
'
Gamma-ray astronomy
'
gsfc.nasa.govSlide10
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?Slide11
Several models
Polar cap (inner gap or space-charge limited flow)
Outer gap
Slot gap and TPC
Striped windSlide12
Inner gap (polar cap) modelSlide13
Outer gap modelSlide14
Slot gap and TPC model
Gonthier et al. 2004
Dyks, Rudak 2003Slide15
Polar vs. Slot (TPC) gap
Harding
arXiv:0710.3517Slide16
In brief
Fermi data favors outer gapSlide17
Population synthesis of gamma-ray PSRs
(following Gonthier et al astro-ph/0312565)
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 AGILESlide18
Beams
1. Radio beam
2. Gamma beam.
Geometry of gamma-ray beam was adapted from
the slot gap model (Muslimov, Harding 2003)Slide19
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)Slide20
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 parametersSlide21
P-Pdot diagrams
Detected
SimulatedSlide22
Comparison of distributions
Shaded – detected, plain - simulatedSlide23
Distributions on the skySlide24
Results for Fermi
Crosses – radio-quiet
Dots – radio-loud
Examples of pulse profilesSlide25
Predictions for Fermi and AGILE
(prediction just for detection as a source,
not as a pulsating sources!)Slide26
Spatial distribution of gamma sourcesSlide27
New population synthesis
Watters, Romani arXiv: 1009.5305
Outer gap model is preferedSlide28
Another one
Takata et al. arXiv: 1010.5870
Outer gapSlide29
The first Fermi catalogue
56 pulsating sources out from 1451 sources in total
arXiv: 1002.2280Slide30
Blind searches
arXiv: 1007.2183
PSR J1957+5033
24 PSRs found in blind searches.
See details in arXiv: 1009.0748 and arXiv: 1006.2134Slide31
Blind search
arXiv: 1009.0748
Up to now few (3) are found
also in radio, but it is not easy!Slide32
Pulsar timing
arXiv: 1007.2183
PSR J1836+5925
18 months timingSlide33
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.Slide34
P-Pdot diagram
arXiv: 1007.2183
63 PSRs detected by FermiSlide35
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.