1. Scuola nazionale de Astrofisica Radio Pulsars 1: Pulsar Basics
Dick Manchester
Australia Telescope National Facility, CSIRO
Outline
Rotating neutron stars, SN associations, Binaries, MSPs
Pulse profiles, polarisation, beaming, RVM model
Pulse fluctuations: drifting, nulling, mode changing

2. Basic References Books Review Articles
Manchester & Taylor 1977 “Pulsars”
Lyne & Smith 2005 “Pulsar Astronomy”
Lorimer & Kramer 2005 “Handbook of Pulsar Astronomy”
Review Articles
Rickett 1990, ARAA - Scintillation
Science, 23 April Three articles: NS, Isolated Pulsars, Binary Pulsars
Living Reviews articles: (
Stairs 2003: GR and pulsar timing
Lorimer 2005: Binary and MS pulsars
Will, 2006: GR theory and experiment
SKA science: New Astron.Rev. 48 (2004)
Cordes et al.: Pulsars as tools
Kramer et al.: Strong-field tests of GR

3. Jocelyn Bell and Tony Hewish Bonn, August 1980
The Discovery of Pulsars
Nobel Prize 1974
Jocelyn Bell and Tony Hewish Bonn, August 1980
The sound of a pulsar:

4. * Total known: 129 in 24 clusters (Paulo Freire’s web page)
Spin-Powered Pulsars: A Census
Number of known pulsars: 1765
Number of millisecond pulsars: 170
Number of binary pulsars: 131
Number of AXPs: 12
Number of pulsars in globular clusters: 99*
Number of extragalactic pulsars: 20
* Total known: 129 in 24 clusters (Paulo Freire’s web page)
Data from ATNF Pulsar Catalogue, V1.25 ( Manchester et al. 2005)

5. Pulsar Model . . . Rotating neutron star
Light cylinder RLC = c/ = 5 x 104 P(s) km
Charge flow along open field lines
Radio beam from magnetic pole (in most cases)
High-energy emission from outer magnetosphere
Rotation braked by reaction to magnetic-dipole radiation and/or charge acceleration:  = -K -3
Characteristic age: c = P/(2P)
Surface dipole magnetic field: Bs ~ (PP)1/2 . . .
(Bennet Link)

6. Pulsar Formation ~30 young pulsars associated with SNR
Core of red giant collapses when its mass exceeds “Chandrasekhar Mass”
Energy release ~ 3GM/5R2 ~ 3 x 1053 erg ~ 0.1 Mc2
Kinetic energy of SNR ~ 1051 erg; 99% of grav. energy radiated as neutrinos and anti-neutrinos
Asymmetry in neutrino ejection gives kick to NS
Measured proper motions: <V2D> = 211 km s-1
<V3D> = 4<V2D>/ = 2<V1D> for isotropic velocities
ESO-VLT
Guitar Nebula
PSR B
(Hobbs et al. 2005)
(Cordes et al. 2003)

7. Neutron Stars
Formed in Type II supernova explosion - core collapse of massive star
Diameter km
Mass ~ 1.4 Msun
(MT77)
(Stairs 2004)
(Lattimer & Prakash 2004)

8. . P vs P . . Galactic disk pulsars Most pulsars have P ~ 10-15
MSPs have P smaller by about 5 orders of magnitude
Most MSPs are binary
Only a few percent of normal pulsars are binary
AXPs are slow X-ray pulsars with very strong fields - “magnetars”
Some young pulsars are only detected at X-ray or -ray wavelengths .
ATNF Pulsar Catalogue (

9. Pulsar Recycling . . Young pulsars live for 106 or 107 years
MSPs have c 109 or 1010 years and most are binary
Accretion from an evolving binary companion leads to:
Increased spin rate for NS - angular momentum transferred from orbit to NS
Decreased Bs - mechanism not understood. Could be simple “burial” of field by accreted matter . .
Minimum spin period: Pmin ~ (B9)6/7 (M/MEdd)-3/7
Short-period MSPs from low-mass binary companions - long evolution time
Recycling is very effective in globular clusters - more than half of all MSPs in globular clusters: 22 in 47 Tucanae, 33 in Terzan 5 (Ransom et al. 2005, Friere 2007)
Old NS in core of cluster captured by low-mass stars and then recycled
About 30% of MSPs are single - what has happened to companion?
Blown away by relativistic wind from pulsar - ?
Lost in 3-body encounter - only in core of globular cluster
47 Tucanae

10. Pulsar Energetics
Spin-down Luminosity:
Radio Luminosity:

11. Pulsar Electrodynamics
For a typical pulsar, P = 1s and P = 10-15, Bs ~ 108 T or 1012 G.
Typical electric field at the stellar surface E ~ WRBs/c ~ 109 V/cm
Electrons reach ultra-relativistic energies in < 1 mm.
Emit g-ray photons by curvature radiation. These have energy >> 1 MeV and hence decay into electron-positron pairs in strong B field.
These in turn are accelerated to ultra-relativistic energies and in turn pair-produce, leading to a cascade of e+/e- pairs.
Relativistic pair-plasma flows out along ‘open’ field lines.
Instabilities lead to generation of radiation beams at radio to g-ray energies.

12. Rotating neutron-star model: magnetospheric gaps
W.B = 0
Regions of particle acceleration!
Inner (polar cap) gap
Outer gaps
Cheng et al. (1986); Romani (2000)

13. Coherent Radio Emission
Source power is very large, but source area is very small
Specific intensity is very large
Pulse timescale gives limit on source size ~ ct
Brightness temperature: equivalent black-body temperature in Rayleigh-Jeans limit
Radio emission must be from coherent process!

14. Frequency Dependence of Mean Pulse Profile
Pulse width generally increases with decreasing frequency.
Consistent with ‘magnetic-pole’ model for pulse emission.
Lower frequencies are emitted at higher altitudes.
Phillips & Wolsczcan (1992)

15. Magnetic-Pole Model for Emission Beam
Emission beamed tangential to open field lines
Radiation polarised with position angle determined by projected direction of magnetic field in (or near) emission region (Rotating Vector Model)

16. Mean pulse shapes and polarisation
P.A.
Stokes I
Linear
Stokes V
Lyne & Manchester (1988)

17. Orthogonal-mode emission – PSR B2020+28V
P.A. %L I
Stinebring et al. (1984)

18. Mean pulse profile of PSR J0437-4715
P.A.
Mean pulse profile of PSR J
Stokes I
Binary millisecond pulsar
P = 5.75 ms
Pb = 5.74 d
Linear
Stokes V
Complex profile, at least seven components
Complex PA variation, including orthogonal transition I L V
Navarro et al. (1997)

19. Wide Beams from Young and MS Pulsars
Pulsed (non-thermal) X-ray and -ray profiles from young pulsars have wide “double” shape
Emitted from field lines high in magnetosphere associated with a single magnetic pole
Some young radio pulsars have a similar pulse profile, e.g. PSR B
Class of young pulsars with very high (~100%) linear polarisation, e.g. Vela, PSR B
Radio emission from high in pulsar magnetosphere?
MSPs also have very wide profiles - also single-pole emission from high in magnetosphere?
Crab
(Ulmer et al. 1994)
PSR B
PSR B

20. Other Examples:
Vela
PSR B
PSR J A

21. Drifting subpulses and periodic fluctuations
PULSE LONGITUDE
Taylor et al. (1975)
Backer (1973)

22. Pulse Modulation
Extensive survey of pulse modulation properties at Westerbork pulsars
Observations at 1.4 GHz, 80 MHz bw
Modulation indices, longitude-resolved and 2D fluctuation spectra computed
42 new cases of drifting subpulses
At least 60% of all pulsars show evidence for drifting behaviour
“Coherent” drifters have large characteristic age, but drifting seen over most of P - P diagram .
(Weltevrede et al. 2006)

23. Pulsar Nulling
Parkes observations of 23 pulsars, mostly from PM survey
Large null fractions (up to 96%) - mostly long-period pulsars
Nulls often associated with mode changing
(Wang et al. 2006)

24. PSR B0826-34 P = 1.848 s, pulsed emission across whole of pulse period
In “null” state ~80% of time
5-6 drift bands across profile, variable drift rate with reversals
Weak emission in “null” phase, ~2% of “on” flux density
Different pulse profile in “null” phase:
Null is really a mode change. On
“Null”
(Esamdin et al. 2005)

25. PSR B1931+24 - An extreme nuller
Quasi-periodic nulls: on for 5-10 d, off for d
Period derivative is ~35% smaller when in null state!
Implies cessation of braking by current with G-J density
Direct observation of current responsible for observed pulses
(Kramer et al. 2006)

26. Giant Pulses Crab Giant Pulses
Intense narrow pulses with a pulse energy many times that of an average pulse - characterised by a power-law distribution of pulse energies.
First observed in the Crab pulsar - discovered through its giant pulses!
Crab Giant Pulses
Arecibo observations at 5.5 GHz
Bandwidth 0.5 GHz gives 2 ns resolution
Flux density > 1000 Jy
implies Tb > 1037 K!
Highly variable polarisation
Suggests emission from plasma turbulence on scales ~ 1 m
(Hankins et al. 2003)

27. Giant Pulses from Millisecond Pulsars
PSR B
Giant pulses seen from several MSPs with high BLC
Most also have pulsed non-thermal emission at X-ray energies
Giant pulses occur at phase of X-ray emission
RXTE
PSR J
BeppoSAX
GBT 850 MHz
Radio
Chandra kev
(Cusumano et al. 2003)
(Knight et al. 2006, Kuiper et al. 2004, Rutledge et al. 2004)

28. Transient Pulsed Radio Emission from a Magnetar
AXP XTE J outburst in which X-ray luminosity increased by ~100
X-ray pulsations with P = 5.54 s observed
Detected as a radio source at VLA, increasing and variable flux density: mJy at 1.4 GHz (Halpern et al. 2005)
Within PM survey area, not detected in two obs. in 1997, 1998, S1.4 < 0.4 mJy
Observed in March 2006 at Parkes (Camilo et al. 2006)
Pulsar detected!
S1.4 ~ 6 mJy
Very unusual flat spectrum - individual pulses detected in GBT observations at 42 GHz!
Earlier unconfirmed detections (e.g. Malofeev et al 2005) accounted for by transient and highly variable nature of pulsed emission?

29. End of Part 1