pulsars + parkes = awesome

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Pulsars + Parkes = Awesome Ryan Shannon Postdoctoral Fellow, CSIRO Astronomy and Space Science Credit: John Sarkissian

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Credit: John Sarkissian. Pulsars + Parkes = Awesome. Ryan Shannon Postdoctoral Fellow, CSIRO Astronomy and Space Science. Outline. Post main sequence stellar evolution A few of the properties of pulsars that make them hella cool. Pulsar timing: the bread and butter of pulsar observing - PowerPoint PPT Presentation

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Page 1: Pulsars + Parkes = Awesome

Pulsars + Parkes = Awesome

Ryan Shannon Postdoctoral Fellow, CSIRO Astronomy and Space Science

Cre

dit:

John

Sar

kiss

ian

Page 2: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Outline

• Post main sequence stellar evolution

• A few of the properties of pulsars that make them hella cool.

• Pulsar timing: the bread and butter of pulsar observing

• What I like about pulsars: Get to work on a lot of different areas of physics and astrophysics

Crab Pulsar Wind Nebula

Page 3: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

End of Stellar Evolution

Main sequence star Compact Remnant

White dwarf 0.1 to ~ 1.2 Msun

Degenerate electron pressure0.1 to 8 Msun

8 to 20 (?) Msun

> 20 Msun

Neutron star 1.3 to < 3 Msun

Degenerate neutron pressure

Black hole >3 Msun

Gravity wins

Complications: mass exchange in binary systems

Page 4: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Background:1931: understanding of white dwarfs

(Chandrasekhar)1932: neutron discovered (Chadwick)1933: neutron stars (Baade & Zwicky)1939: first models (Oppenheimer & Volkoff)

Detectable? Thermal radiation (106 K, 10 km) bleak1967: Radio pulsars (serendipitous)

Gamma-ray bursts (ditto)

1968: Pulsar discovery announcedCrab pulsar discovered

1969: Crab pulsar spindown measured& clinched the NS hypothesis (T. Gold)

Historical background

Page 5: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

How to build a pulsar in 50 Mega year

• Maser

• Massive Star

• Supernova explosion

• Neutron Star• Conservation of angular

momentum: spins fast• Conservation of magnetic

flux: high magnetic fields.• Compact ~ 1.4 solar masses

of material in 10 km.• Assymetric SN explosion-

pulsar has high velocity (mashes up ISM)

• Pulsar: a class of neutron star that emits pulsed radiation

• Rotation powered -

Supernova 1987a, in the LMC

Page 6: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Pulsar radiation is pulsed

• Periodicity of the emission: rotation period of neutron star

• Spin period for radio-bright neutron stars 1 ms to 10 s

• Emission region: located near magnetic pole of star

Page 7: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Pulsar radiation is pulsed

Single pulses from PSR B0834+06

• Periodicity of the emission: rotation period of neutron star

• Spin period for radio-bright neutron stars 1 ms to 10 s

• Emission region: located near magnetic pole of star

Page 8: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Pulsar radiation is periodically pulsed

• Each pulsar has a unique fingerprint (pulse profile)

• Pulsed emission averages towards a standard that is usually statistically identical at all observing epochs

• If the profile stays the same, we can very accurately track the rotation history of the pulsars

• Precision pulsar timing: most powerful use of pulsars (next to CMB, the most powerful use of any form of astrophysical radiation)

Page 9: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Pulsars have unique Period and Period derivatives

• Two fundamental observables of pulsars

• Period • Period derivative

• Describe the pulsar population

• Estimate other properties based on P and Pdot.

• Age (103 – 109 yr)• Surface magnetic field

strength (108 to1015 G)• Surface voltage

potential (1012 V)

log

Per

iod

der

ivat

ive

(s s

-1)

Period (sec)

MSPs

Canonical Pulsars

Some pulsars are recycled

Page 10: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Pulsar radiation is erratic

Bhat et. al.

• Single pulses vary in shape

• Some pulsars show ultra-bright giant pulses

• Some pulsars occasionally miss pulses (nulling)

• Some pulsars only occasionally emit pulses (rotating radio transients RRATS)

Page 11: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Pulsar radiation is dispersed

• Warm plasma in the ISM is refractive, and the index of refraction depends on RF.

• At higher frequencies pulsed emission arrive earlier

• Level of dispersion depends on total column density along the line of sight (Dispersion measure DM).

• Dispersion is an excellent discriminator

• Allows us to distinguish pulsars from RFI (radar, microwaves, guitar hero)

• Corollary: Pulsars can be used to study ISM and Galactic Structure 0 < DM < 1200 for known pulsars

Page 12: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Pulsar Radiation is Multi-wavelength

• Non-thermal emission observed across entire EM spectrum• Some pulsars are prodigious producers of gamma-ray

emission.

• The number of high energy pulsars has grown by a factor of 10 since the launch of the Fermi space telescope.

Page 13: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Step 1: Finding Pulsars

The Parkes radio telescope has found more than twice as many pulsars as the rest of the world’s telescopes put

together.

Talk to Mike Keith

Page 14: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar26 May 2011 UWashington 14

• Repeat for L epochs spanning N=T/P spin periods (T=years)

• N ~ 108 – 1010 cycles in one year

• Period determined to

Pulsar Timing: The Basics of Pulsars as Clocks

• Stack M pulses (M=1000s) • Time-tag using template fitting

P …MP

W

• J1909-3744: eccentricity < 0.00000013 (Jacoby et al. 2006)

• B1937+21: P = 0.00155780649243270.0000000000000004 s

Page 15: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

What influences pulse arrival times?

• Pulsar spindown

• Random spindown variations

• Intrinsic variation in shape and/or phase of emitted pulse (jitter)

• Reflex Motion from companions

• Gravitational Waves

• Pulsar position, proper motion, distance

• Warm electrons in the ISM

• Solar system• Mass of planets (Champion et al. 2010)• Location of solar system barycentre (John

Lopez)

Pulsar

EarthGoal: including as many of the perturbations as possible in timing model.

Page 16: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

What influences pulsar arrival times?

te = tr – D/c2

+ DM/2

+ R + E + S

- R - E - S

+ TOAISM

+ TOAorbit noise

+ TOAspin noise

+ TOAgrav. waves

+ …

Path length

Plasma dispersion (ISM)

Solar system (Roemer, Einstein, Shapiro)

Binary pulsar (R,E,S delays)

ISM scattering fluctuations

Orbital perturbations

Intrinsic spin (torque) noise

Gravitational wave backgrounds

Want to include as many of these perturbations as possible in model

Page 17: Pulsars + Parkes = Awesome

CASS Colloquium 3/8/11Insert presentation title, do not remove CSIRO from start of footer

pulsar

Earth

20 ms 10 µs 500 ns

Relative Day Relative Day

Relative Day

5 ms

Relative Day

No Spindown

Relative Amplitudes of Contributions

Simulated TOAs for MSP J1713+0747

Proper motion off by 1 mas/yr Parallax off by 1 masRA off by 1”

ΔT

ΔT ΔT

ΔT

0 1000 0 1000 0 1000

Relative Day0 1000

Page 18: Pulsars + Parkes = Awesome

CASS Colloquium 3/8/11Insert presentation title, do not remove CSIRO from start of footer

Massive (white dwarf) companion

20 s

1000

ΔT

0 Relative Day

Reflex MotionKonacki & Wolszczan (2004): Three planets around MSP B1257+12: 4.3 MEarth,

3.9 MEarth, and 0.02 MEarth

1990 2002

2 ms

20 µs

20 µs

Page 19: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Example: What pulsar residuals ought to look like: PSR B1855+09

Are

cib

o U

pg

rad

e

AO

Pai

nti

ng

The Residuals are quite white! (Time series from D. Nice)

Year1986 2010

ΔT

s)

6

-6

Page 20: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Example: What Residuals from Most Pulsars Look Like

0 18

-50

40

ΔT

OA

s)

Time (yr)

Origin: Intrinsic spin instabilities (spin noise)Asteroid belt?

Page 21: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Applications of pulsar timing

• Neutron stars with companions• Known companions: white dwarfs, neutron stars, planets

• Need to incorporate general relativity to model orbits of WD and NS binary systems

• Tests of general relativity

• Holy grails: • A pulsar orbiting another pulsar (two clocks, dude)

• Pulsar orbiting a black hole

• Direct detection of gravitational waves

• What Ryan works on: understanding astrophysical “noise” in timing observations

Page 22: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

First binary pulsar: The Hulse-Taylor Binary B1913+16

Pulse period: 59 ms

Orbital Period: 7h 45m

Double neutron-star system

Velocity at periastron: ~0.001 of velocity of light

•Periastron advance: 4.226607(7) deg/year (same advance in a day as Mercury advances in a century)

Page 23: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation SeminarCSIRO. Gravitational wave detection

• Prediction based on measured Keplerian parameters and Einstein’s general relativity due to emission of gravitational waves (1.5cm per orbit)

•After ~250 MYr the two neutron stars will collide!

(Weisberg & Taylor 2003)

Gravitational Radiation from B1913+16

Page 24: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

The Next Grail: A double pulsar system

Page 25: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

First Double Pulsar: J0737-3939

• Pb=2.4 hrs, d/dt=17 deg/yr

• MA=1.337(5)M, MB=1.250(5)M

Lyne et al.(2004)

002.0000.1exp

obs

s

sTesting GR:

Kramer et al.(2004)

Now to 0.05%

Page 26: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

The Future: Pulsar Black Hole Systems

• Pulsar-BH binaries in the field

• Pulsars orbiting Sag A* (Massive black hole in centre of Galaxy)

Page 27: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Gravitational Wave Detection with Pulsars

Page 28: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Status of gravitational wave detections:

Number of known gravitational wave sources:

0

Page 29: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Spin-down irregularities

No angular signature

Page 30: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

What if gravitational waves exist?

Quadrapolar signature

Page 31: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

A stochastic background of GW sources

Expect backgrounds from:1. Supermassive black-hole binaries2. Relic GWs from the early universe3. Cosmic strings

The stochastic background is made up of a sum of a large number of plane gravitational waves.

Page 32: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Detecting the stochastic background

• The induced timing residuals for different pulsars will be correlated

This is the same for all pulsars.

This depends on the pulsar.

Page 33: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

The expected correlation function

See Hellings & Downs 1983, ApJ, 265, L39

Simulated data

Page 34: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Detection/limits on the background

• No detection yet made

• Good limit coming soon (see my talk next week!)

GW frequencies between 10-9 and 10-8 Hz - complementary to LIGO and LISA

Current data sets are ruling out a few cosmic string models

The square kilometre array should detect GWs or rule out most models

Page 35: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Conclusion

• Pulsars: the end state for intermediate mass stars

• Pulsars can be used to study many different aspects of astronomy and astrophysics

• Pulsar timing has been and continues to be a powerful physical and astrophysical probe.

• Thank you!

Page 36: Pulsars + Parkes = Awesome

Ryan Shannon, Pulsars, Summer Vacation Seminar

Pulsars Have High Velocities:

• VLBI: parallax, proper motion• Pulsar distance:

• NS Population model

• Luminosity (particularly for high energy emission)

• Constrain Galactic electron density model/ Galactic structure

• Pulsar velocity: High velocity some > 1000 km/s (escape the Galaxy)

• Physics of supernvova explosions

• Synthesis imaging: Pulsar environment / Pulsar wind nebulae (PWN)

• Interactions between pulsar wind and the ISM produce synchrotron emission

Chatterjee et al. (2005)