Credit John Sarkissian Pulsars Parkes Awesome Ryan Shannon

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 • What I like about pulsars: Get to work on a lot of different areas of physics and astrophysics Crab Pulsar Wind Nebula Ryan Shannon, Pulsars, Summer Vacation Seminar

End of Stellar Evolution Main sequence star 0. 1 to 8 Msun 8 to 20 (? ) Msun Compact Remnant White dwarf 0. 1 to ~ 1. 2 Msun Degenerate electron pressure Neutron star 1. 3 to < 3 Msun Degenerate neutron pressure > 20 Msun Black hole Gravity wins Complications: mass exchange in binary systems Ryan Shannon, Pulsars, Summer Vacation Seminar >3 Msun

Historical background Background: 1931: 1932: 1933: 1939: Detectable? 1967: understanding of white dwarfs (Chandrasekhar) neutron discovered (Chadwick) neutron stars (Baade & Zwicky) first models (Oppenheimer & Volkoff) Thermal radiation (106 K, 10 km) bleak Radio pulsars (serendipitous) Gamma-ray bursts (ditto) 1968: Pulsar discovery announced Crab pulsar discovered 1969: Crab pulsar spindown measured & clinched the NS hypothesis (T. Gold) 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 explosionpulsar has high velocity (mashes up ISM) • Pulsar: a class of neutron star that emits pulsed radiation • Rotation powered - Ryan Shannon, Pulsars, Summer Vacation Seminar Supernova 1987 a, in the LMC

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 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 Ryan Shannon, Pulsars, Summer Vacation Seminar Single pulses from PSR B 0834+06

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) Ryan Shannon, Pulsars, Summer Vacation Seminar

Pulsars have unique Period and Period derivatives • Period derivative • Describe the pulsar population • Estimate other properties based on P and Pdot. • Age (103 – 109 yr) • Surface magnetic field strength (108 to 1015 G) • Surface voltage potential (1012 V) log Period derivative (s s-1) • Two fundamental observables of pulsars Canonical Pulsars MSPs Some pulsars are recycled Period (sec) Ryan Shannon, Pulsars, Summer Vacation Seminar

Pulsar radiation is erratic • Single pulses vary in shape • Some pulsars show ultrabright giant pulses • Some pulsars occasionally miss pulses (nulling) • Some pulsars only occasionally emit pulses (rotating radio transients RRATS) Bhat et. al. 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 Ryan Shannon, Pulsars, Summer Vacation Seminar 0 < DM < 1200 for known pulsars

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. Ryan Shannon, Pulsars, Summer Vacation Seminar

Step 1: Finding Pulsars Talk to Mike Keith The Parkes radio telescope has found more than twice as many pulsars as the rest of the world’s telescopes put together. Ryan Shannon, Pulsars, Summer Vacation Seminar

Pulsar Timing: The Basics of Pulsars as Clocks P • • M P … Stack M pulses (M=1000 s) Time-tag using template fitting W • Repeat for L epochs spanning N=T/P spin periods (T=years) • N ~ 108 – 1010 cycles in one year • Period determined to • B 1937+21: P = 0. 0015578064924327 0. 000000004 s • J 1909 -3744: eccentricity < 0. 00000013 (Jacoby et al. 2006) 26 May 2011 Ryan Shannon, Pulsars, Summer Vacation Seminar UWashington 14

What influences pulse arrival times? • Pulsar spindown Pulsar • 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) Goal: including as many of the perturbations as possible in timing model. Ryan Shannon, Pulsars, Summer Vacation Seminar Earth

What influences pulsar arrival times? D/c 2 te = tr – + 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 Ryan Shannon, Pulsars, Summer Vacation Seminar

No Spindown Relative Amplitudes of Contributions ΔT 5 ms 0 Relative Day pulsar Simulated TOAs for MSP J 1713+0747 Earth 1000 Relative Day Parallax off by 1 mas 20 ms 0 CASS Colloquium 3/8/11 1000 10 µs 0 Relative Day 1000 Insert presentation do not Relativetitle, Day remove CSIRO from start of footer ΔT Proper motion off by 1 mas/yr ΔT ΔT RA off by 1” 500 ns 0 Relative Day 1000

Reflex Motion Konacki & Wolszczan (2004): Three planets around MSP B 1257+12: 4. 3 MEarth, 3. 9 MEarth, and 0. 02 MEarth Massive (white dwarf) companion 2 ms ΔT 20 µs 0 Relative Day CASS Colloquium 3/8/11 1000 1990 Insert presentation title, do not remove CSIRO from start of footer 2002

Example: What pulsar residuals ought to look like: PSR B 1855+09 AO Painting ΔT (µs) Arecibo Upgrade 6 -6 1986 Year The Residuals are quite white! (Time series from D. Nice) Ryan Shannon, Pulsars, Summer Vacation Seminar 2010

Example: What Residuals from Most Pulsars Look Like 40 ΔTOA (µs) Origin: Intrinsic spin instabilities (spin noise) Asteroid belt? -50 0 Time (yr) Ryan Shannon, Pulsars, Summer Vacation Seminar 18

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 Ryan Shannon, Pulsars, Summer Vacation Seminar

First binary pulsar: The Hulse-Taylor Binary B 1913+16 Pulse period: 59 ms Orbital Period: 7 h 45 m 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) Ryan Shannon, Pulsars, Summer Vacation Seminar

Gravitational Radiation from B 1913+16 • Prediction based on measured Keplerian parameters and Einstein’s general relativity due to emission of gravitational waves (1. 5 cm per orbit) • After ~250 MYr the two neutron stars will collide! (Weisberg & Taylor 2003) CSIRO. Gravitational wave detection Ryan Shannon, Pulsars, Summer Vacation Seminar

The Next Grail: A double pulsar system Ryan Shannon, Pulsars, Summer Vacation Seminar

First Double Pulsar: J 0737 -3939 Lyne et al. (2004) • Pb=2. 4 hrs, d /dt=17 deg/yr • MA=1. 337(5)M , MB=1. 250(5)M Testing GR: Now to 0. 05% Ryan Shannon, Pulsars, Summer Vacation Seminar Kramer et al. (2004)

The Future: Pulsar Black Hole Systems • Pulsar-BH binaries in the field • Pulsars orbiting Sag A* (Massive black hole in centre of Galaxy) Ryan Shannon, Pulsars, Summer Vacation Seminar

Gravitational Wave Detection with Pulsars Ryan Shannon, Pulsars, Summer Vacation Seminar

Status of gravitational wave detections: Number of known gravitational wave sources: 0 Ryan Shannon, Pulsars, Summer Vacation Seminar

Spin-down irregularities No angular signature Ryan Shannon, Pulsars, Summer Vacation Seminar

What if gravitational waves exist? Quadrapolar signature Ryan Shannon, Pulsars, Summer Vacation Seminar

A stochastic background of GW sources Expect backgrounds from: 1. Supermassive black-hole binaries 2. Relic GWs from the early universe 3. Cosmic strings The stochastic background is made up of a sum of a large number of plane gravitational waves. Ryan Shannon, Pulsars, Summer Vacation Seminar

Detecting the stochastic background This is the same for all pulsars. This depends on the pulsar. • The induced timing residuals for different pulsars will be correlated Ryan Shannon, Pulsars, Summer Vacation Seminar

The expected correlation function Simulated data See Hellings & Downs 1983, Ap. J, 265, L 39 Ryan Shannon, Pulsars, Summer Vacation Seminar

Detection/limits on the background • No detection yet made • Good limit coming soon (see my talk next week!) Current data sets are ruling out a few cosmic string models The square kilometre array should detect GWs or rule out most models Ryan Shannon, Pulsars, Summer Vacation Seminar GW frequencies between 10 -9 and 10 -8 Hz complementary to LIGO and LISA

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! 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 Ryan Shannon, Pulsars, Summer Vacation Seminar Chatterjee et al. (2005)