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Pulsars + Parkes = Awesome

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

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Pulsars + Parkes = Awesome

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

  2. 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

  3. End of Stellar Evolution Main sequence star Compact Remnant White dwarf 0.1 to ~ 1.2 Msun Degenerate electron pressure 0.1 to 8 Msun 8 to 20 (?) Msun Neutron star 1.3 to < 3 Msun Degenerate neutron pressure Black hole >3 Msun Gravity wins > 20 Msun Complications: mass exchange in binary systems Ryan Shannon, Pulsars, Summer Vacation Seminar

  4. Historical background 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)  bleak 1967: 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

  5. 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 Ryan Shannon, Pulsars, Summer Vacation Seminar

  6. 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

  7. 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 Single pulses from PSR B0834+06 Ryan Shannon, Pulsars, Summer Vacation Seminar

  8. 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

  9. log Period derivative (s s-1) Period (sec) 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) Canonical Pulsars MSPs Some pulsars are recycled Ryan Shannon, Pulsars, Summer Vacation Seminar

  10. Pulsar radiation is erratic • 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) Bhat et. al. Ryan Shannon, Pulsars, Summer Vacation Seminar

  11. 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 Ryan Shannon, Pulsars, Summer Vacation Seminar

  12. 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

  13. 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

  14. Pulsar Timing: The Basics of Pulsars as Clocks Stack M pulses (M=1000s) Time-tag using template fitting MP P … W Repeat for L epochs spanning N=T/P spin periods (T=years) N ~ 108 – 1010 cycles in one year Period determined to B1937+21: P = 0.00155780649243270.0000000000000004 s J1909-3744:eccentricity < 0.00000013 (Jacoby et al. 2006) 26 May 2011 UWashington 14 Ryan Shannon, Pulsars, Summer Vacation Seminar

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

  16. What influences pulsar arrival times? 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 te = tr – D/c2 + DM/2 + R + E + S - R - E - S + TOAISM + TOAorbit noise + TOAspin noise + TOAgrav. waves + … Ryan Shannon, Pulsars, Summer Vacation Seminar

  17. Relative Amplitudes of ContributionsSimulated TOAs for MSP J1713+0747 No Spindown pulsar 5 ms ΔT Earth 0 1000 Relative Day Relative Day RA off by 1” Parallax off by 1 mas Proper motion off by 1 mas/yr ΔT ΔT ΔT 10 µs 20 ms 500 ns 0 0 0 1000 1000 1000 Relative Day Relative Day Relative Day Insert presentation title, do not remove CSIRO from start of footer

  18. Massive (white dwarf) companion ΔT 20 s 0 Relative Day 1000 Reflex Motion Konacki & Wolszczan (2004): Three planets around MSP B1257+12: 4.3 MEarth, 3.9 MEarth, and 0.02 MEarth 2 ms 20 µs 20 µs 1990 2002 Insert presentation title, do not remove CSIRO from start of footer

  19. Example: What pulsar residuals ought to look like: PSR B1855+09 6 Arecibo Upgrade ΔT (µs) AO Painting -6 2010 Year 1986 The Residuals are quite white! (Time series from D. Nice) Ryan Shannon, Pulsars, Summer Vacation Seminar

  20. 40 ΔTOA (µs) -50 0 18 Time (yr) Example: What Residuals from Most Pulsars Look Like Origin: Intrinsic spin instabilities (spin noise) Asteroid belt? Ryan Shannon, Pulsars, Summer Vacation Seminar

  21. 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

  22. 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) Ryan Shannon, Pulsars, Summer Vacation Seminar

  23. Gravitational Radiation from B1913+16 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) CSIRO. Gravitational wave detection Ryan Shannon, Pulsars, Summer Vacation Seminar

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

  25. Testing GR: Kramer et al.(2004) First Double Pulsar: J0737-3939 Lyne et al.(2004) Pb=2.4 hrs, d/dt=17 deg/yr MA=1.337(5)M, MB=1.250(5)M Now to 0.05% Ryan Shannon, Pulsars, Summer Vacation Seminar

  26. 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

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

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

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

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

  31. A stochastic background of GW sources Expect backgrounds from: Supermassive black-hole binaries Relic GWs from the early universe 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

  32. 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. Ryan Shannon, Pulsars, Summer Vacation Seminar

  33. The expected correlation function Simulated data See Hellings & Downs 1983, ApJ, 265, L39 Ryan Shannon, Pulsars, Summer Vacation Seminar

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

  35. Conclusion Ryan Shannon, Pulsars, Summer Vacation Seminar 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!

  36. Pulsars Have High Velocities: Chatterjee et al. (2005) • 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

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