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Pulsars + Parkes = Awesome Ryan Shannon Postdoctoral Fellow, CSIRO Astronomy and Space Science Credit: John Sarkissian Slide 2 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 Slide 3 Ryan Shannon, Pulsars, Summer Vacation Seminar End of Stellar Evolution Main sequence starCompact Remnant White dwarf 0.1 to ~ 1.2 M sun Degenerate electron pressure 0.1 to 8 M sun 8 to 20 (?) M sun > 20 M sun Neutron star 1.3 to < 3 M sun Degenerate neutron pressure Black hole >3 M sun Gravity wins Complications: mass exchange in binary systems Slide 4 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 (10 6 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) Historical background Slide 5 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 Slide 6 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 Slide 7 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 Slide 8 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) Slide 9 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 (10 3 10 9 yr) Surface magnetic field strength (10 8 to10 15 G) Surface voltage potential (10 12 V) log Period derivative (s s -1 ) Period (sec) MSPs Canonical Pulsars Some pulsars are recycled Slide 10 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) Slide 11 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 Slide 12 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. Slide 13 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 worlds telescopes put together. Talk to Mike Keith Slide 14 Ryan Shannon, Pulsars, Summer Vacation Seminar 26 May 2011UWashington14 Repeat for L epochs spanning N=T/P spin periods (T=years) N ~ 10 8 10 10 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 MPMP W J1909-3744: eccentricity < 0.00000013 (Jacoby et al. 2006) B1937+21: P = 0.0015578064924327 0.0000000000000004 s Slide 15 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 Earth Goal: including as many of the perturbations as possible in timing model. Slide 16 Ryan Shannon, Pulsars, Summer Vacation Seminar What influences pulsar arrival times? t e = t r D/c 2 + DM/ 2 + R + E + S - R - E - S + TOA ISM + TOA orbit noise + TOA spin noise + TOA grav. 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 Slide 17 CASS Colloquium 3/8/11 Insert presentation title, do not remove CSIRO from start of footer pulsar Earth 20 ms 10 s 500 ns 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 mas RA off by 1 TT TT TT TT 0 1000 0 0 Relative Day 0 1000 Slide 18 CASS Colloquium 3/8/11 Insert presentation title, do not remove CSIRO from start of footer Massive (white dwarf) companion 20 s 1000 TT 0 Relative Day Reflex Motion Konacki & Wolszczan (2004): Three planets around MSP B1257+12: 4.3 M Earth, 3.9 M Earth, and 0.02 M Earth 19902002 2 ms 20 s Slide 19 Ryan Shannon, Pulsars, Summer Vacation Seminar Example: What pulsar residuals ought to look like: PSR B1855+09 Arecibo Upgrade AO Painting The Residuals are quite white! (Time series from D. Nice) Year 1986 2010 T (s) 6 -6 Slide 20 Ryan Shannon, Pulsars, Summer Vacation Seminar Example: What Residuals from Most Pulsars Look Like 0 18 -50 40 TOA (s) Time (yr) Origin: Intrinsic spin instabilities (spin noise) Asteroid belt? Slide 21 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 Slide 22 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) Slide 23 Ryan Shannon, Pulsars, Summer Vacation Seminar CSIRO. Gravitational wave detection Prediction based on measured Keplerian parameters and Einsteins 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 Slide 24 Ryan Shannon, Pulsars, Summer Vacation Seminar The Next Grail: A double pulsar system Slide 25 Ryan Shannon, Pulsars, Summer Vacation Seminar First Double Pulsar: J0737-3939 P b =2.4 hrs, d /dt=17 deg/yr M A =1.337(5)M , M B =1.250(5)M Lyne et al.(2004) Testing GR: Kramer et al.(2004) Now to 0.05% Slide 26 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) Slide 27 Ryan Shannon, Pulsars, Summer Vacation Seminar Gravitational Wave Detection with Pulsars Slide 28 Ryan Shannon, Pulsars, Summer Vacation Seminar Status of gravitational wave detections: Number of known gravitational wave sources: 0 Slide 29 Ryan Shannon, Pulsars, Summer Vacation Seminar Spin-down irregularities No angular signature Slide 30 Ryan Shannon, Pulsars, Summer Vacation Seminar What if gravitational waves exist? Quadrapolar signature Slide 31 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. Slide 32 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. Slide 33 Ryan Shannon, Pulsars, Summer Vacation Seminar The expected correlation function See Hellings & Downs 1983, ApJ, 265, L39 Simulated data Slide 34 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 Slide 35 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! Slide 36 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)