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Forefront of neutron star science Precision astrometry using the VLBA Bowshocks and jets

Pulsars in Motion: Astrometry, Kicks, ALFA and the SKA Jim Cordes, Cornell University. Forefront of neutron star science Precision astrometry using the VLBA Bowshocks and jets Pulsar velocities: Bimodality Kick mechanisms: tie-ins to cosmology? ALFA: A massive pulsar survey at Arecibo

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Forefront of neutron star science Precision astrometry using the VLBA Bowshocks and jets

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  1. Pulsars in Motion:Astrometry, Kicks, ALFA and the SKA Jim Cordes, Cornell University • Forefront of neutron star science • Precision astrometry using the VLBA • Bowshocks and jets • Pulsar velocities: • Bimodality • Kick mechanisms: tie-ins to cosmology? • ALFA: A massive pulsar survey at Arecibo • SKA: toward a full Galactic census of pulsars U. Illinois

  2. Pulsars… • embody physics of the EXTREME • surface speed ~0.1c • 10x nuclear density in center • some have B > Bq = 4.4 x 1013 G • Voltage drops ~ 1012 volts • FEM = 109Fg = 109 x 1011FgEarth • Tsurf ~ million K • …relativistic plasma physics in action • …probes of turbulent and magnetized ISM • …precision tools, e.g. - Period of B1937+21: P = 0.00155780649243270.0000000000000004 s - Orbital eccentricity of J1012+5307: e<0.0000008 U. Illinois

  3. Pulsar Populations: P – Pdot diagram • Canonical • P~ 20ms – 5s • B ~ 1012±1 G • Millisecond pulsars (MSPs) • P ~ 1.5 – 20ms • B ~ 108 – 109 ms • High field • P ~ 5 – 8 s • B ~ few x 1013 G • Braking index n: • Pdot  P2-n, n=3 magnetic dipole radiation • Death line • Strong selection effects log Period derivative (s s-1) Period (sec) U. Illinois

  4. Forefronts in NS Science • Understanding NS populations and their physical differences • Radio pulsars and their progenitors • Magnetars • Radio quiet/Gamma-ray loud objects • Branching ratios in supernovae • The physics of NS runaway velocities • Are “neutron stars” neutron stars? U. Illinois

  5. Forefronts in NS Science • Finding compact relativistic binary pulsars for use as laboratories • Gravity • Relativistic plasma physics in strong B • Finding spin-stable MSPs for use as gravitational wave detectors ( ~ light years) • h ~ TOA T-1 (T = data span length) • Complete surveys of the transient radio sky • pulsars as prototype coherent radio emission U. Illinois

  6. 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 U. Illinois Now to 0.1%

  7. Velocity Distribution • Gunn and Ostriker 1970 • Early estimates using interstellar scintillation measurements of radio pulsars • Millisecond pulsars: • High velocity by stellar standards • Slow by comparison to high-B objects (V~100 km s-1) • Canonical pulsars: • <V> ~ 400 km s-1 (Lyne and Lorimer 1994) • Bimodal PDF (Cordes and Chernoff 1998) U. Illinois

  8. 1994 2001 Bow Shocks Palomar Hα Image • Manifestations of high NS velocities • Probe relativistic winds from NS • Probe microstructure in the ISM • Guitar Nebula: • Ordinary pulsar • P = 0.68 s • B = 2.6 x 1012 G • s = 1.1 Myr • E = I  1033.1 erg s-1 • D  1.9 kpc (from DM) • 1600 km s-1 at nominal distance • Will escape the Milky Way HST WFPC2 Hα · · ·˙ U. Illinois

  9. A: pulsar wind cavity B: shocked pulsar wind C: shocked ISM TS: termination shock CD: contact discontinuity BS: bow shock Rs Standoff radius for an isotropic, relativistic wind: Edot Consistent with all known NS bow shocks modulo ISM density and inclination (Chatterjee & Cordes 2002). No evidence for wind anisotropy in measured bowshock contours U. Illinois

  10. 1994 2001 Bow Shocks Palomar H image • Guitar Nebula: • Ordinary pulsar • P = 0.68 s • B = 2.6 x 1012 G •  = 1.1 Myr • E = I  1033.1 erg s-1 • D  1.9 kpc (from DM) • 1600 km s-1 at nominal distance • Will escape the Milky Way HST WFPC2 H • Radius of curvature of bowshock nose increased from 1994 to 2001, corresponding to a 33% decrease in ISM density • The pulsar is emerging from a region of enhanced density Chatterjee & Cordes 2004 U. Illinois

  11. Bow Shocks MSPs Low V High Edot J2124-3358 Gaensler et al B1957+20 (Kulkarni & Hester; Gaensler et al. J0437-47 (Fruchter et al.) Mouse Duck RXJ1856 B0740-28 Canonical pulsars High V, low to high Edot J0617 U. Illinois

  12. Velocity Distribution for Canonical Pulsars: bimodal Escape from the Galaxy Best-fit model: two components Cordes & Chernoff 1998 Arzoumanian, Chernoff & Cordes 2002 U. Illinois

  13. Uncertainties in the Velocity PDF • Pulsar survey selection effects: • Beaming • Period dependence of pulsar luminosity • Frequency and period dependent selection effects • ISM propagation (dispersion, scattering) • Velocity selection in volume limited pulsar surveys • Low-Galactic latitude surveys miss high-V pulsars born in the Galactic plane • CC98 not corrected for selection effects, but high-V component ~ x5 too low • ACC02 corrected for selection effects but uses distance estimates with large errors U. Illinois

  14. Pulsar Distances U. Illinois

  15. VLBI / VLBA U. Illinois

  16. Pulsar astrometryScience Case(Brisken et al. 2002, Chatterjee et al. 2001-2004) • Pulsar Origins: • SNR associations • NS birth sites in stellar clusters / OB associations • True ages • Astrophysics: • NS atmospheres, cooling curves etc. need absolute distances • Evolution: • NS distribution and population velocities • Environments: • Galactic electron density • local ISM U. Illinois

  17. In-Beam calibration • In-beam calibration: • referencing to a source within the primary telescope beam • 20 arcmin at 1.4 GHz on the VLBA antennas • less for e.g. AO and GBT and at higher frequency U. Illinois

  18. Parallax / Proper Motion • B1929+10 • both at 1.4 and 5 GHz • D = 361+10-8 pc • V = 177+4-5 km/s Chatterjee et al. 2004 U. Illinois

  19. Current Status of Large Astrometry Program Using the VLBA • 26 pulsars observed at 8 epochs over 2 years • 2/3 use in-beam calibration • Expect 20 new parallaxes “soon” (Brisken et al., Chatterjee et al., + applications, in preparation) • http://www.astro.cornell.edu/~shami/psrvlb/ • Another set of pulsars is now being observed U. Illinois

  20. Ongoing Parallax Programs • 53 pulsars using VLBA antennas only at 1.4 GHz(systematics: ionospheric phase) • Chatterjee, Brisken et al. (2002-2004) • Currently can reach ~ 2 kpc • 6 strong pulsars, VLBA-only at 5 GHz • Ionosphere less important • Chatterjee, Vlemmings, Cordes et al. (2001-ongoing) • VLBA + Arecibo + GBT + … • Initial tests • Expect to do ~100 pulsars in 5 years, some to 5 kpc • Future: SKA  superior phase calibration, sensitivity, can reach >10 kpc U. Illinois

  21. Vlemmings, Cordes, Chatterjee (2004) Separated at Birth • B2021+51 and B2020+28 originate from same binary • Disrupted in second SN explosion • 1.9 Myr ago • c.f. spindown ages of 2.88 and 2.75 Myr • Birth Location: the Cygnus Superbubble • Birth velocities: • 200 km/s kick • 150 km/s (B2021) • 500 km/s (B2020) • Second created pulsar (B2020) • P0 ~ 200 ms U. Illinois

  22. Cygnus 14o x 10o MSX Mid IR Image Shaded band: kinematic constraints Black pair of curves: spindown ages vs braking index for the two objects Red, Green: P0 vs age for 3 values of braking index U. Illinois

  23. Chatterjee et al. In preparation B1508+55 ,b = 91.3o, 52.3o D = 2.450.25 kpc V = 1114-94+132 km s-1 P = 0.74 s B = 2x1012 G s = P/2Pdot = 2.36 Myr The highest measured velocity using direct distance measurement 2.5x further than electron density model based distance estimate (NE2001) Possibly born in Cyg OB 7 U. Illinois

  24. NE2001: Galactic Distribution of Free Electrons + Fluctuations Paper I = the model (astro-ph/0207156) Paper II = methodology & particular lines of sight (astro-ph/0301598) Based on ~ 1500 lines of sight to pulsars and extragalactic objects Code + driver files + papers: www.astro.cornell.edu/~cordes/NE2001 U. Illinois

  25. Local ISM Components of NE2001 B1508+55 is further than its DM implies most likely because it is viewed through one or more Galactic chimneys (supernova blowouts) U. Illinois

  26. Pulsar Velocity Distribution Using only Parallax Distances • Likelihood analysis for birth parameters: • using pulsars with accurate astrometry • 1 component model • V1 = 175 km/s • hz = 0.2 kpc • 2 component model • V1 = 86 km/s • V2 = 296 km/s • hz = 0.16 kpc U. Illinois

  27. Understanding the Velocity Distribution • Two components suggest  2 processes • E.g. orbital disruption + asymmetric supernovae • But two independent processes will not produce a bimodal PDF • Convolution  unimodal PDF • Need “kick” processes to be selective • Extreme case: Bombaci and Popov (2004): • Low V NS are hadronic • High V “NS” are quark stars that undergo two kicks (including one corresponding to phase transition to quark matter) U. Illinois

  28. Pulsar Jets Crab pulsar P = 33 ms • Magnetospheric Jets • Along spin axis  • Nearly ║ to V • 0.1 to 1 pc in length Vela pulsar P = 89 ms Chandra images U. Illinois

  29. Pulsar Jets • Guitar Nebula Jet • Chandra 50 ksec ACIS obs • Misaligned from Guitar axis  proper motion direction Cordes et al. in preparation U. Illinois

  30. Pulsar Jets • Guitar Nebula Jet • Chandra 50 ksec ACIS obs • Misaligned from Guitar axis  proper motion direction • Jet luminosity is much larger fraction of Edot than in Crab and Vela pulsars • One-sided = two-sided + relativistic beaming? • Jet is straight for ~1pc • Consistent with synchrotron energy losses,  ~0.3c and jet within 30o of LOS • Explanation: magnetic reconnection in bow-shock nose Cordes et al. 2005 (in prep) U. Illinois

  31. Simulated Bow Shocks Romanova, Chulsky & Lovelace 2001, 2005 U. Illinois

  32. Pulsar Jets Gaensler et al 2002 Hα • J2124-3358 • MSP: P = 4.93s • B = 3.2x108 G • s = 3.8 Gyr • Probably a magnetospheric jet • Bent by the shocked ISM flow • Chatterjee et al. in preparation Chandra U. Illinois

  33. Pulsar Kicks Pulsar space velocity: VPSR = VGal + Vpeculiar = VGal + Vprogenitor + Vkick, orb + Vkick, natal • Present day pulsar motions require that large contributions from disrupted orbital motion and from near instantaneous natal “kicks” • Most pulsars are isolated though most originated in binary stellar systems • Symmetric supernova explosions unbind binaries if Mlost > ½ pre-supernova total system mass (Blaauw mechanism) • NS velocity = pre-SN orbital velocity • Maximum NS velocity  103 km s-1 (but will be rare) • Natal kicks: • Can unbind binaries with less mass loss • Manifestations depend on time scale kick relative to • Porbital • Pspin (of proto NS) Spruit & Phinney 1998 Lai et al. 2001 U. Illinois

  34. Characteristics of NS Binaries (kicks are required, not just binary breakup): • Pulsar-MS binaries: Orbital plane precession and orbital decay PSR J0045-7319 binary (Kaspi et al. 1996; Lai et al. 1995; Lai 1996; Kumar & Quataert 1997) PSR J1740-3052 (Stairs et al. 2003) • Double NS Binaries: Geodetic precession, orbital eccentricities, systemic motion PSR B1913+16 (Kramer 1998; Wex et al. 2000; Weisberg & Taylor 2002); PSR B1534+12 PSR J0737-3039 (Dewi & van den Heuvel 2004; Willems et al 2004; Ransom et al. 2004) • High-Mass X-ray Binaries: High eccentricities of Be/X-ray binaries (Verbunt & van den Heuvel 1995; but Pfahl et al. 2002) High radial velocity (430 km/s) of Circinus X-1 (Tauris et al. 1999) • Evolutionary studies of NS population (e.g., Dewey & Cordes 1987; Fryer & Kalogera 1997; Fryer, Burrows & Benz 1998) Evidence for NS Kicks • Pulsar proper motion  V ~ 200-500 km/s, some with V>103 km/s (Hansen & Phinney 1997; Lorimer et al. 1997; Cordes & Chernoff 1998; Arzoumanian et al. 2002) • Bow shock from fast moving pulsars in ISM (e.g., PSR 2224+65  V>800 km/s; Cordes et al.1993; Chatterjee & Cordes 2002) • NS-SNR association  large NS velocity up to ~ 103 km/s Large NS Velocities (>> progenitors’ velocities ~ 30 km/s): U. Illinois

  35. L S SB SB SB He star Vkick S L S PSR 1913+16A Geodetic precession (spin-orbit GR effect) Assume SB was aligned ==> Vkick must not be aligned with SB. PSR B spin period? ~ 1s Similarly for double pulsar J0737-3939 PSR B U. Illinois

  36. Clues about Kicks • Bimodality of the net velocity distribution • Includes combined effects of orbital disruption and natal kicks • The proper motion is nearly aligned with jets seen in the Crab and Vela pulsars • + a few other objects • common or chance? • Intrinsic to the kick mechanism or imposed by rotation? (Spruit & Phinney 1998; Lai et al. 2001) U. Illinois

  37. Kick Mechanisms (after Bombaci and Popov 2004) U. Illinois

  38. Adapted from Janka et al Convection in the the shocked mantle (and in proto-NS) can lead to asymmetric matter ejection and associated neutrino emission. How much? U. Illinois

  39. Numerical experiments of Scheck et al.(2004) Adjust L(t) from proto-NS so that explosion sets in slowly (100’s ms--seconds) Slow explosion leads to large kick (100’s km/s) U. Illinois

  40. Toward a Galactic Census of Radio Pulsars The first 30 years of pulsars: ~ 700 radio pulsars ~ 1% binaries Parkes Multibeam Survey 1997-2004: ~ 800 new pulsars + Other surveys: ~ 100 MSPs 6 relativistic binary pulsars (NS-NS) No PSR-BH binary (yet) c.f. ~105 active radio pulsars (20% beamed to us) U. Illinois

  41. Why more pulsars? • Extreme Pulsars: • P < 1 ms P > 5 sec • Porb < hours B >> 1013 G (link to magnetars?) • V > 1000 km s-1 • Population & Stellar Evolution Issues • NS-NS & NS-BH binaries: strong gravity effects probed with pulse timing • The high-energy connection (e.g. GLAST) • Physics payoff (EOS of NS matter, GR, LIGO, GRBs…) • Serendipity (strange stars, transient sources) • Mapping the Galactic magnetoionic medium • New instruments (AO, GBT, SKA) can dramatically increase the volume searched (Galactic & extragalactic) U. Illinois

  42. Arecibo + SKA Surveys U. Illinois

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  45. ALFA Galactic Plane Survey Survey Galactic Plane • |b| < 5o  = 32o-77o and  = 168o-214o • 300 s / sky position (~30s needed to match PMB sensitivity) • Greater sensitivity to MSPs (narrower frequency channels) • 2000 hr telescope time over a 3-5 year period 103 new pulsars • Reach edge of Galactic population for much of luminosity function • High sensitivity to millisecond pulsars and binary pulsars • Dmax = 2 to 3 times greater than for Parkes MB Sensitivity to transient sources Data management: • Keep all raw data (~ 1 Petabyte after 5 years) at the Cornell Theory Center Database of raw data, data products, end products • Web based tools for Linux-Windows interface (mysql  ServerSql) • VO linkage (in future) U. Illinois

  46. Blue: known pulsars (prior to Parkes MB) Red: Parkes MB Green: PALFA simulated pulsars U. Illinois

  47. The First ALFA Pulsar U. Illinois

  48. A pulsar found through its single-pulse emission, not its periodicity (c.f. Crab giant pulses). Algorithm: matched filtering in the DM-t plane. ALFA’s 7 beams provide powerful discrimination between celestial and RFI transients U. Illinois

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  50. The Square Kilometer Array • Why needed? • The International SKA Project • The US SKA Consortium • SKA science case • Key science areas • Discovery space (Exploration of the Unknown) • Pulsar science with the SKA U. Illinois

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