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What science can initial LIGO do with pulsars?

What science can initial LIGO do with pulsars?. Ben Owen. Detections or upper limits. Owen in Amaldi. New emission mechanisms Magnetic mountains Magnetic bottling Mountains all the way down Types of searches Known pulsars (radio) Low-mass x-ray binaries X-ray point sources

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What science can initial LIGO do with pulsars?

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  1. What science can initial LIGO do with pulsars? Ben Owen Penn State Sources & Simulations

  2. Detections or upper limits Owen in Amaldi • New emission mechanisms • Magnetic mountains • Magnetic bottling • Mountains all the way down • Types of searches • Known pulsars (radio) • Low-mass x-ray binaries • X-ray point sources • Unknown objects Penn State Sources & Simulations

  3. “Old” emission mechanisms • Key number is “ellipticity” • From moment of inertia:  = (Ixx - Iyy)/Izz • Roughly quadrupole/inertia or R/R • Standard answer:  < few 10-7 • Observation of x-ray binaries • Theory of mountains in crust, r-modes, … • Since h ~ , this means advanced LIGO • Free precession is OK for advanced LIGO too Penn State Sources & Simulations

  4. Magnetic mountains • Cutler PRD 2002 • Differential rotation creates toroidal field • Field pinches star • Rotation spreads star • Stable when winding axis orthogonal to rotation axis (cigar) • Flip timescale determined by crust Penn State Sources & Simulations

  5. Magnetic mountains • Max  > 10-5 , but… • Observations say flip doesn’t go all the way • B field pops out if wound too tight (1016G? Magnetars?) • B field diffuses through resistive matter if too high-lifetime? Penn State Sources & Simulations

  6. Magnetic bottling • Melatos & Payne MNRAS 2005 • Accreting millisecond pulsars: B ~ 108 G • Accreted plasma/metal conducts electricity • Crosses B field lines slowly (resistivity) • Funneled and bottled at poles by field Penn State Sources & Simulations

  7. Magnetic bottling • Can’t have B >> 108 G (field repels) • Need high accretion rate to build mountain • But that heats matter, reduces conductivity • Max. 10-5 for observed B fields • But needs T = 107 K (hard to get) • And makes x-rays… Penn State Sources & Simulations

  8. Mountains all the way down • Owen PRL next week • Strange quark stars might be all solid • Quark-baryon hybrids might have solid cores • Meson condensates too (generic mechanism) • Order of magnitude is calculable (surprise!) Penn State Sources & Simulations

  9. Mountains all the way down • Quark stars < few 10-4 • Hybrid stars < 10-5 • Meson stars < 10-5 • Highly dependent on poorly explored parameters • How to drive mountains to maximum height? Penn State Sources & Simulations

  10. Known pulsar search • Known signal phase means matched filtering, including Doppler shifts from LIGO motion • Radio is the only timing data good enough • Abbott et al. PRL 2005: 28 isolated pulsars, some S2 upper limits were  < 10-5 • But radio spindown puts better limits so far • d/dt = 8.5 10-13 (/50Hz)5 (/10-5)2 • Spindown  < 10-8 for old millisecond pulsars • Young ones should be different population… Penn State Sources & Simulations

  11. Known pulsar search • Sensitivity goes as hrms T1/2 • S6: cut 3 yr to 1.5 yr for 2 upgrade in hrms? • J0534+2200 (Crab) at 60 Hz, 2 kpc • Spindown  = 7.4 10-4 • S5 1 yr gets 1.1 10-4, upgrade gets 4.6 10-4 • J1952+3252 (CTB 80) at 50 Hz, 2.5 kpc • Spindown  = 1.1 10-4 • Upgrade gets 9 10-5 • (J1913+1011 still missed by 2 with upgrade) Penn State Sources & Simulations

  12. Known pulsar search • Pulsars in globular clusters: • Generally older, further away, thus worse • But some spin-downs are questionable (spin-up!) • Masked by cluster dynamics ~ 10-14 Hz/s • J2129+1210D in M15 at 5 10-13 Hz/s • Check ANTF catalogue: • 90 in globular clusters • 4 or so with maskable spindown (25-50 Hz) Penn State Sources & Simulations

  13. Low-mass x-ray binaries • Accretion spin-up = GW spin-down means ellipticity given by x-ray flux • Implies  < few 10-7 for known ones, GW too faint for initial detectors • Any =10-5 must be unseen for some reason • Data analysis: computationally limited because of poorly known phase: frequency, orbit, accretion random walk Penn State Sources & Simulations

  14. X-ray point sources • Like Cas A • Doppler shifts known • Spindown unknown, could be very large • Coherent integration OK up to few weeks (courtroom notes) • Just getting started • List of candidates? Penn State Sources & Simulations

  15. Unknown objects • All-sky, all-frequency: biggest CPU sink, can’t do full matched filtering • But try http://einstein.phys.uwm.edu/ • Sensitivity scales as T1/4 or so, favors upgrade • Abbott et al. gr-qc/0508065 and upcoming • Can’t untangle ellipticity from distance without proper motion frequency shift & advanced LIGO (Seto PRD 2005) • Could get GW fraction of spindown (me) Penn State Sources & Simulations

  16. So what’s the answer? • Detect high ellipticity • Only untangled from distance for known pulsars or (some) x-ray point sources • Means not a normal neutron star • Non-detections (upper limits) • Known: Can’t rule out a matter model, though many (advanced) could weigh against it • Unknowns: How to phrase exclusion region? Start making galactic population synthesis? Penn State Sources & Simulations

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