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Searching for Radio Pulsars

Vicky Kaspi, McGill University CIFAR AGM 2012. Searching for Radio Pulsars. Why Do We Need More Radio Pulsars?. Want to build a `Pulsar Timing Array’ (PTA) to detect gravitational waves

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Searching for Radio Pulsars

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  1. Vicky Kaspi, McGill University CIFAR AGM 2012 Searchingfor Radio Pulsars

  2. Why Do We Need MoreRadioPulsars? • Want to build a `Pulsar Timing Array’ (PTA) to detect gravitational waves • Need many MSPs distributed ~isotropically on the sky, timed with very high precision simultaneously over many years • Also, individual objects can be astrophysically very interesting!

  3. Arecibo Observatory (credit: NAIC) The PALFA Survey • Surveying Galactic plane with 305-m Areciboradio telescope with ALFA receiver • International consortium, ~30 members • 1.4 GHz, 5 min ptgs, 64us, 1 Petabyte 7-beam PALFA Receiver

  4. PALFA Survey Status 96pulsars discovered so far, including 14 MSPs

  5. PALFA MSPs vs. ATNF Catalogue. (Credit: D. Nice)

  6. GBT Driftscan Survey • Used GBT during 2007 summer track refurbishing • Dish stuck at zenith, sky drifted overhead • 134 Tb at 350 MHz • Covered 12,000 sqdeg (1491 hrs) with gaps • 24 new pulsars, 5 msps, 20-30 RRATs!

  7. GBNCC 350 MHz Survey Green Bank North Celestial Cap Survey

  8. GBNCC 350 MHz Survey 20 pulsars so far,including 3 MSPs

  9. New Nearby GBNCC MSP! Courtesy Ryan Lynch

  10. InterestingDriftscanBinary Pulsar J0348+0432 • Based on observational work by Ryan Lynch, Paulo Freire, JohnAntoniadis, Norbert Wex • Work in preparation…allinfopreliminary • P=39ms, Porb=2.4 hr • Highly relativistic! • WD companion, mass well determined from spectrum, models: 0.172+/-0.002 sm • WD absorption lines show orbital Doppler shifts Preliminary!!!

  11. White Dwarf Radial Velocities q=11.85+/-0.10 Preliminary!!! Courtesy John Antoniadis

  12. J0348: Massive & Relativistic Preliminary!!! • Combination of q, Mc yields Mp=2.039 +/- 0.029 solar masses • Relevant to EOS; Demorest et al. 2010 • J0348: first massive NS in relativistic orbit! • Astronomical object with the strongest gravitational fields inside matter • Can test GR in new regime Courtesy John Antoniadis

  13. Testing Dipolar Radiation Damping: tensor-scalar theories • Radio timing of pulsar at GBT, Arecibo determines relativistic parameter Pbdot = (0.035+/-0.05)x10^-12 (PRELIMINARY) • PSR J0348+0432: • Note that this is better constraint that expected from GW experiments(Damour & Esposito-Farese 1998) A B Preliminary!!!

  14. J0348 and aLIGO/Virgo • To detect merging NS-binaries, need template as aLIGO/Virgo data noisy • More realistic template = greater sensitivity • Major effort to calculate post-Newtonian (PN)approximation to GR • But alternative tensor-scalar (TS) theoriescould pose problem with this strategy GR TS Courtesy Norbert Wex

  15. Merger of a 2 M NS and a 10 M BH (fISCO = 366 Hz) Number of cycles in the aLIGO/VIRGO band (10 – 1000 Hz) GR TS GR - TS PRELIMINARY 0348 today Figure courtesy Norbert Wex

  16. Merger of a 2 M NS and a 1.4 M NS (fISCO = 1293 Hz) Number of cycles in the aLIGO/VIRGO band (10 – 1000 Hz) GR TS GR - TS PRELIMINARY 0348 today Figure courtesy Norbert Wex

  17. J0348:Good News for GWs • Binary pulsars are very useful for testing TS gravity • Was true for low-mass NSs (Damour & Esposito-Farese 1998) • Now true for high-mass NSs • Good news for calculating templates: • Limit from J0348 suggests PN formalism should work for massive NSs as well

  18. Conclusions • PALFA, Driftscan, GBNCC pulsar searches in support of IPTA are yielding fruit • New MSPs for timing • Interesting binary pulsars • PSR J0348+0432: 1st high-mass neutron star in a relativistic orbit • Paper in preparation…

  19. Sky positions of all known MSPs suitable for PTA studies Courtesy D. Manchester • 63 Galactic (non-GC MSPs) • Only ~30 “good” sources

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