Vicky Kaspi, McGill University CIFAR AGM 2012

Why Do We Need More Radio Pulsars?  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!

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

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

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

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, RRATs!

GBNCC 350 MHz Survey Green Bank North Celestial Cap Survey

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

New Nearby GBNCC MSP! Courtesy Ryan Lynch

Interesting Driftscan Binary Pulsar J  Based on observational work by Ryan Lynch, Paulo Freire, John Antoniadis, Norbert Wex  Work in preparation…all info preliminary  P=39 ms, Porb=2.4 hr  Highly relativistic!  WD companion, mass well determined from spectrum, models: / sm  WD absorption lines show orbital Doppler shifts Preliminary!!!

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

J0348: Massive & Relativistic  Combination of q, Mc yields Mp= / solar masses  Relevant to EOS; Demorest et al  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 Preliminary!!!

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 J :  Note that this is better constraint that expected from GW experiments (Damour & Esposito-Farese 1998) A B Preliminary!!!

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) theories could pose problem with this strategy GR TS Courtesy Norbert Wex

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

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

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

Conclusions  PALFA, Driftscan, GBNCC pulsar searches in support of IPTA are yielding fruit  New MSPs for timing  Interesting binary pulsars  PSR J : 1 st high-mass neutron star in a relativistic orbit  Paper in preparation…

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