SEARCHING FOR RADIO PULSARS

Vicky Kaspi, McGill UniversityCIFAR 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

Areciboradio 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, 20-30 RRATs!

GBNCC 350 MHz Survey

Green Bank North Celestial Cap Survey

GBNCC 350 MHz Survey

20 pulsars so far,including3 MSPs

New Nearby GBNCC MSP!

Courtesy Ryan Lynch

Interesting DriftscanBinary Pulsar J0348+0432

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: 0.172+/-0.002 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=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

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 J0348+0432:

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) theoriescould pose problem with this strategy

GR

TS

Courtesy Norbert Wex

Number of cycles in the aLIGO/VIRGO band (10 – 1000 Hz)

GRTSGR - TS

0348 today

Merger of a 2 M NS and a 10 M BH (fISCO = 366 Hz)

Figure courtesy Norbert Wex

PRELIMINARY

Number of cycles in the aLIGO/VIRGO band (10 – 1000 Hz)

GRTSGR - TS

0348 today

Merger of a 2 M NS and a 1.4 M NS (fISCO = 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 J0348+0432: 1st 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

CourtesyD. Manchester