vicky kaspi, mcgill university cifar agm 2012. why do we need more radio pulsars? want to build a...
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SEARCHING FOR RADIO PULSARS
Vicky Kaspi, McGill UniversityCIFAR AGM 2012
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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!
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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
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PALFA Survey Status
96 pulsars discovered so far, including 14 MSPs
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PALFA MSPs vs. ATNF Catalogue. (Credit: D. Nice)
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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!
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GBNCC 350 MHz Survey
Green Bank North Celestial Cap Survey
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GBNCC 350 MHz Survey
20 pulsars so far,including3 MSPs
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New Nearby GBNCC MSP!
Courtesy Ryan Lynch
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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!!!
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White Dwarf Radial Velocities
Courtesy John Antoniadis
q=11.85+/-0.10
Preliminary!!!
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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!!!
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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!!!
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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
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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
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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
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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
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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…
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Sky positions of all known MSPs suitable for PTA studies
• 63 Galactic (non-GC MSPs)
• Only ~30 “good” sources
CourtesyD. Manchester