Vicky Kaspi, McGill University Harvard/Smithsonian …The Double Pulsar at a Glance Pulsar A: 23 ms...
Transcript of Vicky Kaspi, McGill University Harvard/Smithsonian …The Double Pulsar at a Glance Pulsar A: 23 ms...
![Page 1: Vicky Kaspi, McGill University Harvard/Smithsonian …The Double Pulsar at a Glance Pulsar A: 23 ms (Burgay et al. 2003, Nature) Pulsar B: 2.8 s (Lyne et al. 2004, Science) 2.4 hour](https://reader033.fdocuments.in/reader033/viewer/2022052801/5f1799723597537bf709bd62/html5/thumbnails/1.jpg)
TESTING GR WITH PULSARS III NEW TESTS + THE FUTURE
Vicky Kaspi, McGill University Harvard/Smithsonian GR Conference May 2012
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Outline
Eclipses in double pulsar and relativistic spin precession
New pulsar surveys
New exciting relativistic binary
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The Double Pulsar at a Glance
Pulsar A: 23 ms (Burgay et al. 2003, Nature)
Pulsar B: 2.8 s (Lyne et al. 2004, Science)
2.4 hour orbital period
System viewed edge-on:
We see eclipse for 30 s each 2.4 hour orbit
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Lyne et al. 2004, Kaspi et al. 2004
Pulsar A Eclipse
Pulsar A eclipsed for ~30s each orbit
Eclipse duration >> projected size of B’s surface
eclipse frequency independent, asymmetric GBT
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B Modulates A in Eclipse!
McLaughlin et al. 2004
Phase of B shown with dashed lines
Average eclipse, summed coherently with B phase
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Modulation at B’s Period During A’s Eclipse
Dynamic FFT of light curve of A
Shows modulation at B’s period (or at a harmonic)
Only occurs during eclipse
Breton et al. 2012
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Eclipse behavior nearly radio-frequency independent
Main frequency effects at edges of eclipses
Breton et al. 2012
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Periodicity within eclipses radio-frequency independent across 300-2000 MHz
Breton et al. 2012
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Eclipse duration depends on phase of pulsar B
Breton et al. 2012
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Breton et al. 2012
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Eclipse Model
The Lyutikov & Thompson Model (2006): • Closed field lines within pulsar B magnetosphere are
populated with hot relativistic plasma Results in synchrotron absorption of pulsar A radio
emission Magnetic field configuration is a dipole truncated
outside some radius.
Constructing a model eclipse light curve requires evaluating the synchrotron opacity
along different lines of sight through the magnetosphere
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Geometry for Double Pulsar
Lyutikov & Thompson 2005
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Pulsar A Eclipse Modelling
Breton et al. 2008
A eclipse modulation offers new way to measure geometry precisely – can look for relativistic precession of B’s spin!
![Page 14: Vicky Kaspi, McGill University Harvard/Smithsonian …The Double Pulsar at a Glance Pulsar A: 23 ms (Burgay et al. 2003, Nature) Pulsar B: 2.8 s (Lyne et al. 2004, Science) 2.4 hour](https://reader033.fdocuments.in/reader033/viewer/2022052801/5f1799723597537bf709bd62/html5/thumbnails/14.jpg)
Precession of the spin angular momentum of a body is expected in relativistic systems.
The precession of pulsar B is predicted to be due to: 1. the orbital motion of pulsar B in a curved space-time
(geodetic precession aka de Sitter/Fokker precession),
2. the “frame-dragging” due to the translational orbital motion of pulsar A around the center of mass (Lense-Thirring precession).
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In general theories of gravity, SO precession rate is (Damour & Taylor 1992):
Rewriting with observable timing parameters:
Yields a test of the strong-field parameters
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Collected 63 eclipses over 4 years at Green Bank Telescope in collaboration with timing team
McGill PhD thesis of Rene Breton
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Evolution of B’s Spin Axis
For each of 63 eclipses LT model was fit using Markov Chain Monte Carlo
3 free parameters:
Show Movie
, ,
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Breton et al. 2008, Science
Relativistic Spin Precession Detected
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Results
0 Bt
B yr
4 77 0 65
0 66. deg/.
.
B yr 50734 00007. . deg/
GR PREDICTION Breton et al. 2008
Compare with GPB: 0.0018 deg/yr
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( ) . .c
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Results, Differently
Any successful theory of gravity in
this framework must predict
this value.
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Continued Monitoring?
In principle, longer baseline = better measurement
BUT systematics: B’s profile changing;
challenging to measure pulse phase
B has disappeared!! Perera et al. 2012
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On-Going Radio Pulsar Surveys
Also all-sky HTRU Survey using Parkes, Effelsberg
GBT
Arecibo
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GBNCC 350 MHz Survey
20 pulsars so far, including 3 MSPs
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Interesting GBT Driftscan Binary Pulsar J0348+0432
Based on observational work by Ryan Lynch, Paulo Freire, John Antoniadis; theory by 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!!!
![Page 26: Vicky Kaspi, McGill University Harvard/Smithsonian …The Double Pulsar at a Glance Pulsar A: 23 ms (Burgay et al. 2003, Nature) Pulsar B: 2.8 s (Lyne et al. 2004, Science) 2.4 hour](https://reader033.fdocuments.in/reader033/viewer/2022052801/5f1799723597537bf709bd62/html5/thumbnails/26.jpg)
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!
Also highly asymmetric binary, q=11.85
Can test GR in new regime!
Courtesy John Antoniadis
Preliminary!!!
![Page 28: Vicky Kaspi, McGill University Harvard/Smithsonian …The Double Pulsar at a Glance Pulsar A: 23 ms (Burgay et al. 2003, Nature) Pulsar B: 2.8 s (Lyne et al. 2004, Science) 2.4 hour](https://reader033.fdocuments.in/reader033/viewer/2022052801/5f1799723597537bf709bd62/html5/thumbnails/28.jpg)
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 than expected from GW experiments (Damour & Esposito-Farese 1998)
A B
Preliminary!!!
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Couresy N. Wex
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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) theories could 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)
GR TS GR - 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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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 from J0348 (work in prep.)
Good news for calculating templates:
Limit from J0348 suggests assuming GR should work for massive NSs as well
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Conclusions
Double pulsar system spectacular eclipses provide unique test of gravity theories…
But pulsar B is gone
Ongoing pulsar surveys are finding other interesting sources: E.g. PSR J0348+0432 – first massive NS in
relativistic binary
Sets strict limits on dipolar gravitational wave damping
Stay tuned for more!