Potpourri of Fundamental Physics with Pulsar Binaries

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1 Potpourri of Fundamental Physics with Pulsar Binaries Rene Breton University of Manchester SKA Bursary Conference 29 November 2017 SDO/AIA/AEI John Rowe Animation Australia Telescope National Facility, CSIRO

2 How Can We Do AstroPHYSICS? Astrophysical objects are far away We rely on spherical cow physics a lot! The Sun is a very good blackbody

3 How Can We Do AstroPHYSICS? Astrophysical objects are far away We rely on spherical cow physics a lot! Pulsars in binary systems are almost perfect spherical cows Nearly perfect clock dynamical studies Compact object tidal effects negligible Excellent probes for gravitational studies nuclear physics at ultra high density extreme interaction with their environment

4 Pulsars in a Nutshell Neutron stars are macroscopic atoms Density ~10 14 g/cm 3 stellar mass mountain size Mass ~1.4 M Radius ~15 km faster than kitchen blenders powerful magnets P spin ~1.399ms s B dipole ~ G Pulsars are blinking neutron stars visible through the lighthouse effect Michael Kramer

5 The Pulsar Family Two main observables in pulsars spin period spin period derivative Rotating dipoles in vacuum age magnetic field dissipated energy Binaries make 10% of population fastest spinning oldest pulsars

6 Studying Gravity Galileo s experiment: objects fall at the same speed regardless of their mass Equivalence principle: inertial mass = gravitational mass

7 Studying Gravity Galileo s experiment: objects fall at the same speed regardless of their mass Equivalence principle: inertial mass = gravitational mass Some gravitational theories agree with GR in the Solar System, but not around pulsars

8 Testing the Strong Equivalence Principle

9 Testing Gravity with Pulsars Orbital Doppler shift yields Keplerian parameters (orbital period, eccentricity, etc) masses and orbital inclination are unknown Arpad Horvath (Wikipedia) At large velocity, Newtonian dynamics breaks down Need post-keplerian parameters phenomenological orbital perturbations for a theory of gravity, link Keplerian parameters and masses Esposito-Farese (2004)

10 Examples of Post-Keplerian Parameter Precession of orbital periastron Discovered by Le Verrier in 1859 Mercury s orbit precesses an extra 43 per century Solved by Einstein in 1915 Erklärung der Perihelbewegung des Merkur aus der allgemeinen Relativitätstheorie. Von A. Einstein. i r ( I e) Die Rechnimg liefert für den Planeten Merkur ein Vorschreiten des Perihels um 43" in hundert Jahren, während die Astronomen 45" ±5" als unerklärten Rest zwischen Beobachtungen und NEwxoNscher Theorie angeben. Dies bedeutet volle Übereinstimmung. C.M. Gravitational redshift Time dilation near massive objects C.M.

11 Evidence of Gravitational Waves Pulsar B , the first known binary pulsar Discovered by Hulse and Taylor (1974; Nobel 1993)) Double neutron star binary Evidence of gravitational wave radiation (Taylor et al. 1979) Perturbations of GR field equations imply wave-like solutions Predicted by Einstein in 1916 Carry energy Two-body orbital shrink over time Wex 2014 Taylor et al Weisberg & Taylor 2005

12 The Double Pulsar A dozen known DNS so far PSR J : first and only known pulsar-pulsar system Pulsar A (23 ms, Burgay et al. 2003) Pulsar B (2.8 s, Lyne et al. 2004) 2.4 hour e=0.08 John Rowe Animation Australia Telescope National Facility, CSIRO Best test of GR in strong-field regime (Kramer et al. 2006) Theory-independent mass ratio 6 post-keplerian parameters (Kramer et al. 2006, Breton et al. 2008) Kramer et al. (2006), Breton et al. (2008)

13 Spin-Orbit Coupling Like in quantum mechanics, spin-orbit couple takes place in GR Geodetic precession can be written (Damour & Taylor, 1992, Phys. Rev. D): In terms of observables: Spin-orbit coupling constant The Double Pulsar is the only system providing all observables required for a theory independent test of the spin-orbit coupling (Breton et al. 2008)

14 Figure 5. Constraints Freire et al. on(2012) system & Antoniadis masses andet orbital al. (2012) inclination from radio and optical measurements of PSR J and its WD companion. The mass ratio q and the companion mass m c are theory-independent (indicated in black), but the constraints from the Strong Equivalence Principle PSR J is a pulsar + white dwarf system System parameters known from radio + optical observations Optical photometry + spectroscopy Relativistic orbital decay Mass ratio: radio timing + optical spectroscopy q. P b q m c m c. P b

15 Strong Equivalence Principle Violation of strong equivalence principle Dipolar gravitational wave emission Only if self-energy of two bodies is different Excess of orbital decay P xs b = P Ṁb + P T b + P D b + P Ġb Freire et al. (2012) & Antoniadis et al. (2012) perte de masse marées ondes gravitationnelles dipolaires changement de la constante de gravitation P b D q ' 2 n b T m c q +1 apple D(s psr s comp ) 2 where s psr,comp ' /M psr,comp c 2 Very different binding energy s psr 6= s comp

16 Nuclear Physics at Ultra High Density Neutron stars explore different regime of nuclear physics than heavy ion collisions Ultra high density particularly sensitive to symmetry energy Exotic particles / state transition near the core? Bulk properties (mass, radius, moment of inertia) can be used as probes J J Demorest et al. 2010

17 The Pulsar Mass Landscape. How to measure masses? Where to look? Radio timing and PSR-NS relativistic effects PSR-WD Redbacks J Redbacks J optical observations (velocity, spectral type) Black widows Black widows B optical observations (velocity, light curve) J

18 Spiders Taxonomy Same behaviours, different species Fast millisecond pulsars ( 5 ms) Compact orbits (75 minutes - 26 hours) Energetic pulsar (E dot = few erg/s) Irradiated companion Radio eclipses (0-70% of the orbit) Optical flux/colour modulation Black Widows Redbacks First: PSR B (Fruchter et al. 1988) Very low companion mass (~0.02 M )? First: PSR J (Archibald et al. 2009) Low companion mass (~0.2 M ) Some show state transitions MSP LMXB

19 The Fermi Revolution Number of known spiders (in the Galactic field) Pre-Fermi: ~4 Now: 4-5 dozens Most discoveries in deep radio searches of Fermi point sources (e.g. Ray et al. 2012, Camilo et al. 2015) Evident bias in the radio: strongly eclipsed systems Gamma-ray is luminosity-limited (i.e. infinite optical depth) Credit: Fermi-LAT 5 Years

20 Stellar Braai van Kerkwijk et al Determining the system geometry is possible using Pulsar radio timing 5 Keplerian parameters (Unknown masses and orbital inclination) Optical follow-up of the companion Light curves orbital inclination, temperatures, companion size Spectroscopy mass ratio (from projected velocity)

21 Extreme Pulsar Interaction #1 A majority of spider binaries show radio eclipses Mass stripped from companion Full evaporation within Hubble time? Exact mechanism unknown In original black widow, PSR B , later concluded not sufficient mass-loss rate (Eichler & Levinson 1988)

22 Calibrated using standard LOFAR software and image Modern Take on Radio Eclipses using 1 minute time intervals Flux extracted with PyBDSF Comprehensive set of eclipsing spiders observed with LOFAR ( MHz) Low frequency is key window to probe: Local changes in electron column density Out-gasing / ablation physics Important findings: Non-eclipse Radio flux completely absorbed (confirming Broderick et al. 2016) Pulse phase Eclipse region must be clumpy Time Polzin et al. in prep E. Polzin (JBCA) The eclipses of black widow pulsar J

23 Radio Eclipse Studies Asymmetry and chromatic effects indicate sweptback trailing material Evaporation rate: Black widows might become isolated after all 150 MHz: 6x10-13 M /yr 350 MHz: M /yr Ablation in 5 Gyr: 9x10-12 M /yr Polzin et al. in prep

24 Extreme Pulsar Interaction #2 The Double Pulsar is also a radio eclipsing system Pulsar A eclipsed by Pulsar B every orbit for ~30 sec Caused by synchrotron absorption in closed field line of B s magnetosphere A (23 ms) B (2.8 s)

25 The Double Pulsar Eclipses Direct probe of magnetosphere on 10,000 km scale Canonical dipolar magnetic field works! Large plasma density required Sharp outer boundary to plasmasphere Spin precession made Pulsar B in Will be back in 2024!

26 Conclusions Orbital Period PSR + WD SEP violation preferred frame effects (statistical) Binary pulsars offer great tools to study gravitation matter at extreme density extreme interaction G time-variation TeVeS/MOND dipolar GW PSR + NS PSR + BD* NS EoS tensor-scalar preferred frame effects (individual) spin-orbit coupling relativistic effects pulsar magnetospheres irradiation physics binary evolution Eccentricity