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GENERAL RELATIVITY AND PRECISE MEASUREMENTS OF PULSAR MASSES

GENERAL RELATIVITY AND PRECISE MEASUREMENTS OF PULSAR MASSES. D.G. Yakovlev. Ioffe Physical Technical Institute, St.-Petersburg, Russia. Introduction X-ray binaries Double neutron star binaries Pulsar – white dwarf binaries Summary. FFC , Pulkovo Observatory, October 10, 201 3.

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GENERAL RELATIVITY AND PRECISE MEASUREMENTS OF PULSAR MASSES

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  1. GENERAL RELATIVITY AND PRECISE MEASUREMENTS OF PULSAR MASSES D.G. Yakovlev Ioffe Physical Technical Institute, St.-Petersburg, Russia • Introduction • X-ray binaries • Double neutron star binaries • Pulsar – white dwarf binaries • Summary FFC, Pulkovo Observatory,October10, 2013

  2. INTRODUCION Galaxy, stars and the Sun Galaxy:more than 1011stars Luminosity: L~1046 erg/s Sun:M=2x1033 g, R=700,000km, L=3.83x1033 erg/s, meandensity of matter= 1.4 g/cm3, surface temperature ~6,000 К, internal temperature 15.7 MК. Composition: rarefied plasma, pressureP=nkT~1017dyn/cm2. Supported by thermonuclear reactions in central region

  3. i=isolated b=binary SCHEME! M<8 MSUN Quiet removal of outer shell, birth of white dwarf (WD) WD i, b WD SN Ia b M=(8—25) MSUN Core-collapsed supernova (SN II) birth of neutron star Normal star Giant star NS i, b NS b BH BH M>25 MSUN collapse into black hole (BH) WD, NS, BH = graveyard

  4. Extreme Physics Problem: EOS, High B, High Tc Main mystery: EOS of super-dense core – longstanding fundamental problem of physics and astrophysics complicated by high B and Tc Main practical problem: How to relate EOS to observables

  5. MOTIVES TO ACCURATELY MEASURE NS MASSES • Мass – most important parameter of any star • To find critical mass which separates NSs and BHs • To constrain EOS of superdense matter in NS core • Most massive NSs are most important!

  6. X-ray binaries Companion in binary system NS Riccardo Giacconi Nobel Prize: 2002

  7. Kepler Orbits Integrals of motion: Orbital period: Need more parameters: Measuring radial velocities of companion 1: 2 Measuring radial velocities of companion 2: 1

  8. Vela X-1 Vela X-1 (=4U 0900--40) GP Vel (=HD 77581, B0.5 Ib supergiant) Pspin=283 s, Pb=8.96 d, e=0.09 a=50 Rsun, i>70o, R2=30 Rsun Discovery: Chodil et al. (1967) GP Vel: Brucato & Kristian (1972), Hiltner et al. (1972) K2 for GP Vel: Hiltner et al. (1972) P for Vela X-1: McClintock et al. (1976) K1 for Vela X-1: Rappaport et al. (1976) Quaintrell et al. (2003):

  9. Masses of Neutron Stars in X-ray Binaries

  10. SUMMARY: NEUTRON STAR MASSES IN X-RAY BINARIES (1) There is a wide spectrum of neutron star masses in XRBs (2) XRBs almost certainly contain massive neutron stars (3) The best candidates are Vela X-1 (M>1.62 MSUN) Cyg X-2 4U 1700—37 (4) The prospects to accurately measure M are poor

  11. Magnetic axis Radio Pulsars in Compact Binaries Spin axis L

  12. Relativistic Objects: Radio Pulsar – Compact Companion Advantages: (1) Very precise timing P(t) (2) Point-like masses (3) GR effects Evolution of orbital parameters: Peters & Mathews (1963), Peters (1963) Energy and orbital momentum:

  13. Example: Timing of pulsars and NS mass measurements Stage 1: Measurements of Keplerian parameters : 2 extra equations are required Stage 2: Measurements of relativistic parameters (a) Pereastron advance: (b) Transverse Doppler effect + gravitational dilation of signals by М2: . (c) Shapiro parameters: (d) Orbital decay: Up to 5 extra equations can be obtained!

  14. Russel Hulse and Joseph Taylor The Arecibo 305-m radio telescope (NAIC-Arecibo Observatory, NSF)

  15. The Hulse-Taylor Pulsar(PSR B1913+16) Discovery: 2 June 1974 (ApJ Lett, January 15, 1975) 5083 observations from 1981 to 2001 Nobel Prize: 1993 Orbit: Relativistic effects (Weisberg & Taylor, 2010) : (a) Rotation by125оin 30 years (Mercury: 43’’in 100 yrs) (b) Observations: (c) Theoretical prediction:

  16. The mass of the Hulse-Taylor Pulsar(PSR B1913+16) MASSES OF PSR B1913+16 & COMPANION (Weisberg, Nice, Taylor, 2010)

  17. Evolution of the Hulse-Taylor pulsar At birth: Now: In 200 Myr:

  18. The last 10 Years of the Hulse-Taylor Pulsar Time to merging = 300 Myr M31 10 years before death: 1 ms before death :

  19. Geodetic precession of the Hulse-Taylor pulsar Barker & O’Connell (1975):

  20. Ideal Wolszczan Pulsar (PSR B1534+12) Discovery: Wolszczan (1991) All 5 GR parameters measured: Neutron star masses (Stairs et al. 2003):

  21. J0737-3039 Aand B: Double Pulsar Binary Burgay et al. (2003)Observation: PulsarА 4.5 mininAugust 2001 + systematic observationssince 2003 (5 months) Lyne et al. (2004) PulsarB Systematic observations sinceMay 2003 (7 months) Results: Fifth binary with short lifetime Radio eclipses

  22. Double Neutron Star Binaries

  23. MASSES OF DOUBLE NEUTRON STAR BINARIES • 5 DNSB = 10 neutron star • masses accurately measured • All masses are in narrow range • HT pulsar is most massive • among them • No recent progress with these • objects

  24. RADIO PULSARS AND WHITE DWARFS (or other compact companions) • Advantages: • Compact stars – point-like masses • Often – recycled millisecond pulsars: • pulsars can be massive, • short periods – good timing, • weak magnetic fields – no glitches or pulsar noise • Disadvantages: • Underwent active accretion phase – as a rule, almost circular orbits = • difficult to measure periastron advanceand gamma-parameter • Low-mass companions – difficult to measure Shapiro effect • anddPb/dt • Specific feature: • Often observed in globular clusters

  25. Neutron Stars and White Dwarfs White dwarfs: M2—Pb

  26. Neutron Stars and White Dwarfs

  27. Ideal System Radio Pulsar—WhiteDwarf (PSR J1141—6545) Discovery: Kaspi et al. (2000) Three GR parameters measured: Masses (Bailes et al. 2003):

  28. Ideal Binary Radio Pulsar—White Dwarf (PSR J1909—3744) Discovery: Jacoby et al. (2003) Two relativistic parameters measures:s, r Masses of stars (Jacoby et al. 2005):

  29. Fallen Down Angel Radio Pulsar—WhiteDwarf (PSR J0751+1807) Discovery: Lundgren et al. (1995) One relativistic parameter measured: dPb/dt Shapiro effect is poorly pronounced: i~65-850 Masses of companions (Nice, Splaver, Stairs 2004, 2005): After 2007 (Nice, Stairs, Kasian 2008):

  30. Radio Pulsar—White Dwarf (PSR J1911—5958A) Discovery: D’Amico et al. (2001) No relativistic parameters measured Bassa et al. (2006), Cocozza et al. (2006) – radial velocity curve and mass of white dwarfare measured in optical observations

  31. PSR J1903+0327 (2009) Discovery: Cordes et al. (2006) The first eccentric binary MCP in the galactic disk Companion: MS star,M~1 MSUN Evolutionary scenario:unclear Measured: periastron advance +s, r Problem: large size of companion can affect periastron advance Perspective: timing, refined measurements of periastron advance, s, r

  32. Most Massive Known Neutron Star PSR J1614-2230+ WD 28 0ct. 2010, Nature 467, 1081 Discovery: 2002 (Hessels et al. 2005) Measured: Shapiro effect,s, r Most massive neutron star currently known

  33. Most Massive Known Neutron Star Shapiro delay in PSR J1614-2230+ WD Time residual, microseconds 1.0 0 0.5 Orbital phase Demorest et al. (2010)

  34. THE SECOND MOST MASSIVE NEUTRON STAR PSR J0348+0432+ WD Science, 26 April 2013, Vol. 340, Issue 6131, 448 Radio observations: Green Bank (USA) 2007 Publication: Lynch et al. (2013) Pulsar: moderately spun up by accretion WD: low-massive, He core Age of the system: about 3 Gyrs Measured: radial velocities of PSR and WDand spectroscopic WD mass

  35. THE SECOND MOST MASSIVE NEUTRON STAR PSR J0348+0432+ WD Measured without GR effects Checked by orbital decay: Theory Observations Time to merging: 400 Myr Ideal binary for checking GR!

  36. Summary of NS-WD and NS-NS binaries Kiziltan et al. (2013)

  37. MOST MASSIVE NEUTRON STAR VERSUS TIME PSR J0751+1807 PSR J0348+0432 PSR J1614—2230 PSR J1903+0327 PSR B1913+16

  38. Mass—Radius Diagram for Exploring EOS of Superdense General Relativity Causality PSR J1614-2230 PSR J0348+0432 HT pulsar

  39. RESULTS • General Relativity Theory was tested • Gravitational radiation discovered • Geodetic precession discovered • Double neutron star mergers were discovered • Gravitational observatories of new generation are built • General Relativity has become useful tool • Masses of some neutron stars accurately measured • Currently: Mmax>2 MSUN • => soft and moderate EOSs are ruled out • => EOS is stiff => little room for exotic matter Main feature at present: Rapid progress! Unsolved Problems • MMAX = ? • Stiff EOS = just stiff or superstiff?

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