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Physics of Neutron stars Sanjay K. Ghosh Department of Physics And

Physics of Neutron stars Sanjay K. Ghosh Department of Physics And Centre for Astroparticle Physics & Space Science Bose Institute Kolkata. ATHIC November 14 – 17, 2012, PUSAN. Plan: Theory & Observation (a) Mass (b) Cooling

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Physics of Neutron stars Sanjay K. Ghosh Department of Physics And

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  1. Physics of Neutron stars Sanjay K. Ghosh • Department of Physics • And • Centre for Astroparticle Physics & Space Science • Bose Institute • Kolkata ATHIC November 14 – 17, 2012, PUSAN

  2. Plan: • Theory & Observation (a) Mass (b) Cooling (c) Gravitational Wave 2. Hadron - quark transition: (a) Consequences (b) Transition Mechanism 3. Neutron Star Physics at FAIR-CBM 3. Summary ATHIC 2012

  3. ATHIC 2012

  4. NS M  R-3 SS M  R3 ATHIC 2012

  5. SS vs. NS ATHIC 2012

  6. Lattimer 2012 ATHIC 2012

  7. ATHIC 2012

  8. Mallick et al. JPG2012 ATHIC 2012

  9. Lattimer& Prakash 2007 ATHIC 2012

  10. Accreting mass M=Ma (P/ms)-2/3 Ma = characteristic accretion mass when pulsar is spun-up to 1 ms M= M0 + M M0= 1.4  0.07 M Ma= 0.43 23 M Mass versus spin period for 39 NSs. Horizontal line M = 1 M (3.2 M)  measured minimum mass Vertical line at 20 ms separates the samples into two groups, MSP (<20 ms) and less recycled NS (>20 ms). Mass averages of two groups are found to be, respectively, 1.57 ± 0.35 M and 1.37 ± 0.23 M. The solid curve stands for the relation between accretion mass and spin period of recycled pulsar. Zhang et al. A&A 527 A83 (2011). ATHIC 2012

  11. NS Cooling • Cooling 1. Direct URCA Relativistic NM, Unpaired QM, pion and kaon condensates single flavour pairing 2. Modified URCA NM at lower density (proton fraction < 0.1) 3. CFL phase Iwamoto, Ann. Phys. 141 (1982) Ghosh et al. MPLA9 (1994), IJMPE5 (1996) Jaikumar et al. PRD66 (2002) Reddy et al. NPA714 (2003) ATHIC 2012

  12. Thermal Relaxation Global Thermal Balance Observations of surface temperatures and upper bounds for several isolated neutron stars. The solid line is the basic theoretical cooling curve of a nonsuperfluid neutron star with M = 1.3 M Yakovlev &Pethick2004 ATHIC 2012

  13. ATHIC 2012

  14. ATHIC 2012

  15. Cassiopeia A (CAS A) • Youngest known supernovae remnant in milky way • Distance ~ 3.4 Kpc • Age ~ 340 Yrs. • Mass 1.5 – 2.4 M • radius 8 – 18 Km • Carbon Atmosphere • B  1011 G • Surface temperature Ts ~ 2 X 106 K • surface temperature drop last 10 Yrs. 4% Explanation: • n & p pair breaking- formation – Schternin et al., Page et al. 2011 • Nuclear medium cooling scenario – Blashke et al.2011

  16. Blaschke et al Page et al.

  17. Gravitational Waves (GW) • Ripples in space-time curvature propagating through space at the speed of light • Massive compact binary system – energy lose Grav. Waves – Change in orbital period (Hulse & Taulor 1993) • NS of same mass, diff. radii will emit different Grav. Waveform in the late stage of binary spiral (Markakis et al. JPG conf. 2009) • Correlation between frequency peak of postmerger GW emission and physical properties of nuclear EOS (Bauswein et al. PRL 2012) • Dynamical behaviour of SS and NS merger are different • Can be detected through their GW emission – proof of strange matter hypothesis (Bauswein et al. PRD2010) ATHIC 2012

  18. Consequences • r – Mode instability - bulk flow known as Rossby modes or r (rotational) mode - coriolis force effect - transfer the angular momentum into gravitational radiation - so above a critical frequency spin slow down - critical frequency is limited by viscous damping - r-mode rules out CFL quark stars - may provide signature of hybrid stars Madsen PRL85, Andersson et al. IJMPD10, 381 (2001), Anderssonet al. MNRAS337, 1224 (2002), Drago et al. Astron. Astrophys. 445, 053 (2006) ATHIC 2012

  19. Hadron-quark phase transition – GRB connection What happens in phase transition ? • Hadronic sector : small no. of strange baryons, small strangeness fraction (strange baryon density/total baryon density) • Quark sector : Strangeness fraction ~ 1 Ghosh et al. Zphys C1995 ATHIC 2012

  20. GRB connection… µ = Cos    polar angle  Sharp peak - µ = 0.1 and 0.24  ≈ 12 degrees ATHIC 2012 Bhattacharyya et al. PLB635 (2006)

  21. GRB connection …. • Time scale • Normally small energy deposition • The high gravity environment might enhance the deposition (Salmonson & Wilson APJ, 517 (1999) 859 Result of two effects • Path bending of neutrinos • Gravitational red shift  10% energy deposit Effect of rotation and gravitation : Increase in deposition rate Asymmetry in deposition Bhattacharyya et al. IJP 2012 ATHIC 2012

  22. Mechanism of phase transition: Conversion Two step process: (a) Strong – Nuclear  2 flavour (b) Weak 2 Flavour  3 flavour (a) Nuclear to 2-flavour conversion ATHIC 2012

  23. Bhattacharyya et al. PRC74, 065804 (2006) Drago et. al. Astrophys. J.659, 1519 (2007) ATHIC 2012

  24. I. Tokareva, A. Nusser, V. Gurovich, and V. Folomeev, Int. J., Mod. Phys. D 14, 33 (2005). Bhattacharyya et al. PRC74, 065804 (2006) ATHIC 2012

  25. (b) 2- flavour to 3-flavour conversion ATHIC 2012

  26. Mechanism of phase transition • Two step process (a) hadronic matter to two flavour matter - deconfinement - t ~ milliseconds (b) two flavour to three flavour matter - s quark via weak process - t ~ 100 seconds Presence of two fronts ? ATHIC 2012

  27. Rotating Star: Density Profile : R/Re = s/(1-s) R: radius Re = equatorial radius R/Re = s/(1 − s) Equator s = 0.5 AB, SKG, SR PL B635 (2006) 195 ATHIC 2012

  28. General relativistic effects Bhattacharyya et al. PRC76, 052801(R) (2007) ATHIC 2012

  29. http://www.atnf.csiro.au/research/pulsar/psrcat ATHIC 2012

  30. ATHIC 2012 http://www.atnf.csiro.au/research/pulsar/psrcat

  31. Equation of continuiy Euler equation ATHIC 2012

  32. Static Star First we perform our calculation for the static star considering both poloidal and toroidal field configuration following Colaiuda et al. (2008), for the field extending throughout the star where  provides the relative weight factor for the contribution of toroidal field. The force is purely poloidal if = 0, and both poloidal and toroidal contribute if = 1. For both the cases the hydrodynamic equation gets modified due to the inclusion of the magnetic field. ATHIC 2012

  33. Rotating star Canonical picture: we assume that the magnetic field of the NS is due to a dipole at the center of the star. ATHIC 2012

  34. Alternate field configurations Bocquet et al. 1995 Field configuration proposed for magnetars Chakraborty et al. 1997 ATHIC 2012

  35. Variation of the velocity of the conversion front with a different magnetic field configuration obtained from (Bocquet et al 1995; Konno et al. 1999) ATHIC 2012

  36. Variation of the velocity of the conversion front with a different magnetic field configuration given by (Chakrabarty et al. 1997). ATHIC 2012

  37. Summary • High density physics has interesting posssibilities • Better radius measurements and next generation Gravitational wave detectors are expected to put very strong constraints on EOS. • CBM experiment may help us to understand the physics of Neutron stars. ATHIC 2012

  38. Thank you ATHIC 2012

  39. PNJL MODEL ATHIC 2012

  40. ATHIC 2012

  41. ATHIC 2012 Comparison of charge neutral trajectory in NJL and PNJL model

  42. The contour of scaled baryon number density nB/n0; (scaled by normal nuclear matter density) along with phase diagram at μe=40 for (a) NJL model and (b) for PNJL model; (From left nB/n0 = 0.5, 1, 3, 5, 10 respectively) ATHIC 2012

  43. The contour of net strangeness fraction (ns/nB) along with nB/n0 at μe=40 for (a) NJL model and (b) PNJL model; the values of nB/n0 are 0.5, 1, 3, 5 and 10 (from left). ATHIC 2012

  44. The isentropic trajectories along with phase diagram for (a) at μe=0, 2+1-flavor PNJL, (b) at μe=40, 2+1-flavor PNJL, (c) at μe=0, 2-flavor PNJL and (d) at μe=40, 2+1-flavor NJL model. s/nB=300,100,30,10,5,3.5 (from left). ATHIC 2012

  45. ATHIC 2012

  46. Magnetic field – Magnetar - SS connection • Initial association – to explain the SGR burst intensity - much larger than Eddington limit Eddington limit does not apply to bare strange star – self bound Present Scenario: To explain large magnetic field For example – quark phase with pion condensate – carries large magnetic moment and hance can give magnetized core Bhattacharyya & Soni – astro-ph/0705.0592 Ferromagnetism in quark phase – OGE interaction Tatsumi – 2000, Maruyama et al. NPA Other problems exist - High frequency quasi periodic oscillation in giant flares from SGR1806-20 and SGR1900+14 can not be explained by quark star - Watts & Reddy astro-ph/0609364 ATHIC 2012

  47. Origin of magnetic field Flux conservation • generation of magnetic fluxes earlier in progenitor stars and then its subsequent trapping inside the compact objects. • But fields inside a main sequence progenitor may not be enough to yield the needed magnetic field inside a neutron star as the neutron star contains only aound 15% of the progenitor mass • (Spruit ) 2008 (Rudderman1972; Reisenegger2001; Ferrario & Wickramasinghe 2005a,b, 2006) . • Dynamo processes • astrophysical dynamo (electric + kinetic = magnetic field) • Pulsars - rotating and convecting fluid. (Thompson & Duncan 1993) (Duncan & Thompson 1992; Thompson & Duncan 1995, 1996). ATHIC 2012

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