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Neutron Stars 2: Phenomenology

Neutron Stars 2: Phenomenology. Chandra x-ray images of the PWNs surrounding the ( A ) Crab and ( B ) Vela pulsars. [Credit: NASA/CXC/Smithsonian Astrophysical Observatory, NASA/Pennsylvania State University, and G. Pavlov]. Andreas Reisenegger Depto. de Astronomía y Astrofísica

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Neutron Stars 2: Phenomenology

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  1. Neutron Stars 2: Phenomenology Chandra x-ray images of the PWNs surrounding the (A) Crab and (B) Vela pulsars. [Credit: NASA/CXC/Smithsonian Astrophysical Observatory, NASA/Pennsylvania State University, and G. Pavlov] Andreas Reisenegger Depto. de Astronomía y Astrofísica Pontificia Universidad Católica de Chile

  2. Outline • “Radio” pulsars: • Classical pulsars • Millisecond pulsars • Binary radio pulsars & General Relativity • X-ray binaries: high & low mass • Evolution, connections of pulsars & XRBs • Magnetars • Thermal emitters: isolated & in SNRs • RRATs

  3. Bibliography Radio pulsars: • Lyne & Graham-Smith, Pulsar Astronomy, 2nd ed., Cambridge Univ. Press (1998) • Lorimer & Kramer, Handbook of Pulsar Astronomy, Cambridge Univ. Press (2005) • Manchester, Observational Properties of Pulsars, Science, 304, 542 (2004) Binary systems: • Stairs, Pulsars in Binary Systems: Probing Binary Stellar Evolution & General Relativity, Science, 304, 547 (2004) • Lorimer, Binary & Millisecond Pulsars, Living Reviews in Relativity, 8, 7 (2005) Others: See below.

  4. NS Phenomenology • The structure of a NS is almost entirely determined by its mass. • The observable phenomenology, however, depends much more on several kinds of “hair”: • Rotation () • Magnetic field (B) • Accretion ( )

  5. “Radio” pulsars • Very wide range of photon energies • Mostly non-thermal • Thermal X-ray bump  cooling • UV/soft X-ray “hole” from interstellar absorption D. J. Thompson, astro-ph/0312272

  6. Spin-down(magnetic dipole model) Spin-down time (age?): Magnetic field: Lyne 2000, http://online.kitp.ucsb.edu/online/neustars_c00/lyne/oh/03.html

  7. The spin-down time generally agrees (roughly) with independent ages from: historic SNe (Crab) expansion of SNRs travel time from Galactic disk cooling of white-dwarf companions Spin-down time vs. age

  8. Problem: “Braking index” K involves the dipole moment (strength & orientation) & the moment of inertia of the star. can only be measured in cases when is large & rapidly changing: young pulsars When measured, n  2.0 - 2.8 (< 3): • The dipole spin-down model is wrong, or • the dipole moment is increasing with time.

  9. “Magnetars” Kaspi et al. 1999 Classical pulsars Millisecond pulsars

  10. Magnetic field strengths From R. Duncan’s “magnetar” web page, http://solomon.as.utexas.edu/~duncan/magnetar.html

  11. “Magnetars” Classical pulsars Millisecond pulsars circled: binary systems Manchester et al. 2002

  12. “Classical” P ~ 8 s – 16 ms ts  P/(2P’) ~ 103-8 yr B  (PP’)1/2 ~ 1011-13 G Very few binaries. Many of the youngest are associated with supernova remnants (SNRs). Galactic disk.  “Population I” Millisecond P ~ 20 ms – 1.4 ms ts  P/(2P’) ~ 108-10 yr B  (PP’)1/2 ~ 108-9 G Most in binaries, esp. with cool white dwarfs. No associations with SNRs. Many in globular clusters.  “Population II” 2 populations of radio pulsars “The Sounds of Pulsars”: Jodrell Bank obs. Web page: http://www.jb.man.ac.uk/~pulsar/Education/Sounds/sounds.html

  13. High-mass companion (HMXB): Young X-ray pulsars: magnetic chanelling of accretion flow Cyclotron resonance features  B=(1-4)1012G Low-mass companion (LMXB): Likely old (low-mass companions, globular cluster environment) Mostly non-pulsating (but QPOs, ms pulsations): weak magnetic field http://wwwastro.msfc.nasa.gov/xray/openhouse/ns/ X-ray binaries

  14. “Classical” radio pulsars born in core-collapse supernovae evolve to longer P, with B  const. eventually turn off (“death line”) Millisecond pulsars descend from low-mass X-ray binaries. Mass transfer in LMXBs produces spin-up magnetic field decay? Origin & evolution of pulsars: the standard paradigm Classical pulsars Millisecond pulsars

  15. The binary pulsar & GR Kramer et al. 2006, Science, 314, 97

  16. Magnetars: Brief history- 1 • Strongest magnetic field that could possibly be contained in a NS: • Woltjer (1964): Flux conservation from progenitor star could lead to NSs with B~1014-15G. • Mazets & Golenetskii (1981): Multiple soft gamma-ray bursts from a single source (SGR 1806-20) detected by Venera spacecraft since Jan 1979. • Mazets et al. (1979): “March 5 event”: Giant flare (highly super-Eddington) from SGR 0526-66 in LMC (possibly associated w. SNR N49). • Fahlman & Gregory (1981): First “Anomalous X-ray Pulsar” (AXP): soft spectrum, at center of SNR, no optical counterpart. • Koyama et al. (1987): AXP is spinning down, but X-ray luminosity much too high to attribute to rotational energy loss of a NS.

  17. Bursting magnetar in supernova remnant N49 From R. Duncan’s “Magnetar” web site,http://solomon.as.utexas.edu/~duncan/magnetar.html

  18. Magnetars: Brief history- 2 • Thompson & Duncan (TD 1993): Dynamo action just after formation of a rapidly spinning NS can lead to B~1016G. • DT (1992), Paczynski (1992), TD (1995, 1996): Strong, decaying field could explain super-Eddington bursts and persistent emission of SGRs & AXPs. TD 1996 predict slow pulsations and fast spin-down. • Kouveliotou et al. (1998) measure P=7.5 s & B~1015G in SGR 1806-20. • Gavriil et al. (2002); Kaspi et al. (2003): Several bursts detected from 2 different AXPs. • SGRs & AXPs share • fairly long periods ~5-12 s, • persistent X-ray luminosities ~1035-36 erg/s (BB T ~ 0.4-0.7 keV+ high-energy tail), too high to be explained from rotation, • strong spin-down (inferred B~ 1014-15 G).

  19. Woods & Thompson, astro-ph/0406133

  20. Woods & Thompson, astro-ph/0406133

  21. Woods & Thompson, astro-ph/0406133

  22. Isolated, dim, thermal X-ray emitters Burwitz et al. 2003, A&A, 399, 1109

  23. Nebula around isolated NS van Kerkwijk & Kulkarni 2001, A&A, 380, 221

  24. Compact Central Objects (CCOs) • Near center of SNRs • No radio or gamma-ray emission • No pulsar wind nebula • Thermal X-ray spectrum: temperature & luminosity intermediate between magnetars and dim isolated neutron stars Cas A - Hwang et al. 2004

  25. “Rotating RAdio Transients” (RRATs; McLaughlin et al. 2006, Nature, 439, 817) emit occasional, bright radio bursts of 2-30 ms duration • Intervals 4 min – 3 hr are multiples of a period P ~ 0.4 - 7 s, like slow radio pulsars or magnetars • Hard to detect (visible ~ 1 s/day): True number should be much larger than for radio pulsars. McLaughlin et al. 2006; Nature, 439, 817

  26. RRATs vs. pulsars & magnetars • pulsars (dots) • magnetars (squares) • the 1 radio-quiet isolated neutron star with a measured period and period derivative (diamond) • the 3 RRATs having measured periods and period derivatives (stars) • vertical lines atthe top of the plot mark the periods of the other 7 RRATs McLaughlin et al. 2006; Nature, 439, 817

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