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Fastest neutron star, 1100 km/second

  1. Sep 9, 2005 #1

    marcus

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    press release from NRAO
    http://www.nrao.edu/pr/2005/fastpulsar/
    The fastest-moving neutron star ever seen, clocked at 1100 kilometers per second, a speed that will take it out of the Milky Way galaxy, was given its initial "kick-off" by the supernova that formed it.

    journal article
    http://arxiv.org/abs/astro-ph/0509031
    Getting Its Kicks: A VLBA Parallax for the Hyperfast Pulsar B1508+55
    S. Chatterjee et al.
    5 pages, including 2 figures
    Astrophys.J. 630 (2005) L61-L64
    "The highest velocity neutron stars establish stringent constraints on natal kicks, asymmetries in supernova core collapse, and the evolution of close binary systems. Here we present the first results of a long-term pulsar astrometry program using the VLBA. We measure a proper motion and parallax for the pulsar B1508+55, leading to model-independent estimates of its distance (2.37+0.23-0.20 kpc) and transverse velocity (1083+103-90 km/s), the highest velocity directly measured for a neutron star. We trace the pulsar back from its present Galactic latitude of 52.3 degrees to a birth site in the Galactic plane near the Cyg OB associations, and find that it will inevitably escape the Galaxy. Binary disruption alone is insufficient to impart the required birth velocity, and a natal kick is indicated. A composite scenario including a large kick along with binary disruption can plausibly account for the high velocity.

    popular magazine account:
    http://www.astronomy.com/asy/default.aspx?c=a&id=3471

    a discussion of various "kick" mechanisms that might give neutron stars high speeds is in this paper, see bottom of page 7
    http://arxiv.org/abs/astro-ph/0106159
     
  2. jcsd
  3. Sep 9, 2005 #2

    SpaceTiger

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    ...and that doesn't even include the unknown radial component -- though, considering selection biases, it's likely small. Good find.
     
  4. Sep 9, 2005 #3

    marcus

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    Tiger could you please summarize the prevailing idea(s) of how a supernova delivers such a kick to the neutronstar remnant?

    why is the SN collapse not symmetric?

    I can see orbit disruption of a binary system contributing a part, but these papers indicate that would not be enough
     
  5. Sep 10, 2005 #4

    Labguy

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    Hello, Marcus, long time no-type. I'm not Tiger, but there are many supernovae models, and observations, that show evidence for non-symmetric SN explosions. S.E. Woosley is probably considered the foremost astrophysicist today working on supernovae properties. His paper at: http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v475n2/33428/33428.html is one of the best and discusses Type Ia carbon deflagration/detonation asymmetries.

    There is a lot more information on SN explosion asymmetries, including type Ic and Type II, that has agreed with observations for quite some time. Take a look at these for lots of info:
    http://newton.ex.ac.uk/aip/glimpse.txt/physnews.181.1.html
    And;
    http://arxiv.org/abs/astro-ph/9605186
    http://www.journals.uchicago.edu/cgi-bin/resolve?id=doi:10.1086/308773
    http://xxx.sf.nchc.gov.tw/abs/astro-ph/0505199
    http://adsabs.harvard.edu/cgi-bin/n.....267..433Y&db_key=AST&data_type=HTML&format=
    Some of the condensed quotes from these sites are:
    and much more.
     
  6. Sep 10, 2005 #5

    marcus

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    Same here! Long time no, Labguy. I havent been around Astronomy forum as much lately.

    Interesting looking bunch of links. keep me busy trying to understand supernovas in my spare time.

    it never occurred to me that an explosion like that could be lopsided
     
  7. Sep 17, 2005 #6

    marcus

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    Labguy here is one to add to your collection of links. Maybe you already have it by i didnt see it in your post

    http://arxiv.org/abs/astro-ph/0007272
    Pulsar Jets: Implications for Neutron Star Kicks and Initial Spins
    Dong Lai, David F. Chernoff, James M. Cordes (Cornell)
    ApJ, Vol.549 (March 10, 2001)
    We study implications for the apparent alignment of the spin axes, proper-motions, and polarization vectors of the Crab and Vela pulsars. The spin axes are deduced from recent Chandra X-ray Observatory images that reveal jets and nebular structure having definite symmetry axes. The alignments indicate these pulsars were born either in isolation or with negligible velocity contributions from binary motions. We examine the effects of rotation and the conditions under which spin-kick alignment is produced for various models of neutron star kicks. If the kick is generated when the neutron star first forms by asymmetric mass ejection or/and neutrino emission, then the alignment requires that the protoneutron star possesses an original spin with period $P_s$ much less than the kick timescale, thus spin-averaging the kick forces. The kick timescale ranges from 100 ms to 10 s depending on whether the kick is hydrodynamically driven or neutrino-magnetic field driven. For hydrodynamical models, spin-kick alignment further requires the rotation period of an asymmetry pattern at the radius near shock breakout (>100 km) to be much less than ~100 ms; this is difficult to satisfy unless rotation plays a dynamically important role in the core collapse and explosion ($P_s\lo 1$ ms). Aligned kick and spin vectors are inherent to the slow process of asymmetric electromagnetic radiation from an off-centered magnetic dipole. We reassess the viability of this effect, correcting a factor of 4 error in Harrison and Tademaru's calculation that increases the size of the effect. To produce a kick velocity of order a few hundred km/s requires that the neutron star be born with an initial spin close to 1 ms and that spindown due to r-mode driven gravitational radiation be inefficient compared to standard magnetic braking."
     
  8. Sep 17, 2005 #7

    Labguy

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    Thanks, Marcus. I hadn't seen that one.
     
  9. Sep 18, 2005 #8

    Chronos

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    I'm less inclined to think the explosion was that unbalanced. More like a gravitational sling shot event.
     
  10. Sep 19, 2005 #9

    SpaceTiger

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    And a brand new one:

    Wang, Lai, & Han 2005

    Neutron Star Kicks in Isolated and Binary Pulsars: Observational Constraints and Implications for Kick Mechanisms
    Authors: Chen Wang, Dong Lai, JinLin Han
    Comments: 30 pages, 2 figures, submitted to ApJ

    We study observational constraints on neutron star (NS) kicks for isolated pulsars and for neutron stars in binary systems. We are particularly interested in the evidence of kick-spin alignment/misalignment and its dependence on the neutron star initial spin period. For several young pulsars, X-ray observations of compact nebulae showed that pulsar proper motion is aligned with the spin direction as defined by the symmetry axis of the nebula. We also critically examine the measurements of the proper motion and the projected spin axis from a large sample of pulsars with well-calibrated polarization data. We find that among the two dozen pulsars for which reliable measurements are available, there is a significant correlation between the spin axis and the proper motion. For various NS binaries, including double NS systems, binaries with massive main-sequence star companion and binaries with massive white-dwarf companion, we obtain constraints on the kick magnitudes and directions from the observed orbital characteristics of the system. The kick velocity is generally misaligned with the NS spin axis, particularly when the initial spin period (when available) is long. These constraints, together with spin-kick alignment observed in many isolated pulsars, suggest that the kick time scale is about 1 s, so that spin-kick alignment or misalignment can be obtained depending on the initial spin period of the NS. We discuss the implication of our result for various NS kick mechanisms.
     
  11. Sep 19, 2005 #10
  12. Sep 20, 2005 #11

    marcus

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