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Massive Stars and Magnetars

Massive Stars and Magnetars. Michael Muno (Caltech). B=10 14 G. -10. 10 3 yr. Log 10 (Period derivative). 10 12 G. 10 5 yr. -16. 10 7 yr. 0.1. 0.01. 1. 10. P (s). A Zoo of Neutron Stars. Radio pulsars & NS High Mass X-ray Binaries (2000) Magnetars (16)

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Massive Stars and Magnetars

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  1. Massive Stars and Magnetars Michael Muno (Caltech)

  2. B=1014 G -10 103 yr Log10 (Period derivative) 1012 G 105 yr -16 107 yr 0.1 0.01 1 10 P (s) A Zoo of Neutron Stars • Radio pulsars & NS High Mass X-ray Binaries (2000) • Magnetars (16) • Rotating Radio Transients (11) • Isolated Cooling Neutron Stars (7) (plus Central Compact Objects) McLaughlin et al. (2006)

  3. B=1014 G -10 103 yr Log10 (Period derivative) 1012 G 105 yr -16 107 yr 0.1 0.01 1 10 P (s) What Properties are Inherited? • Which stars form magnetars? • How often are magnetars produced?

  4. WhichStars Form Neutron Stars?

  5. The Scant Connections to Progenitors • Model the initial masses of supernovae known to have produced compact objects. • Model individual high mass X-ray binaries. • Search for associations between compact objects and star clusters for which we know the masses of stars that died.

  6. A Massive Young Star Cluster Westerlund 1 • 100 stars with M>35 Msun • Mass: 5x104 Msun • Extent: ~6 pc across • Age: 3.6 +/- 0.7 Myr The cluster is coeval, and old enough to have produced supernovae. Est. rate: 1 per 10,000 years! 1 pc VRI from 2.2m MPG/ESO+WFI Clark et al. 2005

  7. A Pulsar with a >50 Msun Progenitor! 10.6 s pulsar 1 pc Chandra ACIS (Muno et al. 2006) VRI from 2.2m MPG/ESO+WFI Clark et al. (2005)

  8. WhichStars Form Neutron Stars? Wd 1

  9. Massive stars can lose 95% of their mass! • Through winds (e.g., Heger et al 2003), • Via binary mass transfer (Wellstein & Langer 1999), • Or during supernovae (Akiyama & Wheeler 2005).

  10. The MagnetarCXO J164710.2-455216 • Period: 10.6107(1) s • LX = 3x1033 erg s-1 (not a radio pulsar) • Spectrum: kT = 0.6 keV (not a cooling NS) • No IR counterpart with K<20.0 (not an X-ray binary) • Spin-down: 4x10-5 s yr-1 • B ~ 1014 G Muno et al. (2006) This pulsar is a magnetar. (Spin down measured by Woods et al. 2006; Israel et al. 2006)

  11. Other Magnetars with >30 Msun Progenitors 1E 1048.1-5937 SGR 1806-20 • Neutral H from a wind-blown bubble (Gaensler et al. 2005; but see Durant & van Kerkwijk 2006). • Another ~3 Myr old star cluster(Figer et al. 2005). • (also Vrba et al. 2000 for SGR 1900+14).

  12. Massive Stars and Magnetars • B-fields appear important in extreme mass loss: • Massive stars could produce rapidly-rotating cores (e.g., Duncan & Thomas 1992; Heger et al. 2005). • Or magnetars could form from highly-magnetic progenitors (e.g., Ferrario & Wickramasinghe 2005).

  13. Conclusions • Some stars lose >95% of their mass as they evolve. • Magnetic fields appear to play a role. ?

  14. An Archival Study of the Birth Rate of Magnetars • We searched 506 Chandra and 441 XMM-Newton observations within |b|<5o. • No new candidate magnetars with 5<P<30 s. Muno et al. 2008

  15. The Depth of the Survey For a given pulse fraction and luminosity, compute the depth of each observation. • Requires a model for Galactic extinction.

  16. A Complication:Transient Magnetars CXOU J164710.2-455216 brightened by a factor of 150 over 5 days in September 2006 (Muno et al. 2007, Israel et al. 2007).

  17. Magnetar Birth Rates Assume a magnetar lifetime of 104 yr, Arms=12%. (Kouveliotou et al. 1999; Gaensler et al. 1999) • Standard AXP (LX=3x1035 erg/s): 0.003 .. 0.016 yr-1 • Detectable in 4% of Galaxy, 59+92-32 total. • Transient AXP (LX=3x1033 erg/s): 0.008 .. 0.06 yr-1 • Detectable in 0.5% of Galaxy, up to 600 total. (Muno et al. 2008) For comparison: • Core-collapse supernova rate: 0.01 .. 0.04 yr-1(Cappallaro et al. 1993; van den Bergh & McClure 1994). • Radio pulsar birth rate: 0.014 .. 0.03 yr-1(Faucher-Giguere & Kaspi 2006; Lorimer et al. 2006).

  18. Conclusions • Some stars lose >95% of their mass as they evolve. • Magnetic fields appear to play a role. • At least 10% of neutron stars are born as magnetars. • Need to search for transient magnetars. ?

  19. A Massive Young Star Cluster • 100 stars with Mi>35 Msun • Mass: 5x104 Msun • Extent: ~6 pc across • Age: 3.6 +/- 0.7 Myr The cluster is coeval, and old enough to have produced supernovae. Est. rate: 1 per 10,000 years! Brandner et al. 2007

  20. Magnetars (16 known!) A neutron star with: • Strong magnetic fields (B~1014 G). • X-ray luminosity larger than their spin-down power. • Soft gamma-ray bursts. NASA/Swift/Sonoma State University/A. Simonnet

  21. Neutron Stars: The Densest, Most Magnetized Objects Known • Densities: 1015 g cm-3 • Magnetic fields: 108 to 1015 G • Spin periods: 1 ms to several hours Crab Pulsar (Chandra)

  22. The End Points of Massive Stars SN 386AD & Pulsar NGC 3603 LBV eta Carina ? How much mass is lost? Supernova X-ray binary illustration Why do stars explode?

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