1. A Neutron Star with a Massive Progenitor in the Star Cluster Westerlund 1 Michael Muno (UCLA/Hubble Fellow) J. S. Clark (Open U)R. de Grijs (U Sheffield) P. Crowther (U Sheffield)S. Dougherty (DAO) I. Negueruela (Alicante)D. Pooley (Berkeley) S. McMillan (Drexel)S. Portegies Zwart (Amsterdam) C. Law (Northwestern)F. Yusef-Zadeh (Northwestern) M. Morris (UCLA)

2. Were do Neutron Stars and Black Holes Come From? M > 20 Msun 8 < M < 20 Msun M < 8 Msun Mass From “Stellar Evolution: A Journey with Chandra”

3. 92540100140260 Initial Mass (Solar Masses) White Dwarf Metallicity solar metal-free The Mapping Between Initial Masses and Compact Remnants. Heger et al. 2003

4. The Unusual Stellar Population in Westerlund 1 Over 25 Wolf-Rayet stars. One confirmed LBV. Several red supergiants. Five yellow hypergiants. Over 80 OB supergiants. Main sequence 06 stars. (e.g., Westerlund 1987, Clark et al. 2005) 1 pc VRI from 2.2m MPG/ESO+WFI Clark et al. (2005)

5. VRI from 2.2m MPG/ESO+WFI Clark et al. (2005) A Galactic Super Star Cluster? 150 stars with M>35 M sun Mass: 10 5 M sun Extent: ~6 pc across Distance: 5 kpc Age: 4 +/- 1 Myr The cluster is coeval, and old enough to have produced supernovae. Est. rate: 1 per 10,000 years! 1 pc

6. Chandra Observations VRI from 2.2m MPG/ESO+WFI Clark et al. (2005) Chandra ACIS 1 pc We see diffuse X-rays from the cluster wind and unresolved pre-main-sequence stars, point-like emission from colliding wind binaries, and black holes.

7. Chandra Observations VRI from 2.2m MPG/ESO+WFI Clark et al. (2005) Chandra ACIS 1 pc We see diffuse X-rays from the cluster wind and unresolved pre-main-sequence stars, point-like emission from colliding wind binaries, and a pulsar! pulsar

8. Pulsar CXO J164710.2-455216 Period: 10.6107(1) s Spin-down: <2x10 -10 s s - 1 L X = 3x10 33 erg s -1 (not a radio pulsar) Spectrum: kT = 0.6 keV blackbody (not a cooling NS) No IR counterpart, so K>18.5 (M count. < 1M sun ; not an X-ray binary) This pulsar is almost certainly a magnetar.

9. The Progenitor Was >40 M sun The Pulsar is in Wd 1 (99.95% confidence) –A search of 300 archival Chandra and XMM fields reveals no new 5-30 s pulsars, so there is a <0.5% chance of finding one in any field (Nechita, Gaensler, Muno, et al. in prep). –The pulsar is well within the cluster, with a <10% chance of being an unrelated X-ray source. Position of pulsar Expected density of interlopers (dashed line, very small number)

10. Other Neutron Stars with >30 M sun Progenitors A HI shell around 1E 1048.1-5937 was interpreted as the wind-blown bubble from a 30-40 M sun progenitor (Gaensler et al. 2005) SGR 1806-20 is the member of a star cluster ~3 Myr old, and so had a ~50 M sun progenitor (Figer et al. 2005; also Vrba et al. 2000 for SGR 1900+14). 1E 1048.1-5937 SGR 1806-20

11. 92540100140260 Initial Mass (Solar Masses) White Dwarf Metallicity solar metal-free Which Stars Form Black Holes? Heger et al. 2003 Wd 1

12. 92540100140260 Initial Mass (Solar Masses) White Dwarf Metallicity solar metal-free Which Stars Form Black Holes? Heger et al. 2003 Wd 1 Cyg X-1 GX 301-2

13. Massive Progenitors to Neutron Stars These pulsars show that 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). As magnetars, B-fields appear important: –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).