A Neutron Star with a Massive Progenitor in Westerlund 1

By M. Muno, J. Clark, P. Crowther, S. Dougherty, Richard de Grijs, C. Law, S. McMillan, Mark R. Morris, I. Negueruela, D. Pooley and 2 more. 2005

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We report the discovery of an X-ray pulsar in the young, massive Galactic star cluster Westerlund 1. We detected a coherent signal from the brightest X-ray source in the cluster, CXO J164710.2-455216, during two Chandra observations on 2005 May 22 and June 18. The period of the pulsar is 10.6107(1) s. We place an upper limit to the period derivative of < 2 × 10-10 s s-1, which implies that the spin-down luminosity is ≤ 3 × 1033 ergs s-1. The X-ray luminosity of the pulsar is LX ≈ 3 × 1033(D/5 kpc)2 ergs s-1, and the spectrum can be described by a kT = 0.61 keV blackbody with a radius of Rbb = 0.27 ± 0.03(D/5 kpc) km. Deep infrared observations reveal no counterpart with K < 18.5, which rules out a binary companion with M > 1 M☉. Taken together, the properties of the pulsar indicate that it is a magnetar. The rarity of slow X-ray pulsars and the position of CXO J164710.2-455216 only 1.′6 from the core of Westerlund 1 indicates that it is a member of the cluster with >99.97% confidence. Westerlund 1 contains 07 V stars with initial masses Mi ≈ 35 M☉ and >50 post-main-sequence stars that indicate the cluster is 4 ± 1 Myr old. Therefore, the progenitor to this pulsar had an initial mass Mi > 40 M☉. This is the most secure result among a handful of observational limits to the masses of the progenitors to neutron stars.

Subfields: Astronomy and Astrophysics, Geophysics

View Paper: https://www.semanticscholar.org/paper/a4238adef3b96c89100bc7d8e964dace9535db4d

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Citations in the corpus

A Survey About Nothing: Monitoring a Million Supergiants for Failed Supernovae (2008, background): “…et al. 2003, 2006; Livne et al. 2004; Ohnishi et al. 2006; and in 3D: e.g., Fryer & Warren 2002) it is dif- 4 There is the intriguing observation by Muno et al. (2006) of a probable magnetar in a star cluster containing M ≃ 35M⊙ stars, but Belczynski & Taam (2008) recently presented a binary…”
The Proto-Magnetar Model for Gamma-Ray Bursts (2010, result): “We note that there is indeed evidence that some Galactic magnetars may have stellar progenitors with masses ∼> 40M⊙ (Muno et al. 2006), although (consistent with Fig.”
A census of the Wolf–Rayet content in Westerlund 1 from near-infrared imaging and spectroscopy (2006, background): “We know of at least one pulsar in Westerlund 1 which has probably been formed as a result of massive close binary evolution (Muno et al. 2006).”
THE McGILL MAGNETAR CATALOG (2013, result): “This discrepancy may argue in favor of the hypothesis that magnetars are born from massive progenitors (Figer et al. 2005; Muno et al. 2006) if the OB star scale height depends on stellar mass such that more massive O stars have a scale height that agrees with that of the magnetars.”
Young Massive Star Clusters (2010, background): “2-455216 (Muno et al. 2006), and a wealth of x-ray sources (Clark et al. 2008).”
BRIGHT SUPERNOVAE FROM MAGNETAR BIRTH (2009, unknown): “The presupernova star here was the remnant of a 60 M main sequence star of solar metallicity, again taken from the study of Woosley & Heger (2007), and might be a representative if magnetars come from a population that is much heavier than ordinary supernovae (Muno et al. 2006).”
Stellar black holes at the dawn of the universe (2011, background): “Recently formed neutron stars observed as soft gamma ray repeaters and anomalous X-ray pulsars are found in young clusters of large metal content that contain stars with masses of 40–50 solar masses (Figer et al. 2005; Muno et al. 2006).”
Formation and evolution of compact binaries in globular clusters – II. Binaries with neutron stars (2007, background): “Currently, there are no AXPs detected in old GCs, and only one AXP is detected in a young “super star cluster,” Westerlund 1 (Muno et al. 2006).”
Progenitors of Core-Collapse Supernovae (2009, background): “Muno et al. (2006) have discovered an x-ray pulsar only 1.7 arcmin from the core of the massive, young cluster Westerlund 1.”