A neutron star with a massive progenitor in Westerlund

Michael P. Muno; J. Simon Clark; Paul A. Crowther; Sean M. Dougherty; Richard De Grus; Casey Law; Stephen L W Mcmillan; Mark R. Morris; Ignacio Negueruela; David Pooley; Simon Portegies Zwart; Farhad Yusef-Zadeh

doi:10.1086/499776

A neutron star with a massive progenitor in Westerlund

Michael P. Muno^*, J. Simon Clark, Paul A. Crowther, Sean M. Dougherty, Richard De Grus, Casey Law, Stephen L W Mcmillan, Mark R. Morris, Ignacio Negueruela, David Pooley, Simon Portegies Zwart, Farhad Yusef-Zadeh

^*Corresponding author for this work

Physics and Astronomy

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Abstract

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 Ṗ < 2 × 10^-10 s s^-1, which implies that the spin-down luminosity is Ė ≤ 3 × 10³³ ergs s^-1. The X-ray luminosity of the pulsar is L_x ≈ 3_-2⁺¹⁰ × 10³³(D/5 kpc)² ergs s^-1, and the spectrum can be described by a kT = 0.61_-0.02^+0.02 keV blackbody with a radius of A_bb = 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 M_l ≈ 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 M_l > 40 M_⊙. This is the most secure result among a handful of observational limits to the masses of the progenitors to neutron stars.

Original language	English (US)
Pages (from-to)	L41-L44
Journal	Astrophysical Journal
Volume	636
Issue number	1 II
DOIs	https://doi.org/10.1086/499776
State	Published - Jan 1 2006

Funding

We thank B. M. Gaensler and B. Hansen for discussions, L. Hadfield for calibrating the photometry in the infrared image, and A. Nechita for carrying out the archival search for X-ray pulsars. C. L. and F. Y.-Z. were supported by a grant from the CXC, M. P. M. through a Hubble Fellowship, and D. P. through a Chandra Fellowship.

Keywords

Open clusters and associations: individual (Westerlund 1)
Stars: neutron
X-rays: stars

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1086/499776

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@article{23b555644ab44e8181d6aac3d3b67b18,

title = "A neutron star with a massive progenitor in Westerlund",

abstract = "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 Ṗ < 2 × 10-10 s s-1, which implies that the spin-down luminosity is Ė ≤ 3 × 1033 ergs s-1. The X-ray luminosity of the pulsar is Lx ≈ 3-2+10 × 1033(D/5 kpc)2 ergs s-1, and the spectrum can be described by a kT = 0.61-0.02+0.02 keV blackbody with a radius of Abb = 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 Ml ≈ 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 Ml > 40 M⊙. This is the most secure result among a handful of observational limits to the masses of the progenitors to neutron stars.",

keywords = "Open clusters and associations: individual (Westerlund 1), Stars: neutron, X-rays: stars",

author = "Muno, {Michael P.} and Clark, {J. Simon} and Crowther, {Paul A.} and Dougherty, {Sean M.} and {De Grus}, Richard and Casey Law and Mcmillan, {Stephen L W} and Morris, {Mark R.} and Ignacio Negueruela and David Pooley and Zwart, {Simon Portegies} and Farhad Yusef-Zadeh",

note = "Funding Information: We thank B. M. Gaensler and B. Hansen for discussions, L. Hadfield for calibrating the photometry in the infrared image, and A. Nechita for carrying out the archival search for X-ray pulsars. C. L. and F. Y.-Z. were supported by a grant from the CXC, M. P. M. through a Hubble Fellowship, and D. P. through a Chandra Fellowship.",

year = "2006",

month = jan,

day = "1",

doi = "10.1086/499776",

language = "English (US)",

volume = "636",

pages = "L41--L44",

journal = "Astrophysical Journal",

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T1 - A neutron star with a massive progenitor in Westerlund

AU - Muno, Michael P.

AU - Clark, J. Simon

AU - Crowther, Paul A.

AU - Dougherty, Sean M.

AU - De Grus, Richard

AU - Law, Casey

AU - Mcmillan, Stephen L W

AU - Morris, Mark R.

AU - Negueruela, Ignacio

AU - Pooley, David

AU - Zwart, Simon Portegies

AU - Yusef-Zadeh, Farhad

N1 - Funding Information: We thank B. M. Gaensler and B. Hansen for discussions, L. Hadfield for calibrating the photometry in the infrared image, and A. Nechita for carrying out the archival search for X-ray pulsars. C. L. and F. Y.-Z. were supported by a grant from the CXC, M. P. M. through a Hubble Fellowship, and D. P. through a Chandra Fellowship.

PY - 2006/1/1

Y1 - 2006/1/1

N2 - 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 Ṗ < 2 × 10-10 s s-1, which implies that the spin-down luminosity is Ė ≤ 3 × 1033 ergs s-1. The X-ray luminosity of the pulsar is Lx ≈ 3-2+10 × 1033(D/5 kpc)2 ergs s-1, and the spectrum can be described by a kT = 0.61-0.02+0.02 keV blackbody with a radius of Abb = 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 Ml ≈ 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 Ml > 40 M⊙. This is the most secure result among a handful of observational limits to the masses of the progenitors to neutron stars.

AB - 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 Ṗ < 2 × 10-10 s s-1, which implies that the spin-down luminosity is Ė ≤ 3 × 1033 ergs s-1. The X-ray luminosity of the pulsar is Lx ≈ 3-2+10 × 1033(D/5 kpc)2 ergs s-1, and the spectrum can be described by a kT = 0.61-0.02+0.02 keV blackbody with a radius of Abb = 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 Ml ≈ 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 Ml > 40 M⊙. This is the most secure result among a handful of observational limits to the masses of the progenitors to neutron stars.

KW - Open clusters and associations: individual (Westerlund 1)

KW - Stars: neutron

KW - X-rays: stars

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JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 1 II

ER -

A neutron star with a massive progenitor in Westerlund

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