Astronomy:CXOU J164710.2−455216

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Anomalous X-ray pulsar in Westerlund 1
CXOU J164710.2−455216
Artist’s impression of the magnetar in the star cluster Westerlund 1.jpg
Artist's impression of CXOU J164710.2-455216
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
Constellation Ara
Right ascension  16h 47m 10.20s
Declination −45° 52′ 16.8″
Evolutionary stage Neutron star
Apparent magnitude ([math]\displaystyle{ \begin{smallmatrix}K_s \end{smallmatrix} }[/math]) >18.5[1]
Distanceapprox. 16,000 ly
(approx. 5,000 pc)
Other designations
CXO J164710.20−455217, CXOU J164710.2−455217
Database references

CXOU J164710.2−455216 is an anomalous X-ray pulsar in the massive galactic open cluster Westerlund 1. It is the brightest X-ray source in the cluster, and was discovered in 2005 in observations made by the Chandra X-ray Observatory.[1][2] The Westerlund 1 cluster is believed to have formed in a single burst of star formation,[3] implying that the progenitor star must have had a mass in excess of 40 solar masses. The fact that a neutron star was formed instead of a black hole implies that more than 95% of the star's original mass must have been lost before or during the supernova that produced the magnetar.[4][5]

On 21 September 2006 the Swift satellite detected a 20ms soft gamma-ray burst in Westerlund 1. Fortuitously, XMM-Newton observations had been made four days earlier, and repeat observations 1.5 days after the burst revealed the magnetar to be the source of the burst, with the X-ray luminosity increasing by a factor of 100 during the outburst.[6]


Coordinates: Sky map 16h 47m 10.20s, −45° 52′ 16.8″