CXOU J164710.2−455216

CXOU J164710.2−455216 is an anomalous X-ray pulsar and magnetar 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]

CXOU J164710.2−455216

Artist's impression of CXOU J164710.2-455216
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Ara
Right ascension	16h 47m 10.20s
Declination	−45° 52′ 16.8″
Characteristics
Evolutionary stage	Neutron star
Apparent magnitude (${\displaystyle {\begin{smallmatrix}K_{s}\end{smallmatrix}}}$)	>18.5[1]
Astrometry
Distance	approx. 16,000 ly (approx. 5,000 pc)
Details
Rotation	10.6105(1)s
Other designations
CXO J164710.20−455217, CXOU J164710.2−455217
Database references
SIMBAD	data

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]