X-ray pulses from Xi1 CMa
X-ray emission from the B-type star Xi1 Canis Majoris (Xi1 CMa) has been measured using ESA's XMM-Newton observatory. This is the first detection of pulsed X-ray emission from a non-degenerate, massive star.
The sequence of X-ray images (above) of Xi1 CMa, clearly shows the intensity of emission changing with time. This is also shown in the lightcurve (below), which shows the count rate measured by the EPIC PN camera on the y-axis and the time after the start of the observation on the x-axis.
These measurements were made in October 2012 when XMM-Newton observed Xi1 CMa continuously for almost 29 hours.
Xi1 CMa is an extremely bright star with a surface temperature of approximately 27 500K, and a mass of approximately 15 times that of the Sun. It lies some 1400 light years away in the constellation Canis Major. The star has a notably strong magnetic field, about 5000 times stronger than our Sun's.