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19th of February 2020
Multiwavelength observations of a transitional millisecond pulsar binary
De Martino et al. have described multiwavelength observations of transitional millisecond pulsar binary XSS J12270-4859 during its current rotation-powered state, including observations with the NuSTAR X-ray satellite and the Parkes radio-telescope. The radio pulsar, which has a spin period of 1.7 milliseconds, displays eclipses over about 40% of its 6.91 hour orbital cycle. The team used 2.5 years of radio monitoring to derive an updated radio ephemeris to study the 3-79 keV X-ray light curve, which varies over an orbit by almost 30%. Comparison with archival X-ray XMM-Newton observations confirms that the modulation amplitudes vary on timescales of a few months, indicative of a non-stationary contribution of the intrabinary shock formed by the colliding winds of the pulsar and the companion.

The figure above summarises the radio observations (dashed lines) and detections (solid lines) performed between June 2014 and February 2017. The observations at 20 cm (1.4 GHz) are plotted in light blue, those at 10 cm (3.1 GHz) in black and those at 50 cm (0.7 GHz) in orange. The grey dotted area marks the orbital phases where the pulsar was never detected. Observations were preferentially scheduled at orbital phases were radio detections were expected to be made. More details are available from the preprint of the paper, to be published in Monthly Notices of the Royal Astronomical Society.

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