The Bright Optical Companion to the Eclipsing Millisecond Pulsar in NGC 6397
Ferraro, Francesco R.; Sabbi, Elena; Possenti, Andrea; D'Amico, Nichi
Italy
Abstract
We report the optical identification of the companion to the eclipsing millisecond pulsar PSR J1740-5340 in the globular cluster NGC 6397. A bright variable star with an anomalous red color and optical variability (~0.2 mag) that nicely correlates to the orbital period of the pulsar (~1.35 days) has been found close to the pulsar position. The peculiar shape of the optical light curves is unprecedented for a millisecond pulsar companion and is a clear signature of tidal distortions.