Photometry and Spectroscopy of the Optical Companion to the Pulsar PSR J1740-5340 in the Globular Cluster NGC 6397

Abstract

We present photometric and spectroscopic observations of the optical companion to the millisecond radio pulsar PSR J1740-5340 in the globular cluster NGC 6397. An analysis of the photometric variability in the B, V, and I-bands indicates an inclination of the system of 43.9+-2.1 degrees if the optical companion fills its Roche lobe (a semi-detached configuration). The spectroscopic data show a radial velocity variation with a semi-amplitude of K=137.2 +- 2.4 km/sec, and a system velocity gamma=17.6 +- 1.5 km/sec, consistent with cluster membership. We use these results to derive a mass of the optical companion of M1=0.296 +- 0.034 Msol and M2=1.53 +- 0.19 Msol for the pulsar. There is evidence for secular change of the amplitude of the optical light curve of the variable measured over seven years. The change does not have interpretation and its presence complicates reliable determination of the absolute parameters of the binary.

24 pages, 9 figures, submitted to AJ

References in corpus (2)

• Chandra Study of a Complete Sample of Millisecond Pulsars in 47Tuc and NGC6397
• The eclipsing millisecond pulsar PSR J1740-5340 and its red straggler companion

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• The formation of helium lines in the spectrum of COM J1740-5340