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The complex Halpha line profile of the bright companion to PSR J1740-5340 in NGC 6397

E. Sabbi·R. Gratton·F. R. Ferraro·A. Bragaglia·A. Possenti·N. D'Amico·F. Camilo
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Abstract

We present a detailed study of the Halpha and He I spectral features of COM J1740-5340 (the companion to PSR J1740-5340 in the Galactic Globular Cluster NGC 6397), exploiting a series of high resolution spectra obtained at different orbital phases. The Halpha absorption line shows a complex two-component structure, revealing that optically thin hydrogen gas resides outside the Roche lobe of COM J1740-5340. The line morphology precludes the existence of any residual disk around the millisecond pulsar, and suggests the presence of a stream of material going from the companion toward the neutron star. This material never reaches the neutron star surface, being driven back by the pulsar radiation far beyond COM J1740-5340. By analyzing the He I absorption lines as a function of orbital phase, we infer the presence of an overheated longitudinal strip (about 150 times narrower than it is long) on the COM J1740-5340 surface facing the radio pulsar.

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E. Sabbi, R. Gratton, F. R. Ferraro, A. Bragaglia, A. Possenti, N. D'Amico, F. Camilo. 2003-04-09. The complex Halpha line profile of the bright companion to PSR J1740-5340 in NGC 6397. https://doi.org/10.1086/375729

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