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The Complex H Line Profile of the Bright Companion to PSR J1740-5340 in NGC 6397

2003; IOP Publishing; Volume: 589; Issue: 1 Linguagem: Inglês

10.1086/375729

1538-4357

Elena Sabbi, R. Gratton, F. R. Ferraro, A. Bragaglia, Andrea Possenti, N. D’Amico, F. Camilo,

Pulsars and Gravitational Waves Research

We present a detailed study of the Hα 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 Hα 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.