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The Helium White Dwarf orbiting the Millisecond Pulsar in the halo of the Globular Cluster NGC 6752

Francesco R. Ferraro·Andrea Possenti·Elena Sabbi·Nichi D'Amico
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Abstract

We have used deep high-resolution multiband images taken at the ESO Very Large Telescope to identify the optical binary companion to the millisecond pulsar (PSR J1911-5958A) located in the halo of the Galactic Globular Cluster NGC6752. The object turns out to be a blue star whose position in the Color Magnitude Diagram is consistent with the cooling sequence of a low mass (M~0.17-0.20Mo), low metallicity Helium white dwarf (He-WD) at the cluster distance. This is the second He-WD which has been found to orbit a millisecond pulsar in GGCs. Curiously both objects have been found to lie on the same mass He-WD cooling sequence. The anomalous position of PSR J1911-5958A with respect to the globular cluster center (~6') suggested that this system has recently (<1 Gyr) been ejected from the cluster core as the result of a strong dynamical interaction. The data presented here allows to constrain the cooling age of the companion within a fairly narrow range (~1.2-2.8 Gyr), therefore suggesting that such dynamical encounter must have acted on an already recycled millisecond pulsar.

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Francesco R. Ferraro, Andrea Possenti, Elena Sabbi, Nichi D'Amico. 2003-09-04. The Helium White Dwarf orbiting the Millisecond Pulsar in the halo of the Globular Cluster NGC 6752. https://doi.org/10.1086/379536

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