* Astronomy

Title: Multi-jets structure rather than rotation of the NGC 1333 IRAS 4A2 protostellar jets
Authors: Noam Soker, Liron Mcley (Technion, Israel)

We analyse the velocity gradient across the jets of the young stellar object (YSO) NGC 1333 IRAS 4A2 and explain it by decomposing the two opposite jets to two opposite sub-jets. The two sub-jets have the same radial velocity and the angle between them is only several degrees. Each of the two sub-jets is composed of two components. We also show that the alternative interpretation of jets' rotation is unlikely to account for the velocity gradient. The two sub-jets directions are constant, and there is no indication for precession. The line connecting the centers of the sub-jets defines a preferred direction in a plane parallel to the accretion disk launching the jets. We suggest that the preferred constant direction in the accretion disk is determined by the semi-major axis of a highly eccentric orbit of a brown dwarf or a massive planet companion. At each periastron passage the companion perturbs the accretion disk with a quadrupole mode, e.g., two spiral arms, that lead to the launching of the two sub-jets. We predict that a careful monitoring of the system will reveal a periodic activity with a period of few months to several years.

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