Effect of tides on the orbital evolution of the redback system PSR 1723–2837

NOVARINO, M L; ECHEVESTE, M; BENVENUTO, O G; DE VITO, M A; FERRERO, G A

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2021 vol. 508 p. 3812 - 3819

0035-8711

The standard model of stellar evolution in close binary systems assumes that during mass transfer episodes, the system is in a synchronized and circularized state. Remarkably, the redback system PSR J1723-2837 has an orbital period derivative P˙orb too large to be explained by this model. Motivated by this fact, we investigate the action of tidal forces in between two consecutive mass transfer episodes for a system under irradiation feedback, which is a plausible progenitor for PSR J1723-2837. We base our analysis on Hut´s treatment of equilibrium tidal evolution, generalized by considering the donor as a two layers object that may not rotate as a rigid body. We also analyse three different relations for the viscosity with the tidal forcing frequency. We found that the large value measured for P˙orb can be reached by systems where the donor star rotates slower (by few per cent) than the orbit just after mass transfer episodes. Van Staden & Antoniadis have observed this object and reported a lack of synchronism, opposite to that required by the Hut´s theory to account for the observed P˙orb . Motivated by this discrepancy, we analyse photometric data obtained by the spacecraft Kepler second mission K2, with the purpose of identifying the periods present in PSR J1723-2837. We notice several periods close to those of the orbit and the rotation. The obtained periods pattern reveals the presence of a more complex phenomenology, which would not be well described in the frame of the weak friction model of equilibrium tides.