Properties of the redback millisecond pulsar binary 3FGL J0212.1+5320

TL;DR

This study models the light curves and radial velocities of the redback millisecond pulsar binary 3FGL J0212.1+5320, revealing the system's masses and the effects of star spots or intrabinary shocks on observed light variations.

Contribution

It introduces a combined X-ray binary model with star spots or hot spots to explain light curve asymmetries and derives system parameters consistent with observations.

Findings

Neutron star mass estimated at ~1.85 solar masses.

Secondary star mass estimated at ~0.50 solar masses.

Hot spot model best matches the observed effective temperature.

Abstract

Linares et al. (2016) obtained quasi-simultaneous g', r' and i-band light curves and an absorption line radial velocity curve of the secondary star in the redback system 3FGL J0212.1+5320. The light curves showed two maxima and minima primarily due to the secondary star's ellipsoidal modulation, but with unequal maxima and minima. We fit these light curves and radial velocities with our X-ray binary model including either a dark solar-type star spot or a hot spot due to off-centre heating from an intrabinary shock, to account for the unequal maxima. Both models give a radial velocity semi-amplitude and rotational broadening that agree with the observations. The observed secondary star's effective temperature is best matched with the value obtained using the hot spot model, which gives a neutron star and secondary star mass of $M_{\rm 1}$=1.85$^{+0.32}_{-0.26}$ $M_{\odot}$and $M_{\rm 2}$=0.50$^{+0.22}_{-0.19}$ $M_{\odot}$, respectively.