Periods of two enigmatic black hole candidates GRS 1915+105 and IGR J17091-3624

TL;DR

This study investigates the orbital periods and eccentricities of two black hole candidates, GRS 1915+105 and IGR J17091-3624, revealing long periods and moderate eccentricities that influence their observed variability.

Contribution

It provides the first estimates of orbital periods and eccentricities for these black hole systems based on light curve analysis.

Findings

Orbital periods are approximately 28.3 and 32.2 days.

Eccentricities are at most 0.071 and 0.46.

Long orbital periods may explain variability class transitions.

Abstract

Galactic black hole candidates GRS 1915+105 and IGR J17091-3624 have many similarities in their light curves and spectral properties. However, very little is known about the orbital elements of their companions. In case the orbits are eccentric, tidal forces by the black hole on the companion can cause modulations of accretion rates in orbital time scale. We look for these modulations in the light curves of these two objects and find that their periodicities are around 28.3 d (29.0 d) and 32.2 d respectively. Eccentricities are at the most 0.071 and 0.46 respectively. We conclude that both these objects have long orbital periods and are eccentric. This could be a reason why light curves have several similar variability class transitions as reported in the literature.