A unified solution for the orbit and light-time effect in the V505 Sgr system

TL;DR

This paper investigates the V505 Sgr system to determine if a fourth, unseen body can explain observed orbital and timing variations, using numerical simulations and data analysis, though the hypothesis has low likelihood.

Contribution

It provides a comprehensive N-body simulation approach to test the fourth-body hypothesis for V505 Sgr, integrating multiple observational data types.

Findings

A fourth body can explain all observed data but with low likelihood.

Alternative explanations for minima timing variations are discussed.

Further observations are needed to constrain the model.

Abstract

The multiple system V505 Sagittarii is composed of at least three stars: a compact eclipsing pair and a distant component, which orbit is measured directly using speckle interferometry. In order to explain the observed orbit of the third body in V505 Sagittarii and also other observable quantities, namely the minima timings of the eclipsing binary and two different radial velocities in the spectrum, we thoroughly test a fourth-body hypothesis - a perturbation by a dim, yet-unobserved object. We use an N-body numerical integrator to simulate future and past orbital evolution of 3 or 4 components in this system. We construct a suitable chi^2 metric from all available speckle-interferometry, minima-timings and radial-velocity data and we scan a part of a parameter space to get at least some of allowed solutions. In principle, we are able to explain all observable quantities by a presence of a fourth body, but the resulting likelihood of this hypothesis is very low. We also discuss other theoretical explanations of the minima timings variations. Further observations of the minima timings during the next decade or high-resolution spectroscopic data can significantly constrain the model.