NSVS 14256825: period variation and orbital stability analysis of two possible substellar companions

TL;DR

This study investigates the eclipse timing variations of the binary system NSVS 14256825, proposing the presence of two substellar companions and analyzing their orbital stability through combined observational data and dynamical simulations.

Contribution

The paper introduces a comprehensive approach combining grid search optimization, Keplerian and N-body fits, and stability analysis to identify and validate potential circumbinary companions.

Findings

A circumbinary planet of about 11 Jupiter masses with a 7-year orbit is likely present.

Outer companion's orbit is unconstrained, with a period between 20-50 years and mass 11-70 Jupiter masses.

Multiple stable orbital configurations were identified, remaining stable for up to 100 million years.

Abstract

Recent period investigations of the Post-Common Envelop Binary (PCEB) NSVS 14256825 suggested that two circumbinary companions were necessary to explain the observed Eclipse Timing Variations (ETVs). Our objective was to search for the best-fitting curve of two LTTE terms in the ETV diagram, implementing a grid search optimization scheme of Keplerian (kinematic) and Newtonian (N-body) fits, alongside a dynamical stability analysis of N-body simulations. We compiled two datasets of archival photometric data covering a different timeline and updated them with new observations and with three new times of minima (TOMs) calculated from the Transiting Exoplanet Survey Satellite (\textit{TESS}). A grid search optimization process was implemented and the resulted solutions, that fell within the $90\%$ confidence interval of the best-fitting curve of the ETV diagram, were tested for orbital stability using N-body simulations and the MEGNO chaos indicator. The Keplerian and Netwonian fits are in close agreement and hundreds of stable configurations were identified for both datasets reaching a lifetime of 1 Myr. Our results suggest that the ETV data can be explained by the presence of a circumbinary planet with mass $m_b=11 M_{Jup.}$ in a nearly circular inner orbit of period $P_b = 7$ yr. The outer orbit is unconstrained with a period range $P_c=20-50$ yr (from 3:1 to 7:1 MMR) for a circumbinary body of substellar mass ($m_c=11-70 M_{Jup.}$). The stable solutions of the minimum and maximum reduced chi-square value were integrated for 100 Myr and confirmed a non-chaotic behavior. Their residuals in the ETV data could be explained by a spin-orbit-coupling model (Applegate-Lanza). Continuous monitoring of the system is required in order to refine and constrain the proposed solutions.