# Orbital period modulation of the eclipsing binary system ER Vulpeculae: Real or not?

## Abstract

The reanalysis of the timing data of the binary system ER Vulpeculae revealed the superposition of a relatively slow increasing linear trend in the orbital period, having a relative period change rate of 2:73 108 yr1, and a low amplitude (3.5 min) periodic modulation with a period of about 17.78 yr. This periodicity is significantly shorter than that previously published, i.e., 30.6 yr.

We propose a methodology relying on Monte Carlo simulations which is intended to evaluate the detectability of the inferred signal. Both frequentist and Bayesian approaches have been considered. The actual amplitude of the orbital period modulation might be lower than that obtained via nonlinear least-squares modelling of the timing data, namely about 2.0 min. Consequently, the amplitude of the underlying mechanism will be lower too. In the case of ER Vul, within the hypothesis of a third companion in the system, it could be a low mass star of about 113.8 MJupiter, but also a brown dwarf of about 64.7 MJupiter.

Further theoretical and observational studies are needed in order to discriminate between this mechanism and the cyclic magnetic activity occurring in both component stars, as possible causes of the observed period variation.

## Authors

C. Vamoș
-Tiberiu Popoviciu Institute of Numerical Analysis, Romanian Academy

A. Pop

## Keywords

data analysis; statistical Binaries; Eclipsing Stars; individual ER Vulpeculae

## Cite this paper as:

A. Pop, C. Vamoş, Orbital period modulation of the eclipsing binary system ER Vulpeculae: Real or not?, New Astronomy 23-24, 27-35 (2013), doi: 10.1016/j.newast.2013.02.003

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Elsevier

1384-1076

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