The cyclic behaviour of ( O–C ) residuals of eclipse timings in the sdB+M eclipsing binary NSVS 14256825 was previously attributed to one or two Jovian-type circumbinary planets .
We report 83 new eclipse timings that not only fill in the gaps in those already published but also extend the time span of the ( O–C ) diagram by three years .
Based on the archival and our new data spanning over more than 17 years we re-examined the up to date system ( O–C ) .
The data revealed systematic , quasi-sinusoidal variation deviating from an older linear ephemeris by about 100 s. It also exhibits a maximum in the ( O-C ) near JD 2,456,400 that was previously unknown .
We consider two most credible explanations of the ( O-C ) variability : the light propagation time due to the presence of an invisible companion in a distant circumbinary orbit , and magnetic cycles reshaping one of the binary components , known as the Applegate or Lanza–Rodonó effect .
We found that the latter mechanism is unlikely due to the insufficient energy budget of the M-dwarf secondary .
In the framework of the third-body hypothesis , we obtained meaningful constraints on the Keplerian parameters of a putative companion and its mass .
Our best-fitting model indicates that the observed quasi-periodic ( O-C ) variability can be explained by the presence of a brown dwarf with the minimal mass of 15 Jupiter masses rather than a planet , orbiting the binary in a moderately elliptical orbit ( e \simeq 0.175 ) with the period of \sim 10 years .
Our analysis rules out two planets model proposed earlier .