A photospheric and chromospheric activity analysis of the quiescent retrograde-planet host ν Octantis A

The single-lined spectroscopic binary $\nu$ Octantis provided evidence of the first conjectured circumstellar planet demanding an orbit retrograde to stellar orbits. planet-like behaviour is now based on 1437 radial velocities (RVs) acquired from 2001 2013. Oct's semimajor axis only 2.6 AU with candidate orbiting Oct A about midway between. These details seriously challenge our understanding formation and decisive modelling reconfiguration stability scenarios. However, all non-planetary explanations are also inconsistent numerous qualitative quantitative tests including previous studies bisectors line-depth ratios, photometry Hipparcos more recent space missions TESS GAIA (whose increased parallax classifies closer still a subgiant ~ K1 IV). We conducted large survey A's chromosphere: 198 Ca II H-line 1160 H $\alpha$ indices using spectra RV campaign (2009-2013). 135 (2018-2020) primarily used for additional which extremely sensitive photosphere's temperature. found no significant RV-correlated variability. Our ratios indicate temperature variations $\pm$ 4 K, as achieved previously. atypical analysis models in terms S/N includes covariance significantly their errors. have quasi-periodic variability we demonstrate due telluric lines. new provides further multiple arguments realistically favor planet.