Multi-band high resolution spectroscopy rules out the hot Jupiter BD+20 1790b - First data from the GIARPS Commissioning

TL;DR

This study uses multi-band high-resolution spectroscopy to distinguish stellar activity from planetary signals in young stars, conclusively ruling out a previously claimed hot Jupiter around BD+20 1790 by comparing visible and near-infrared data.

Contribution

First simultaneous multi-band VIS-NIR spectroscopy with GIARPS demonstrates the effectiveness of wavelength-dependent RV analysis in young active stars.

Findings

NIR RV amplitudes are significantly lower than VIS, indicating stellar activity.

Simultaneous multi-wavelength data can effectively differentiate between stellar activity and planetary signals.

The claimed massive planet around BD+20 1790 is ruled out by the new data.

Abstract

Context. Stellar activity is currently challenging the detection of young planets via the radial velocity (RV) technique. Aims. We attempt to definitively discriminate the nature of the RV variations for the young active K5 star BD+20 1790, for which visible (VIS) RV measurements show divergent results on the existence of a substellar companion. Methods. We compare VIS data with high precision RVs in the near infrared (NIR) range by using the GIANO - B and IGRINS spectrographs. In addition, we present for the first time simultaneous VIS-NIR observations obtained with GIARPS (GIANO - B and HARPS - N) at Telescopio Nazionale Galileo (TNG). Orbital RVs are achromatic, so the RV amplitude does not change at different wavelengths, while stellar activity induces wavelength-dependent RV variations, which are significantly reduced in the NIR range with respect to the VIS. Results. The NIR radial velocity measurements from GIANO - B and IGRINS show an average amplitude of about one quarter with respect to previously published VIS data, as expected when the RV jitter is due to stellar activity. Coeval multi-band photometry surprisingly shows larger amplitudes in the NIR range, explainable with a mixture of cool and hot spots in the same active region. Conclusions. In this work, the claimed massive planet around BD+20 1790 is ruled out by our data. We exploited the crucial role of multi- wavelength spectroscopy when observing young active stars: thanks to facilities like GIARPS that provide simultaneous observations, this method can reach its maximum potential.