TW Hydrae: evidence of stellar spots instead of a Hot Jupiter

TL;DR

This study investigates whether stellar spots, rather than a hot Jupiter, cause the observed radial-velocity variations in TW Hydrae, using optical and infrared data to support the spot hypothesis.

Contribution

The paper demonstrates that stellar spots can explain TW Hydrae's RV variations, challenging previous claims of a hot Jupiter companion.

Findings

A cold spot model reproduces RV variations without requiring a planet.

Infrared RV data shows minimal variation inconsistent with a planetary orbit.

Optical RV variations are better explained by stellar spots than a hot Jupiter.

Abstract

TW Hydrae shows significant radial-velocity variations in the optical regime. They have been attributed to a 10 Jupiter Mass planet orbiting the star at 0.04 AU. In this work, we have tested whether the observed RV variations can be caused by stellar spots. We have also analyzed new optical and infrared data to confirm the signal of the planet companion. We fitted the RV variations of TW Hya using a cool spot model. Our model shows that a cold spot covering 7% of the stellar surface and located at a latitude of 54 deg can reproduce the reported RV variations. The model also predicts a bisector semi-amplitude variation <10 m/s, which is less than the errors of the RV measurements discussed in an earlier publication. The analysis of new optical RV data, with typical errors of 10 m/s, shows a larger RV amplitude that varies depending on the correlation mask used. A slight correlation between the RV variation and the bisector is also observed, although not at a very significant level. The infrared H-band RV curve is almost flat, showing a small variation (<35 m/s) that is not consistent with the optical orbit. All these results support the spot scenario rather than the presence of a hot Jupiter around TW Hya.