A Young Planet Search in Visible and IR Light: DN Tau, V836 Tau, and V827 Tau

TL;DR

This study investigates the challenge of distinguishing between starspots and planetary companions as sources of radial velocity variations in young stars, emphasizing the importance of infrared spectroscopy for accurate detection.

Contribution

It demonstrates that infrared spectroscopy can effectively differentiate starspot activity from planetary signals in young, active stars, improving exoplanet detection methods.

Findings

Visible light radial velocity signals can be caused by starspots.

Infrared spectroscopy reveals starspots as the true cause of variations.

Infrared follow-up is essential for confirming planetary companions.

Abstract

In searches for low-mass companions to late-type stars, correlation between radial velocity variations and line bisector slope changes indicates contamination by large starspots. Two young stars demonstrate that this test is not sufficient to rule out starspots as a cause of radial velocity variations. As part of our survey for substellar companions to T Tauri stars, we identified the ~2 Myr old planet host candidates DN Tau and V836 Tau. In both cases, visible light radial velocity modulation appears periodic and is uncorrelated with line bisector span variations, suggesting close companions of several M_Jup in these systems. However, high-resolution, infrared spectroscopy shows that starspots cause the radial velocity variations. We also report unambiguous results for V827 Tau, identified as a spotted star on the basis of both visible light and infrared spectroscopy. Our results suggest that infrared follow up observations are critical for determining the source of radial velocity modulation in young, spotted stars.