Starspot-induced optical and infrared radial velocity variability in T Tauri star Hubble 4

TL;DR

This study detects and analyzes starspot-induced radial velocity variations in the T Tauri star Hubble 4 across optical and infrared wavelengths, revealing long-lived surface spots affecting stellar measurements.

Contribution

First infrared resolution of spot-induced radial velocity modulation in an active T Tauri star, demonstrating the impact of starspots on stellar velocity signals.

Findings

Radial velocity variations are phase-coherent over hundreds of days.

Lower amplitude in infrared indicates cool starspots as the cause.

Starspots on Hubble 4 are large and long-lived.

Abstract

We report optical (6150 Ang) and K-band (2.3 micron) radial velocities obtained over two years for the pre-main sequence weak-lined T Tauri star Hubble I 4. We detect periodic and near-sinusoidal radial velocity variations at both wavelengths, with a semi-amplitude of 1395\pm94 m/s in the optical and 365\pm80 m/s in the infrared. The lower velocity amplitude at the longer wavelength, combined with bisector analysis and spot modeling, indicates that there are large, cool spots on the stellar surface that are causing the radial velocity modulation. The radial velocities maintain phase coherence over hundreds of days suggesting that the starspots are long-lived. This is one of the first active stars where the spot-induced velocity modulation has been resolved in the infrared.