Persistent starspot signals on M dwarfs: multi-wavelength Doppler observations with the Habitable-zone Planet Finder and Keck/HIRES

摘要: Young, rapidly-rotating M dwarfs exhibit prominent starspots, which create quasiperiodic signals in their photometric and Doppler spectroscopic measurements. The periodic can mimic radial velocity (RV) changes expected from orbiting exoplanets. Exoplanets be distinguished activity-induced false positives by the chromaticity long-term incoherence of starspot signals, but these qualities are poorly constrained for fully-convective stars. Coherent on may persist hundreds rotations, wavelength dependence RV not consistent between stars due to differences magnetic fields active regions. We obtained precise multi-wavelength RVs four (AD Leo, G 227-22, GJ 1245B, 3959) using near-infrared (NIR) Habitable-zone Planet Finder, optical Keck/HIRES spectrometer. Our complemented photometry Kepler, TESS, Las Cumbres Observatory (LCO) network telescopes. found that all large spot-induced at rotation periods, investigated longevity optical-to-NIR signals. phase curves remain coherent much longer than is typical Sunlike Their varies, one star (GJ exhibits NIR modulation both amplitude. In general, though, we find amplitudes lower counterparts. conclude frequently remains stellar gives rise that, this coherence, mistaken