The Surface Magnetic Activity of the Weak-Line T Tauri Stars TWA 7 and TWA 25

Abstract

We present an analysis of spectropolarimetric observations of the low-mass weak-line T Tauri stars TWA 25 and TWA 7. The large-scale surface magnetic fields have been reconstructed for both stars using the technique of Zeeman Doppler imaging. Our surface maps reveal predominantly toroidal and non-axisymmetric fields for both stars. These maps reinforce the wide range of surface magnetic fields that have been recovered, particularly in pre-main sequence stars that have stopped accreting from the (now depleted) central regions of their discs. We reconstruct the large scale surface brightness distributions for both stars, and use these reconstructions to filter out the activity-induced radial velocity jitter, reducing the RMS of the radial velocity variations from 495 m/s to 32 m/s for TWA 25, and from 127 m/s to 36 m/s for TWA 7, ruling out the presence of close-in giant planets for both stars. The TWA 7 radial velocities provide an example of a case where the activity-induced radial velocity variations mimic a Keplerian signal that is uncorrelated with the spectral activity indices. This shows the usefulness of longitudinal magnetic field measurements in identifying activity-induced radial velocity variations.

14 pages, 19 figures, Accepted for publication in the Monthly Notices of the Royal Astronomical Society

References in corpus (20)

• The Gaia mission
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Detection Limits from the McDonald Observatory Planet Search Program
• Magnetospheric accretion on the T Tauri star BP Tauri
• Magnetic fields and accretion flows on the classical T Tauri star V2129 Oph
• SPIRou: nIR velocimetry & spectropolarimetry at the CFHT
• Lithium Depletion of Nearby Young Stellar Associations
• The evolution of surface magnetic fields in young solar-type stars II: The early main sequence (250-650 Myr)
• Placing the spotted T Tauri star LkCa 4 on an HR diagram
• Fundamental parameters and infrared excesses of Tycho-Gaia stars
• Bistability and hysteresis of dipolar dynamos generated by turbulent convection in rotating spherical shells
• A hot Jupiter around the very active weak-line T Tauri star TAP 26
• Modelling the magnetic activity & filtering radial velocity curves of young Suns: the weak-line T Tauri star LkCa 4
• Magnetic Properties of Young Stars in the TW Hydrae Association
• Origin and evolution of magnetic fields in PMS stars : influence of rotation and structural changes
• The Pan-Pacific Planet Search. VIII. Complete results and the occurrence rate of planets around low-luminosity giants
• Pursuing the planet-debris disk connection: Analysis of upper limits from the Anglo-Australian Planet Search
• Magnetic topologies of young suns: The weak-line T Tauri stars TWA 6 and TWA 8A
• Magnetic activity and radial velocity filtering of young Suns: The weak-line T Tauri stars Par 1379 and Par 2244