Abstract
In this short review we present the results of a study of the large-scale magnetic topologies of T Tauri stars (TTS). A small spectropolarimetric survey of 8 young stars was carried out within two international projects MaPP (Magnetic Protostars and Planets) and MaTYSSE (Magnetic Topologies of Young Stars and the Survival of massive close-in Exoplanets) between 2009 and 2016. For each of our targets we reconstructed the brightness map and the magnetic field topology using Zeeman–Doppler imaging (ZDI). This review contains a brief description of spectropolarimetricdata, the ZDI method, one example of the reconstruction of brightness and magnetic maps, and the properties of magnetic fields of 8 TTS. Our results suggest that AA Tau and LkCa 15 interact with their disks in the propeller mode when their rotation is actively slowed by the star/disk magnetic coupling. We find that magnetic fields of some TTS are variable on a time scale of a few years and are thus intrinsically nonstationary. We report on the detection of a giant exoplanet around V830 Tau and TAP 26. These two new detections suggest that the type II disk migration is efficient at generating newborn hot Jupiters (hJs) around young TTS. The result of our survey is compared to the global picture of magnetic field properties of twenty TTS in the Hertzsprung–Russell diagram. The comparison shows that WTTS exhibit a wider range of field topologies as compared to CTTS, and that magnetic fields of all TTS (CTTS and WTTS as a whole) are mostly poloidal and axisymmetric when they are mostly convective and cooler than 4300 K. This needs to be confirmed with a larger sample of stars.
Highlights
T Tauri stars (TTS) are young low-mass stars of late spectral types which are at the stage of gravitational contracting and have not reached the main-sequence (MS) yet
The basic information on stars and derived spectral data is summarized in Table 1, where we note the name of a star, its type (“c” if classical” TTS (CTTS), or “w” if WTTS), effective temperature, v sin i value, rotation period, mass, age, epoch of spectral observations, the number of observational seasons (Ns), the number of spectra, the range of values of the signal-to-noise ratio (S/N), and the average value of the signal-to-noise ratio (S/N)
In the brightness map there is a reconstruction of the elongated spotted region of complex configuration which extends to almost 180◦ in the latitudinal direction (Fig. 3, top left panel)
Summary
T Tauri stars (TTS) are young low-mass stars of late spectral types which are at the stage of gravitational contracting and have not reached the main-sequence (MS) yet. Some of these objects, “classical” TTS (CTTS), are surrounded by massive accretion gas and dust protoplanetary disks. With the aim of studying the large-scale topology of TTS magnetic fields two international research programs MaPP (Magnetic Protostars and Planets) and MaTYSSE (Magnetic Topologies of Young Stars and the Survival of massive close-in Exoplanets) were organized.
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