Magnetospheric accretion on the T Tauri star BP Tauri

By J. Donati, M. Jardine, S. Gregory, P. Petit, F. Paletou, J. Bouvier, C. Dougados, F. Ménard, A. Cameron, Tim Harries and 8 more. 2008

168 citations recorded by the source corpus.

From observations collected with the ESPaDOnS and NARVAL spectropolarimeters, we report the detection of Zeeman signatures on the classical T Tauri star BP Tau. Circular polarisation signatures in photospheric lines and in narrow emission lines tracing magnetospheric accretion are monitored throughout most of the rotation cycle of BP Tau at two different epochs in 2006. We observe that rotational modulation dominates the temporal variations of both unpolarised and circularly polarised spectral proxies tracing the photosphere and the footpoints of accretion funnels. From the complete data sets at each epoch, we reconstruct the large-scale magnetic topology and the location of accretion spots at the surface of BP Tau using tomographic imaging. We find that the field of BP Tau involves a 1.2 kG dipole and 1.6 kG octupole, both slightly tilted with respect to the rotation axis. Accretion spots coincide with the two main magnetic poles at high latitudes and overlap with dark photospheric spots; they cover about 2% of the stellar surface. The strong mainly-axisymmetric poloidal field of BP Tau is very reminiscent of magnetic topologies of fully-convective dwarfs. It suggests that magnetic fields of fully-convective cTTSs such as BP Tau are likely not fossil remants, but rather result from vigorous dynamo action operating within the bulk of their convective zones. Preliminary modelling suggests that the magnetosphere of BP Tau extends to distances of at least 4 R* to ensure that accretion spots are located at high latitudes, and is not blown open close to the surface by a putative stellar wind. It apparently succeeds in coupling to the accretion disc as far out as the corotation radius, and could possibly explain the slow rotation of BP Tau.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/b4cfc91e954602634f29db6064be8333b290eac0

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Citations in the corpus

Large-scale magnetic topologies of late M dwarfs★: Magnetic topologies of late M dwarfs (2010, methodology): “From the analysis of a sample of early and mid M dwarfs Donati et al. (2008b) and Morin et al. (2008b) (hereafter D08 and M08b respectively) observed a strong change near the theoretical fullconvection threshold: while partly convective stars possess a weak non-axisymmetric field with a significant…”
Large-scale magnetic topologies of late M dwarfs⋆ (2008, methodology): “4.1, the local Stokes I and V line profiles are computed from a simple model based on UnnoRachkovsky’s equations (Unno 1956), similar to that used by Donati et al. (2008).”
Magnetic Fields of Nondegenerate Stars (2009, methodology): “Very recently, first evidence for global polarity switches was reported in a staro her than the Sun, namely the Jupiterhosting F8 starτ Boo (Donati et al. 2008d).”
Least-squares deconvolution of the stellar intensity and polarization spectra (2010, methodology): “This approach is frequently used in recent Doppler imaging studies of the stellar surface structure and magnetic fields (e.g., Donati et al. 2008; Morin et al. 2008; Folsom et al. 2008).”
ACCRETION RATES FOR T TAURI STARS USING NEARLY SIMULTANEOUS ULTRAVIOLET AND OPTICAL SPECTRA (2013, methodology): “Evidence for multiple accretion spots is seen in maps of the magnetosphere (Donati et al. 2008) and also in fits of the broad He and Ca emission, which require inhomogeneity in the hot spots (Dodin et al. 2013).”
Large-scale magnetic topologies of early M dwarfs (2008, methodology): “This model has proved rather successful at reproducing the observed times series of Stokes V profiles in midM dwarfs (M08) and classical T Tauri stars (Donati et al. 2008); we therefore use it again for the present study.”
Stellar magnetism: empirical trends with age and rotation (2014, background): “Donati et al. (2008a) suggested that the step in the saturation level between early-Ms and mid-Ms is caused by different efficiencies at producing large-scale versus smallscale fields, where rapidly-rotating mid-M dwarfs generate fields on larger spatial scales than early-M dwarfs (see also Reiners…”