A measure of the size of the magnetospheric accretion region in TW Hydrae

AbstractIn the presently favored picture of star formation, mass is transferred from disk to star via magnetospheric accretion and out of the system via magnetically driven outflows. This magnetically mediated mass flux is a fundamental process upon which the evolution of the star, disk, and forming planetary system depends. Our current understanding of these processes is heavily rooted in young solar analogs, T Tauri Stars (TTS). We have come to understand recently, however, that the higher mass pre-main sequence (PMS) Herbig AeBe (HAeBe) stars have dramatically weaker dipolar fields than their lower mass counterparts. We present our current observational and theoretical efforts to characterize magnetospherically mediated mass transfer within HAeBe star+disk systems. We have gathered a rich spectroscopic and interferometric data set for several dozen HAeBe stars in order to measure accretion and mass loss rates, assess wind and magnetospheric accretion properties, and determine how spectral lines and interferometric visibilities are diagnostic of these processes. For some targets, we have observed spectral line variability and will discuss ongoing time-series spectroscopic efforts.

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Time variable funnel flows

Proceedings of the International Astronomical Union ◽

10.1017/s174392130700943x ◽

2007 ◽

Vol 3 (S243) ◽

pp. 71-82 ◽

Cited By ~ 2

Author(s):

Silvia H. P. Alencar

Keyword(s):

Field Configuration ◽

Time Variable ◽

T Tauri Stars ◽

Magnetic Field Configuration ◽

Accretion Process ◽

T Tauri ◽

Model Predictions ◽

The Magnetic Field ◽

Disk Region ◽

Magnetospheric Accretion

AbstractMagnetospheric accretion models are the current consensus to explain the main observed characteristics of classical T Tauri stars. In recent years the concept of a static magnetosphere has been challenged by synoptic studies of classical T Tauri stars that show strong evidence for the accretion process to be dynamic on several timescales and governed by changes in the magnetic field configuration. At the same time numerical simulation results predict evolving funnel flows due to the interaction between the stellar magnetosphere and the inner disk region. In this contribution we will focus on the main recent observational evidences for time variable funnel flows and compare them with model predictions.

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Modeling the Hαline emission around classical T Tauri stars using magnetospheric accretion and disk wind models

Astronomy and Astrophysics ◽

10.1051/0004-6361/201014490 ◽

2010 ◽

Vol 522 ◽

pp. A104 ◽

Cited By ~ 42

Author(s):

G. H. R. A. Lima ◽

S. H. P. Alencar ◽

N. Calvet ◽

L. Hartmann ◽

J. Muzerolle

Keyword(s):

T Tauri Stars ◽

Disk Wind ◽

T Tauri ◽

Magnetospheric Accretion

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The accretion process in the magnetic Herbig Ae star HD 104237

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319003880 ◽

2018 ◽

Vol 14 (A30) ◽

pp. 137-137

Author(s):

Markus Schöller ◽

Mikhail A. Pogodin

Keyword(s):

Rotation Period ◽

Primary Component ◽

Stellar Rotation ◽

Spectroscopic Parameters ◽

Disk Wind ◽

Accretion Process ◽

Emission Line Spectrum ◽

Spectroscopic Signatures ◽

Periodogram Analysis ◽

Magnetospheric Accretion

AbstractAfter successfully retrieving the known rotation period P = 42.076 d in the Herbig Ae star HD 101412 using spectroscopic signatures of accretion tracers (Schöller et al.2016), we have studied magnetospheric accretion in the Herbig Ae SB2 system HD 104237 using spectroscopic parameters of the He i 10830, Paγ, and He i 5876 lines, formed in the accretion region. Employing 21 spectra obtained with ISAAC and X-shooter, we found that the temporal behavior of these parameters can be explained by a variable amount of matter being accreted in the region between the star and the observer. Using a periodogram analysis, we examined the possible origin of the accretion flow in HD 104237 and considered the following four scenarios: matter flows from the circumbinary envelope, mass exchange between the system’s components, magnetospheric accretion (MA) from the disk onto the star, and fast high-latitude accretion from a disk wind onto a weakly magnetized star. Based on a correlation analysis, we were able to show that the primary component is responsible for the observed emission line spectrum of the system. Since we do not find any correlation of the spectroscopic parameters with the phase of the orbital period (P ≍ 20 d), we can reject the first two scenarios. We found a variation period of about 5 d, which likely represents the stellar rotation period of the primary and favors the MA scenario.

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Observations of magnetic fields in Herbig Ae/Be stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319003764 ◽

2018 ◽

Vol 14 (A30) ◽

pp. 123-123

Author(s):

Markus Schöller ◽

Swetlana Hubrig

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

T Tauri Stars ◽

Be Stars ◽

T Tauri ◽

Weak Magnetic Fields ◽

Order Of Magnitude ◽

Field Geometry ◽

Herbig Ae Stars ◽

Magnetospheric Accretion

AbstractModels of magnetically driven accretion reproduce many observational properties of T Tauri stars. For the more massive Herbig Ae/Be stars, the corresponding picture has been questioned lately, in part driven by the fact that their magnetic fields are typically one order of magnitude weaker. Indeed, the search for magnetic fields in Herbig Ae/Be stars has been quite time consuming, with a detection rate of about 10% (e.g. Alecian et al. 2008), also limited by the current potential to detect weak magnetic fields. Over the last two decades, magnetic fields were found in about twenty objects (Hubrig et al. 2015) and for only two Herbig Ae/Be stars was the magnetic field geometry constrained. Ababakr, Oudmaijer & Vink (2017) studied magnetospheric accretion in 56 Herbig Ae/Be stars and found that the behavior of Herbig Ae stars is similar to T Tauri stars, while Herbig Be stars earlier than B7/B8 are clearly different. The origin of the magnetic fields in Herbig Ae/Be stars is still under debate. Potential scenarios include the concentration of the interstellar magnetic field under magnetic flux conservation, pre-main-sequence dynamos during convective phases, mergers, or common envelope developments. The next step in this line of research will be a dedicated observing campaign to monitor about two dozen HAeBes over their rotation cycle.

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