|dc.contributor.author||Johns-Krull, Christopher M.
Valenti, Jeff A.
Jeffers, Sandra V.
Piskunov, Nikolai E.
Johns-Krull, Christopher M., Chen, Wei, Valenti, Jeff A., et al.. "Magnetically Controlled Accretion on the Classical T Tauri Stars GQ Lupi and TQ Hydrae." The Astrophysical Journal, 765, (2013) The American Astronomical Society: 11-22. http://dx.doi.org/10.1088/0004-637X/765/1/11.
We present high spectral resolution (R ≈ 108,000) Stokes V polarimetry of the classical T Tauri stars (CTTSs)
GQ Lup and TW Hya obtained with the polarimetric upgrade to the HARPS spectrometer on the ESO 3.6 m
telescope. We present data on both photospheric lines and emission lines, concentrating our discussion on the
polarization properties of the He i emission lines at 5876 Å and 6678 Å. The He i lines in these CTTSs contain both
narrow emission cores, believed to come from near the accretion shock region on these stars, and broad emission
components which may come from either a wind or the large-scale magnetospheric accretion flow.We detect strong
polarization in the narrow component of the two He i emission lines in both stars. We observe a maximum implied
field strength of 6.05 ± 0.24 kG in the 5876 Å line of GQ Lup, making it the star with the highest field strength
measured in this line for a CTTS. We find field strengths in the two He i lines that are consistent with each other,
in contrast to what has been reported in the literature on at least one star. We do not detect any polarization in the
broad component of the He i lines on these stars, strengthening the conclusion that they form over a substantially
different volume relative to the formation region of the narrow component of the He i lines.
The American Astronomical Society
Magnetically Controlled Accretion on the Classical T Tauri Stars GQ Lupi and TQ Hydrae
The Astrophysical Journal