Magnetic fields and differential rotation on the pre-main sequence – II. The early-G star HD 141943 – coronal magnetic field, Hα emission and differential rotation
Article first published online: 1 APR 2011
© 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS
Monthly Notices of the Royal Astronomical Society
Volume 413, Issue 3, pages 1939–1948, May 2011
How to Cite
Marsden, S. C., Jardine, M. M., Ramírez Vélez, J. C., Alecian, E., Brown, C. J., Carter, B. D., Donati, J.-F., Dunstone, N., Hart, R., Semel, M. and Waite, I. A. (2011), Magnetic fields and differential rotation on the pre-main sequence – II. The early-G star HD 141943 – coronal magnetic field, Hα emission and differential rotation. Monthly Notices of the Royal Astronomical Society, 413: 1939–1948. doi: 10.1111/j.1365-2966.2011.18272.x
- Issue published online: 11 MAY 2011
- Article first published online: 1 APR 2011
- Accepted 2010 December 29. Received 2010 December 9; in original form 2010 September 15
- magnetic fields;
- stars: activity;
- stars: imaging;
- stars: individual: HD 141943
Spectropolarimetric observations of the pre-main sequence early-G star HD 141943 were made at three observing epochs (2007, 2009 and 2010). The observations were made using the 3.9-m Anglo-Australian Telescope with the UCLES echelle spectrograph and the SEMPOL spectropolarimeter visitor instrument. The brightness and surface magnetic field topologies (given in Paper I) were used to determine the star’s surface differential rotation and reconstruct the coronal magnetic field of the star.
The coronal magnetic field at the three epochs shows on the largest scales that the field structure is dominated by the dipole component with possible evidence for the tilt of the dipole axis shifting between observations. We find very high levels of differential rotation on HD 141943 (∼8 times the solar value for the magnetic features and ∼5 times solar for the brightness features), similar to that evidenced by another young early-G star, HD 171488. These results indicate that a significant increase in the level of differential rotation occurs for young stars around a spectral type of early-G. We also find for the 2010 observations that there is a large difference in the differential rotation measured from the brightness and magnetic features, similar to that seen on early-K stars, but with the difference being much larger. We find only tentative evidence for temporal evolution in the differential rotation of HD 141943.