Letter to the Editor

Rotationally modulated variations and the mean longitudinal magnetic field of the Herbig Ae star HD 101412^⋆,⋆⋆

¹ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
e-mail: shubrig@aip.de
² Department of Theoretical Physics and Astrophysics, Masaryk University, Brno, Czech Republic
³ Observatory and Planetarium of J. Palisa, VŠB – Technical University, Ostrava, Czech Republic
⁴ Instituto de Ciencias Astronomicas, de la Tierra, y del Espacio (ICATE), 5400 San Juan, Argentina
⁵ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
⁶ Departamento de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Chile
⁷ Department of Astronomy, University of Michigan, Ann Arbor, MI 48109-1042, USA
⁸ Jeremiah Horrocks Institute of Astrophysics, University of Central Lancashire, Preston PR1 2HE, UK
⁹ Pulkovo Observatory, Saint-Petersburg, 196140, Russia
¹⁰ Isaac Newton Institute of Chile, Saint-Petersburg Branch, Russia

Received: 22 September 2010
Accepted: 10 November 2010

Abstract

Context. Despite the importance of magnetic fields to a full understanding of the properties of accreting Herbig Ae/Be stars, these fields have scarcely been studied until now over the rotation cycle. One reason for the paucity of these observations is the lack of knowledge of their rotation periods. The sharp-lined young Herbig Ae star HD 101412 with a strong surface magnetic field has become in the past few years one of the most well-studied targets among the Herbig Ae/Be stars.

Aims. We present our multi-epoch polarimetric spectra of this star acquired with FORS 2 to search for a rotation period and constrain the geometry of the magnetic field.

Methods. We measured longitudinal magnetic fields for 13 different epochs distributed over 62 days. These new measurements and our previous measurements of the magnetic field in this star were combined with available photometric observations to determine the rotation period.

Results. We find the rotation period to be P = 42.076 ± 0.017 d. According to near-infrared imaging studies, the star is observed nearly edge-on. The star exhibits a single-wave variation in the longitudinal magnetic field during the stellar rotation cycle. These observations are usually considered as evidence of a dominant dipolar contribution to the magnetic field topology.