Probing the Structure of the Accretion Region in a Sample of Magnetic Herbig Ae/Be Stars

TL;DR

This study investigates the accretion region structure in magnetic Herbig Ae/Be stars using spectroscopic data, revealing rotational modulation effects, magnetic field complexities, and determining the rotation period of HD104237.

Contribution

It provides the first measurement of HD104237's rotation period and inclination, and uncovers complex magnetic field structures in these stars.

Findings

Rotational modulation explains line profile variability.

Magnetic field of HD104237's secondary component detected.

HD190073's magnetic field likely has a complex structure.

Abstract

We present the results of a study of the temporal behaviour of several diagnostic lines formed in the region of the accretion-disk/star interaction in the three magnetic Herbig Ae stars HD101412, HD104237, and HD190073. More than 100 spectra acquired with the ISAAC, X-shooter, and CRIRES spectrographs installed at the VLT-8m telescope (ESO, Chile), as well as at other observatories (OHP, Crimean AO) were analyzed. The spectroscopic data were obtained in the He I lambda10830, Pa gamma and He I lambda5876 lines. We found that the temporal behaviour of the diagnostic lines in the spectra of all program stars can be widely explained by a rotational modulation of the line profiles generated by a local accretion flow. This result is in good agreement with the predictions of the magnetospheric accretion model. For the first time, the rotation period of HD104237 (P_rot = 5.37+-0.03 days), as well as the inclination angle (i = 21+-4deg) were determined. Additional analysis of the HARPSpol spectra of HD104237 and HD190073, taken from the ESO archive, with the use of the SVD method shows that the magnetic field structure of HD190073 is likely more complex than a simple dipole and contains a circumstellar component. For the first time, the magnetic field of the secondary component of the binary system HD104237 was also detected (<B_z> = 128+-10G).