Spectroscopic signatures of magnetospheric accretion in Herbig Ae/Be stars

Abstract

Context. Models of magnetically-driven accretion and outflows reproduce many observational properties of T Tauri stars. This concept is not well established for the more massive Herbig Ae/Be stars. Aims. We intend to examine the magnetospheric accretion in Herbig Ae/Be stars and search for rotational modulation using spectroscopic signatures, in this first paper concentrating on the well-studied Herbig Ae star HD 101412. Methods. We used near-infrared spectroscopic observations of the magnetic Herbig Ae star HD 101412 to test the magnetospheric character of its accretion disk/star interaction. We reduced and analyzed 30 spectra of HD 101412, acquired with the CRIRES and X-shooter spectrographs installed at the VLT (ESO, Chile). The spectroscopic analysis was based on the He i λ10 830 and Paγ lines, formed in the accretion region. Results. We found that the temporal behavior of these diagnostic lines in the near-infrared spectra of HD 101412 can be explained by rotational modulation of line profiles generated by accreting gas with a period P = 20 d .53 ± 1 d .68. The discovery of this period, about half of the magnetic rotation period P m = 42 d .076 previously determined from measurements of the mean longitudinal magnetic field, indicates that the accreted matter falls onto the star in regions close to the magnetic poles intersecting the line-of-sight two times during the rotation cycle. We intend to apply this method to a larger sample of Herbig Ae/Be stars.

Spectroscopic analysis of accretion/ejection signatures in the Herbig Ae/Be stars HD 261941 and V590 Mon

“…Except for the region around the stellar rest velocity, the entire line is correlated, which indicates that most of this line is formed in a single region of the system. Many authors have suggested that HBe systems, like V590 Mon, are not simple scaled versions of CTTS, and that there is no clear evidence that magnetospheric accretion is ongoing in these systems (Vink et al 2002;Cauley & Johns-Krull 2014Ababakr et al 2015;Fairlamb et al 2015;Schöller et al 2016). The Hα emission line may therefore come mostly from a high density wind without a significant magnetospheric accretion contribution (Boehm & Catala 1995).…”

Searching for Magnetospheres around Herbig Ae/Be Stars

“…The right of Figure 3 illustrates the phase dependencies of the He I λ10830 line taken from [17,18]. As the MA model predicts, the V r2 parameter is at its maximum when B z reaches its minimal or maximal value.…”

Spectropolarimetry of Stars Across the H-R Diagram

“…A second outcome of their research was the confirmation that Herbig Ae stars are similar to T Tauri stars in displaying a line polarization effect, while depolarization is more common among Herbig Be stars. Using near-infrared multi-epoch spectroscopic data obtained with the CRIRES and X-shooter spectrographs installed at the VLT, Schöller et al (2016) examined the magnetospheric accretion in the Herbig Ae star HD 101412. Spectroscopic signatures in He I 10830 and Paγ, two near-infrared lines that are formed in a Herbig star's accretion region, were presenting temporal modulation.…”