TY - JOUR

T1 - On the Brγ line emission of the Herbig Ae/Be star MWC 120

AU - Kreplin, Alexander

AU - Tambovtseva, Larisa

AU - Grinin, Vladimir

AU - Kraus, Stefan

AU - Weigelt, Gerd

AU - Wang, Yang

N1 - Funding Information: This research has made use of NASA's Astrophysics Data System Bibliographic Services. We thank the European Southern Observatory staff at Paranal for their support during the observations. We acknowledge support from a Science and Technology Facilities Council Rutherford Fellowship (ST/J004030/1), Rutherford Grant (ST/K003445/1) and European Research Council Starting Grant (Grant Agreement No. 639889) Publisher Copyright: © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. Copyright: Copyright 2018 Elsevier B.V., All rights reserved.

PY - 2018/6/1

Y1 - 2018/6/1

N2 - The origin of the Br γ line in Herbig Ae/Be stars is still an open question. It has been proposed that a fraction of the 2.166-μm Br γ emission might emerge from a disc wind, the magnetosphere and other regions. Investigations of the Br γ line in young stellar objects are important to improve our understanding of the accretion-ejection process. Near-infrared longbaseline interferometry enables the investigation of the Br γ line-emitting region with high spatial and high spectral resolution. We observed the Herbig Ae/Be star MWC 120 with the Astronomical Multi-Beam Recombiner (AMBER) on theVery Large Telescope Interferometer (VLTI) in different spectral channels across the Br γ linewith a spectral resolution of R~1500. Comparison of the visibilities, differential and closure phases in the continuum and the lineemitting region with geometric and radiative transfer disc-wind models leads to constraints on the origin and dynamics of the gas emitting the Br γ light. Geometric modelling of the visibilities reveals a line-emission region about two times smaller than the K-band continuum region, which indicates a scenario where the Br γ emission is dominated by an extended disc wind rather than by a much more compact magnetospheric origin. To compare our data with a physical model, we applied a state-of-the-art radiative transfer disc-wind model. We find that all measured visibilities, differential and closure phases of MWC 120 can be approximately reproduced by a disc-wind model. A comparison with other Herbig stars indicates a correlation of the modelled inner disc-wind radii with the corresponding Alfvén radii for late spectral type stars.

AB - The origin of the Br γ line in Herbig Ae/Be stars is still an open question. It has been proposed that a fraction of the 2.166-μm Br γ emission might emerge from a disc wind, the magnetosphere and other regions. Investigations of the Br γ line in young stellar objects are important to improve our understanding of the accretion-ejection process. Near-infrared longbaseline interferometry enables the investigation of the Br γ line-emitting region with high spatial and high spectral resolution. We observed the Herbig Ae/Be star MWC 120 with the Astronomical Multi-Beam Recombiner (AMBER) on theVery Large Telescope Interferometer (VLTI) in different spectral channels across the Br γ linewith a spectral resolution of R~1500. Comparison of the visibilities, differential and closure phases in the continuum and the lineemitting region with geometric and radiative transfer disc-wind models leads to constraints on the origin and dynamics of the gas emitting the Br γ light. Geometric modelling of the visibilities reveals a line-emission region about two times smaller than the K-band continuum region, which indicates a scenario where the Br γ emission is dominated by an extended disc wind rather than by a much more compact magnetospheric origin. To compare our data with a physical model, we applied a state-of-the-art radiative transfer disc-wind model. We find that all measured visibilities, differential and closure phases of MWC 120 can be approximately reproduced by a disc-wind model. A comparison with other Herbig stars indicates a correlation of the modelled inner disc-wind radii with the corresponding Alfvén radii for late spectral type stars.

KW - Be

KW - Circumstellar matter

KW - Stars: emission-line

KW - Stars: formation

KW - Stars: individual: MWC 120

KW - Stars: pre-main-sequence

KW - Techniques: interferometric

UR - http://www.scopus.com/inward/record.url?scp=85045468704&partnerID=8YFLogxK

U2 - 10.1093/mnras/sty567

DO - 10.1093/mnras/sty567

M3 - Article

AN - SCOPUS:85045468704

VL - 476

SP - 4520

EP - 4526

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 4

ER -