Astronomy and Astrophysics, volume 589, L4-4 (2016/5-1)
Tracing jet emission at the base of a high-mass YSO. First AMBER/VLTI observations of the Brγ emission in IRAS 13481-6124.
CARATTI O GARATTI A., STECKLUM B., WEIGELT G., SCHERTL D., HOFMANN K.-H., KRAUS S., OUDMAIJER R.D., DE WIT W.J., SANNA A., GARCIA LOPEZ R., KREPLIN A. and RAY T.P.
Abstract (from CDS):
Aims. To probe the circumstellar environment of IRAS 13481-6124, a 20M☉ high-mass young stellar object (HMYSO) with a collimated parsec-scale jet and an accretion disc, we investigate the origin of its Brγ emission line through near-infrared (NIR) interferometry.
Methods. We present the first AMBER/VLTI observations of the Brγ emitting region in an HMYSO at medium spectral resolution (R=1500).
Results. Our AMBER/VLTI observations reveal a spatially and spectrally resolved Brγ line in emission with a strong P Cygni profile, indicating outflowing matter with a terminal velocity of ∼500km/s. Visibilities, differential phases, and closure phases are detected in our observations within the spectral line and in the adjacent continuum. Both total visibilities (continuum plus line emitting region) and pure-line visibilities indicate that the Brγ-emitting region is more compact (2-4mas in diameter or ∼6-13au at 3.2kpc) than the continuum-emitting region (∼5.4mas or ∼17au). The absorption feature is also spatially resolved at the longest baselines (81 and 85m) and has a visibility that is slightly smaller than the continuum-emitting region. The differential phases at the four longest baselines display an "S"-shaped structure across the line, peaking in the blue- and red-shifted high-velocity components. The calibrated photocentre shifts are aligned with the known jet axis, i.e they are probably tracing an ionised jet. The high-velocity components (vr∼100-500km/s) are located far from the source, whereas the low-velocity components (0-100km/s) are observed to be closer, indicating a strong acceleration of the gas flow in the inner 10 au. Finally, a non-zero closure phase along the continuum is detected. By comparing our observations with the synthetic images of the continuum around 2.16µm, we confirm that this feature originates from the asymmetric brightness distribution of the continuum owing to the inclination of the inner disc.
© ESO, 2016
stars: formation - circumstellar matter - stars: protostars - stars: massive - techniques: interferometric - techniques: high angular resolution
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