Near-infrared line spectropolarimetry of hot massive stars

Abstract

In order to study the inner parts of the circumstellar material around optically faint, infrared bright objects, we present the first medium-resolution spectropolarimetric data taken in the near-infrared. In this paper we discuss Pa beta line data of GL 490, a well-known embedded massive young stellar object, and of MWC 349A and MWC 342, two optically faint stars that are proposed to be in the pre-main sequence phase of evolution. As a check on the method, the classical Be star zeta Tau, known to display line polarization changes at optical wavelengths, was observed as well. Three of our targets show a ``line effect'' across Pa beta. For zeta Tau and MWC 349A this line effect is due to depolarisation by a circumstellar electron-scattering disk. In both cases, the position angle of the polarisation is consistent with that of the larger scale disks imaged at other wavelengths, validating infrared spectropolarimetry as a means to detect flattening on small scales. The tentative detection of a rotation in the polarization position angle at Pa beta in the embedded massive young stellar object GL 490 suggests the presence of a small scale rotating accretion disk with an inner hole - similar to those recently discovered at optical wavelengths in Herbig Ae and T Tauri stars.

arXiv comment6 pages, MNRAS in press

References in corpus (8)

• Probing the circumstellar structure of Herbig Ae/Be stars
• Halpha spectropolarimetry of B[e] and Herbig Be stars
• Probing the circumstellar structures of T Tauri stars and their relationship to those of Herbig stars
• Polarimetric line profiles for scattering off rotating disks
• Near-IR speckle imaging of massive young stellar objects
• Bispectrum speckle interferometry of the B[e] star MWC 349A
• Spectropolarimetric Clues to the Structure and Evolutionary Status of MWC 349A
• Linear spectropolarimetry of young and other emission line stars

Cited by in corpus (10)

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• Spectroscopic survey of emission-line stars. I. B[e] stars
• On the presence and absence of disks around O-type stars
• An equatorial wind from the massive young stellar object S140 IRS 1
• Spectropolarimetric Observations of Herbig Ae/Be Stars. II. Comparison of Spectropolarimetric Surveys: HAeBe, Be and Other Emission-Line Stars
• The Role of Evolutionary Age and Metallicity in the Formation of Classical Be Circumstellar Disks II. Assessing the Evolutionary Nature of Candidate Disk Systems
• Tracers of Discs and Winds around Intermediate and High Mass Young Stellar Objects
• Linear line spectropolarimetry of Herbig Ae/Be stars
• Calibrating and Stabilizing Spectropolarimeters with Charge Shuffling and Daytime Sky Measurements
• Spectropolarimetry and the study of circumstellar disks