SMuK 2021 – scientific programme

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EP: Fachverband Extraterrestrische Physik

EP 9: Astrophysics I

EP 9.6: Talk

Friday, September 3, 2021, 12:45–13:00, H5

Nebular kinematics and variability of the Galactic B[e] supergiant star MWC 137 — •Michaela Kraus — Astronomical Institute, Czech Academy of Sciences, Ondrejov, Czech Republic

The Galactic object MWC 137, with its large-scale optical bipolar ring nebula and high-velocity jet and knots, is a rather atypical representative of the B[e] supergiant class. To shed light on the physical conditions and kinematics of the nebula we performed multi-wavelength observations spreading from the optical to the radio regimes. Our data reveal a new bow-shaped feature at a distance of 80" from MWC 137. Moreover, we found that large amounts of cool molecular gas and warm dust embrace the large-scale optical nebula in the east, south, and west. The radial velocities of the nebula display a complex behavior but, in general, the northern nebular features are predominantly approaching while the southern ones are mostly receding. The electron density shows strong variations across the nebula with higher densities closer to MWC 137 and in regions of intense emission. In regions with high radial velocities the density decreases significantly. A disk of hot molecular gas revolves the star on small scales and possibly triggers the jet. The emission of this disk is reflected by dust arranged in arc-like structures and clumps surrounding MWC 137. Furthermore, we detect a period of 1.93 d in the time series photometry collected with the TESS satellite, which could suggest stellar pulsations. Other, low-frequency variability is seen as well. Whether these signals are caused by internal gravity waves in the early-type star or by variability in the wind and circumstellar matter currently cannot be distinguished.