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arXiv · 1807.09815

Velocity resolved [O I] 63 $\mu$m emission in the HD 50138 circumstellar disk

G. Sandell·C. Salyk·M. van den Ancker·W. -J. de Wit·E. Chambers·R. Güsten·H. Wiesemeyer·H. Richter
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Abstract

HH 50138 is one of the brightest B[e] stars at a distance of $\sim$ 380 pc with strong infrared excess. The star was observed in [O I] 63 $\mu$m and [C II] 158 $\mu$m with high velocity resolution with upGREAT on SOFIA. The velocity resolved [O I] emission provides evidence for a large gas-disk, $\sim$ 760 au in size, around HD 50138. Whereas previous interferometric observations give strong evidence for a hot gas and dust disk in Keplerian rotation, our bservations are the first to provide unambiguous evidence for a large warm disk around the star. Herschel/PACS observations showed that the [C II] emission is extended, therefore the [C II] emission most likely originates in an ionized gas shell created by a past outflow event. We confirm the isolated nature of HD 50138. It is far from any star forming region and has low proper motion. Neither is there any sign of a remnant cloud from which it could have formed. The extended disk around the star appears carbon poor. It shows OH and [O I] emission, but no CO. The CO abundance appears to be at least an order of magnitude lower than that of OH. Furthermore $^{13}$CO is enriched by more than a factor of five, confirming that the star is not a Herbig Be star. Finally we note that our high spectral resolution [O I] and [C II] observations provide a very accurate heliocentric velocity of the star, 40.8 $\pm$ 0.2 km~s$^{-1}$.

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G. Sandell, C. Salyk, M. van den Ancker, W. -J. de Wit, E. Chambers, R. Güsten, H. Wiesemeyer, H. Richter. 2018-07-25. Velocity resolved [O I] 63 $\mu$m emission in the HD 50138 circumstellar disk. https://doi.org/10.3847/1538-4357/aad639

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