Wallström, SHJ, Lagadec, E, Muller, S et al. (12 more authors) (2017) ALMA Compact Array observations of the Fried Egg nebula. Astronomy & Astrophysics, 597. A99-A99. ISSN 0004-6361
Abstract
Yellow hypergiants are rare and represent a fast evolutionary stage of massive evolved stars. That evolutionary phase is characterised by a very intense mass loss, the understanding of which is still very limited. Here we report ALMA Compact Array observations of a 50′′-mosaic toward the Fried Egg nebula, around one of the few Galactic yellow hypergiants IRAS 17163-3907. The emission from the 12CO J = 2–1 line, H30α recombination line, and continuum is imaged at a resolution of ~8′′, revealing the morphology of the molecular environment around the star. The continuum emission is unresolved and peaks at the position of the star. The radio recombination line H30α shows unresolved emission at the star, with an approximately Gaussian spectrum centered on a velocity of 21 ± 3km s-1 with a width of 57 ± 6km s-1. In contrast, the CO 2–1 emission is complex and decomposes into several components beyond the contamination from interstellar gas in the line of sight. The CO spectrum toward the star is a broad plateau, centered at the systemic velocity of +18 km s-1 and with an expansion velocity of 100 ± 10km s-1. Assuming isotropic and constant mass-loss, we estimate a mass-loss rate of 8 ± 1.5 × 10-5M⊙ yr-1. At a radius of 25′′ from the star, we detect CO emission associated with the dust ring previously imaged by Herschel. The kinematics of this ring, however, is not consistent with an expanding shell, but show a velocity gradient of vsys ± 20km s-1. In addition, we find a puzzling bright feature radially connecting the star to the CO ring, at a velocity of +40 km s-1 relative to the star. This spur feature may trace a unidirectional ejection event from the star. Our ACA observations reveal the complex morphology around IRAS 17163 and illustrate the breakthroughs that ALMA will bring to the field of massive stellar evolution.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2017 ESO. Reproduced in accordance with the publisher's self-archiving policy. |
Keywords: | circumstellar matter; stars: AGB and post-AGB; stars: mass-loss; stars: individual: IRAS 17163-3907 |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds) > Astrophysics (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 21 Apr 2017 10:28 |
Last Modified: | 12 Aug 2019 15:56 |
Published Version: | https://doi.org/10.1051/0004-6361/201628416 |
Status: | Published |
Publisher: | EDP Sciences |
Identification Number: | 10.1051/0004-6361/201628416 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:115271 |