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Evidence for localized onset of episodic mass loss in Mira

Perrin, G. and Ridgway, S. T. and Lacour, S. and Haubois, X. and Thiébaut, É. and Berger, J. P. and Lacasse, M. G. and Millan-Gabet, R. and Monnier, J. D. and Pedretti, E. and Ragland, S. and Traub, W. (2020) Evidence for localized onset of episodic mass loss in Mira. Astronomy and Astrophysics, 642 . Art. No. A82. ISSN 0004-6361. doi:10.1051/0004-6361/202037443.

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Context. Mass loss from long-period variable stars (LPV) is an important contributor to the evolution of galactic abundances. Dust formation is understood to play an essential role in mass loss. It has, however, proven difficult to develop measurements that strongly constrain the location and timing of dust nucleation and acceleration. Aims. Interferometric imaging has the potential to constrain the geometry and dynamics of mass loss. High angular resolution studies of various types have shown that LPVs have a distinct core-halo structure. These have also shown that LPV images commonly exhibit a non-circular shape. The nature of this shape and its implications are yet to be understood. Methods. Multi-telescope interferometric measurements taken with the Interferometric Optical Telescope Array (IOTA) provide imagery of the LPV Mira in the H-band. This wavelength region is well suited to studying mass loss given the low continuum opacity, which allows for emission to be observed over a very long path in the stellar atmosphere and envelope. Results. The observed visibilities are consistent with a simple core-halo model to represent the central object and the extended molecular layers but, in addition, they demonstrate a substantial asymmetry. An analysis with image reconstruction software shows that the asymmetry is consistent with a localized absorbing patch. The observed opacity is tentatively associated with small dust grains, which will grow substantially during a multi-year ejection process. Spatial information along with a deduced dust content of the cloud, known mass loss rates, and ejection velocities provide evidence for the pulsational pumping of the extended molecular layers. The cloud may be understood as a spatially local zone of enhanced dust formation, very near to the pulsating halo. The observed mass loss could be provided by several such active regions around the star. Conclusions. This result provides an additional clue for better understanding the clumpiness of dust production in the atmosphere of AGB stars. It is compatible with scenarios where the combination of pulsation and convection play a key role in the process of mass loss.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Ridgway, S. T.0000-0003-2557-7132
Lacour, S.0000-0002-6948-0263
Haubois, X.0000-0001-7878-7278
Thiébaut, É.0000-0002-8908-7493
Berger, J. P.0000-0001-5025-0428
Lacasse, M. G.0000-0001-8627-9708
Millan-Gabet, R.0000-0003-0447-5866
Monnier, J. D.0000-0002-3380-3307
Pedretti, E.0000-0002-6214-0282
Additional Information:© G. Perrin et al. 2020. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Received 3 January 2020 / Accepted 14 August 2020. This research has made use of NASA’s Astrophysics Data System Bibliographic Services, the SIMBAD and AFOEV databases, operated at CDS, Strasbourg, France and of the AAVSO database. The work of STR is supported by NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. We thank the anonymous referee for suggestions which improved the content and presentation of the report.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:stars: atmospheres / stars: AGB and post-AGB / stars: mass-loss / techniques: interferometric / infrared: stars / stars: individual: Mira
Record Number:CaltechAUTHORS:20201008-083809769
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Official Citation:Evidence for localized onset of episodic mass loss in Mira G. Perrin, S. T. Ridgway, S. Lacour, X. Haubois, É. Thiébaut, J. P. Berger, M. G. Lacasse, R. Millan-Gabet, J. D. Monnier, E. Pedretti, S. Ragland and W. Traub A&A, 642 (2020) A82 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105917
Deposited By: George Porter
Deposited On:08 Oct 2020 18:08
Last Modified:16 Nov 2021 18:47

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