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λ And: a post-main-sequence wind from a solar-mass star

Ó Fionnagáin, D. and Vidotto, A. A. and Petit, P. and Neiner, C. and Manchester, W., IV and Folsom, C. P. and Hallinan, G. (2021) λ And: a post-main-sequence wind from a solar-mass star. Monthly Notices of the Royal Astronomical Society, 500 (3). pp. 3438-3453. ISSN 0035-8711.

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We investigate the wind of λ And, a solar-mass star that has evolved off the main sequence becoming a subgiant. We present spectropolarimetric observations and use them to reconstruct the surface magnetic field of λ And. Although much older than our Sun, this star exhibits a stronger (reaching up to 83 G) large-scale magnetic field, which is dominated by the poloidal component. To investigate the wind of λ And, we use the derived magnetic map to simulate two stellar wind scenarios, namely a ‘polytropic wind’ (thermally driven) and an ‘Alfven-wave-driven wind’ with turbulent dissipation. From our 3D magnetohydrodynamics simulations, we calculate the wind thermal emission and compare it to previously published radio observations and more recent Very Large Array observations, which we present here. These observations show a basal sub-mJy quiescent flux level at ∼5 GHz and, at epochs, a much larger flux density (>37 mJy), likely due to radio flares. By comparing our model results with the radio observations of λ And, we can constrain its mass-loss rate Ṁ. There are two possible conclusions. (1) Assuming the quiescent radio emission originates from the stellar wind, we conclude that λ And has Ṁ ≃ 3×10⁻⁹ M_⊙ yr⁻¹, which agrees with the evolving mass-loss rate trend for evolved solar-mass stars. (2) Alternatively, if the quiescent emission does not originate from the wind, our models can only place an upper limit on mass-loss rates, indicating that Ṁ ≲ 3×10⁻⁹ M_⊙ yr⁻¹.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Ó Fionnagáin, D.0000-0001-9747-3573
Vidotto, A. A.0000-0001-5371-2675
Petit, P.0000-0001-7624-9222
Neiner, C.0000-0003-1978-9809
Manchester, W., IV0000-0003-0472-9408
Hallinan, G.0000-0002-7083-4049
Alternate Title:Lambda And: A post-main sequence wind from a solar-mass star
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 November 1. Received 2020 October 30; in original form 2020 February 26. Published: 11 November 2020. DOF and AAV would like to acknowledge funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Framework Programme (grant agreement No 817540, ASTROFLOW). WM is supported by NASA grant NNX16AL12G. The authors wish to acknowledge the SFI/HEA Irish Centre for High-End Computing (ICHEC) for the provision of computational facilities and support. This work used the BATS-R-US tools developed at the University of Michigan Center for Space Environment Modeling and made available through the NASA Community Coordinated Modeling Center. The authors would like to thank S. R. Cranmer for access to stellar data used in Fig. 1. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We thank the anonymous referees for their constructive feedback, which helped enhance the quality of our manuscript. Data Availability: The data described in this article will be shared on reasonable request to the corresponding author.
Group:Astronomy Department
Funding AgencyGrant Number
European Research Council (ERC)817540
Subject Keywords:stars: late-type – stars: magnetic field – stars: winds, outflows – λ And (HD 222107)
Issue or Number:3
Record Number:CaltechAUTHORS:20210202-103629939
Persistent URL:
Official Citation:D Ó Fionnagáin, A A Vidotto, P Petit, C Neiner, W Manchester IV, C P Folsom, G Hallinan, λ And: a post-main-sequence wind from a solar-mass star, Monthly Notices of the Royal Astronomical Society, Volume 500, Issue 3, January 2021, Pages 3438–3453,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107870
Deposited By: Tony Diaz
Deposited On:02 Feb 2021 18:51
Last Modified:02 Feb 2021 18:51

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