Differential rotation on both components of the pre-main-sequence binary system HD 155555
Article
Article Title | Differential rotation on both components of the pre-main-sequence binary system HD 155555 |
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ERA Journal ID | 1074 |
Article Category | Article |
Authors | Dunstone, N. J. (Author), Hussain, G. A. J. (Author), Collier Cameron, A. (Author), Marsden, S. C. (Author), Jardine, M. (Author), Barnes, J. R. (Author), Ramirez Velez, J. C. (Author) and Donati, J. -F. (Author) |
Journal Title | Monthly Notices of the Royal Astronomical Society |
Journal Citation | 387 (4), pp. 1525-1536 |
Number of Pages | 12 |
Year | 2008 |
Publisher | Oxford University Press |
Place of Publication | United Kingdom |
ISSN | 0035-8711 |
1365-2966 | |
Digital Object Identifier (DOI) | https://doi.org/10.1111/j.1365-2966.2008.13338.x |
Web Address (URL) | https://academic.oup.com/mnras/article/387/4/1525/1088936 |
Abstract | We present the first measurements of surface differential rotation on a pre-main-sequence binary system. Using intensity (Stokes I) and circularly polarized (Stokes V) time-series spectra, taken over 11 nights at the Anglo-Australian Telescope (AAT), we incorporate a solarlike differential rotation law into the surface imaging process. We find that both components of the young, 18 Myr, HD 155555 (V824 Ara, G5IV + K0IV) binary system show significant differential rotation. The equator-pole lap times as determined from the intensity spectra are 80 d for the primary star and 163 d for the secondary. Similarly, for the magnetic spectra we obtain equator-pole lap times of 44 and 71 d, respectively, showing that the shearing timescale ofmagnetic regions is approximately half of that found for stellar spots. Both components are therefore found to have rates of differential rotation similar to those of the same spectraltype main-sequence single stars. The results for HD 155555 are therefore in contrast to those found in other, more evolved, binary systems where negligible or weak differential rotation has been discovered. We discuss two possible explanations for this: first that at the age of HD 155555 binary tidal forces have not yet had time to suppress differential rotation and secondly that the weak differential rotation previously observed on evolved binaries is a consequence of their large convection zone depths. We suggest that the latter is the more likely solution and show that both temperature and convection zone depth (from evolutionary models) are good predictors of differential rotation strength. Finally, we also examine the possible consequences of the measured differential rotation on the interaction of binary star coronae. |
Keywords | binaries; spectroscopic; pre-main-sequence; stars; coronae; imaging; magnetic fields; rotation |
ANZSRC Field of Research 2020 | 510109. Stellar astronomy and planetary systems |
519999. Other physical sciences not elsewhere classified | |
490402. Algebraic and differential geometry | |
Public Notes | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2008 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
Byline Affiliations | University of St Andrews, United Kingdom |
Anglo-Australian Observatory, Australia | |
University of Hertfordshire, United Kingdom | |
Paris Sciences and Letters University, France | |
Institute for Research in Astrophysics and Planetology, France | |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q2qz5/differential-rotation-on-both-components-of-the-pre-main-sequence-binary-system-hd-155555
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