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Binarity as the Origin of Long Secondary Periods in Red Giant Stars

Soszyński, I. and Olechowska, A. and Ratajczak, M. and Iwanek, P. and Skowron, D. M. and Mróz, P. and Pietrukowicz, P. and Udalski, A. and Szymanski, M. K. and Skowron, J. and Gromadzki, M. and Poleski, R. and Kozłowski, S. and Wrona, M. and Ulaczyk, K. and Rybicki, K. (2021) Binarity as the Origin of Long Secondary Periods in Red Giant Stars. Astrophysical Journal Letters, 911 (2). Art. No. L22. ISSN 2041-8205. doi:10.3847/2041-8213/abf3c9.

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Long secondary periods (LSPs), observed in a third of pulsating red giant stars, are the only unexplained type of large-amplitude stellar variability known at this time. Here we show that this phenomenon is a manifestation of a substellar or stellar companion orbiting the red giant star. Our investigation is based on a sample of about 16,000 well-defined LSP variables detected in the long-term OGLE photometric database of the Milky Way and Magellanic Clouds, combined with the mid-infrared data extracted from the NEOWISE-R archive. From this collection, we selected about 700 objects with stable, large-amplitude, well-sampled infrared light curves and found that about half of them exhibit secondary eclipses, thus presenting an important piece of evidence that the physical mechanism responsible for LSPs is binarity. Namely, the LSP light changes are due to the presence of a dusty cloud orbiting the red giant together with the companion and obscuring the star once per orbit. The secondary eclipses, visible only in the infrared wavelength, occur when the cloud is hidden behind the giant. In this scenario, the low-mass companion is a former planet that has accreted a significant amount of mass from the envelope of its host star and grown into a brown dwarf.

Item Type:Article
Related URLs:
URLURL TypeDescription
Soszyński, I.0000-0002-7777-0842
Olechowska, A.0000-0003-0481-3116
Ratajczak, M.0000-0002-3218-2684
Iwanek, P.0000-0002-6212-7221
Skowron, D. M.0000-0001-9439-604X
Mróz, P.0000-0001-7016-1692
Pietrukowicz, P.0000-0002-2339-5899
Udalski, A.0000-0001-5207-5619
Szymanski, M. K.0000-0002-0548-8995
Skowron, J.0000-0002-2335-1730
Gromadzki, M.0000-0002-1650-1518
Poleski, R.0000-0002-9245-6368
Kozłowski, S.0000-0003-4084-880X
Wrona, M.0000-0002-3051-274X
Ulaczyk, K.0000-0001-6364-408X
Rybicki, K.0000-0002-9326-9329
Additional Information:© 2021. The American Astronomical Society. Received 2021 February 24; revised 2021 March 23; accepted 2021 March 31; published 2021 April 16. We thank the anonymous referee for constructive comments that helped us to improve the manuscript. We are grateful to Andrzej Niedzielski for helpful suggestions that improved the paper. This work has been supported by the National Science Centre, Poland, grant MAESTRO No. 2016/22/A/ST9/00009. The OGLE project has received funding from the Polish National Science Centre grant MAESTRO No. 2014/14/A/ST9/00121. This publication makes use of data products from the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), which is a joint project of the Jet Propulsion Laboratory/California Institute of Technology and the University of Arizona. NEOWISE is funded by the National Aeronautics and Space Administration.
Funding AgencyGrant Number
National Science Centre (Poland)2016/22/A/ST9/00009
National Science Centre (Poland)2014/14/A/ST9/00121
Subject Keywords:Asymptotic giant branch stars; Long period variable stars; Close binary stars; Circumstellar dust; Brown dwarfs
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Asymptotic giant branch stars (2100); Long period variable stars (935); Close binary stars (254); Circumstellar dust (236); Brown dwarfs (185)
Record Number:CaltechAUTHORS:20210423-164855726
Persistent URL:
Official Citation:I. Soszyński et al 2021 ApJL 911 L22
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108831
Deposited By: George Porter
Deposited On:27 Apr 2021 15:03
Last Modified:16 Nov 2021 19:32

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