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Prevalence of SED Turndown among Classical Be Stars: Are All Be Stars Close Binaries?

Klement, Robert and Carciofi, A. C. and Rivinius, T. and Ignace, R. and Matthews, L. D. and Torstensson, K and Gies, D. and Vieira, R. G. and Richardson, N. D. and de Souza, A. Domiciano and Bjorkman, J. E. and Hallinan, G. and Faes, D. M. and Mota, B. and Gullingsrud, A. D. and de Breuck, C. and Kervella, P. and Curé, M. and Gunawan, D. (2019) Prevalence of SED Turndown among Classical Be Stars: Are All Be Stars Close Binaries? Astrophysical Journal, 885 (2). Art. No. 147. ISSN 1538-4357. doi:10.3847/1538-4357/ab48e7.

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Rapid rotation is a fundamental characteristic of classical Be stars and a crucial property allowing for the formation of their circumstellar disks. Past evolution in a mass and angular momentum transferring binary system offers a plausible solution to how Be stars attained their fast rotation. Although the subdwarf remnants of mass donors in such systems should exist in abundance, only a few have been confirmed due to tight observational constraints. An indirect method of detecting otherwise hidden companions is offered by their effect on the outer parts of Be star disks, which are expected to be disrupted or truncated. In the context of the infrared and radio continuum excess radiation originating in the disk, the disk truncation can be revealed by a turndown in the spectral energy distribution due to reduced radio flux levels. In this work, we search for signs of spectral turndown in a sample of 57 classical Be stars with radio data, which include new data for 23 stars and the longest-wavelength detections so far (λ ≈ 10 cm) for two stars. We confidently detect the turndown for all 26 stars with sufficient data coverage (20 of which are not known to have close binary companions). For the remaining 31 stars, the data are inconclusive as to whether the turndown is present or not. The analysis suggests that many if not all Be stars have close companions influencing their outer disks. If confirmed to be subdwarf companions, the mass transfer spin-up scenario might explain the existence of the vast majority of classical Be stars.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Klement, Robert0000-0002-4313-0169
Carciofi, A. C.0000-0002-9369-574X
Ignace, R.0000-0002-7204-5502
Gies, D.0000-0001-8537-3583
Richardson, N. D.0000-0002-2806-9339
Hallinan, G.0000-0002-7083-4049
de Breuck, C.0000-0002-6637-3315
Kervella, P.0000-0003-0626-1749
Additional Information:© 2019 The American Astronomical Society. Received 2019 July 17; revised 2019 September 25; accepted 2019 September 26; published 2019 November 11. R.K. is grateful for a postdoctoral associateship funded by the Provost's Office of Georgia State University. A.C.C. acknowledges support from CNPq (grant 307594/2015-7). D.M.F. acknowledges FAPESP (grant 2016/16844-1). M.C. is thankful for support from FONDECYT project 1190485 and Centro de Astrofísica de Valparaíso Chile. This publication is partly based on observations made with ESO telescopes at the La Silla Paranal Observatory under program IDs 092.F-9708, 0.95.F-9709, 296.C-5004, and 099.F-0005. Support for CARMA construction was derived from the states of California, Illinois, and Maryland; the James S. McDonnell Foundation; the Gordon and Betty Moore Foundation; the Kenneth T. and Eileen L. Norris Foundation; the University of Chicago; the Associates of the California Institute of Technology; and the National Science Foundation. This publication is partly based on observations made with CARMA under program ID c1100. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The VLA data presented here were obtained from programs VLA/10B-143 (AI141) and VLA/18A-348 (AK972). This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. The James Clerk Maxwell Telescope has historically been operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the United Kingdom, the National Research Council of Canada, and the Netherlands Organisation for Scientific Research. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This research has made use of the VizieR catalog access tool, CDS, Strasbourg, France. This work has made use of the BeSS database, operated at LESIA, Observatoire de Meudon, France: This work used the BeSOS Catalogue, operated by the Instituto de Física y Astronomía, Universidad de Valparaíso, Chile (, and funded by Fondecyt iniciación No. 11130702. Software: CRUSH (Kovács 2008), MIRIAD (Sault et al. 1995), CASA (McMullin et al. 2007), Astropy (Astropy Collaboration et al. 2013), Matplotlib (Hunter 2007).
Funding AgencyGrant Number
Georgia State UniversityUNSPECIFIED
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)307594/2015-7
Fundação de Amparo à Pesquisa do Estado de Sao Paulo (FAPESP)2016/16844-1
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1190485
Centro de Astrofísica de Valparaíso ChileUNSPECIFIED
State of CaliforniaUNSPECIFIED
State of IllinoisUNSPECIFIED
State of MarylandUNSPECIFIED
James S. McDonnell FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Kenneth T. and Eileen L. Norris FoundationUNSPECIFIED
University of ChicagoUNSPECIFIED
Associates of the California Institute of TechnologyUNSPECIFIED
Subject Keywords:Be stars; Circumstellar disks; Binary stars; Radio continuum emission; Early-type emission stars; Stellar rotation; Stellar evolution; Infrared excess; Stellar astronomy; Circumstellar matter; Radio astronomy; Subdwarf stars
Issue or Number:2
Record Number:CaltechAUTHORS:20191111-075806338
Persistent URL:
Official Citation:Robert Klement et al 2019 ApJ 885 147
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99764
Deposited By: Tony Diaz
Deposited On:12 Nov 2019 21:48
Last Modified:16 Nov 2021 17:49

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