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A High Angular Resolution Survey of Massive Stars in Cygnus OB2: JHK Adaptive Optics Results from the Gemini Near-Infrared Imager

Caballero-Nieves, S. M. and Gies, D. R. and Baines, E. K. and Bouchez, A. H. and Dekany, R. G. and Goodwin, S. P. and Rickman, E. L. and Roberts, L. C., Jr. and Taggart, K. and ten Brummelaar, T. A. and Turner, N. H. (2020) A High Angular Resolution Survey of Massive Stars in Cygnus OB2: JHK Adaptive Optics Results from the Gemini Near-Infrared Imager. Astronomical Journal, 160 (3). Art. No. 115. ISSN 1538-3881.

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We present results of a high angular resolution survey of massive OB stars in the Cygnus OB2 association that we conducted with the Near-Infrared Imager camera and ALTAIR adaptive optics system of the Gemini North telescope. We observed 74 O- and early-B-type stars in Cyg OB2 in the JHK infrared bands in order to detect binary and multiple companions. The observations are sensitive to equal-brightness pairs at separations as small as 0.”08, and progressively fainter companions are detectable out to ΔK = 9 mag at a separation of 2''. This faint contrast limit due to read noise continues out to 10'' near the edge of the detector. We assigned a simple probability of chance alignment to each companion based upon its separation and magnitude difference from the central target star and upon areal star counts for the general star field of Cyg OB2. Companion stars with a field membership probability of less than 1% are assumed to be physical companions. This assessment indicates that 47% of the targets have at least one resolved companion that is probably gravitationally bound. Including known spectroscopic binaries, our sample includes 27 binary, 12 triple, and 9 systems with 4 or more components. These results confirm studies of high-mass stars in other environments that find that massive stars are born with a high-multiplicity fraction. The results are important for the placement of the stars in the Hertzsprung–Russell diagram, the interpretation of their spectroscopic analyses, and for future mass determinations through measurement of orbital motion.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Caballero-Nieves, S. M.0000-0002-8348-5191
Gies, D. R.0000-0001-8537-3583
Baines, E. K.0000-0002-5684-3424
Dekany, R. G.0000-0002-5884-7867
Goodwin, S. P.0000-0001-6396-581X
Rickman, E. L.0000-0003-4203-9715
Roberts, L. C., Jr.0000-0003-3892-2900
Taggart, K.0000-0002-5748-4558
ten Brummelaar, T. A.0000-0002-0114-7915
Additional Information:© 2020 The American Astronomical Society. Received 2019 September 26; revised 2020 June 30; accepted 2020 July 9; published 2020 August 14. Based on observations obtained at the Gemini Observatory, (GN-2005B-Q-64, GN-2008A-Q-85, GN-2008B-Q-95) which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). We thank the staff of the Gemini North Observatory and especially Dr. Andrew Stephens for their support of this program. The data were processed using the Gemini IRAF package. This paper contains observations obtained at the Hale Telescope, Palomar Observatory. This research has made use of the Washington Double Star Catalog maintained at the US Naval Observatory. This publication also made use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration (NASA) and the National Science Foundation. This work was directly supported by the National Science Foundation under grants AST-1009080 and AST-1411654. Institutional support has been provided from the GSU College of Arts and Sciences and from the Research Program Enhancement fund of the Board of Regents of the University System of Georgia, administered through the GSU Office of the Vice President for Research and Economic Development. A portion of the research in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Financial support was provided to S.M.C.N. by the Science and Technology Facilities Council for part of this work at the University of Sheffield, with current support provided by the Florida Institute of Technology. We are grateful for all this support. Facility: Gemini (NIRI). - Software: FITSTARS (ten Brummelaar et al. 2000), SExtractor (Bertin & Arnouts 1996).
Funding AgencyGrant Number
Georgia State UniversityUNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
University of SheffieldUNSPECIFIED
Florida Institute of TechnologyUNSPECIFIED
Subject Keywords:Massive stars ; Early-type stars ; Wide binary stars ; OB associations ; OB stars
Issue or Number:3
Classification Code:Unified Astronomy Thesaurus concepts: Massive stars (732); Early-type stars (430); Wide binary stars (1801); OB associations (1140); OB stars (1141)
Record Number:CaltechAUTHORS:20200817-101035105
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Official Citation:S. M. Caballero-Nieves et al 2020 AJ 160 115
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104975
Deposited By: Tony Diaz
Deposited On:17 Aug 2020 19:02
Last Modified:17 Aug 2020 19:02

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