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SU Lyncis, a Hard X-Ray Bright M Giant: Clues Point to a Large Hidden Population of Symbiotic StarsSymbiotic star surveys have traditionally relied almost exclusively on low resolution optical spectroscopy. However, we can obtain amore reliable estimate of their total Galactic population by using all available signatures of the symbiotic phenomenon. Here we report the discovery of a hard X-ray source, 4PBC J0642.9+5528, in the Swift hard X-ray all-sky survey, and identify it with a poorly studied red giant, SU Lyn, using pointed Swift observations and ground-based optical spectroscopy. The X-ray spectrum, the optical to UV spectrum, and the rapid UV variability of SU Lyn are all consistent with our interpretation that it is a symbiotic star containing an accreting white dwarf. The symbiotic nature of SU Lyn went unnoticed until now, because it does not exhibit emission lines strong enough to be obvious in low resolution spectra. We argue that symbiotic stars without shell-burning have weak emission lines, and that the current lists of symbiotic stars are biased in favour of shell-burning systems. We conclude that the true population of symbiotic stars has been underestimated, potentially by a large factor.
Document ID
20160010354
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Mukai, K.
(Maryland Univ. Baltimore County Baltimore, MD, United States)
Luna, G. J. M.
(Instituto de Astronomia y Fisica del Espacio Buenos Aires, Argentina)
Cusumano, G.
(Istituto di Astrofisica Spaziale e Fisica Cosmica (INAF-IASF) Palermo, Italy)
Segreto, A.
(Istituto di Astrofisica Spaziale e Fisica Cosmica (INAF-IASF) Palermo, Italy)
Munari, U.
(Osservatorio Astronomico Padova, Italy)
Sokoloski, J. L.
(Columbia Univ. New York, NY, United States)
Lucy, A. B.
(Columbia Univ. New York, NY, United States)
Nelson, T.
(Pittsburgh Univ. Pittsburgh, PA, United States)
Nunez, N. E.
(Consejo Nacional de Inverstigaciones Cientificas y Tecnicas San Juan, Argentina)
Date Acquired
August 15, 2016
Publication Date
May 5, 2016
Publication Information
Publication: Monthly Notices of the Royal Astronomical Society
Publisher: Oxford University Press
Volume: 461
Issue: 1
e-ISSN: 1365-8711
Subject Category
Astrophysics
Astronomy
Report/Patent Number
GSFC-E-DAA-TN32425
GSFC-E-DAA-TN41432
Funding Number(s)
CONTRACT_GRANT: NNX15AF19G
CONTRACT_GRANT: ANPCYT-PICT0478/14
CONTRACT_GRANT: NNG06EO90A
Distribution Limits
Public
Copyright
Other
Keywords
binaries: symbiotic aEuro" stars: individual: SU Lyn aEuro" X-rays: binaries

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