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An Extreme Analogue of є Aurigae: An M-giant Eclipsed Every 69 Years by a Large Opaque Disk Surrounding a Small Hot Source

Rodriguez, Joseph E. and Stassun, Keivan G. and Lund, Michael B. and Siverd, Robert J. and Pepper, Joshua and Tang, Sumin and Kafka, Stella and Gaudi, B. Scott and Conroy, Kyle E. and Beatty, Thomas G. and Stevens, Daniel J. and Shappee, Benjamin J. and Kochanek, Christopher S. (2016) An Extreme Analogue of є Aurigae: An M-giant Eclipsed Every 69 Years by a Large Opaque Disk Surrounding a Small Hot Source. Astronomical Journal, 151 (5). Art. No. 123. ISSN 0004-6256. https://resolver.caltech.edu/CaltechAUTHORS:20160606-094933545

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Abstract

We present TYC 2505-672-1 as a newly discovered and remarkable eclipsing system comprising an M-type red giant that undergoes a ~3.45 year long, near-total eclipse (depth of ~4.5 mag) with a very long period of ~69.1 years. TYC 2505-672-1 is now the longest-period eclipsing binary system yet discovered, more than twice as long as that of the currently longest-period system, є Aurigae. We show from analysis of the light curve including both our own data and historical data spanning more than 120 years and from modeling of the spectral energy distribution, both before and during eclipse, that the red giant primary is orbited by a moderately hot source (T_(eff) ≈ 8000 K) that is itself surrounded by an extended, opaque circumstellar disk. From the measured ratio of luminosities, the radius of the hot companion must be in the range of 0.1–0.5 R_⊙ (depending on the assumed radius of the red giant primary), which is an order of magnitude smaller than that for a main sequence A star and 1–2 orders of magnitude larger than that for a white dwarf. The companion is therefore most likely a "stripped red giant" subdwarf-B type star destined to become a He white dwarf. It is, however, somewhat cooler than most sdB stars, implying a very low mass for this "pre-He-WD" star. The opaque disk surrounding this hot source may be a remnant of the stripping of its former hydrogen envelope. However, it is puzzling how this object became stripped, given that it is at present so distant (orbital semimajor axis of ~24 au) from the current red giant primary star. Extrapolating from our calculated ephemeris, the next eclipse should begin in early UT 2080 April and end in mid UT 2083 September (eclipse center UT 2081 December 24). In the meantime, radial velocity observations would establish the masses of the components, and high-cadence UV observations could potentially reveal oscillations of the hot companion that would further constrain its evolutionary status. In any case, this system is poised to become an exemplar of a very rare class of systems, even more extreme in several respects than the well studied archetype є Aurigae.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.3847/0004-6256/151/5/123DOIArticle
http://iopscience.iop.org/article/10.3847/0004-6256/151/5/123PublisherArticle
http://arxiv.org/abs/1601.00135arXivDiscussion Paper
ORCID:
AuthorORCID
Rodriguez, Joseph E.0000-0001-8812-0565
Stassun, Keivan G.0000-0002-3481-9052
Lund, Michael B.0000-0003-2527-1598
Siverd, Robert J.0000-0001-5016-3359
Pepper, Joshua0000-0002-3827-8417
Tang, Sumin0000-0002-6225-8918
Gaudi, B. Scott0000-0003-0395-9869
Conroy, Kyle E.0000-0002-5442-8550
Beatty, Thomas G.0000-0002-9539-4203
Shappee, Benjamin J.0000-0003-4631-1149
Kochanek, Christopher S.0000-0001-6017-2961
Additional Information:© 2016. The American Astronomical Society. Received 2015 October 9; accepted 2016 January 1; published 2016 April 26. Early work on KELT-North was supported by NASA Grant NNG04GO70G. J.A.P. and K.G.S. acknowledge support from the Vanderbilt Office of the Provost through the Vanderbilt Initiative in Data-intensive Astrophysics. This work has made use of NASA's Astrophysics Data System and the SIMBAD database operated at CDS, Strasbourg, France. Work by B.S.G. and D.J.S. was partially supported by NSF CAREER Grant AST-1056524. Work by K.G.S. was supported by NSF PAARE grant AST-1358862. The DASCH project at Harvard is grateful for partial support from NSF grants AST-0407380, AST-0909073, and AST-1313370. The CSS survey is funded by the National Aeronautics and Space Administration under Grant No. NNG05GF22G issued through the Science Mission Directorate Near-Earth Objects Observations Program. The CRTS survey is supported by the U.S. National Science Foundation under grants AST-0909182 and AST-1313422. Development of ASAS-SN has been supported by NSF grant AST-0908816 and CCAPP at the Ohio State University. ASAS-SN is supported by NSF grant AST-1515927, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, the Mt. Cuba Astronomical Foundation, George Skestos, and the Robert Martin Ayers Sciences Fund. B.S. is supported by NASA through Hubble Fellowship grant HF-51348.001 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. CSK is supported by NSF grants AST-1515876 and AST-1515927.
Funders:
Funding AgencyGrant Number
NASANNG04GO70G
Vanderbilt UniversityUNSPECIFIED
NSFAST-1056524
NSFAST-1358862
NSFAST-0407380
NSFAST-0909073
NSFAST-1313370
NASANNG05GF22G
NSFAST-0909182
NSFAST-1313422
NSFAST-0908816
Ohio State University Center for Cosmology and Astro-Particle PhysicsUNSPECIFIED
NSFAST-1515927
Mt. Cuba Astronomical FoundationUNSPECIFIED
Robert Martin Ayers Sciences FundUNSPECIFIED
NASAHF-51348.001
NASANAS 5-26555
NSFAST-1515876
NSFAST-1515927
George SkestosUNSPECIFIED
Subject Keywords:binaries: eclipsing; circumstellar matter; stars: AGB and post-AGB; stars: individual (TYC 2505-672-1) ; stars: massive
Issue or Number:5
Record Number:CaltechAUTHORS:20160606-094933545
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20160606-094933545
Official Citation:Joseph E. Rodriguez et al 2016 The Astronomical Journal 151 123
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:67681
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:06 Jun 2016 20:44
Last Modified:09 Mar 2020 13:19

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