Precision Orbit of δ Delphini and Prospects for Astrometric Detection of Exoplanets
American Astronomical Society / IOP Publishing
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Currently under an indefinite embargo pending publication by American Astronomical Society. No embargo required on publication.
Combining visual and spectroscopic orbits of binary stars leads to a determination of the full 3D orbit, individual masses, and distance to the system. We present a full analysis of the evolved binary system Delphini using astrometric data from the MIRC and PAVO instruments on the CHARA long-baseline interferometer, 97 new spectra from the Fairborn Observatory, and 87 unpublished spectra from Lick Observatory. We determine the full set of orbital elements for Del, along with masses of 1:78 0:07 M and 1:62 0:07 M for each component, and a distance of 63:61 0:89 pc. These results are important in two contexts: for testing stellar evolution models and de ning the detection capabilities for future planet searches. We nd that the evolutionary state of this system is puzzling, as our measured ux ratios, radii, and masses imply a 200 Myr age di erence between the components using standard stellar evolution models. Possible explanations for this age discrepancy include mass transfer scenarios with a now ejected tertiary companion. For individual measurements taken over a span of 2 years we achieve < 10 -arcsecond precision on di erential position with 10- minute observations. The high precision of our astrometric orbit suggests that exoplanet detection capabilities are within reach of MIRC at CHARA. We compute exoplanet detection limits around Del, and conclude that if this precision is extended to wider systems we should be able to detect most exoplanets > 2 MJ
This work is based upon observations obtained with the Georgia State University Center for High Angular Resolution Astronomy Array at Mount Wilson Observatory. The CHARA Array is supported by the National Science Foundation under Grants No. AST-1211929 and AST-1411654. Institutional support has been provided from the GSU College of Arts and Sciences and the GSU Office of the Vice President for Research and Economic Development. This research has made use of the Jean-Marie Mariotti Center SearchCal service2 . JDM and TG wish to gratefully acknowledge support by NASA XRP Grant NNX16AD43G. Astronomy at Tennessee State University is supported by the state of Tennessee through its Centers of Excellence program. SK acknowledges support from an European Research Council Starting Grant (Grant Agreement No. 639889) and STFC Rutherford Fellowship (ST/J004030/1). D.H. acknowledges support by the National Aeronautics and Space Administration under Grant NNX14AB92G issued through the Kepler Participating Scientist Program. TRW acknowledges the support of the Villum Foundation (research grant 10118).
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