The Binary Dwarf Carbon Star SDSS J125017.90+252427.6
Abstract
Although dwarf carbon (dC) stars are universally thought to be binaries in order to explain the presence of C_2 in their spectra while still near main-sequence luminosity, direct observational evidence for their binarity is remarkably scarce. Here, we report the detection of a 2.92 day periodicity in both the photometry and radial velocity of SDSS J125017.90+252427.6, an r = 16.4 dC star. This is the first photometric binary dC, and only the second dC spectroscopic binary. The relative phase of the photometric period to the spectroscopic observations suggests that the photometric variations are a reflection effect due to heating from an unseen companion. The observed radial velocity amplitude of the dC component (K = 98.8 ± 10.7 km s^(−1)) is consistent with a white dwarf companion, presumably the evolved star that earlier donated the carbon to the dC, although substantial orbital evolution must have occurred. Large synoptic photometric surveys such as the Palomar Transient Factory, which was used for this work, may prove useful for identifying binaries among the shorter-period dC stars.
Additional Information
© 2018 The American Astronomical Society. Received 2017 November 22; revised 2018 March 1; accepted 2018 March 2; published 2018 March 19. We are grateful to P. Green for numerous conversations about dC stars, and thank E. Ofek for comments on the manuscript. Observations were obtained with the Samuel Oschin Telescope at the Palomar Observatory as part of the Palomar Transient Factory and Intermediate Palomar Transient Factory project, a scientific collaboration between the California Institute of Technology, Columbia University, Las Cumbres Observatory, the Lawrence Berkeley National Laboratory, the National Energy Research Scientific Computing Center, the University of Oxford, the Weizmann Institute of Science, Los Alamos National Laboratory, the University of Wisconsin, Milwaukee, the Oskar Klein Center, the TANGO Program of the University System of Taiwan, and the Kavli Institute for the Physics and Mathematics of the Universe. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS web site is http://www.sdss.org/. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facilities: Keck:II (ESI) - , Sloan - , Hale - , PO:1.2 m - , PO:1.5m.Attached Files
Published - Margon_2018_ApJL_856_L2.pdf
Accepted Version - 1803.01052.pdf
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Additional details
- Eprint ID
- 85440
- Resolver ID
- CaltechAUTHORS:20180327-075241554
- Alfred P. Sloan Foundation
- Participating Institutions
- NSF
- Department of Energy (DOE)
- NASA
- Japanese Monbukagakusho
- Max Planck Society
- Higher Education Funding Council for England
- W. M. Keck Foundation
- Created
-
2018-03-27Created from EPrint's datestamp field
- Updated
-
2021-11-15Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC), Astronomy Department, Division of Geological and Planetary Sciences