White Dwarf–Red Dwarf Systems Resolved with the Hubble Space Telescope. II. Full Snapshot Survey Results
- Creators
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Farihi, J.
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Hoard, D. W.
- Wachter, S.
Abstract
Results are presented for a Hubble Space Telescope Advanced Camera for Surveys high-resolution imaging campaign of 90 white dwarfs with known or suspected low-mass stellar and substellar companions. Of the 72 targets that remain candidate and confirmed white dwarfs with near-infrared excess, 43 are spatially resolved into two or more components, and a total of 12 systems are potentially triples. For 68 systems where a comparison is possible, 50% have significant photometric distance mismatches between their white dwarf and M dwarf components, suggesting that white dwarf parameters derived spectroscopically are often biased due to the cool companion. Interestingly, 9 of the 30 binaries known to have emission lines are found to be visual pairs and hence widely separated, indicating an intrinsically active cool star and not irradiation from the white dwarf. There is a possible, slight deficit of earlier spectral types (bluer colors) among the spatially unresolved companions, exactly the opposite of expectations if significant mass is transferred to the companion during the common envelope phase. Using the best available distance estimates, the low-mass companions to white dwarfs exhibit a bimodal distribution in projected separation. This result supports the hypothesis that during the giant phases of the white dwarf progenitor, any unevolved companions either migrate inward to short periods of hours to days, or outward to periods of hundreds to thousands of years. No intermediate projected separations of a few to several AU are found among these pairs. However, a few double M dwarfs (within triples) are spatially resolved in this range, empirically demonstrating that such separations were readily detectable among the binaries with white dwarfs. A straightforward and testable prediction emerges: all spatially unresolved, low-mass stellar and substellar companions to white dwarfs should be in short-period orbits. This result has implications for substellar companion and planetary orbital evolution during the post-main-sequence lifetime of their stellar hosts.
Additional Information
© 2010 American Astronomical Society. Received 2010 June 8; accepted 2010 August 12; published 2010 September 17. The authors thank the anonymous referee for a valuable and thorough report that improved the quality of the manuscript, and D. Koester for the use of his white dwarf spectral models. This work is based on observations made with the Hubble Space Telescope which is operated by the Association of Universities for Research in Astronomy under NASA contract NAS 5-26555. Support for Program number 10255 was provided by NASA through grant HST-GO-10255 from the Space Telescope Science Institute. This publication makes 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 NASA and the National Science Foundation. This work includes data taken with the NASA Galaxy Evolution Explorer, operated for NASA by the California Institute of Technology under NASA contract NAS5-98034. Some data presented herein are part of the Sloan Digital Sky Survey, which is managed by the Astrophysical Research Consortium for the Participating Institutions (http://www.sdss.org/). Facility: HST (ACS)Attached Files
Published - Farihi2010p12044Astrophys_J_Suppl_S.pdf
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Additional details
- Eprint ID
- 21275
- Resolver ID
- CaltechAUTHORS:20101209-121703534
- HST-GO-10255
- NASA
- Created
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2010-12-10Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field