Absence of a Metallicity Effect for Ultra-short-period Planets
- Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08540 (United States)
- Department of Astronomy, University of California, Berkeley, CA 94720 (United States)
- Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)
- Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Hobart and William Smith Colleges, Geneva, NY 14456 (United States)
Ultra-short-period (USP) planets are a newly recognized class of planets with periods shorter than one day and radii smaller than about 2 R {sub ⊕}. It has been proposed that USP planets are the solid cores of hot Jupiters that have lost their gaseous envelopes due to photo-evaporation or Roche lobe overflow. We test this hypothesis by asking whether USP planets are associated with metal-rich stars, as has long been observed for hot Jupiters. We find the metallicity distributions of USP-planet and hot-Jupiter hosts to be significantly different ( p = 3 × 10{sup −4}) based on Keck spectroscopy of Kepler stars. Evidently, the sample of USP planets is not dominated by the evaporated cores of hot Jupiters. The metallicity distribution of stars with USP planets is indistinguishable from that of stars with short-period planets with sizes between 2 and 4 R {sub ⊕}. Thus, it remains possible that the USP planets are the solid cores of formerly gaseous planets that are smaller than Neptune.
- OSTI ID:
- 22663374
- Journal Information:
- Astronomical Journal (Online), Vol. 154, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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