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Abstract

More than 200 extrasolar planets have been discovered around relatively nearby stars, primarily through the Doppler line shifts owing to reflex motions of their host stars, and more recently through transits of some planets across the faces of the host stars. The detection of planets with the shortest known periods, 1.2–2.5 days, has mainly resulted from transit surveys which have generally targeted stars more massive than 0.75 M, where M is the mass of the Sun. Here we report the results from a planetary transit search performed in a rich stellar field towards the Galactic bulge. We discovered 16 candidates with orbital periods between 0.4 and 4.2 days, five of which orbit stars of masses in the range 0.44–0.75 M. In two cases, radial-velocity measurements support the planetary nature of the companions. Five candidates have orbital periods below 1.0 day, constituting a new class of ultra-short-period planets, which occur only around stars of less than 0.88 M. This indicates that those orbiting very close to more-luminous stars might be evaporatively destroyed or that jovian planets around stars of lower mass might migrate to smaller radii.

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Acknowledgements

This article is based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the AURA, Inc. under a NASA contract, and with the Very Large Telescope at the ESO, Paranal, Chile. We thank R. Gilliland for his generous contribution of time and efforts for this project, and D. Bradstreet, I. Jordan, G. Kovacs, D. VandenBerg and the late A. Lubenow for their help at various stages of the project.

Author information

Affiliations

  1. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218, USA

    • Kailash C. Sahu
    • , Stefano Casertano
    • , Howard E. Bond
    • , Jeff Valenti
    • , T. Ed Smith
    • , Mario Livio
    • , Nino Panagia
    • , Thomas M. Brown
    • , Will Clarkson
    •  & Stephen Lubow
  2. Universidad Catolica de Chile, Av. Vicuña Mackenna 4860, Santiago 22, Chile

    • Dante Minniti
    •  & Manuela Zoccali
  3. Uppsala University, Box 515, S-751 20 Uppsala, Sweden

    • Nikolai Piskunov
  4. High Altitude Observatory, 3450 Mitchell Lane, Boulder, Colorado 80307, USA

    • Timothy Brown
  5. INAF–Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy

    • Alvio Renzini
  6. University of California at Los Angeles, Los Angeles, California 90095-1562, USA

    • R. Michael Rich

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Competing interests

Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests.

Corresponding author

Correspondence to Kailash C. Sahu.

Supplementary information

Word documents

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    Supplementary Figures Legends

    This file contains text to accompany the below Supplementary Figures.

Image files

  1. 1.

    Supplementary Figure 1a

    Full-resolution transit light curves.

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    Supplementary Figure 1b

    Full-resolution transit light curves.

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    Supplementary Figure 1c

    Full-resolution transit light curves.

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    Supplementary Figure 1d

    Full-resolution transit light curves.

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    Supplementary Figure 2a

    Binned transit light curves.

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    Supplementary Figure 2b

    Binned transit light curves.

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    Supplementary Figure 2c

    Binned transit light curves.

  8. 8.

    Supplementary Figure 2d

    Binned transit light curves.

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DOI

https://doi.org/10.1038/nature05158

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