Letter to the Editor

Cold DUst around NEarby Stars (DUNES). First results^*

A resolved exo-Kuiper belt around the solar-like star ζ² Ret

¹ Dpt. Física Teórica, Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain e-mail: carlos.eiroa@uam.es
² Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
³ John Hopkins University, Dept. of Physics and Astronomy, 3701 San Martin drive, Baltimore, MD 21210, USA
⁴ INSA at ESAC, 28691 Villanueva de la Cañada, Madrid, Spain
⁵ ESA Space Environment and Effects Section, ESTEC, PO Box 299, 2200 AG Noordwijk, The Netherlands
⁶ ESA Astrophysics & Fundamental Physics Missions Division, ESTEC/SRE-SA, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
⁷ Université Joseph Fourier/CNRS, Laboratoire d'Astrophysique de Grenoble, UMR 5571, Grenoble, France
⁸ ESA-ESAC Gaia SOC. PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain
⁹ LAEX, Centro de Astrobiología (INTA-CSIC), LAEFF Campus, European Space Astronomy Center (ESAC), PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain
¹⁰ NASA Herschel Science Center, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA
¹¹ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
¹² Onsala Space Observatory, Chalmers University of Technology, Se-439 92 Onsala, Sweden
¹³ European Space Observatory, Alonso de Cordova 3107, Vitacura Casilla 19001, Santiago 19, Chile
¹⁴ Institut d'Astrophysique et de Géophysique, Université de Liège, 17 Allée du Six Août, 4000 Sart Tilman, Belgium
¹⁵ NASA ExoPlanet Science Institute California Inst. of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA
¹⁶ NASA Goddard Space Flight Center, Exoplanets and Stellar Astrophysics, Code 667, Greenbelt, MD 20771, USA
¹⁷ UNINOVA-CA3, Campus da Caparica, Quinta da Torre, Monte de Caparica, 2825-149 Caparica, Portugal
¹⁸ Christian-Albrechts-Universität zu Kiel, Institut für Theoretische Physik und Astrophysik, Leibnizstr. 15, 24098 Kiel, Germany
¹⁹ Nagoya University, Japan
²⁰ Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
²¹ Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands
²² Astrophysikalisches Institut und Universitätssternwarte, Friedrich-Schiller-Universität, Schillergäßchen 2-3, 07745 Jena, Germany
²³ Herschel Science Center, ESAC/ESA, PO BOX 78, 28691 Villanueva de la Cañada, Madrid, Spain
²⁴ Department of Physics and Astrophysics, Open University, Walton Hall, Milton Keynes MK7 6AA, UK
²⁵ Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Dpt. Astrofísica, av. Complutense s/n. 28040 Madrid, Spain
²⁶ Observatoire de la Côte d'Azur, Boulevard de l'Observatoire, BP 4229, 06304 Nice Cedex 4, France
²⁷ Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1, Yoshinodai, Sagamihara, Kanagawa, 229-8510, Japan
²⁸ Department of Astronomy, Stockholm University, AlbaNova University Center, Roslagstullsbacken 21, 106 91 Stockholm, Sweden
²⁹ Institut de Ciències de l'Espai (CSIC-IEEC), Campus UAB, Facultat de Ciències, Torre C5, parell, 2a pl., 08193 Bellaterra, Barcelona, Spain
³⁰ LESIA, Observatoire de Paris, 92195 Meudon, France
³¹ Rutherford Appleton Laboratory, Chilton OX11 0QX, UK

Received: 31 March 2010
Accepted: 11 May 2010

Abstract

We present the first far-IR observations of the solar-type stars δ Pav, HR 8501, 51 Peg and ζ² Ret, taken within the context of the DUNES Herschel open time key programme (OTKP). This project uses the PACS and SPIRE instruments with the objective of studying infrared excesses due to exo-Kuiper belts around nearby solar-type stars. The observed 100 μm fluxes from δ Pav, HR 8501, and 51 Peg agree with the predicted photospheric fluxes, excluding debris disks brighter than L_dust/ ~ 5 × 10^-7 (1σ level) around those stars. A flattened, disk-like structure with a semi-major axis of ~100 AU in size is detected around ζ² Ret. The resolved structure suggests the presence of an eccentric dust ring, which we interpret as an exo-Kuiper belt with L_dust/ ≈ 10^-5.