Gas and dust in the TW Hydrae association as seen by the Herschel Space Observatory^⋆

¹ Centro de Astrobiología – Depto. Astrofísica (CSIC–INTA), ESAC Campus, PO Box 78 28691 Villanueva de la Cañada Spain
e-mail: riviere@cab.inta-csic.es; barrado@cab.inta-csic.es
² UJF – Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique (IPAG) UMR 5274, 38041 Grenoble, France
³ Laboratorio Franco-Chileno de Astronomia (UMI 3386: CNRS – U de Chile/PUC/U Conception), Santiago, Chile
⁴ Calar Alto Observatory, Centro Astronómico Hispano-Alemán C/Jesús Durbán Remón, 2-2, 04004 Almería, Spain
⁵ Dep. de Física Teórica, Fac. de Ciencias, UAM Campus Cantoblanco, 28049 Madrid, Spain
⁶ Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
⁷ Department of Astronomy, University of Maryland, College Park, MD 230742, USA
⁸ Exoplanets and Stellar Astrophysics Lab, NASA Goddard Space Flight Center, Code 667, Greenbelt, MD 20771, USA
⁹ NASA Herschel Science Center, California Institute of Technology, MC 100-22, Pasadena, CA 91125, USA
¹⁰ SOFIA – USRA, NASA Ames Research Center, USA
¹¹ Institute for Astronomy, University of Hawaii, Honolulu, HI 96822, USA
¹² ALMA, Avda Apoquindo 3846, Piso 19, Edificio Alsacia, Las Condes, Santiago, Chile
¹³ Astronomy Department, University of California, Berkeley, CA 94720-3411, USA

Received: 19 March 2013
Accepted: 10 May 2013

Abstract

Context. Circumstellar discs are the places where planets form, therefore knowledge of their evolution is crucial for our understanding of planet formation. The Herschel Space Observatory is providing valuable data for studying disc systems, thanks to its sensitivity and wavelength coverage. This paper is one of several devoted to analysing and modelling Herschel-PACS observations of various young stellar associations from the GASPS open time key programme.

Aims. The aim of this paper is to elucidate the gas and dust properties of circumstellar discs in the ~10 Myr TW Hya association (TWA) using new far-infrared (IR) imaging and spectroscopy from Herschel-PACS.

Methods. We obtained far-IR photometric data at 70, 100, and 160 μm of 14 TWA members; spectroscopic observations centred on the [OI] line at 63.18 μm were also obtained for 9 of the 14. The new photometry for each star was incorporated into its full spectral energy distribution.

Results. We detected excess IR emission that is characteristic of circumstellar discs from five TWA members, and computed upper limits for another nine. Two TWA members (TWA 01 and TWA 04B) also show [OI] emission at 63.18 μm. Discs in the TWA association display a variety of properties, with a wide range of dust masses and inner radii, based on modified blackbody modelling. Both transitional and debris discs are found in the sample. Models for sources with a detected IR excess give dust masses in the range from ~0.15 M_⊕ to ~63 M_⊕.