HD 172555: detection of 63 μm [OI] emission in a debris disc

P. Riviere-Marichalar , D. Barrado , J. -C. Augereau (1) , W. F. Thi (1) , A. Roberge , C. Eiroa , B. Montesinos , G. Meeus , C. Howard , G. Sandell , G. Duchêne (1) , W. R. F. Dent , J. Lebreton (1) , I. Mendigutía , N. Huélamo , F. Ménard (1, 2) , C. Pinte (1)

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
2 LFCA - Laboratoire Franco-Chilien d'Astronomie

Context.HD 172555 is a young A7 star belonging to the β Pictoris moving group that harbours a debris disc. The Spitzer/IRS spectrum of the source showed mid-IR features such as silicates and glassy silica species, indicating the presence of a warm dust component with small grains, which places HD 172555 among the small group of debris discs with such properties. The IRS spectrum also shows a possible emission of SiO gas.
Aims: We aim to study the dust distribution in the circumstellar disc of HD 172555 and to asses the presence of gas in the debris disc.
Methods: As part of the GASPS open time key programme, we obtained Herschel/PACS photometric and spectroscopic observations of the source. We analysed PACS observations of HD 172555 and modelled the spectral energy distribution with a modified blackbody and the gas emission with a two-level population model with no collisional de-excitation.
Results: We report for the first time the detection of [OI] atomic gas emission at 63.18 μm in the HD 172555 circumstellar disc. We detect excesses due to circumstellar dust toward HD 172555 in the three photometric bands of PACS (70, 100, and 160 μm). We derive a large dust particle mass of (4.8 ± 0.6) × 10^-4 M_⊕ and an atomic oxygen mass of 2.5 × 10^-2R² M_⊕, where R in AU is the separation between the star and the inner disc. Thus, most of the detected mass of the disc is in the gaseous phase.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendices A and B are available in electronic form at http://www.aanda.org

Keywords: line: formation; Kuiper belt: general; stars: pre-main sequence; circumstellar matter; stars: individual: HD 172555

Domains: Sciences of the Universe [physics]; Astrophysics [astro-ph]

P. Riviere-Marichalar, D. Barrado, J. -C. Augereau, W. F. Thi, A. Roberge, et al.. HD 172555: detection of 63 μm [OI] emission in a debris disc. Astronomy and Astrophysics - A&A, 2012, 546, ⟨10.1051/0004-6361/201219745⟩. ⟨insu-03612404⟩