Upper limits on the water vapour content of the beta Pictoris debris disk
Journal article, 2019

Context. The debris disk surrounding beta Pictoris has been observed with ALMA to contain a belt of CO gas with a distinct peak at similar to 85 au. This CO clump is thought to be the result of a region of enhanced density of solids that collide and release CO through vaporisation. The parent bodies are thought to be comparable to solar system comets, in which CO is trapped inside a water ice matrix. Aims. Since H2O should be released along with CO, we aim to put an upper limit on the H2O gas mass in the disk of beta Pictoris. Methods. We used archival data from the Heterodyne Instrument for the Far-Infrared (HIFI) aboard the Herschel Space Observatory to study the ortho-H2O 1(10)-1(01) emission line. The line is undetected. Using a python implementation of the radiative transfer code RADEX, we converted upper limits on the line flux to H2O gas masses. The resulting lower limits on the CO/H2O mass ratio are compared to the composition of solar system comets. Results. Depending on the assumed gas spatial distribution, we find a 95% upper limit on the ortho-H2O line flux of 7.5 x 10(-20) W m(-2) or 1.2 x 10(-19) W m(-2). These translate into an upper limit on the H2O mass of 7.4 x 10(16)-1.1 x 10(18) kg depending on both the electron density and gas kinetic temperature. The range of derived gas-phase CO/H2O ratios is marginally consistent with low-ratio solar system comets.

methods: observational

submillimeter: planetary systems

stars: individual: beta Pictoris

circumstellar matter

Author

M. Cavallius

Stockholm University

G. Cataldi

Japan Soc Promot Sci

Hungarian Academy of Sciences

University of Toronto

National Astronomical Observatory of Japan

Stockholm University

A. Brandeker

Stockholm University

G. Olofsson

Stockholm University

B. Larsson

Stockholm University

René Liseau

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 628 A127

Subject Categories

Energy Engineering

Astronomy, Astrophysics and Cosmology

Atom and Molecular Physics and Optics

DOI

10.1051/0004-6361/201935655

More information

Latest update

12/16/2019