Upper limits on the water vapour content of the beta Pictoris debris disk
Artikel i vetenskaplig tidskrift, 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


M. Cavallius

Stockholms universitet

G. Cataldi

Japan Soc Promot Sci

Magyar Tudomanyos Akademia

University of Toronto

National Astronomical Observatory of Japan

Stockholms universitet

A. Brandeker

Stockholms universitet

G. Olofsson

Stockholms universitet

B. Larsson

Stockholms universitet

René Liseau

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik, Galaktisk astrofysik

Astronomy and Astrophysics

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

Vol. 628 A127



Astronomi, astrofysik och kosmologi

Atom- och molekylfysik och optik



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