The Surprisingly Low Carbon Mass in the Debris Disk around HD 32297

Gianni Cataldi*, Yanqin Wu, Alexis Brandeker, Nagayoshi Ohashi, Attila Moor, Goran Olofsson, Peter Abraham, Ruben Asensio-Torres, Maria Cavallius, William R. F. Dent, Carol Grady, Thomas Henning, Aya E. Higuchi, A. Meredith Hughes, Markus Janson, Inga Kamp, Agnes Kospal, Seth Redfield, Aki Roberge, Alycia WeinbergerBarry Welsh

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

5 Citations (Scopus)

Abstract

Gas has been detected in a number of debris disks. It is likely secondary, i.e., produced by colliding solids. Here, we report ALMA Band 8 observations of neutral carbon in the CO-rich debris disk around the 15-30 Myr old A-type star HD 32297. We find that C0 is located in a ring at ∼110 au with an FWHM of ∼80 au and has a mass of (3.5 ± 0.2) × 10-3 M . Naively, such a surprisingly small mass can be accumulated from CO photodissociation in a time as short as ∼104 yr. We develop a simple model for gas production and destruction in this system, properly accounting for CO self-shielding and shielding by neutral carbon, and introducing a removal mechanism for carbon gas. We find that the most likely scenario to explain both C0 and CO observations is one where the carbon gas is rapidly removed on a timescale of order a thousand years and the system maintains a very high CO production rate of ∼15 M Myr-1, much higher than the rate of dust grind-down. We propose a possible scenario to meet these peculiar conditions: The capture of carbon onto dust grains, followed by rapid CO re-formation and rerelease. In steady state, CO would continuously be recycled, producing a CO-rich gas ring that shows no appreciable spreading over time. This picture might be extended to explain other gas-rich debris disks.

Original languageEnglish
Article number99
Number of pages15
JournalAstrophysical Journal
Volume892
Issue number2
DOIs
Publication statusPublished - 1-Apr-2020

Keywords

  • Exoplanet formation
  • Submillimeter astronomy
  • Radio interferometry
  • Atomic spectroscopy
  • Debris disks
  • Circumstellar gas
  • ELECTRON-ION RECOMBINATION
  • BETA-PICTORIS
  • EXOCOMETARY GAS
  • DUST
  • CO
  • COEFFICIENTS
  • ORIGIN
  • GRAINS
  • STARS
  • RING

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