Stellar winds can affect gas dynamics in debris disks and create observable belt winds

Abstract

Context: Gas is now detected in many extrasolar systems around mature stars aged between 10 Myr to $\sim$ 1 Gyr with planetesimal belts. Gas in these mature disks is thought to be released from planetesimals and has been modelled using a viscous disk approach. At low densities, this may not be a good assumption as the gas could be blown out by the stellar wind instead. Methods: We developed an analytical model for A to M stars that can follow the evolution of gas outflows and target when the transition occurs between a disk or a wind. The crucial criterion is the gas density for which gas particles stop being protected from stellar wind protons impacting at high velocities on radial trajectories. Results: We find that: 1) Belts of radial width $\Delta R$ with gas densities $<7(\Delta R/50\mathrm{au}{)}^{-1}$ cm${}^{-3}$ would create a wind rather than a disk, which would explain the recent outflowing gas detection in NO Lup. 2) The properties of this belt wind can be used to measure stellar wind properties such as their densities and velocities. 3) Debris disks with low fractional luminosities $f$ are more likely to create gas winds, which could be observed with current facilities. Conclusions: The systems containing low gas masses such as Fomalhaut or TWA 7 or more generally, debris disks with fractional luminosities $f\lesssim 10^{-5}(L_{\star }/L_{\odot }{)}^{-0.37}$ or stellar luminosity $\gtrsim 20L_{\odot }$ (A0V or earlier) would rather create gas outflows (or belt winds) than gas disks. Gas observed to be outflowing at high velocity in the young system NO Lup could be an example of such belt winds. The detection of these gas winds is possible with ALMA (CO and CO${}^{+}$ could be good wind tracers) and would allow us to constrain the stellar wind properties of main-sequence stars, which are otherwise difficult to measure.

18 pages, 13 figures, abstract shortened, accepted for publication in A&A

References in corpus (28)

• Molecular Gas Clumps from the Destruction of Icy Bodies in the $\beta$ Pictoris Debris Disk
• Stellar Winds on the Main-Sequence II: the Evolution of Rotation and Winds
• Detection of exocometary CO within the 440 Myr-old Fomalhaut belt: a similar CO+CO${}_2$ ice abundance in exocomets and Solar System comets
• ALICE: The Ultraviolet Imaging Spectrograph aboard the New Horizons Pluto-Kuiper Belt Mission
• Exocometary gas structure, origin and physical properties around $\beta$ Pictoris through ALMA CO multi-transition observations
• Unusually High CO Abundance of the First Active Interstellar Comet
• Molecular gas in debris disks around young A-type stars
• A Complete ALMA Map of the Fomalhaut Debris Disk
• Stellar Winds on the Main-Sequence I: Wind Model
• ALMA observations of the $\eta$ Corvi debris disc: inward scattering of CO-rich exocomets by a chain of 3-30 M${}_{\oplus }$ planets?
• The thermal, mechanical, structural, and dielectric properties of cometary nuclei after Rosetta
• CO in distantly active comets
• CO mass upper limits in the Fomalhaut ring - the importance of NLTE excitation in debris discs and future prospects with ALMA
• Solution to the debris disc mass problem: planetesimals are born small?
• Population synthesis of exocometary gas around A stars
• On the Ubiquity and Stellar Luminosity Dependence of Exocometary CO Gas: Detection around M Dwarf TWA 7
• Cometary Activity Begins at Kuiper Belt Distances: Evidence from C/2017 K2
• A re-assessment of the Kuiper belt size distribution for sub-kilometer objects, revealing collisional equilibrium at small sizes
• Survey of planetesimal belts with ALMA: gas detected around the Sun-like star HD 129590
• Expelled grains from an unseen parent body around AU Mic
• A Gaia Survey for Young Stars Associated with the Lupus Clouds
• Formation of secondary atmospheres on terrestrial planets by late disk accretion
• Stellar Winds and Dust Avalanches in the AU Mic Debris Disk
• Lack of other molecules in CO-rich debris discs: is it primordial or secondary gas?
• Effect of the solar wind density on the evolution of normal and inverse coronal mass ejections
• Rapid CO gas dispersal from NO Lup's class III circumstellar disc
• Physical conditions of gas components in debris disks of 49 Ceti and HD 21997
• The search for gas in debris discs: ALMA detection of CO gas in HD 36546

Cited by in corpus (4)

• Primordial or Secondary? Testing models of debris disk gas with ALMA
• An impact-free mechanism to deliver water to terrestrial planets and exoplanets
• Resonant structures in exozodiacal clouds created by exo-Earths in the habitable zone of late-type stars
• Resolving the large exoKuiper belt of the HD 126062 debris disc and extended gas emission in its vicinity