A Radiatively Driven Wind from the eta Tel Debris Disk

Abstract

We present far- and near-ultraviolet absorption spectroscopy of the $\sim$23 Myr edge-on debris disk surrounding the A0V star $\eta$ Telescopii, obtained with the Hubble Space Telescope Space Telescope Imaging Spectrograph. We detect absorption lines from C I, C II, O I, Mg II, Al II, Si II, S II, Mn II, Fe II, and marginally N I. The lines show two clear absorption components at $-22.7\pm 0.5$ km s${}^{-1}$ and $-17.8\pm 0.7$ km s${}^{-1}$, which we attribute to circumstellar (CS) and interstellar (IS) gas, respectively. CO absorption is not detected, and we find no evidence for star-grazing exocomets. The CS absorption components are blueshifted by $-16.9\pm 2.6$ km s${}^{-1}$ in the star's reference frame, indicating that they are outflowing in a radiatively driven disk wind. We find that the C/Fe ratio in the $\eta$ Tel CS gas is significantly higher than the solar ratio, as is the case in the $\beta$ Pic and 49 Cet debris disks. Unlike those disks, however, the measured C/O ratio in the $\eta$ Tel CS gas is consistent with the solar value. Our analysis shows that because $\eta$ Tel is an earlier type star than $\beta$ Pic and 49 Cet, with more substantial radiation pressure at the dominant C II transitions, this species cannot bind the CS gas disk to the star as it does for $\beta$ Pic and 49 Cet, resulting in the disk wind.

Accepted to AJ; 24 pages, 18 figures

References in corpus (16)

• The NumPy array: a structure for efficient numerical computation
• The Structure of the Local Interstellar Medium V: Electron Densities
• On the age of the $\beta$ Pictoris moving group
• Spitzer IRS Spectroscopy of IRAS-Discovered Debris Disks
• Molecular Gas Clumps from the Destruction of Icy Bodies in the $\beta$ Pictoris Debris Disk
• The Carbon-Rich Gas in the Beta Pictoris Circumstellar Disk
• Exocometary gas structure, origin and physical properties around $\beta$ Pictoris through ALMA CO multi-transition observations
• Molecular gas in debris disks around young A-type stars
• Survival of icy grains in debris discs. The role of photosputtering
• Gas and dust in the Beta Pictoris Moving Group as seen by the Herschel Space Observatory
• The Dust and Gas Around beta Pictoris
• Resolved debris disk emission around eta Tel: a young Solar System or ongoing planet formation?
• A CO survey in planet-forming disks: characterizing the gas content in the epoch of planet formation
• Volatile-Rich Circumstellar Gas in the Unusual 49 Ceti Debris Disk
• Expelled grains from an unseen parent body around AU Mic
• Spectroscopic metallicities of Vega-like stars

Cited by in corpus (5)

• Primordial or Secondary? Testing models of debris disk gas with ALMA
• Vertical evolution of exocometary gas: I. How vertical diffusion shortens the CO lifetime
• Stellar winds can affect gas dynamics in debris disks and create observable belt winds
• Astrometric and photometric characterization of $\eta$ Tel B combining two decades of observations
• Resolving the large exoKuiper belt of the HD 126062 debris disc and extended gas emission in its vicinity