X-Ray-Irradiated Protoplanetary Disk Atmospheres. I. Predicted Emission-Line Spectrum and Photoevaporation

By Barbara Ercolano, J. Drake, J. C. Raymond, C. Clarke. 2008

133 citations recorded by the source corpus.

We present mocassin two-dimensional photoionization and dust radiative transfer models of a prototypical T Tauri disk irradiated by X-rays from the young pre-main-sequence star. The calculations demonstrate a layer of hot gas reaching temperatures of ~106 K at small radii and ~104 K at a distance of 1 AU. The gas temperatures decrease sharply with depth, but appear to be completely decoupled from dust temperatures down to a column depth of ~5 × 1021 cm−2. We predict that several fine-structure and forbidden lines of heavy elements, as well as recombination lines of hydrogen and helium, should be observable with current and future instrumentation, although optical lines may be smothered by the stellar spectrum. Predicted line luminosities are given for the brightest collisionally excited lines (down to ~10−8 L☉) and for recombination transitions from several levels of H I and He I. The mass-loss rate due to X-ray photoevaporation estimated from our models is of the order of 10−8 M☉ yr−1, implying a dispersal timescale of a few Myr for a disk of mass 0.027 M☉, which is the mass of the disk structure model we employed. We discuss the limitations of our model and highlight the need for further calculations that should include the simultaneous solution of the two-dimensional radiative transfer problem and the one-dimensional hydrostatic equilibrium problem in the polar direction.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b4c3ec97113c3280d40275c228428d485dc60168

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In Astronomy and Astrophysics

1. S. Andrews
2. D. Wilner
3. T. Birnstiel
4. Simon Bruderer
5. Xue-Ning Bai
6. J. Owen
7. Zhaohuan Zhu
8. C. Dullemond

In Instrumentation

1. S. Andrews
2. T. Birnstiel
3. D. Wilner
4. Simon Bruderer
5. Xue-Ning Bai
6. Zhaohuan Zhu
7. J. Owen
8. A. Hughes

Citations in the corpus

• On the theory of disc photoevaporation (2011, methodology): “Recently, a lot of attention has been paid to other high-energy radiation fields: X-rays (Alexander, Clarke & Pringle 2004; Ercolano et al. 2008, 2009a; Owen et al. 2010; Owen, Ercolano & Clarke 2011b) and FUV (Gorti & Hollenbach 2008, 2009; Gorti, Dullemond & Hollenbach 2009).”
• Radiation-hydrodynamic models of X-ray and EUV photoevaporating protoplanetary discs (2009, methodology): “The version of the code used for these models was modified by Ercolano et al. (2008b, 2009b) and we refer to these articles for a detailed description of the code and model setup.”
• The Disk Substructures at High Angular Resolution Project (DSHARP). II. Characteristics of Annular Substructures (2018, background): “X-ray photoevaporation has been proposed as a mechanism for dispersing disks from the inside-out (e.g., Ercolano et al. 2008; Owen et al. 2010; Ercolano et al. 2017).”
• TRANSITIONAL DISKS AS SIGNPOSTS OF YOUNG, MULTIPLANET SYSTEMS (2011, background): “More recently, however, it has been argued that X-ray photoevaporation should be the dominant disk-clearing process and produce much higher mass-loss rates than UV (e.g. Ercolano et al. 2008).”
• Survival of molecular gas in cavities of transition disks - I. CO (2013, background): “Photoevaporation (e.g. Bally & Scoville 1982; Hollenbach et al. 1994; Clarke et al. 2001; Alexander et al. 2006; Ercolano et al. 2008; Gorti & Hollenbach 2009) has short processing time-scales and once its effect sets in, would quickly lead to a gas free cavity.”
• Protoplanetary disc evolution and dispersal: the implications of X-ray photoevaporation (2010, methodology): “…to extreme ultraviolet radiation -EUV- (Clarke et al 2001; Alexander et al 2006a,b; Richling & Yorke 2000), X-ray radiation (Alexander et al. 2004; Ercolano et al 2008b, 2009; Gorti & Hollenbach 2009, Owen et al. 2010) and far ultraviolet radiation -FUV- (Gorti & Hollenbach 2009; Gorti et al.…”
• Dynamics of Protoplanetary Disks (2010, background): “…at T ≈ 107 K, with a hotter component at T ≈ 3 × 107 K. X-ray photoionization calculations (Glassgold, Najita & Igea 1997), and Monte Carlo simulations (Ercolano et al. 2008, Igea & Glassgold 1999), show that these spectra and luminosities imply enough hard X-ray photons to ionize significant…”
• Planetary evaporation by UV and X‐ray radiation: basic hydrodynamics (2012, background): “The discrepancy may not be as bad as one would originally expect though, since as discussed in Section 2, X-ray photo-electron heating, and line cooling, are typically done by the same metal species, with Oxygen and Carbon typically being the dominant species (Ercolano et al. 2008).”
• The warm gas atmosphere of the HD 100546 disk seen by Herschel - Evidence of a gas-rich, carbon-poor atmosphere? (2012, background): “Appendices A and B are available in electronic form at http://www.aanda.org upper atmosphere, a disk-wind is driven, which may eventually disperse the disk (Alexander et al. 2006; Ercolano et al. 2008; Gorti & Hollenbach 2009).”
• PHOTOEVAPORATION OF CIRCUMSTELLAR DISKS BY FAR-ULTRAVIOLET, EXTREME-ULTRAVIOLET AND X-RAY RADIATION FROM THE CENTRAL STAR (2008, background): “Alexander et al. (2004) considered X-rays from the central star and found that they were unlikely to lead to significant photoevaporation rates (also see Ercolano et al. 2008).”
• TIME EVOLUTION OF VISCOUS CIRCUMSTELLAR DISKS DUE TO PHOTOEVAPORATION BY FAR-ULTRAVIOLET, EXTREME-ULTRAVIOLET, AND X-RAY RADIATION FROM THE CENTRAL STAR (2009, background): “Ercolano et al. (2008, 2009), however, find that X-ray heating may result in substantial mass loss.”
• RESOLVED IMAGES OF LARGE CAVITIES IN PROTOPLANETARY TRANSITION DISKS (2011, background): “However, there is growing consensus that X-rays drive substantially higher wind mass-loss rates, and therefore that photoevaporation has a much more prominent effect on disk structures at early times (Ercolano et al. 2008, 2009; Drake et al. 2009; Owen et al. 2010).”