Protoplanetary disc evolution and dispersal: the implications of X-ray photoevaporation

By J. Owen, Barbara Ercolano, C. Clarke. 2010

248 citations recorded by the source corpus.

We explore the role of X-ray photoevaporation in the evolution and dispersal of viscously evolving T Tauri discs. We show that the X-ray photoevaporation wind rates scale linearly with X-ray luminosity, such that the observed range of X-ray luminosities for solar-type T Tauri stars (10 28 -10 31 erg s -1 ) gives rise to vigorous disc winds with rates of the order of 10 -10 to 10 -7 M ⊙ yr -1 . These mass-loss rates are comparable to typically observed T Tauri accretion rates, immediately demonstrating the relevance of X-ray photoevaporation to disc evolution. We use the wind solutions from radiation-hydrodynamic models, coupled to a viscous evolution model, to construct a population synthesis model so that we may study the physical properties of evolving discs and so-called 'transition discs'. Current observations of disc lifetimes and accretion rates can be matched by our model assuming a viscosity parameter α = 2.5 x 10- 3 . Our models confirm that X-rays play a dominant role in the evolution and dispersal of protoplanetary discs giving rise to the observed diverse population of inner-hole 'transition' sources which include those with massive outer discs, those with gas in their inner holes and those with detectable accretion signatures. To help understand the nature of observed transition discs we present a diagnostic diagram based on accretion rates versus inner-hole sizes that demonstrate that, contrary to recent claims, many of the observed accreting and non-accreting transition discs can easily be explained by X-ray photoevaporation. However, we draw attention to a smaller but still significant population of strongly accreting (∼10 -8 M ⊙ yr -1 ) transition discs with large inner holes (>20 au) that lie outside the predicted X-ray photoevaporation region, suggesting a different origin for their inner holes. Finally, we confirm the conjecture of Drake et al. that accretion is suppressed by the X-rays through 'photoevaporation-starved accretion' and predict that this effect can give rise to a negative correlation between X-ray luminosity and accretion rate, as reported in the Orion data. We also demonstrate that our model can replicate the observed difference in X-ray properties between accreting and non-accreting T Tauri stars.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/efb92006baa2dd0e07020ced9e7c80aeba853720

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. S. Andrews
2. T. Birnstiel
3. D. Wilner
4. Simon Bruderer
5. J. Owen
6. Anders Johansen
7. C. Dullemond
8. A. Hughes

In Education

1. J. Owen
2. Alan P. Jackson
3. Yanqin Wu
4. C. Clarke
5. Barbara Ercolano

In Instrumentation

1. S. Andrews
2. T. Birnstiel
3. D. Wilner
4. J. Owen
5. Anders Johansen
6. Simon Bruderer
7. A. Hughes
8. E. Chiang

Citations in the corpus

• Accretion onto Pre-Main-Sequence Stars (2016, background): “F or p er so na l u se o nl y. that ultimately removes disk gas (see, e.g., Owen et al. 2011 and references therein).”
• Gas density drops inside dust cavities of transitional disks around young stars observed with ALMA (2015, result): “For the sources studied here, photoevaporation by itself is unlikely based on just the large cavity sizeand high accretion rates (Owen et al. 2011; Rosotti et al. 2013) and our results further strengthen this hypothesis.”
• RESOLVED IMAGES OF LARGE CAVITIES IN PROTOPLANETARY TRANSITION DISKS (2011, background): “In this sample, the Rcav and Ṁ values for a given LX are much too large to be consistent with their formation via photoevaporative mass-loss (as noted by Owen et al. 2011).”
• On the theory of disc photoevaporation (2011, methodology): “The most convincing argument that the higher energy photons ( 0.3–0.4 keV) are dominating the heating to temperatures 5000 K is provided by the exercise conducted in Owen et al. (2010).”
• Dust Evolution and the Formation of Planetesimals (2016, background): “…clear, that opacity effects from grain growth can be ex- cluded (Birnstiel et al. 2012a), and also photoevaporation models alone can currently not account for most of the gap sizes and accretion rates seen in those objects (Owen et al. 2011), but possibly for a subset of them (Owen & Clarke 2012).”
• KEPLER PLANETS: A TALE OF EVAPORATION (2013, background): “We could of course parametrise the initial entropy in terms of some other variables; however, the initial cooling time is perhaps the most interesting as this be compared to protoplanetary discs lifetimes ∼3 Myr (e.g. Haisch et al. 2001; Hernández et al. 2007; Owen et al. 2011; Armitage 2011).”
• BREEDING SUPER-EARTHS AND BIRTHING SUPER-PUFFS IN TRANSITIONAL DISKS (2015, background): “This diffusion time is short, on the order of ∼0.1 Myr (see, e.g., Figure 9 of Owen et al. 2011).”
• TRANSITIONAL DISKS AS SIGNPOSTS OF YOUNG, MULTIPLANET SYSTEMS (2011, background): “Indeed, Owen et al. (2010) found that approximately 50% of observed transition disks could be explained by X-ray photoevaporation.”
• Planetary evaporation by UV and X‐ray radiation: basic hydrodynamics (2012, methodology): “…parameters expected, since the escape temperature from a planetary atmosphere is similar to the escape temperature from the inner disk (1-10 AU) around a solar-type star, we will make use of the temperature-ionization parameter relation of Owen et al. (2010) in this work, as shown in Fig.”