TIME EVOLUTION OF VISCOUS CIRCUMSTELLAR DISKS DUE TO PHOTOEVAPORATION BY FAR-ULTRAVIOLET, EXTREME-ULTRAVIOLET, AND X-RAY RADIATION FROM THE CENTRAL STAR

Journal Article · Tue Nov 10 04:00:00 EST 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/705/2/1237· OSTI ID:21378329

Gorti, U ^[1]; Dullemond, C P ^[2]; Hollenbach, D ^[3]

---

1. NASA Ames Research Center, Moffett Field, CA (United States)
2. Max Planck Institute for Astronomy, Heidelberg (Germany)
3. SETI Institute, Mountain View, CA (United States)

We present the time evolution of viscously accreting circumstellar disks as they are irradiated by ultraviolet and X-ray photons from a low-mass central star. Our model is a hybrid of a one-dimensional (1D) time-dependent viscous disk model coupled to a 1+1D disk vertical structure model used for calculating the disk structure and photoevaporation rates. We find that disks of initial mass 0.1 M{sub sun} around approx1 M{sub sun} stars survive for approx4 x 10{sup 6} yr, assuming a viscosity parameter alpha = 0.01, a time-dependent FUV luminosity L{sub FUV} approx 10{sup -2}-10{sup -3} L{sub sun} and with X-ray and EUV luminosities L{sub X} approx L{sub EUV} approx 10{sup -3} L{sub sun}. We find that FUV/X-ray-induced photoevaporation and viscous accretion are both important in depleting disk mass. Photoevaporation rates are most significant at approx1-10 AU and at approx>30 AU. Viscosity spreads the disk which causes mass loss by accretion onto the central star and feeds mass loss by photoevaporation in the outer disk. We find that FUV photons can create gaps in the inner, planet-forming regions of the disk (approx1-10 AU) at relatively early epochs in disk evolution while disk masses are still substantial. EUV and X-ray photons are also capable of driving gaps, but EUV can only do so at late, low accretion-rate epochs after the disk mass has already declined substantially. Disks around stars with predominantly soft X-ray fields experience enhanced photoevaporative mass loss. We follow disk evolution around stars of different masses, and find that disk survival time is relatively independent of mass for stars with M{sub *}approx< 3 M{sub sun}; for M{sub *}approx> 3 M{sub sun} the disks are short-lived (approx10{sup 5} yr).

• OSTI ID: 21378329
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 705; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
BOSONS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
EVOLUTION
EXTREME ULTRAVIOLET RADIATION
FAR ULTRAVIOLET RADIATION
IONIZING RADIATIONS
LUMINOSITY
MASS
MASSLESS PARTICLES
OPTICAL PROPERTIES
PHOTONS
PHYSICAL PROPERTIES
PLANETS
PROTOPLANETS
RADIATIONS
SOFT X RADIATION
STAR EVOLUTION
STARS
SURVIVAL TIME
TIME DEPENDENCE
ULTRAVIOLET RADIATION
VISCOSITY
X RADIATION