The role of the inner disk in mass accretion to the star in the early phase of star formation
- Author(s)
- Takuya Ohtani, Shigeo S. Kimura, Toru Tsuribe, Eduard Vorobiev
- Abstract
A physical mechanism that drives FU Orionis-type outbursts is reconsidered. We study the effect of the inner part of a circumstellar disk covering a region from near the central star to a radius of approximately 5au (hereafter, the inner disk). Using the fluctuating mass accretion rate onto the inner disk $dotM, rm out$, we consider the viscous evolution of the inner disk and the time variability of the mass accretion rate onto the central star $dotM, rm in$ by means of numerical calculation of an unsteady viscous accretion disk in a one-dimensional axisymmetric model. First, we calculate the evolution of the inner disk assuming an oscillating $dotM, rm out$. It is shown that the time variability of $dotM, rm in$ does not coincide with $dotM, rm out$ due to viscous diffusion. Second, we investigate the properties of spontaneous outbursts with temporally constant $dotM, rm out$. Outbursts occur only in a limited range of mass accretion rates onto the inner disk of $10-10<dotM, rm out< 3times 10-6,Modot :$yr-1 due to the gravo-magneto limit cycle (GML). Finally, we discuss the case with a combination of episodic $dotM, rm out$ and accretion outbursts caused by the GML in the inner disk. The GML can drive accretion outbursts onto the star even for the case of fluctuating $dotM, rm out$, although fluctuations of $dotM,$ decay while transmitting the inner disk inwards. We have newly identified two modes of outburst, one spontaneous and one stimulated. In the stimulated mode of outburst, $dotM, rm out$ does appear directly in $dotM, rm in$ (the latter defining the stellar accretion luminosity). In the spontaneous mode of outburst, $dotM, rm out$ appears as the interval between outbursts.
- Organisation(s)
- Department of Astrophysics
- External organisation(s)
- Osaka University, Ibaraki University, Southern Federal University
- Journal
- Publications of the Astronomical Society of Japan
- Volume
- 66
- ISSN
- 0004-6264
- DOI
- https://doi.org/10.1093/pasj/psu098
- Publication date
- 12-2013
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 103004 Astrophysics
- Keywords
- ASJC Scopus subject areas
- Astronomy and Astrophysics, Space and Planetary Science
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/192855ca-578e-4446-8db6-afd9b11fd8cf