An FUV-detected Accretion Shock at the Star-Disk Boundary of FU Ori
| Autor: | Carvalho, Adolfo S., Hillenbrand, Lynne A., France, Kevin, Herczeg, Gregory J. |
|---|---|
| Rok vydání: | 2024 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | FU Ori objects are the most extreme eruptive young stars known. Their 4 to 5 magnitude photometric outbursts last for decades and are attributed to a factor of up to 10,000 increase in the stellar accretion rate. The nature of the accretion disk-to-star interface in FU Ori objects has remained a mystery for decades. To date, attempts to directly observe a shock or boundary layer have been thwarted by the apparent lack of emission in excess of the accretion disk photosphere down to $\lambda = 2300$ \AA. We present a new NUV and the first high-sensitivity FUV spectrum of FU Ori. The FUV continuum is detected for the first time and, at $\lambda = 1400$ \AA, is more than $10^4$ times brighter than predicted by a viscous accretion disk. We interpret the excess as arising from a shock at the boundary between the disk and the stellar surface. We model the shock emission as a blackbody and find that the temperature of the shocked material is $T_\mathrm{FUV} \approx 16,000 \pm 2000$ K. The shock temperature corresponds to an accretion flow along the surface of the disk that reaches a velocity of 40 km s$^{-1}$ at the boundary, consistent with predictions from simulations. Comment: 16 pages, 8 figures, accepted to ApJL |
| Databáze: | arXiv |
| Externí odkaz: |
|