2024-11-21 カリフォルニア工科大学(Caltech)
＜関連情報＞
- https://www.caltech.edu/about/news/disk-surrounding-star-is-sizzling-hot
- https://hubblesite.org/contents/news-releases/2024/news-2024-037
- https://iopscience.iop.org/article/10.3847/2041-8213/ad74eb
FUオリオン座の星と円盤の境界で、遠紫外線で降着衝撃波が検出される A Far-ultraviolet-detected Accretion Shock at the Star–Disk Boundary of FU Ori
Adolfo S. Carvalho, Lynne A. Hillenbrand, Kevin France, and Gregory J. Herczeg
The Astrophysical Journal Letters Published: 2024 September 23
DOI:10.3847/2041-8213/ad74eb
Abstract
FU Ori objects are the most extreme eruptive young stars known. Their 4–5 mag 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 λ = 2300 Å. We present a new near-ultraviolet and the first high-sensitivity far-ultraviolet (FUV) spectrum of FU Ori. The FUV continuum is detected for the first time and, at λ = 1400 Å, is more than 104 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 TFUV ≈ 16,000 ± 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.
