arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2601.20101astro-ph.SR
收藏

年轻棕矮星2MASS J08440915-7833457的吸积特性

Accretion Properties of the Young Brown Dwarf 2MASS J08440915-7833457

Rice University（莱斯大学）；Johns-Hopkins University（约翰霍普金斯大学）；Peking University（北京大学）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学柯尔夫天文与天体物理研究所）

Toni V. Panzera, Laura S. Flagg, Margaret A. Mueller, Christopher M. Johns-Krull, Gregory J. Herczeg

备注：
Accepted to ApJ
阅读 PDF
arXiv 页面 ↗HTML 原文 ↗

AI总结：

研究年轻棕矮星2MASS J0844的吸积特性，发现其C IV发射异常，暗示磁饱和模型需重新定义。

摘要：

我们利用HST-COS FUV和-STIS光学观测数据，对年轻吸积棕矮星2MASS-J08440915-7833457（J0844）进行了研究，该观测数据来自ULLYSES DDT项目。我们分析了热FUV线（如C IV、Si IV和N V）以及H2的荧光发射。尽管有吸积证据，但C IV线轮廓比典型的经典T Tauri星（CTTSs）更窄，更接近弱线T Tauri星。此外，C IV积分线通量不符合磁饱和状态下吸积物体的预期水平。然而，将J0844与适当的低质量类比星比较，J0844显示出过量的C IV发射，这表明磁饱和水平可能需要重新定义以适应最低质量物体。C IV/Si IV发射线比例如为20，比大多数CTTSs高，少数例外（如TW Hya）。我们拟合STIS光学光谱以计算吸积率，发现为4.2×10⁻¹¹ Msol/yr。基于经验LCIV-Macc关系计算的吸积率比这高两个数量级，表明该关系可能在最低质量时不成立。我们发现H2发射似乎起源于共转半径内，这表明要么盘截断在共转半径内，或者存在我们未考虑的额外H2发射源（如从吸积流本身）。这些数据扩展了我们对吸积和内盘条件的理解，特别是在相对未探索的最低质量范围。

英文摘要：

We present HST-COS FUV and -STIS optical observations towards the young accreting brown dwarf 2MASS-J08440915-7833457 (J0844) from the ULLYSES DDT Program. We analyse hot FUV lines such C IV, Si IV, and N V, as well as fluorescent emission from H2. Despite evidence for accretion, the C IV line profiles are narrower than in typical classical T Tauri stars (CTTSs), resembling weak-lined T Tauri stars more closely. Additionally, the C IV integrated line flux does not follow the level expected of an accreting object in the magnetically saturated regime. However, comparing J0844 to appropriate low mass analogs, J0844 does show excess C IV emission characteristic of accretion, suggesting the magnetic saturation level may need to be redefined for the lowest mass objects. The C IV/Si IV emission line ratio is found to be 20, which is higher than most CTTSs, with a few exceptions (e.g., TW Hya). We fit the STIS optical spectrum to calculate an accretion rate, which we find to be 4.2 x 10-11 Msol/yr. The accretion rate found based on the empirical LCIV-Macc relationship is twoorders of magnitude higher, suggesting this relationship may not hold at the lowest masses. We find the H2 emission appears to originate within the co-rotation radius, pointing to either disc truncation well inside the co-rotation radius or additional sources of H2 emission that we do not consider (e.g., from the accretion flow itself). These data provide an extension of our current understanding of accretion and inner disc conditions to the relatively unexplored lowest mass regime.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

↑