大质量恒星并合体 M101 OT2015-1 的晚期演化
Late-Time Evolution of the Massive Stellar Merger M101 OT2015-1
- Universitat de Barcelona（巴塞罗那大学）
- Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文学中心）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究通过多波段观测和辐射转移建模，追踪了亮红新星 M101 OT2015-1 的晚期尘埃与分子演化，证实大质量前身星并合是宇宙尘埃和分子的高效来源。
AI中文摘要：
亮红新星（LRNe）是由密近双星系统中的不稳定质量转移和公共包层阶段产生的天文瞬变事件，最终导致恒星并合。其冷且膨胀的抛射物为分子和尘埃的形成提供了理想条件。我们利用爆发后约5年内跨越近红外（NIR）和中红外（MIR）的多波段观测，研究了高亮度红新星 M101 OT2015-1（大质量前身星，$18\pm 1$M$_\odot$）的晚期尘埃和分子演化。来自 NEOWISE、Spitzer、Keck NIRC2 和 MOSFIRE 的档案及未发表测光数据通过二维高斯过程回归进行插值。光谱能量分布（SED）采用一维球对称辐射转移模型进行拟合，以追踪尘埃质量、尘埃温度和中心源性质的演化。在峰值后+150天，SED 可由纯恒星黑体（$T_{\rm eff}=3330$K）很好地拟合，尘埃可忽略（log$M_{\rm dust}/$M$_\odot<-6.36$）。快速尘埃凝结始于约+200天（$T_{\rm dust}=1591$K），到+1300天时尘埃质量增加至 log$M_{\rm dust}/$M$_\odot =-3.65$，光学深度达到 $\tau_V =64$。在约600天时出现显著的近红外再增亮（$M_K=-12.04$），伴随尘埃再加热凸起（$T_{\rm dust}=1567$K），表明可能由激波相互作用驱动的第二相尘埃成核。对低分辨率近红外 MOSFIRE 光谱进行了谱线识别分析，并使用 LTE 等温平板模型表征 CO 分子特征。MOSFIRE 光谱揭示了富氧环境，光球膨胀速度约为 $430-530$km s$^{-1}$（由 Pa$\beta$ 发射线测得），以及高 CO 柱密度（在+142天和+197天分别为 log$N_{\rm CO}$/cm$^{-2}=20.9$ 和 $20.7$）。这些结果证实，来自大质量前身星的 LRNe 是宇宙尘埃的高产生产者，也是高效的分子工厂。
英文摘要：
Luminous red novae (LRNe) are astronomical transients arising from unstable mass transfer and common envelope phases in close binary systems, culminating in stellar mergers. Their cold, expanding ejecta provide the ideal conditions for molecule and dust formation. We investigate the late-time dust and molecular evolution of the LRN M101 OT2015-1, a high-mass LRN progenitor ($18\pm 1$M$_\odot$), using multi-band near-infrared (NIR) and mid-infrared (MIR) observations spanning up to ~5 years post-outburst. Archival and unpublished photometry from NEOWISE, Spitzer, Keck NIRC2 and MOSFIRE, are interpolated via 2D Gaussian process regression. Spectral energy distributions (SEDs) are modelled with 1D spherical radiative transfer models to track the evolution of dust mass, dust temperature, and central source properties. At +150d post-peak, the SED is well-fit by a pure stellar blackbody ($T_{\rm eff}=3330$K) with negligible dust (log$M_{\rm dust}/$M$_\odot<-6.36$). Rapid dust condensation begins around day +200 ($T_{\rm dust}=1591$K), with dust mass increasing to log$M_{\rm dust}/$M$_\odot =-3.65$ and optical depth reaching $τ_V =64$ by +1300d. A prominent NIR re-brightening at ~600d ($M_K=-12.04$), accompanied by a dust reheating bump ($T_{\rm dust}=1567$K), highlights a second phase of dust nucleation likely driven by shock interactions. Low-resolution NIR MOSFIRE spectra are analysed for line identification and also using an LTE isothermal slab model to characterise CO molecular features. The MOSFIRE spectra reveal an O-rich environment with photospheric expansion velocities of ~$430-530$km s$^{-1}$, as measured in the Pa$β$ emission line, and high CO column densities (log$N_{\rm CO}$/cm$^{-2}=20.9$ and $20.7$ at +142d and +197d, respectively). These results confirm that LRNe from massive progenitors are prolific producers of cosmic dust and are efficient molecular factories.
