Constraining the Chemical Signatures and the Outburst Mechanism of the Class 0 Protostar HOPS 383
Constraining the Chemical Signatures and the Outburst Mechanism of the Class 0 Protostar HOPS 383
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DOI：
10.3847/1538-4357/abbdf4
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发表时间：
2020-10
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通讯作者：
Rajeeb Sharma;J. Tobin;P. Sheehan;S. Megeath;W. Fischer;J. Jørgensen;E. Safron;Z. Nagy
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作者：
Rajeeb Sharma;J. Tobin;P. Sheehan;S. Megeath;W. Fischer;J. Jørgensen;E. Safron;Z. Nagy
我们使用阿塔卡马大型毫米/亚毫米阵列 (ALMA)、甚大阵列 (VLA) 和亚毫米阵列 (SMA) 展示了对 HOPS 383 的观测，HOPS 383 是位于猎户座分子云内的第一颗已知爆发的 0 级原恒星。 SMA 观测揭示了 HOPS 383 周围 0.85、1.1 和 1.3 mm 处的包络尺度连续体和分子线发射。图像显示 HCO+ 和 H13CO+ 在连续谱上或附近达到峰值，而 N2H+ 在同一位置减少。这反映了潜在的化学反应，即 CO 在原恒星附近蒸发，破坏了 N2H+，同时形成了 HCO+。我们还观察到 12CO ( ) 和 ( ) 追踪的分子流出。在 ALMA 0.87 mm 尘埃连续体中解析出一个圆盘，与流出方向正交，表观半径为 ∼62 au。当适合 ALMA 能见度时，连续体的辐射传递模型给出了 0.02 M⊙ 的圆盘质量。包含 VLA 8 mm 数据的模型表明，由于较长波长下的尘埃不透明度较低，圆盘质量可能增加 10 倍。模型中的盘温度和表面密度分布以及假设的原恒星质量为 0.5 M⊙ 表明，爆发前的 Toomre Q 参数 < 1，如果盘质量足够大，则引力不稳定成为解释早期爆发的可行机制。
We present observations toward HOPS 383, the first known outbursting Class 0 protostar located within the Orion molecular cloud using the Atacama Large Millimeter/submillimeter Array (ALMA), Very Large Array (VLA), and Submillimeter Array (SMA). The SMA observations reveal envelope scale continuum and molecular line emission surrounding HOPS 383 at 0.85, 1.1, and 1.3 mm. The images show that HCO+ and H13CO+ peaks on or near the continuum, while N2H+ is reduced at the same position. This reflects the underlying chemistry where CO evaporating close to the protostar destroys N2H+ while forming HCO+. We also observe the molecular outflow traced by 12CO ( ) and ( ). A disk is resolved in the ALMA 0.87 mm dust continuum, orthogonal to the outflow direction, with an apparent radius of ∼62 au. Radiative transfer modeling of the continuum gives disk masses of 0.02 M⊙ when fit to the ALMA visibilities. The models including VLA 8 mm data indicate that the disk mass could be up to a factor of 10 larger due to lower dust opacity at longer wavelengths. The disk temperature and surface density profiles from the modeling, and an assumed protostar mass of 0.5 M⊙ suggest that the Toomre Q parameter < 1 before the outburst, making gravitational instability a viable mechanism to explain outbursts at an early age if the disk is sufficiently massive.