标题： 恒星诞生时磁活动的证据：来自0类原恒星HOPS 383的强大X射线耀斑 显示英文标题

标题： Evidence for magnetic activity at starbirth: a powerful X-ray flare from the Class 0 protostar HOPS 383

摘要： 上下文。 0类原恒星代表太阳型恒星最早的演化阶段，在此期间，系统质量的大部分存在于向内坠落的气体和尘埃包层中，并尚未进入中心的新生恒星。 尽管X射线是更演化的原恒星和年轻恒星磁活动的关键特征，但这种磁活动是否存在于0类阶段仍存在争议。 目标。 我们的目标是在X射线下检测一个真正的0类原恒星。 方法。 我们在2017年12月用钱德拉X射线天文台（$\sim$84 ks）对HOPS 383进行了X射线观测，并用南方天体物理研究望远镜进行了近红外成像。 结果。 HOPS 383在一次强烈的耀斑期间被检测到X射线。 这种高能（E > 2 keV）X射线对应体在空间上与HOPS 383的西北4厘米成分一致，这将是HOPS 383发射的射电热喷流的基底。 耀斑持续时间为$\sim$3.3小时；在峰值时，X射线光度在2-8 keV能量带达到$\sim$4 x 1E31 erg s --1，这一水平至少比HOPS 383未被检测到的平静辐射大一个数量级。 X射线耀斑谱高度吸收（NH$\sim$ 7 x 1E23 cm --2），并显示出一个等效宽度为$\sim$1.1 keV的6.4 keV发射线，该线来源于中性或低电离铁。 结论。 从HOPS 383检测到强烈的X射线耀斑直接证明了磁活动可以在太阳型恒星的最早形成阶段存在。 显示英文摘要

摘要： Context. Class 0 protostars represent the earliest evolutionary stage of solar-type stars, during which the majority of the system mass resides in an infalling envelope of gas and dust and is not yet in the central, nascent star. Although X-rays are a key signature of magnetic activity in more evolved protostars and young stars, whether such magnetic activity is present at the Class 0 stage is still debated. Aims. We aim to detect a bona fide Class 0 protostar in X-rays. Methods. We observed HOPS 383 in 2017 December in X-rays with the Chandra X-ray Observatory ($\sim$84 ks) and in near-infrared imaging with the Southern Astrophysical Research telescope. Results. HOPS 383 was detected in X-rays during a powerful flare. This hard (E > 2 keV) X-ray counterpart was spatially coincident with the northwest 4 cm component of HOPS 383, which would be the base of the radio thermal jet launched by HOPS 383. The flare duration was $\sim$3.3 h; at the peak, the X-ray luminosity reached $\sim$4 x 1E31 erg s --1 in the 2-8 keV energy band, a level at least an order of magnitude larger than that of the undetected quiescent emission from HOPS 383. The X-ray flare spectrum is highly absorbed (NH $\sim$ 7 x 1E23 cm --2), and it displays a 6.4 keV emission line with an equivalent width of $\sim$1.1 keV, arising from neutral or low-ionization iron. Conclusions. The detection of a powerful X-ray flare from HOPS 383 constitutes direct proof that magnetic activity can be present at the earliest formative stages of solar-type stars.