论文标题
从最冷和最接近的棕色矮人与阿尔玛一起搜索毫米排放
A search for millimeter emission from the coldest and closest brown dwarf with ALMA
论文作者
论文摘要
上下文：Wise J085510.83-071442.5（W0855）是一个唯一的对象：与Teff CA。 250 K，它是最冷的已知棕色矮人（BD），仅位于CA.2.2 PC形成太阳。这是非常微弱的，这使得任何天文观测变得困难。然而，至少一个遥远的超低质量物体，即M9矮人TVLM 513-46546，已证明在高达95 GHz的频率下是一个稳定的无线电发射极，在观察到较强的脉冲发射的情况下，具有叠加的活性状态。目的：我们的目标是确定W0855的毫米无线电性能，深度观测到93 GHz（3.2 mm），以研究该物体的射射体测量是否可行，并测量或设置其磁场上限。方法：我们在2019年12月24日在85.1-100.9 GHz的W0855使用Atacama大毫米阵列（ALMA）12 m天线观察到了94分钟。我们使用了标准的ALMA校准程序，并通过容纳了迄今为止最亮的物体，为我们的分析创建了最终图像。此外，我们创建了一个以30 s时间分辨率的光曲线来搜索脉冲发射。结果：我们的观察结果达到了7.3μjy/beam的噪声RMS，以稳定发射，在聚集的带宽中30 s脉冲的噪声RMS（Stokes I）的噪声RMS为88μjy。在观察时，没有证据表明物体稳定或脉冲发射。在稳定发射时，我们在85 GHz和101 GHz之间的脉冲发射中得出了21.9μjy的3σ上限。结论：与最近在4-8 GHz处W0855的未检测，我们对W0855稳定和脉冲发射的限制证实，该物体既不是无线电大通，也不是磁层特别活跃。
Context: WISE J085510.83-071442.5 (W0855) is a unique object: with Teff ca. 250 K, it is the coldest known brown dwarf (BD), located at only ca.2.2 pc form the Sun. It is extremely faint, which makes any astronomical observations difficult. However, at least one remotely similar ultra-low-mass object, the M9 dwarf TVLM 513-46546, has been shown to be a steady radio emitter at frequencies up to 95 GHz with superimposed active states where strong, pulsed emission is observed. Aims: Our goal is to determine the millimeter radio properties of W0855 with deep observations around 93 GHz (3.2 mm) in order to investigate whether radio astrometry of this object is feasible and to measure or set an upper limit on its magnetic field. Methods: We observed W0855 for 94 min at 85.1-100.9 GHz on 24 December 2019 using 44 of the Atacama Large millimeter Array (ALMA) 12 m antennas. We used the standard ALMA calibration procedure and created the final image for our analysis by accommodating the Quasar 3C 209, the brightest nearby object by far. Furthermore, we created a light curve with a 30 s time resolution to search for pulsed emission. Results: Our observations achieve a noise RMS of 7.3 μJy/beam for steady emission and of 88 μJy for 30 s pulses in the aggregated bandwidth (Stokes I). There is no evidence for steady or pulsed emission from the object at the time of the observation. We derive 3 σ upper limits of 21.9 μJy on the steady emission and of 264 μJy on the pulsed emission of W0855 between 85 GHz and 101 GHz. Conclusions: Together with the recent non-detection of W0855 at 4-8 GHz, our constraints on the steady and pulsed emission from W0855 confirm that the object is neither radio-loud nor magnetospherically particularly active.
