Detection of a Millimeter Flare from Proxima Centauri
Detection of a Millimeter Flare from Proxima Centauri
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DOI：
10.3847/2041-8213/aaad6b
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发表时间：
2018-02
期刊：
影响因子：
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通讯作者：
M. MacGregor;A. Weinberger;D. Wilner;A. Kowalski;S. Cranmer
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作者：
M. MacGregor;A. Weinberger;D. Wilner;A. Kowalski;S. Cranmer
我们对2017年1月21日至4月25日在比邻星系统233 GHz （1.3 mm）频率上的ALMA 12 m和Atacama Compact Array （ACA）观测数据进行了新的分析，灵敏度分别为9.5 μJy和47 μJy beam - 1。这些分析表明，在2017年3月24日ACA的一次观测中，这颗恒星经历了一次重大的耀斑事件。整个事件持续了大约1分钟，峰值通量密度达到100±4 mJy，几乎是恒星静止辐射的1000倍。在耀斑峰处，连续辐射的光谱指数急剧下降，频率为Fν∝να， α = - 1.77±0.45，且有分数线偏振的下限。由于ACA观测没有显示任何静止的过量发射，我们得出结论，没有必要援引1-4 au的尘带的存在。我们还假设，与红外波长推断的74±4 μJy的光球通量密度相比，在12 m观测中观测到的101±9 μJy的轻微过剩通量密度可能是由于连续较小的耀斑引起的日冕加热，就像在AU Mic上看到的那样，它是附近另一颗研究得很好的m矮耀斑星。如果这是真的，那么也就不需要在0.4 au的温度下产生热尘埃了。
We present new analyses of ALMA 12 m and Atacama Compact Array (ACA) observations at 233 GHz (1.3 mm) of the Proxima Centauri system with sensitivities of 9.5 and 47 μJy beam−1, respectively, taken from 2017 January 21 through April 25. These analyses reveal that the star underwent a significant flaring event during one of the ACA observations on 2017 March 24. The complete event lasted for approximately 1 minute and reached a peak flux density of 100 ± 4 mJy, nearly a factor of 1000 times brighter than the star’s quiescent emission. At the flare peak, the continuum emission is characterized by a steeply falling spectral index with frequency Fν ∝ να with α = −1.77 ± 0.45, and a lower limit on the fractional linear polarization of . Because the ACA observations do not show any quiescent excess emission, we conclude that there is no need to invoke the presence of a dust belt at 1–4 au. We also posit that the slight excess flux density of 101 ± 9 μJy observed in the 12 m observations, compared to the photospheric flux density of 74 ± 4 μJy extrapolated from infrared wavelengths, may be due to coronal heating from continual smaller flares, as is seen for AU Mic, another nearby well-studied M dwarf flare star. If this is true, then the need for warm dust at ∼0.4 au is also removed.