Radio detections of southern ultracool dwarfs
Radio detections of southern ultracool dwarfs
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南部超冷矮星的无线电探测
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
C. Ward
中科院分区：
文献类型：
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作者：
C. Lynch;T. Murphy;V. Ravi;G. Hobbs;K. Lo;C. Ward
我们报道了使用澳大利亚望远镜紧凑型阵列进行的一次容量有限的测量结果，以寻找来自15个南半球超冷矮星的瞬时和静态射电发射。我们探测到了2MASSWJ0004348−404405的射电发射，使射电巨响超冷矮星的数量增加到22个。我们还观察到了2MASS J10481463−3956062和2MASSI J0339352−352544的射电发射，这两个源之前已经进行了射电探测。三个探测到的源的射电发射没有显示出可变性或耀斑发射。对这种静态发射进行了模拟，发现它与发射区半径为(1-2)R^*、磁场倾角为20°-80°、场强∼为10-200G、功率电子密度∼为10^4-10^8 cm^(−3)的磁层的光学薄回旋同步辐射是一致的。此外，我们对四颗超冷矮星设定了上限，这些矮星之前没有进行过射电观测。这使得在无线电频率上研究的超冷矮星的数量增加到222颗。分析这15个源样本的射电发射的总体趋势，我们发现，对于较晚的频谱类型和较快的旋转物体，射电活动增加。此外，比较这些源的射电与X射线亮度之比，我们发现2MASSJ10481463−3956062和2MASSIJ0339352−352544违反了古德尔-本茨关系两个数量级以上。
We report the results of a volume-limited survey using the Australia Telescope Compact Array to search for transient and quiescent radio emission from 15 Southern hemisphere ultracool dwarfs. We detect radio emission from 2MASSW J0004348−404405 increasing the number of radio loud ultracool dwarfs to 22. We also observe radio emission from 2MASS J10481463−3956062 and 2MASSI J0339352−352544, two sources with previous radio detections. The radio emission from the three detected sources shows no variability or flare emission. Modelling this quiescent emission we find that it is consistent with optically thin gyrosynchrotron emission from a magnetosphere with an emitting region radius of (1–2)R^*, magnetic field inclination 20°–80°, field strength ∼10–200 G, and power-law electron density ∼10^4–10^8 cm^(−3). Additionally, we place upper limits on four ultracool dwarfs with no previous radio observations. This increases the number of ultracool dwarfs studied at radio frequencies to 222. Analysing general trends of the radio emission for this sample of 15 sources, we find that the radio activity increases for later spectral types and more rapidly rotating objects. Furthermore, comparing the ratio of the radio to X-ray luminosities for these sources, we find 2MASS J10481463−3956062 and 2MASSI J0339352−352544 violate the Gudel–Benz relation by more than two orders of magnitude.
影响因子：
64.8
作者：
G. Hallinan;S. P. Littlefair;G. Cotter;S. Bourke;L. K. Harding;J. Pineda;R. P. Butler;A. Golden;G. Basri;J. Doyle;M. Kao;S. Berdyugina;A. Kuznetsov;M. Rupen;A. Antonova
通讯作者：
G. Hallinan;S. P. Littlefair;G. Cotter;S. Bourke;L. K. Harding;J. Pineda;R. P. Butler;A. Golden;G. Basri;J. Doyle;M. Kao;S. Berdyugina;A. Kuznetsov;M. Rupen;A. Antonova