论文标题
直接无线电发现冷褐色矮人
Direct radio discovery of a cold brown dwarf
论文作者
论文摘要
从某些棕色矮人中检测到了诸如Aurorae和圆形旋转的Cyclotron Maser发射等气体巨头中看到的磁层过程。但是，以前的无线电观察结果针对通过红外发射发现的已知棕色矮人。在这里，我们报告了BDR J1750+3809的发现，这是一种通过Lofar望远镜检测到的圆形极化无线电源，检测到约144 MHz。后续近红外光度法和光谱法表明，BDR J1750+3809是光谱型T $ 6.5 \ pm 1 $的冷甲烷矮人，$ 65^{+9} _ { - 8} _ { - 8} \，{\ rm pc} $。 The quasi-quiescent radio spectral luminosity of BDR J1750+3809 is $\approx 5\times 10^{15}\,{\rm erg}\,{\rm s}^{-1}\,{\rm Hz}^{-1}$ which is over two orders of magnitude larger than that of the known population of comparable spectral type.这可能是由于优先的几何比对或与密切伴侣的电动力相互作用。此外，由于预计发射将发生在电子陀螺频率附近，因此BDR J1750+3809中发射极位的磁场强度为$ B \ GTRSIM 25 \，{\ rm G} $，这与行星尺度磁场相当。我们的发现表明，可以采用低频无线电调查来发现过冷的对象，这些对象太冷，无法在红外调查中检测到。
Magnetospheric processes seen in gas-giants such as aurorae and circularly-polarized cyclotron maser radio emission have been detected from some brown dwarfs. However, previous radio observations targeted known brown dwarfs discovered via their infrared emission. Here we report the discovery of BDR J1750+3809, a circularly polarized radio source detected around 144 MHz with the LOFAR telescope. Follow-up near-infrared photometry and spectroscopy show that BDR J1750+3809 is a cold methane dwarf of spectral type T$6.5\pm 1$ at a distance of $65^{+9}_{-8}\,{\rm pc}$. The quasi-quiescent radio spectral luminosity of BDR J1750+3809 is $\approx 5\times 10^{15}\,{\rm erg}\,{\rm s}^{-1}\,{\rm Hz}^{-1}$ which is over two orders of magnitude larger than that of the known population of comparable spectral type. This could be due to a preferential geometric alignment or an electrodynamic interaction with a close companion. In addition, as the emission is expected to occur close to the electron gyro-frequency, the magnetic field strength at the emitter site in BDR J1750+3809 is $B\gtrsim 25\,{\rm G}$, which is comparable to planetary-scale magnetic fields. Our discovery suggests that low-frequency radio surveys can be employed to discover sub-stellar objects that are too cold to be detected in infrared surveys.
