A BLIND SEARCH FOR MAGNETOSPHERIC EMISSIONS FROM PLANETARY COMPANIONS TO NEARBY SOLAR-TYPE STARS
A BLIND SEARCH FOR MAGNETOSPHERIC EMISSIONS FROM PLANETARY COMPANIONS TO NEARBY SOLAR-TYPE STARS
复制标题
盲目搜索从行星伴星到附近太阳型恒星的磁层发射
DOI：
--
复制
发表时间：
2009
期刊：
影响因子：
--
通讯作者：
L. A. Hennig
中科院分区：
文献类型：
--
作者：
T. Lazio;S. Carmichael;J. Clark;E. Elkins;P. Gudmundsen;Z. Mott;M. Szwajkowski;L. A. Hennig
这篇论文报道了对附近恒星周围行星的磁层辐射的盲搜索。年轻的恒星可能有比太阳强得多的恒星风，因为行星磁层的发射是由恒星风驱动的，更强的恒星风可能会增强任何绕轨道运行的行星的无线电亮度。利用各种恒星目录，我们选择了年龄估计相对较年轻（< 3gyr）的附近恒星（< 30pc）。我们从恒星目录中构建了不同的样本，发现了100到几百颗恒星。我们对来自74 MHz （4 m波长）VLA低频巡天的图像进行了叠加，在10 ~ 33 mJy的叠加图像中得到了行星发射的3σ极限。这些通量密度极限对应于小于5-10 ×1023 erg s−1的行星平均光度。利用最新的恒星风速、密度和磁场与恒星年龄的比例模型，我们估计了样本中相对于太阳的恒星风强度的比例因子。在我们的样本中，恒星风携带的典型动能是太阳的15-50倍，典型的磁能是太阳的5-10倍。如果我们假设每颗恒星都有一颗类似木星的行星环绕，其光度比木星的十度辐射要大，那么我们从叠加分析中得到的行星光度的限制很可能比在统计意义上探测行星所需的光度高10-100倍。未来的仪器，如低频阵列和长波阵列，对观测结果进行类似的统计分析，有望提高10-100倍。
This paper reports a blind search for magnetospheric emissions from planets around nearby stars. Young stars are likely to have much stronger stellar winds than the Sun, and because planetary magnetospheric emissions are powered by stellar winds, stronger stellar winds may enhance the radio luminosity of any orbiting planets. Using various stellar catalogs, we selected nearby stars (≲30 pc) with relatively young age estimates (<3 Gyr). We constructed different samples from the stellar catalogs, finding between 100 and several hundred stars. We stacked images from the 74 MHz (4 m wavelength) VLA Low-frequency Sky Survey, obtaining 3σ limits on planetary emission in the stacked images of between 10 and 33 mJy. These flux density limits correspond to average planetary luminosities less than 5–10 ×1023 erg s−1. Using recent models for the scaling of stellar wind velocity, density, and magnetic field with stellar age, we estimate scaling factors for the strength of stellar winds, relative to the Sun, in our samples. The typical kinetic energy carried by the stellar winds in our samples is 15–50 times larger than that of the Sun, and the typical magnetic energy is 5–10 times larger. If we assume that every star is orbited by a Jupiter-like planet with a luminosity larger than that of the Jovian decametric radiation by the above factors, our limits on planetary luminosities from the stacking analysis are likely to be a factor of 10–100 above what would be required to detect the planets in a statistical sense. Similar statistical analyses with observations by future instruments, such as the Low Frequency Array and the Long Wavelength Array, offer the promise of improvements by factors of 10–100.