文章基本信息

标题：A search for radio emission from exoplanets around evolved stars
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作者：E. O’Gorman ; C. P. Coughlan ; W. Vlemmings 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2018
卷号：612
DOI：10.1051/0004-6361/201731965
语种：English
出版社：EDP Sciences
摘要：The majority of searches for radio emission from exoplanets have to date focused on short period planets, i.e., the so-called hot Jupiter type planets. However, these planets are likely to be tidally locked to their host stars and may not generate sufficiently strong magnetic fields to emit electron cyclotron maser emission at the low frequencies used in observations (typically ≥150 MHz). In comparison, the large mass-loss rates of evolved stars could enable exoplanets at larger orbital distances to emit detectable radio emission. Here, we first show that the large ionized mass-loss rates of certain evolved stars relative to the solar value could make them detectable with the LOw Frequency ARray (LOFAR) at 150 MHz (λ= 2 m), provided they have surface magnetic field strengths >50 G. We then report radio observations of three long period (>1 au) planets that orbit the evolved starsβGem,ιDra, andβUMi using LOFAR at 150 MHz. We do not detect radio emission from any system but place tight 3σupper limits of 0.98, 0.87, and 0.57 mJy on the flux density at 150 MHz forβGem,ιDra, andβUMi, respectively. Despite our non-detections these stringent upper limits highlight the potential of LOFAR as a tool to search for exoplanetary radio emission at meter wavelengths.
关键词：Key wordsenradio continuum: planetary systemsplanets and satellites: detectionplanets and satellites: magnetic fieldsplanets and satellites: auroraestars: evolutionsurveys