分类： 天文学 >> 天文学 提交时间： 2023-02-19
Lei Qian
Zhichen Pan
Hongfei Liu
Hengqian Gan
Jinglong Yu
Lei Zhao
Jiguang Lu
Cun Sun
Jingye Yan
Peng Jiang
摘要： We present the estimation of the solar observation with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). For both the quite Sun and the Sun with radio bursts, when pointing directly to the Sun, the total power received by FAST would be out of the safe operational range of the signal chain, even resulting in the damage to the receiver. As a conclusion, the Sun should be kept at least $\sim 2^{\circ}$ away from the main beam during the observing at $\sim 1.25 {\ \rm GHz}$. The separation for lower frequency should be larger. For simplicity, the angular separation between the FAST beam and the Sun is suggested to be $\sim 5^{\circ}$ for observations on 200 MHz or higher bands.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Lei Qian
Zhichen Pan
Hongfei Liu
Hengqian Gan
Jinglong Yu
Lei Zhao
Jiguang Lu
Cun Sun
Jingye Yan
Peng Jiang
摘要： We present the estimation of the solar observation with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). For both the quite Sun and the Sun with radio bursts, when pointing directly to the Sun, the total power received by FAST would be out of the safe operational range of the signal chain, even resulting in the damage to the receiver. As a conclusion, the Sun should be kept at least $\sim 2^{\circ}$ away from the main beam during the observing at $\sim 1.25 {\ \rm GHz}$. The separation for lower frequency should be larger. For simplicity, the angular separation between the FAST beam and the Sun is suggested to be $\sim 5^{\circ}$ for observations on 200 MHz or higher bands.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shi Dai
Jiguang Lu
Chen Wang
Weiyang Wang
Renxin Xu
Yuanpei Yang
Songbo Zhang
George Hobbs
Di Li
Rui Luo
Miroslav Filipovic
Jinchen Jiang
摘要： Fast spinning (e.g., sub-second) neutron star with ultra-strong magnetic fields (or so-called magnetar) is one of the promising origins of repeating fast radio bursts (FRBs). Here we discuss circularly polarised emissions produced by propagation effects in the magnetosphere of fast spinning magnetars. We argue that the polarisation-limiting region is well beyond the light cylinder, suggesting that wave mode coupling effects are unlikely to produce strong circular polarisation for fast spinning magnetars. Cyclotron absorption could be significant if the secondary plasma density is high. However, high degrees of circular polarisation can only be produced with large asymmetries in electrons and positrons. We draw attention to the non-detection of circular polarisation in current observations of known repeating FRBs. We suggest that the circular polarisation of FRBs could provide key information on their origins and help distinguish different radiation mechanisms.
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