分类: 天文学 >> 天体物理学 提交时间: 2023-07-11
摘要: We propose to use the rotation period to constrain the average density of an object with gravitationally confined surface. The average density is inverse proportional to the square of the rotation period, while independent of the size of the object. The lower limit of the average density can be written as $\rho_0=10.9 {\ \rm g\ cm^{-3}}\left(\frac{{\ \rm hours}}{P}\right)^2$. An asteroid with rotating period shorter than 0.7 h should consist of some unknown matter, or it is a whole rock or a bulk of ice with no rubble piles on the surface.
分类: 天文学 >> 天文学 提交时间: 2016-05-23
摘要: The Five-hundred-meter Aperture Spherical radio Telescope (FAST) will begin its early-science operations during 2016. Drift-scan pulsar surveys will be carried out during this period using an ultra-wide-band receiver system (covering ∼ 270 to 1620 MHz). We describe a method for accounting for the changes in the telescope beam shape and the pulsar parameters when searching for pulsars over such a wide bandwidth. We applied this method to simulated data sets of pulsars in globular clusters that are visible to FAST and found that a representative observation would have a sensitivity of ∼ 40 µJy. Our results showed that a single drift-scan (lasting less than a minute) is likely to find at least one pulsar for observations of four globular clusters. Repeated observations will increase the likely number of detections. We found that pulsars in ∼16 clusters are likely to be found if the data from 100 drift-scan observations of each cluster are incoherently combined.