https://phys.org/news/2020-03-eclipsing-binary-millisecond-pulsar-fast.html Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), astronomers have discovered a new eclipsing binary millisecond pulsar in the globular cluster NGC 6341 (or M92). The newly found object received designation PSR J1717+4308A or M92A. The finding is detailed in a paper published February 24 on arXiv.org. The most rapidly rotating pulsars, those with rotation periods below 30 milliseconds, are known as millisecond pulsars (MSPs). It is assumed that they are formed in binary systems when the initially more massive component turns into a neutron star that is then spun-up due to accretion of matter from the secondary star. A class of extreme binary pulsars with semi-degenerate companion stars is dubbed "spider pulsars." These objects are further categorized as "black widows" if the companion has extremely low mass (less than 0.1 solar masses), while if the secondary star is heavier they are called "redbacks." Now, an international team of astronomers led by Zhichen Pan of the Chinese Academy of Sciences Key Laboratory of FAST in Beijing, China, reports the detection of a new pulsar that appears to be a "redback." The discovery was made using FAST, and the study also contains data from follow-up observations with the Green Bank Telescope (GBT). MORE AT LINK..... the paper: https://arxiv.org/pdf/2002.10337.pdf The FAST discovery of an Eclipsing Binary Millisecond Pulsar in the Globular Cluster M92 (NGC 6341) ABSTRACT: We report the discovery of an eclipsing binary millisecond pulsar in the globular cluster M92 (NGC6341) with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). PSR J1717+4308A or M92A, has a pulse frequency of 316.5 Hz (3.16 ms) and a dispersion measure of 35.45 pc cm−3 . The pulsar is a member of a binary system with an orbital period of 0.20 days around a low-mass companion which has a median mass of ∼0.18 M⊙. From observations so far, at least two eclipsing events have been observed in each orbit. The longer one lasted for ∼5000 s in the orbital phase range 0.1–0.5. The other lasted for ∼500 s and occurred between 1000–2000 s before or after the longer eclipsing event. The lengths of these two eclipsing events also change. These properties suggest that J1717+4308A is a “red-back” system with a low-mass main sequence or sub-giant companion. Timing observations of the pulsar and further searches of the data for additional pulsars are ongoing.
