FAST Detected A Transient Periodic Signal In The Direction of LS I +61 303
ATel #14297; Shan-Shan Weng* (NJNU), ZhiChen Pan* (NAOC), Lei Qian* (NAOC), Peng Jiang (NAOC), Ming-Yu Ge (IHEP), Jing-Zhi Yan (PMO), Qing-Zhong Liu (PMO)
on 1 Jan 2021; 00:00 UT
Credential Certification: Shan-Shan Weng (wengss@ihep.ac.cn)
Subjects: Radio, Gamma Ray, Binary, Neutron Star, Pulsar
The gamma-ray binary, LS I +61 303 contains a rapid rotating B0 Ve star and a compact object with unknown nature. The Five-hundred-meter Aperture Spherical radio Telescope (FAST, Nan et al. 2011, IJMPD, 20, 989; Jiang et al. 2019, SCPMA, 62, 959502) observed it for four times on 2019-11-02, 2020-01-07, 2020-09-02, and 2020-09-03, corresponding to the orbital phases of 0.07, 0.59, 0.58, and 0.62 (Aragona et al. 2009, ApJ, 698, 514). Observations with the 19-beam receiver covering 1.05-1.45 GHz lasted for 2-3 hours on average. We detected a periodic signal (20.8 sigma) with a period of 269.196 ms and a Dispersion Measure (DM) of 241 pc cm-3 in the data obtained on 2020-01-07. The slightly detectable acceleration of the signal might be the hint of a binary system. We adopted a DM range of 0-500 pc cm-3 but did not find any signal in any other data. As it is reported that a magnetar-like short burst was detected in the direction of LS I +61 303 (Torres et al. 2012, ApJ, 744, 106); therefore, this may indicate a strongly magnetized neutron star in the system. More FAST observations will be proposed to unveil the nature of LS I +61 303, and detailed data analysis will be reported later. FAST is a Chinese national mega-science facility, operated by National Astronomical Observatories, Chinese Academy of Sciences. We appreciate the FAST group for their support and assistance during the observations.
