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As of February 2022, over 4900 exoplanets have been confirmed. In this study, we conducted statistical analyses on both the exoplanets and their host stars' parameters. Our findings suggest that the radius and true mass distribution of the exoplanets remain largely unchanged compared to prior research. However, we observed a correlation between the average eccentricity and the number of planets in a system, and fluctuations in the "size" of the planets may contribute to such variation. Moreover, we discovered that, among planets with precise measurements of radius, true mass, and semi-major axis, the true mass-radius relationship follows a power–law distribution. Interestingly, the power–law index tends to decrease from super-Earths to cold Jupiters, potentially due to atmospheric composition. We also revised the radius valley, and determined that M-type host stars with low mass and metal abundance exhibit high planetary ownership rates or harbor large-mass planets, suggesting a different planet formation mechanism than GK-type stars. Lastly, we assessed the possibility of detecting exoplanets using FAST and found that there are three planets in FAST sky that may be detected, namely CoRoT-3 b, GPX-1 b, and TOI-2109 b. [ABSTRACT FROM AUTHOR]

The unprecedented sensitivity provided by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) could shed light on studies of the magnetic field and plasma properties of brown dwarfs by catching polarized radio flares. With the FAST L-band 19-beam receiver, we observe a nearby dwarf stellar system 2MASSW J0746425 + 200032 which has been reported to show 4.86 GHz and 8.46 GHz radio flare emission. The L-band radio signals from the target are searched in both total intensity and circular polarization during the entire 147 min tracking observation. No radio flare down to a sensitivity of ∼13 mJy and ∼2 mJy (5 σ) in Stokes I and V can be identified. The non-detection may lie in the intrinsic physical condition of the stellar system, e.g., the magnetic field strength and the electron density distribution and/or the sampling rate, which should be higher to reveal the sub-second structures but are smeared out with a lower rate in our observations. [ABSTRACT FROM AUTHOR]

Radio radiation has been detected across the Hertzsprung Russell diagram. We selected three objects with radio radiation (a semi-detached eclipsing binary V Crt, and two detached binaries WY Cnc and CG Cyg) that show magnetic activity. We made new photometric observations using a SARA 60 cm and NAOC 85 cm optical telescopes. Then, we obtained their orbital and starspot parameters by analyzing our light curves and published radial velocities using the updated Wilson-Devinney program. We revised the ephemeris information for V Crt and WY Cnc by analyzing the orbital minimum times. The orbital periods increased by 2.8 ( ± 2.1 ) × 10 − 9 d yr − 1 for V Crt, which maybe caused by mass transfer. The orbital periods decreased by −8.641 ( ± 0.004 ) × 10 − 8 d yr − 1 for WY Cnc. Orbital period change for CG Cyg was also found and we used a third-body of M 3 of 0.14 M ⊙ and a period of approximately 59.20 (0.36) yr to explain that. We also analysed the possible second period oscillation of CG Cyg with a cycle about 18.31 (0.06) yr. The long period changes of WY Cnc and CG Cyg might be caused by magnetic activity or stellar wind, rather than mass transfer. [ABSTRACT FROM AUTHOR]

Radio emission has been detected for all types of stars in the Hertzsprung Russell diagram. Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) low and medium-resolution spectroscopic surveys provide a good opportunity to obtain the spectroscopic properties of radio stars. We cross-matched big data from the LAMOST DR7 low resolution spectral survey with a catalogue of radio stars, and obtained 449 stellar spectra of 258 stars. We detected 185 spectra with H α emission. There are a total of 108 objects with repeated low resolution spectral observations, of which 63 show variations in the H α line over a long time, about several months. We cross-matched LAMOST DR7 medium resolution spectra with the radio star catalogue. We obtained 1319 LAMOST medium-resolution spectra of the 156 radio stars and then calculated their equivalent widths ( E W s ) of the H α line. Among them, 93 radio stars with H α emission were found from the LAMOST medium resolution spectra, and 63 objects showed short and long-term variabilities, especially on a short time scale of approximately 20 min. Finally, we estimated the minimal detectable radio flux of the FAST telescope and provided a scientific plan for studying radio stars. [ABSTRACT FROM AUTHOR]