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We report the observations of FRB 20220912A using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We conducted 17 observations totaling 8.67 hours and detected a total of 1076 bursts with an event rate up to 390 hr$^{-1}$. The cumulative energy distribution can be well described using a broken power-law function with the lower and higher-energy slopes of $-0.38\pm0.02$ and $-2.07\pm0.07$, respectively. We also report the L band ($1-1.5$ GHz) spectral index of the synthetic spectrum of FRB~20220912A bursts, which is $-2.6\pm0.21$. The average rotation measure (RM) value of the bursts from FRB~20220912A is $-0.08\pm5.39\ \rm rad\,m^{-2}$, close to 0 $\rm rad\,m^{-2}$ and maintain relatively stable over two months. Most bursts have nearly 100\% linear polarization. About 45\% of the bursts have circular polarization with SNR $>$ 3, and the highest circular polarization degree can reach 70\%. Our observations suggest that FRB~20220912A is located in a relatively clean local environment with complex circular polarization characteristics. These various behaviors imply that the mechanism of circular polarization of FRBs likely originates from an intrinsic radiation mechanism, such as coherent curvature radiation or inverse Compton scattering inside the magnetosphere of the FRB engine source (e.g. a magnetar)., 15 pages, 11 figures, 2 tables, submitted to ApJ, comments are welcome!

We present the interstellar scintillation analysis of fast radio burst (FRB) 20220912A during its extremely active episode in 2022 using data from the Five-hundred-meter Aperture Spherical Radio Telescope (FAST). We detect a scintillation arc in the FRB's secondary spectrum, which describes the power in terms of the scattered FRB signals' time delay and Doppler shift. The arc indicates that the scintillation is caused by a highly localized region of the ionized interstellar medium (IISM). Our analysis favors a Milky Way origin for the localized scattering medium but cannot rule out a host galaxy origin. We present our method for detecting the scintillation arc, which can be applied generally to sources with irregularly spaced bursts or pulses. These methods could help shed light on the complex interstellar environment surrounding the FRBs and in our Galaxy., Comment: Submitted to SCPMA, 9 pages, 7 figures

Fast radio bursts (FRBs) are highly dispersed millisecond-duration radio bursts,[1,2] of which the physical origin is still not fully understood. FRB 20201124A is one of the most actively repeating FRBs. In this paper, we present the collection of 1863 burst dynamic spectra of FRB 20201124A measured with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The current collection, taken from the observation during the FRB active phase from April to June 2021, is the largest burst sample detected for any FRB so far. The standard PSRFITs format is adopted, including dynamic spectra of the burst, and the time information of the dynamic spectra, in addition, mask files help readers to identify the pulse positions are also provided. The dataset is available in Science Data Bank, with the link https://www.doi.org/10.57760/sciencedb.j00113.00076.

We present the interstellar scintillation analysis of fast radio burst (FRB) 20220912A during its extremely active episode in 2022 using data from the Five-hundred-meter Aperture Spherical Radio Telescope (FAST). We detect a scintillation arc in the FRB's secondary spectrum, which describes the power in terms of the scattered FRB signals' time delay and Doppler shift. The arc indicates that the scintillation is caused by a highly localized region of the ionized interstellar medium (IISM). Our analysis favors a Milky Way origin for the localized scattering medium but cannot rule out a host galaxy origin. We present our method for detecting the scintillation arc, which can be applied generally to sources with irregularly spaced bursts or pulses. These methods could help shed light on the complex interstellar environment surrounding the FRBs and in our Galaxy., Submitted to SCPMA, 9 pages, 7 figures

We have performed radio polarization observation experiments of the stars V772 Her and β Per with the Urumqi 25 m radio telescope at the 6 cm waveband, and obtained light curves of the stars after data processing and calibration. A radio flare from the star V772 Her was detected on 2011 April 13. The degree of linear polarization of this flare is about 30%, and the polarization angle is about 4°. We have detected also the slowly-varying component of the radio radiation from β Per, as well as a short flare superposed on it, which has a very weak linear polarization.

The predictions of the modified gravitational model MOND and the model of dark matter for the earth's gravitational system are examined. We focus on the commonly used MOND models. For the simplest of these models, we present a general expression for the gravitational potential in the case of spherical symmetry, and calculate the predicted angular velocity of a satellite moving in the field. It is found that the angular velocity is different in the different MOND models, that the differences between the predictions of these models and the Newtonian theory are very small, but that the difference in the simplest case ( n = 1) is larger. In the case of the moon, actual measurements with existing techniques can be possibly made for this difference in angular velocity. We have also estimated the influence on the angular velocity of the moon due to the model of dark matter, and found it to be far smaller than the effect of the MOND theory. Therefore, the measurement of this difference in angular velocity may provide a criterion for discriminating the MOND theory and the model of dark matter.

On the basis of the new Galactic rotation curve and constants R 0 and V 0 , and using HII regions, giant molecular clouds and other tracer objects, we have revised the pattern of the Sagittarius-Carina arm of our Galaxy. We have derived its pitch angle to be about 12°, and explored the dependence of the pitch angle on the Galactic constants. The result indicates that with decreasing Galactic constants, the pitch angle increases, and so does the number of spiral arms, according to the symmetric logarithmic arms model. In addition, the halo mass of our Galaxy will decrease with the flattening and downward turn of the rotation curve.

We developed a 1.2 GHz bandwidth spectrometer based on combined complex FFT algorithm for radio astronomy. It resolves the contradiction between wide bandwidth and high speed real-time processing by using the combined complex FFT algorithm. Block-RAMs(BRAMs) in FPGA are saved by parallel processing and module multiplexing, while the computation time also decreases significantly due to symmetry properties of intermediate variables in data processing. Observations at Shanghai Astronomical Observatory for pulsars with the developed spectrometer show that the system works well and meets the requirements of the observation.

We have searched 11 304 quasars from the NVSS catalog for radio emission and obtained 2 626 positive detections, of which 301 are new radio detections. We made statistical studies of the radio spectral index, radio luminosity and the fraction of radio-loud quasars versus absolute B magnitude and redshift. We found that the fraction rises between MB = −22 and −30 and that it increases at z = 0.0 until z = 0.8, then goes down at z = 1.5. The degree of polarization shows no dependence on redshift.

The relative spectra of the leading and the trailing components of 23 conal-double pulsars are measured and investigated. They are in a simple power-law generally and the relative spectral indices are concentrated in a narrow range around zero, which suggests that the leading and trailing components come from the same emission ring. The scatter of the relative spectral indices is probably caused by unsymmetrical location of the components with respect to the center.

We made a periodicity analysis for 3197 quasars in the Veron-Cetty and Veron catalogue with accurate redshifts. The result is that there exist high frequency periodicities in the quasar redshift values in several directions, at a high level of confidence. According to our analysis, these periodicities cannot be all due to selection effects, and the distribution of quasars in space probably contains fluctuations on scales around 50 Mpc.

We discussed the physical background of the unified scaling law in spiral galaxies, and qualitatively obtained the power index of the empirical relation among the luminosity L, radius R and the rotation velocity V. We also discussed the possible causes for the data dispersion on the plane in three-dimensional space of these parameters.