Single-pulse Emission Variation of Two Pulsars Discovered by FAST

We investigate the single-pulse emission variations of two pulsars,PSRs J0211+4235 and J0553+4111,observed with the Five-hundred-meter Aperture Spherical radio Telescope at the 1.25 GHz central frequency.The observation sessions span from 2020 December to 2021 July,with 21 and 22 observations for them respectively.The integrated pulse profile of PSR J0211+4235 shows that there is a weak pulse component following the main component,and PSR J0553+4111 displays a bimodal profile with a bridge component in the middle.PSR J0211+4235 presents significant nulling phenomenon with nulling duration lasting from 2 to 115 pulses and burst duration lasting from 2 to 113 pulses.The NF of each observation is determined to be 45%-55%.No emission greater than threeσis found in the mean integrated profile of all nulling pulses.In most cases,the pulse energy changes abruptly during the transition from null to burst,while in the transition from burst to null there are two trends:abrupt and gradual.We find that the nulling phenomenon of PSR J0211+4235 is periodic by the Fourier transform of the null and burst state.In addition,the single-pulse modulation characteristics of these two pulsars are investigated,and the distributions of modulation index,LRFS and 2DFS are analyzed with PSRSALSA.The left peak of PSR J0553+4111 has intensity modulation.Finally,the polarization properties of these two pulsars are obtained through polarization calibration,and their characteristics are analyzed.The possible physical mechanisms of these phenomena are discussed.

Simultaneous 50cm/10cm Single-pulse Polarization Observations of PSR J0953+0755

We report on simultaneous single-pulse observations of PSR J0953+0755 at 732 and 3100 MHz made using the Parkes 64-m radio telescope at two epochs.Another non-simultaneous 1369 MHz observation has also been analyzed to compare polarization properties of this pulsar at different frequencies.The previously reported lowlevel bridge emission between the interpulse and the main pulse is notably present at 732 MHz.However,the bridge emission becomes very weak or undetectable at higher frequencies.The cross-correlation analysis of simultaneous observations indicates that the total intensity of single pulses is highly correlated,which implies the same emission mechanism is responsible for the two frequencies.We confirm that the abrupt position angle jumps are non-orthogonal in this pulsar which probably result from the overlapping emission from two non-orthogonal polarization modes and the separation between different polarization modes is frequency-dependent.At all three frequencies,the dominant modes are clearly associated with negative values of circular polarization,but the association seems unclear for weak modes.