The Frequency-dependent Modulation Features of PSR J1948+3540

TL;DR

This study investigates the frequency-dependent intensity modulation features of pulsar PSR J1948+3540 using multi-wavelength observations, revealing a novel phenomenon where the dominant modulation component varies with frequency, challenging existing theories.

Contribution

The paper reports the first observation of a frequency-dependent change in the dominant modulation component of a pulsar's intensity, providing new insights into pulsar emission behaviors.

Findings

Modulation frequency and period are time-dependent.

Dominant modulation component varies with observing frequency.

Spectral and polarization analyses show complex component behaviors.

Abstract

Using observations from GMRT and FAST, we conducted multi-wavelength studies on PSR J1948+3540 and analyzed its intensity modulation characteristics in detail. We found that the intensity modulation of this pulsar exhibits broad low-frequency modulation features. The modulation frequency/period is time-dependent, but the dominant modulation component varies with the observing frequency. Specifically, at low frequencies, the modulation is dominated by the first half of the middle component, while at high frequencies, it is dominated by the second half of the middle component. Spectral analysis revealed that the intensities of the leading and trailing components vary with the observing frequency, but the middle component does not change significantly. Besides, the polarization analyses reveal that the peak of the radiation intensity is located in the latter half of the middle component, whereas the linear polarization is dominant in the former half. However, due to the low degree of linear polarization, the change of the dominant modulation component with the observed frequency is not caused by the variation in linear polarization. The phenomenon of the dominant modulation component varying with observing frequency has not been reported before and remains difficult to understand within the current theoretical framework.