HIGH-TIME-RESOLUTION MEASUREMENTS OF THE POLARIZATION OF THE CRAB PULSAR AT 1.38 GHz Article Swipe
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· 2015
· Open Access
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· DOI: https://doi.org/10.1088/0004-637x/799/1/70
· OA: W2022767746
Using the Westerbork Synthesis Radio Telescope (WSRT), we obtained\nhigh-time-resolution measurements of the full (linear and circular)\npolarization of the Crab pulsar. Taken at a resolution of 1/8192 of the 34-ms\npulse period (i.e., $4.1~\\mu{\\rm s}$), the 1.38-GHz linear-polarization\nmeasurements are in general agreement with previous lower-time-resolution\n1.4-GHz measurements of linear polarization in the main pulse (MP), in the\ninterpulse (IP), and in the low-frequency component (LFC). We find the MP and\nIP to be linearly polarized at about $24\\%$ and $21\\%$, with no discernible\ndifference in polarization position angle. However, and contrary to theoretical\nexpectations and measurements in the visible, we find no evidence for\nsignificant variation (sweep) in polarization position angle over the MP, the\nIP, or the LFC. Although, the main pulse exhibits a small but statistically\nsignificant quadratic variation in the degree of linear polarization. We\ndiscuss the implications which appear to be in contradiction to theoretical\nexpectations. In addition, we detect weak circular polarization in the main\npulse and interpulse, and strong ($\\approx 20\\%$) circular polarization in the\nlow-frequency component, which also exhibits very strong ($\\approx 98\\%$)\nlinear polarization at a position angle about $40\\degree$ from that of the MP\nor IP. The pulse-mean polarization properties are consistent with the LFC being\na low-altitude component and the MP and IP being high-altitude caustic\ncomponents. Nevertheless, current models for the MP and IP emission do not\nreadily account for the observed absence of pronounced polarization changes\nacross the pulse. Finally, we measure IP and LFC pulse phases relative to the\nMP that are consistent with recent measurements, which have shown that the\nphases of these pulse components are evolving with time.\n
