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Published December 10, 2016 | Published + Submitted
Journal Article Open

Detection of Polarized Quasi-periodic Microstructure Emission in Millisecond Pulsars

Abstract

Microstructure emission, involving short timescale, often quasi-periodic, intensity fluctuations in subpulse emission, is well known in normal period pulsars. In this Letter, we present the first detections of quasi-periodic microstructure emission from millisecond pulsars (MSPs), from Giant Metrewave Radio Telescope observations of two MSPs at 325 and 610 MHz. Similar to the characteristics of microstructure observed in normal period pulsars, we find that these features are often highly polarized and exhibit quasi-periodic behavior on top of broader subpulse emission, with periods of the order of a few μs. By measuring their widths and periodicities from single pulse intensity profiles and their autocorrelation functions, we extend the microstructure timescale–rotation period relationship by more than an order of magnitude down to rotation periods ~5 ms, and find it to be consistent with the relationship derived earlier for normal pulsars. The similarity of behavior is remarkable, given the significantly different physical properties of MSPs and normal period pulsars, and rules out several previous speculations about the possible different characteristics of microstructure in MSP radio emission. We discuss the possible reasons for the non-detection of these features in previous high time resolution MSP studies along with the physical implications of our results, both in terms of a geometric beam sweeping model and temporal modulation model for micropulse production.

Additional Information

© 2016 American Astronomical Society. Received 2016 October 16. Accepted 2016 November 22. Published 2016 December 5. We thank the staff of the GMRT who have made these observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. We would like to thank R. T. Gangadhara for valuable discussions, as well as the anonymous referee for comments that helped significantly improve the paper. K.D. acknowledges support from a fellowship provided by the Kishore Vaigyanik Protsahan Yojana (KVPY) scheme of the Department of Science and Technology, Government of India. Partial support was provided by J. C. Bose Fellowship of Prof. Arnab Rai Choudhuri. This research has made use of NASA's Astrophysics Data System Bibliographic Services.

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Published - De_2016_ApJL_833_L10.pdf

Submitted - 1611.07330v1.pdf

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