A millisecond pulsar discovery in a survey of unidentified Fermi $\gamma$-ray sources with LOFAR

Abstract

Using LOFAR, we have performed a very-low-frequency (115-155 MHz) radio survey for millisecond pulsars (MSPs). The survey targeted 52 unidentified Fermi $\gamma$-ray sources. Employing a combination of coherent and incoherent dedispersion, we have mitigated the dispersive effects of the interstellar medium while maintaining sensitivity to fast-spinning pulsars. Toward 3FGL J1553.1+5437 we have found PSR J1552+5437, the first MSP to be discovered (through its pulsations) at a radio frequency $<$ 200 MHz. PSR J1552+5437 is an isolated MSP with a 2.43 ms spin period and a dispersion measure of 22.9 pc cm${}^{-3}$. The pulsar has a very steep radio spectral index ($\alpha <-$2.8 $\pm$ 0.4). We obtain a phase-connected timing solution combining the 0.74 years of radio observations with $\gamma$-ray photon arrival times covering 7.5 years of Fermi observations. We find that the radio and $\gamma$-ray pulse profiles of PSR J1552+5437 appear to be nearly aligned. The very steep spectrum of PSR J1552+5437, along with other recent discoveries, hints at a population of radio MSPs that have been missed in surveys using higher observing frequencies. Detecting such steep spectrum sources is important for mapping the population of MSPs down to the shortest spin periods, understanding their emission in comparison to slow pulsars, and quantifying the prospects for future surveys with low-frequency radio telescopes like SKA-Low and its precursors.

10 pages, 4 figures, published in ApJL

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• LOFAR discovery of the fastest-spinning millisecond pulsar in the Galactic field
• NICER X-ray Observations of Seven Nearby Rotation-Powered Millisecond Pulsars
• The TRAPUM L-band survey for pulsars in Fermi-LAT gamma-ray sources
• Extending the Event-weighted Pulsation Search to Very Faint Gamma-ray Sources
• The Green Bank North Celestial Cap Survey. VII. 12 New Pulsar Timing Solutions
• Searching for pulsars associated with polarised point sources using LOFAR: Initial discoveries from the TULIPP project
• Exploring the Key Features of Repeating Fast Radio Bursts with Machine Learning
• The LOFAR Two-metre Sky Survey: Deep Fields Data Release 2. I. The ELAIS-N1 field
• A 350-MHz Green Bank Telescope Survey of Unassociated Fermi LAT Sources: Discovery and Timing of Ten Millisecond Pulsars
• 1RXH J082623.6-505741: a new long-period cataclysmic variable with an evolved donor and a low mass transfer rate
• Relativistic scattering of a fast spinning neutron star by a massive black hole
• Fourier-domain dedispersion
• Radio Millisecond pulsars