Millisecond Pulsar Scintillation Studies with LOFAR: Initial Results

Abstract

High-precision timing of millisecond pulsars (MSPs) over years to decades is a promising technique for direct detection of gravitational waves at nanohertz frequencies. Time-variable, multi-path scattering in the interstellar medium is a significant source of noise for this detector, particularly as timing precision approaches 10 ns or better for MSPs in the pulsar timing array. For many MSPs the scattering delay above 1 GHz is at the limit of detectability; therefore, we study it at lower frequencies. Using the LOFAR (LOw-Frequency ARray) radio telescope we have analyzed short (5-20 min) observations of three MSPs in order to estimate the scattering delay at 110-190 MHz, where the number of scintles is large and, hence, the statistical uncertainty in the scattering delay is small. We used cyclic spectroscopy, still relatively novel in radio astronomy, on baseband-sampled data to achieve unprecedented frequency resolution while retaining adequate pulse phase resolution. We detected scintillation structure in the spectra of the MSPs PSR B1257+12, PSR J1810+1744, and PSR J2317+1439 with diffractive bandwidths of $6\pm 3$, $2.0\pm 0.3$, and $\sim 7$ kHz, respectively, where the estimate for PSR J2317+1439 is reliable to about a factor of 2. For the brightest of the three pulsars, PSR J1810+1744, we found that the diffractive bandwidth has a power-law behavior $\Delta {\nu }_d\propto {\nu }^{\alpha }$, where $\nu$ is the observing frequency and $\alpha =4.5\pm 0.5$, consistent with a Kolmogorov inhomogeneity spectrum. We conclude that this technique holds promise for monitoring the scattering delay of MSPs with LOFAR and other high-sensitivity, low-frequency arrays like SKA-Low.

Accepted to ApJL

References in corpus (16)

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Cited by in corpus (19)

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• The NANOGrav 15-Year Data Set: Detector Characterization and Noise Budget
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• Wide-Band, Low-Frequency Pulse Profiles of 100 Radio Pulsars with LOFAR
• The High Time and Frequency Resolution Capabilities of the Murchison Widefield Array
• The Low-Frequency Radio Eclipses of the Black Widow Pulsar J1810+1744
• Scintillation arcs in low-frequency observations of the timing-array millisecond pulsar J0437-4715
• A 24-Hour Global Campaign To Assess Precision Timing of the Millisecond Pulsar J1713+0747
• Searching for pulsars associated with polarised point sources using LOFAR: Initial discoveries from the TULIPP project
• The NANOGrav 12.5-Year Data Set: Monitoring Interstellar Scattering Delays
• Parameter estimation of a two-component neutron star model with spin wandering
• Long-term evolution of anomalous X-ray pulsars and soft gamma repeaters
• Deconvolving Pulsar Signals with Cyclic Spectroscopy: A Systematic Evaluation
• Scattering Delay Mitigation in High Accuracy Pulsar Timing: Cyclic Spectroscopy Techniques
• A Cyclic Spectroscopy Scintillation Study of PSR B1937+21 I. Demonstration of Improved Scintillometry
• Interstellar Medium Mitigation Techniques in Pulsar Timing Arrays
• Noise Budget and Interstellar Medium Mitigation Advances in the NANOGrav Pulsar Timing Array
• Identifying pulsar candidates in interferometric radio images using scintillation