Long-Term Monitoring of Pulsar Scintillation with the ATA (and How It Applies to SETI)

Changes in a pulsar's scintillation characteristics over time can be used as a diagnostic for many physical effects, e.g., tracking changes in the interstellar medium. Monitoring the scintillation bandwidth can additionally be used to correct timing delays in pulse arrival times, which could be a significant source of error for precision pulsar timing projects. Scintillation can also be useful to SETI for differentiating candidate detections from RFI, as scintillation is a characteristic of point-source signals that have traveled long distances through the interstellar medium. To better understand the magnitude and trend of scintillation bandwidth changes over long timescales (months--years), we performed long-term monitoring of pulsar J0332+5434 with the Allen Telescope Array from 899.75 to 1955.75 MHz. In total, we collected over 300 observations of J0332+5434 over the course of 7 months, with observations taken daily to weekly. We find a mean of 3.52 MHz (0.063 μs) with standard deviation 0.19 MHz (0.003 μs) at reference frequency 1187.75 MHz and a mean of 17.73 MHz (0.023 μs) with standard deviation 1.69 MHz (0.002 μs) at reference frequency 1763.75 MHz. These bandwidth measurements are only ~65% of the NE2001 predictions, and they vary significantly over time with a possible periodicity of ~200 days. The Kolmogorov scaling index is also investigated and a new method developed, though no time-dependence was found. We recommend that pulsar timing arrays implement corrections for these variations as pulse arrival time measurements become more precise.