Abstract
We use cyclic spectroscopy to perform high frequency-resolution analyses of
multi-hour baseband Arecibo observations of the millisecond pulsar PSR
B1937+21. This technique allows for the examination of scintillation features
in far greater detail than is otherwise possible under most pulsar timing array
observing setups. We measure scintillation bandwidths and timescales in each of
eight subbands across a 200 MHz observing band in each observation. Through
these measurements we obtain robust, intra-epoch estimates of the frequency
scalings for scintillation bandwidth and timescale. Thanks to our high
frequency resolution and the narrow scintles of this pulsar, we resolve
scintillation arcs in the secondary spectra due to the increased Nyquist limit,
which would not have been resolved at the same observing frequency with a
traditional filterbank spectrum using NANOGrav's current time and frequency
resolutions, and the frequency-dependent evolution of scintillation arc
features within individual observations. We observe the dimming of prominent
arc features at higher frequencies, possibly due to a combination of decreasing
flux density and undetermined effects due to the interstellar medium. We also
find agreement with arc curvature frequency dependence predicted by Stinebring
et al. (2001) in some epochs. Thanks to the frequency resolution improvement
provided by cyclic spectroscopy, these results show strong promise for future
such analyses with millisecond pulsars, particularly for pulsar timing arrays,
where such techniques can allow for detailed studies of the interstellar medium
in highly scattered pulsars without sacrificing the timing resolution that is
crucial to their gravitational wave detection efforts.