Interstellar interferometry: precise curvature measurement from pulsar secondary spectra

Abstract

The parabolic structure of the secondary or conjugate spectra of pulsars is often the result of isolated one-dimensional (or at least highly anisotropic) lenses in the ISM. The curvature of these features contains information about the velocities of the Earth, ISM, and pulsar along the primary axis of the lens. As a result, measuring variations in the curvature over the course of a year, or the orbital period for pulsars in binaries, can constrain properties of the screen and pulsar. In particular the pulsar distance and orbital inclination for binary systems can be found for multiple screens or systems with prior information on sin (i). By mapping the conjugate spectra into a space where the main arc and inverted arclets are straight lines, we are able to make use of the full information content from the inverted arclet curvatures, amplitudes, and phases using eigenvectors to uniquely and optimally retrieve phase information. This allows for a higher precision measurement than the standard Hough transform for systems where these features are available. Our technique also directly yields the best fit 1D impulse response function for the interstellar lens given in terms of the Doppler shift, time delay, and magnification of images on the sky as seen from a single observatory. This can be extended for use in holographic imaging of the lens by combining multiple telescopes. We present examples of this new method for both simulated data and actual observations of PSR B0834+06.

A Scintillation Arc Survey of 22 Pulsars with Low to Moderate Dispersion Measures

“…Note that our weighting is the same as the Jacobian of the transformation to "normalized Doppler profiles" as used in curvature estimation by Reardon et al (2020), which does not assume one-dimensional scattering. It differs from the theta-theta mapping method of Baker et al (2022), which is based on one-dimensional scattering.…”

“…Much of this work was inspired by the remarkable interferometric study of PSR B0834+06 by Brisken et al (2010), and work on interstellar holography (Walker & Stinebring 2005;Walker et al 2008) laid important groundwork, too. Among other highlights in this scintillometry effort are several studies of binary pulsars (Rickett et al 2014;Main et al 2020;Mall et al 2022), the detection of scattering from a supernova remnant around a pulsar (Yao et al 2021), the location of multiple scattering screens toward nearby pulsars (Chen et al 2022;McKee et al 2022), and important new theoretical work (Simard et al 2019a(Simard et al , 2019bSprenger et al 2021;Shi & Xu 2021;Baker et al 2022).…”

A Scintillation Arc Survey of 22 Pulsars with Low to Moderate Dispersion Measures

“…Much of this work was inspired by the remarkable interferometric study of PSR B0834+06 by Brisken et al (2010), and work on interstellar holography (Walker & Stinebring 2005;Walker et al 2008) laid important groundwork, too. Among other highlights in this scintillometry effort are several studies of binary pulsars (Rickett et al 2014;Main et al 2020;Mall et al 2022), the detection of scattering from a supernova remnant around a pulsar (Yao et al 2021), the location of multiple scattering screens toward nearby pulsars (Chen et al 2022;McKee et al 2022), and important new theoretical work (Simard et al 2019a,b;Sprenger et al 2021;Shi & Xu 2021;Baker et al 2022).…”

Double-lens Scintillometry: The variable scintillation of pulsar B1508+55

“…5. However, we found that the method of finding the curvature belonging to the strongest possible eigenvector as described in Baker et al (2022) deviated systematically from measurements done with the manual method described above. This deviation is strongest when the secondary spectra show reappearing stripes in addition to the arclets.…”