# Scintillation kinks, bumps and wiggles in the radio spectrum of the quasar PMN J1106-3647

## TL;DR

This paper presents radio observations of quasar PMN J1106-3647 revealing complex spectral variations caused by interstellar scintillation, highlighting the interplay of refractive and diffractive effects in a compact, mildly boosted synchrotron source.

## Contribution

It provides the first detailed analysis linking spectral features in a quasar to interstellar scintillation effects, distinguishing between refractive and diffractive origins.

## Key findings

- Spectral features include kinks, peaks, and wiggles that vary over short timescales.
- Refractive scintillation likely causes spectral kinks, indicating a sharp boundary in the source.
- Diffractive scintillation may produce wiggles through wave interference.

## Abstract

We report radio observations of the quasar PMN J1106-3647. Our data, taken with the Australia Telescope Compact Array, show large variations in the amplitude and shape of its spectrum, on a short time-scale. A great variety of spectral features is evident, including: sharp kinks; broad spectral peaks; and wiggles. No two spectra are alike. We interpret the variations as interstellar scintillation of a radio source that is compact, but not point-like. Under this interpretation, complex spectral structure can arise purely refractively, under high magnification conditions, or from interference between waves that have been scattered by small-scale density fluctuations (diffractive scintillation). Both effects may be playing a role in J1106-3647, and we tentatively identify kinks with the former, and wiggles with the latter. Diffractive scintillation of AGN is uncommon, as the fringe visibility is low for all but the most compact radio sources. Refractive interpretation of the kink implies that the source has a sharp, concave boundary. Our data are consistent with a mildly boosted synchrotron source, provided the scattering material is at a distance ~50 pc from us.