📝 SummarXiv

Abstract

We present new Very Long Baseline Array (VLBA) imaging of a MHz-peaked spectrum (MPS) source that was found using commensal low-frequency data taken with the Karl G. Jansky Very Large Array (VLA). The source, J0330-2730, was identified in multi-epoch data from the VLA Low-band Ionosphere and Transient Experiment (VLITE). VLITE continuously collects low-frequency data at 340 MHz during regular VLA observations. Our analysis of the VLITE light curve demonstrates that J0330-2730 has significant 340 MHz flux variability at the ~20% level over a timescale of approximately one year. Our VLBA images reveal a resolved, double-lobed morphology with a projected linear size of 64 pc. We consider plausible mechanisms that could explain the observed 340 MHz variability and the source properties on milliarcsecond scales. We rule-out variable Doppler boosting and conclude that refractive interstellar scintillation or variable free-free absorption are the most likely explanations. We argue that the properties of J0330-2730 are consistent with the class of compact symmetric objects (CSOs) and consider the evolutionary stage of the source. The extent of the resolved lobes revealed by the VLBA is significantly smaller than predictions based on the turnover-size relation for a standard synchrotron self-absorbed jet model. We discuss possible explanations for the departure from the turnover-size relation, including jet formation by a transient phenomenon such as a tidal disruption event or a "frustrated jet" impeded by the presence of dense gas or a high-pressure environment. This study highlights the potential of VLITE for the identification of compact and young radio sources.