Speaker
Description
The LHAASO “Peanut” is a composite and off-Galactic plane ultra-high-energy gamma-ray source that is among the most intriguing sources released in the 1LHAASO catalogue. The region, which includes a diffuse strip and point-like sources LHAASO J0216+4239, LHAASO J0207+4300, spans nearly five degrees in extension. Currently, there exists no identified multiwavelength counterpart to the Peanut, likely due to both its large extent and the lack of coverage of off-Galactic-plane regions in many existing archives. Diverse models have attempted to describe the Peanut region, such as a “mirage” pulsar wind nebula driven by the nearby millisecond pulsar (PSR J0218+4232), a microquasar outflow from an unidentified central engine, or perhaps a new source class altogether. Although many of these proposed models provide a plausible description of the LHAASO TeV data, the engine and acceleration mechanisms can only be isolated by identifying a multiwavelength counterpart at lower energies or deeply constraining a lack thereof. Imaging Atmospheric Cherenkov Telescopes (IACTs), such as VERITAS, are well-suited to search for this lower energy counterpart due to their large field of view, finer spatial resolution, and overlapping energy range with LHAASO. Here, we present the first IACT results on the Peanut region and its components, including a comprehensive VERITAS spectromorphological analysis of the full Peanut region. In addition, we present a deep study of the putatively associated PSR J0218+4232 at TeV energies and a detailed Fermi-LAT analysis of the Peanut region. We also expand on one-zone leptonic and hadronic spectral modelling of the source using LHAASO, VERITAS and Fermi-LAT data. Together, these analyses supplement the physical interpretations beyond what is possible with LHAASO data alone, in an effort to understand the nature and acceleration mechanisms of this mysterious source and inform the prospects for detection with CTAO.
