TeV and optical observations of the Be/pulsar binary 1A0535+262 during the 2020 giant outburst

TL;DR

This paper reports on multi-wavelength observations of the Be/pulsar binary 1A0535+262 during its 2020 giant outburst, providing insights into its very high energy gamma-ray and optical variability in an extreme state.

Contribution

It presents the first simultaneous TeV gamma-ray and optical observations of 1A0535+262 during a giant outburst, highlighting the system's extreme activity and potential cosmic ray contributions.

Findings

Detection of TeV gamma-ray emission during the outburst

Observation of rapid optical variability correlated with gamma-ray activity

Enhanced understanding of microquasar emission mechanisms

Abstract

1A 0535+262 is a Be X-ray binary pulsar and one of the only galactic pulsar systems to show radio jet emission. Characterizing the very high energy emission (VHE, >100 GeV) in these extreme microquasars is critical to understanding their contribution to the origin of galactic cosmic rays. The 2020 giant outburst of this system, where X-ray fluxes exceeded 12 Crab, marked a rare opportunity to investigate the gamma-ray and rapid optical variability of these transient systems while in such an extreme state. This month of activity marked the brightest flare measured in this system. VERITAS's developing optical capabilities in tandem with the ability to measure TeV gamma rays allowed for a unique campaign to be undertaken. VERITAS's observations of this system during the outburst will be presented in the context of observations at lower energies and previous observations of this system by imaging atmospheric Cherenkov telescopes.