VERITAS Observations of 1ES 1218+304 during the 2019 VHE High State

TL;DR

This paper reports VERITAS observations of the blazar 1ES 1218+304 during a high flux state in January 2019, highlighting multiwavelength activity and the importance of targeted monitoring during elevated states.

Contribution

It presents the first detailed VERITAS observations of 1ES 1218+304 during an elevated VHE flux state, contributing to blazar variability studies.

Findings

VERITAS detected elevated VHE gamma-ray flux in January 2019.

Multiwavelength observations confirmed increased activity across X-ray and optical bands.

The campaign demonstrates the effectiveness of targeted observations during high states.

Abstract

1ES 1218+304 is a moderate-redshift (z = 0.182) high-frequency-peaked BL Lac object (HBL). Detected by both the MAGIC and VERITAS gamma-ray observatories, 1ES 1218+304 is frequently monitored by VERITAS as part of its long-term blazar monitoring program. On the 3rd of January 2019, during a regularly scheduled blazar snapshot, VERITAS observed 1ES 1218+304 to have an elevated VHE flux state which continued through January 5 (ATEL #12360). In addition to VERITAS observations, MAGIC also detected elevated VHE emission (ATEL #12354) and Swift-BAT/XRT and Tuorla observations, in X-ray and optical respectively, showed increased multiwavelength activity at the time of the VERITAS observations. In this work, VERITAS observations of 1ES 1218+304 taken as part of a target of opportunity campaign during this elevated state, are presented.