The Detailed Light Curve Evolution of V1674 Her (Nova Her 2021)

TL;DR

This paper presents high-cadence photometry of the ultra-fast nova V1674 Her, revealing a previously unobserved plateau in its light curve significantly below maximum brightness, providing new insights into nova evolution.

Contribution

It reports the first detection of a plateau in the light curve of a nova well below peak brightness, expanding understanding of nova light curve features.

Findings

Detection of a plateau at $g ext{~}14$ mag, 8 mag below peak.

Observation of a pre-maximum halt lasting at least three hours.

First observation of such a feature in an ultra-fast nova.

Abstract

We report high-cadence photometry of the ultra-fast ($t_2\sim1.2$ d) nova V1674 Her during its rise to maximum light ($V\sim6.3$) and the beginning of its subsequent decline. These observations from Evryscope and the Mount Laguna Observatory All-Sky Camera reveal a plateau in the pre-maximum light curve at $g\sim14$ ($\sim$8 mag below peak) that lasted for at least three hours. Similar features (so-called pre-maximum halts) have been observed in some novae near maximum light, but to our knowledge the detection of a plateau in the light curve $\sim$8 mag below peak is unprecedented.