A study of the photometric and spectroscopic variations of the prototypical FU Orionis-type star V1057 Cyg

TL;DR

This study presents a decade of photometric and spectroscopic observations of FU Orionis-type star V1057 Cyg, revealing ongoing variability, wind features, and the first detection of certain forbidden emission lines, enhancing understanding of FUor phenomena.

Contribution

It provides the first long-term multi-wavelength monitoring of V1057 Cyg, documenting its variability and spectral features, including new forbidden emission lines.

Findings

Decades-long quasi-periodic brightness variations observed.

Strong wind and shell spectral features detected.

First identification of [S II], [N II], and [O III] lines in V1057 Cyg.

Abstract

Among the low-mass pre-main sequence stars, a small group called FU Orionis-type objects (FUors) are notable for undergoing powerful accretion outbursts. V1057 Cyg, a classical example of an FUor, went into outburst around 1969-1970, after which it faded rapidly, making it the fastest fading FUor known. Around 1995, a more rapid increase in fading occurred. Since that time, strong photometric modulations have been present. We present nearly 10 years of source monitoring at Piszk\'estet\H{o} Observatory, complemented with optical/near-infrared photometry and spectroscopy from the Nordic Optical Telescope, Bohyunsan Optical Astronomy Observatory, Transiting Exoplanet Survey Satellite, and the Stratospheric Observatory for Infrared Astronomy. Our light curves show continuation of significant quasi-periodic variability in brightness over the past decade. Our spectroscopic observations show strong wind features, shell features, and forbidden emission lines. All of these spectral lines vary with time. We also report the first detection of [S II], [N II], and [O III] lines in the star.