The FUor star V2493 Cyg (HBC 722) -- eleven years at maximum brightness

TL;DR

This study monitors the FUor star V2493 Cyg over eleven years, revealing unique photometric stability at maximum brightness and a distinct periodicity, offering new insights into FUor star behavior and circumstellar dust structures.

Contribution

It provides the first long-term optical photometric data of V2493 Cyg at maximum brightness, highlighting its atypical stability and periodicity among FUor stars.

Findings

V2493 Cyg remained at maximum brightness from 2013 to 2021.

Detected a periodicity of approximately 914 days.

Star's brightness variations are smaller and more stable than typical FUors.

Abstract

At the time of stellar evolution, young stellar objects go through processes of increased activity and instability. Star formation takes place in several stages during which the star accumulates enough mass to initiate thermonuclear reactions in the nucleus. A significant percentage of the mass of Sun-like stars accumulates during periods of increased accretion known as FUor outbursts. Since we know only about two dozen stars of this type, the study of each new object is very important for our knowledge. In this paper, we present data from photometric monitoring on a FUor object V2493 Cyg discovered in 2010. Our data were obtained in the optical region with BVRI Johnson-Cousins set of filters during the period from November 2016 to February 2021. The results of our observations show that during this period no significant changes in the brightness of the star were registered. We only detect variations with a small amplitude around the maximum brightness value. Thus, since 2013 V2493 Cyg remains at its maximum brightness, without a decrease in brightness. Such photometric behavior is not typical of other stars from FUor type. Usually the light curves of FUors are asymmetrical, with a very rapid rise and gradual decline of the brightness. V2493 Cyg remains unique in this respect with a very rapid rise in brightness and prolonged retention in maximum light. Our period analysis made for the interval February 2013 - February 2021 reveals a well-defined period of 914+/-10 days. Such periodicity can be explained by dust structures remaining from star formation in orbit around the star.