Gaia22eor: Symbiotic star V2756 Sgr detected in a deep eclipse

TL;DR

This paper reports the discovery of an eclipse in the symbiotic binary V2756 Sgr, confirmed through multi-survey photometry and spectra, refining its orbital period and revealing its eclipsing nature for the first time.

Contribution

The study provides the first evidence of V2756 Sgr being an eclipsing symbiotic binary and refines its orbital period using combined photometric and spectroscopic data.

Findings

V2756 Sgr exhibits an eclipse caused by the cool giant blocking the hot component.

The orbital period of V2756 Sgr is refined to 725 ± 3 days.

Multi-survey data confirm the eclipse and improve understanding of the system's behavior.

Abstract

V2756 Sgr is a long-known S-type symbiotic binary that was recently detected in $\sim$ 1 mag eclipse-like fading by the Gaia satellite. This behavior was reported as a Gaia Science Alert under the designation Gaia22eor. V2756 Sgr has not been reported as an eclipsing symbiotic system. In this contribution, we have investigated the recent light curves of this target obtained by Gaia and ASAS-SN survey and supplemented these data by the photometry from the ASAS survey and DASCH archive. In addition, low-resolution BP/RP spectra from Gaia were examined. Based on the presented analysis, we conclude that the observed fading is indeed an eclipse of the hot component of V2756 Sgr by the cool giant. The data also allowed us to refine the orbital period to 725 $\pm$ 3 days.