Optical photometry of GM Cep: evidence for UXor type of variability

TL;DR

This study presents optical photometry of GM Cep over 2.5 years, revealing large amplitude variability, deep minima, and color reversal, indicating a combination of accretion activity and dust occultation typical of UXor and T Tauri stars.

Contribution

It provides detailed multi-band photometric data and analysis of GM Cep, demonstrating the coexistence of UXor-like and T Tauri variability mechanisms in a pre-main sequence star.

Findings

High amplitude brightness variations (~2.3 mag) observed.

Deep minima with color reversal typical of UX Ori variables.

Variability caused by accretion and circumstellar dust occultation.

Abstract

Results from optical photometric observations of the pre-main sequence star GM Cep are reported in the paper. The star is located in the field of the young open cluster Trumpler 37 - a region of active star formation. GM Cep shows a large amplitude rapid variability interpreted as a possible outburst from EXor type in previous studies. Our data from BVRI CCD photometric observations of the star are collected from June 2008 to February 2011 in Rozhen observatory (Bulgaria) and Skinakas observatory (Crete, Greece). A sequence of sixteen comparison stars in the field of GM Cep was calibrated in the BVRI bands. Our photometric data for a 2.5 years period show a high amplitude variations (Delta V ~ 2.3m) and two deep minimums in brightness are observed. The analysis of collected multicolor photometric data shows the typical of UX Ori variables a color reversal during the minimums in brightness. On the other hand, high amplitude rapid variations in brightness typical for the Classical T Tauri stars also present on the light curve of GM Cep. Comparing our results with results published in the literature, we conclude that changes in brightness are caused by superposition of both: (1) magnetically channeled accretion from the circumstellar disk, and (2) occultation from circumstellar clouds of dust or from features of a circumstellar disk.