EP J194531.8-612009 is a periodic source in optical wavelengths

ATel #17930; N. Palivanas (UNIVAP, Brazil), G. J. M. Luna (Conicet/UNAHUR, Argentina), I. J. Lima (UNESP, Brazil), C. V. Rodrigues (INPE, Brazil), A. S. Oliveira (UNIVAP, Brazil), D. C. Souza (UNIVAP, Brazil)
on 29 Jul 2026; 19:53 UT
Credential Certification: Isabel de Jesus Lima (isabellima01@gmail.com)

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We report the detection of a photometric period derived from TESS observations of Gaia DR3 6442291862707764096 / MASTER OT J194531.90-612009.5 / EP J194531.8-612009. This source was recently identified as a X-ray transient by X. H. Tang et al. (ATel #17926) and earlier reported by P. Balanutsa et al. (ATel #8036) and by Gaia Collaboration, 2022 as a cataclysmic variable candidate. Our analysis is based on eight TESS sectors (13; 27; 67; 94; 101 - 104), including both SPOC and FFI data products. Lomb-Scargle periodograms exhibit a strong peak at 1.897 h present in 6 out of 8 sectors and in the combined light curve as well. The period is not present in sectors 94 and 101. The TESS_localize algorithm (Higgins M. E., Bell K. J., 2023, AJ, 165, 141) provides a highly significant probability that the periodic signal comes from Gaia DR3 6442291862707764096. If this period corresponds to the orbital motion of the system, this CV is below the period gap. In addition, the modulation observed in the light curves is consistent with a non-eclipsing system. Additional optical observations are necessary to determine the nature of this periodicity.