EP J194531.8-612009: a new magnetic cataclysmic variable

ATel #17933; N. Palivanas (UNIVAP, Brazil), G. J. M. Luna (Conicet/UNAHUR, Argentina), E. Martioli (LNA, Brazil), L. Almeida (INPE, Brazil), C. V. Rodrigues (INPE, Brazil), I. J. Lima (UNESP, Brazil), D. C. Souza (UNIVAP, Brazil), A. S. Oliveira (UNIVAP, Brazil), F. J. Jablonski (INPE, Brazil), K. M. G. Silva (Gemini Observatory, Chile), A. C. Moreira João (INPE, Brazil), C. Silva (UFC, Brazil)
on 1 Aug 2026; 01:24 UT
Credential Certification: Claudia V Rodrigues. (claudiavilega@gmail.com)

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EP J194531.8-612009 was previously reported by X. H. Tang et al. (ATel #17926) and P. Balanutsa et al. (ATel #8036) as an X-ray transient and a cataclysmic variable candidate. TESS photometry revealed a strong periodicity at 1.897 h (ATel #17930, N. Palivanas et al.), raising the possibility that the source is a cataclysmic variable below the period gap. Here we report observations that confirm that this source is a magnetic cataclysmic variable. We obtained simultaneous polarimetric time series in the g, r, i, and z bands using the 1.60m Perkin-Elmer telescope and the SPARC4 instrument at the Pico dos Dias Observatory (managed by Laboratorio Nacional de Astrofisica, Brazil), on July 29, 2026. The data were collected over approximately 5 hours, with exposure times of 100 and 200 s. They reveal periodic modulation of the total flux and circular polarization in all bands. The period is similar to that present in TESS observations, but more data and a proper analysis are necessary for a good period estimate. The polarization is always negative, reaching maximum values between 10% and 20%, with the modulation being more pronounced in the r and i bands. These results suggest that EP J194531.8-612009 is a magnetic cataclysmic variable of the polar type, displaying a single active accretion region. This allows us to interpret the period as the spin period of the white dwarf, which rotates synchronously to the orbital motion. The transient nature of the system could be related to the high and low brightness states of this class of interacting binaries. A thorough analysis of this source will be presented in a paper in preparation.