Optical spectroscopic and photometric classification of the X-ray transient EP240309a (EP J115415.8-501810) as an intermediate polar
Scaringi, S.; Monageng, I. M.; Buckley, David A. H.; Potter, Stephen B.; Julie, R. P. M.; Chandra, Sunil; Worters, H. L.; Charles, Philip A.; Egbo, Okwudili D.; Erasmus, N.; van Gend, Carel; Loubser, Egan; Titus, Keegan; Rosie, Kathryn; Gajjar, Hitesh; Hlakola, Moloko
South Africa, United States, United Kingdom
Abstract
We report on optical follow-up observations of an X-ray source initially detected by the Einstein Probe mission. Our investigations categorize the source as an intermediate polar, a class of magnetic cataclysmic variables, exhibiting an orbital period of 3.7614(4) h and a white dwarf spin period of 3.97 min. The orbital period was identified through TESS observations, while our high-speed photometric data, obtained using the 1.9m and Lesedi 1.0m telescopes at the South African Astronomical Observatory, revealed both the spin and beat periods. Additionally, we present orbitally phase-resolved spectroscopic observations using the 1.9m telescope, specifically centred on the H β emission line, which reveal two emission components that exhibit Doppler variations throughout the orbital cycle.