SRGA J115215.0-510656: an unusual long-period eclipsing dwarf nova with disc wind signatures

Abstract We present the first detailed optical study of the cataclysmic variable SRGA J115215.0−510656, based on new time-resolved photometric and spectroscopic observations complemented by long-baseline Transiting Exoplanet Survey Satellite (TESS) data. The TESS light curve reveals deep, recurring eclipses consistent with a high-inclination geometry and an orbital period of 0.43567659(9) d. The eclipse morphology during outburst is consistent with a possible ‘inside-out’ type outburst and supports classification of the system as a U Gem–type dwarf nova. By combining eclipse phase width and ellipsoidal modulation, we constrain the system geometry to a narrow locus in the (q, i) plane, with allowed mass ratios 0.28 ≲ q ≲ 0.84 and inclinations i ≃75–84○. The persistence of single-peaked Balmer lines during outburst, together with strong He II 4686 Å emission and a flattened Balmer decrement, points towards emission arising in a disc wind or vertically extended regions above the disc. Absorption features from a late-type secondary star (approximately K3) are detected, contributing roughly 30percnt of the red optical flux. Comparison with main-sequence expectations suggests that the donor star is moderately inflated, consistent with a mildly evolved secondary. With its long orbital period, modest outburst amplitude, and emission-line characteristics, SRGA J115215.0−510656 appears to be a rare and compelling example of a bright, long-period dwarf nova whose optical properties are influenced by disc-wind processes during outburst.