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arXiv · 2604.26702

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

Nikita Rawat·David A. H. Buckley·John R. Thorstensen·Christian Knigge·Yusuke Tampo·Stephen B. Potter·Anupam Bhardwaj·Simone Scaringi·Ilya A. Mereminskiy·Jeewan C. Pandey·Srinivas M Rao·Alexander A. Lutovinov
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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 $0.28 \lesssim q \lesssim 0.84$ and inclinations $i$ $\simeq$75$-$84$^{\circ}$. The persistence of single-peaked Balmer lines during outburst, together with strong He II emission and a flattened Balmer decrement, points towards emission arising in a disc wind or vertically extended regions above the disc. Absorption features from a late-type secondary star (approximately K3) are detected, contributing roughly 30 per cent of the red optical flux. Comparison with main-sequence expectations suggests that the donor star is moderately inflated, consistent with a mildly evolved secondary. With its long orbital period, modest outburst amplitude, and emission-line characteristics, SRGA J115215.0$-$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.

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Nikita Rawat, David A. H. Buckley, John R. Thorstensen, Christian Knigge, Yusuke Tampo, Stephen B. Potter, Anupam Bhardwaj, Simone Scaringi, Ilya A. Mereminskiy, Jeewan C. Pandey, Srinivas M Rao, Alexander A. Lutovinov. 2026-04-29. SRGA J115215.0$-$510656: an unusual long-period eclipsing dwarf nova with disc wind signatures. https://arxiv.org/abs/2604.26702

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