Blending-induced beating and emission in the symbiotic star Terz V 2513

ABSTRACT We present a detailed analysis of Terz V 2513 (=2MASS J17334728-2719266), a poorly studied symbiotic star. Our motivation was a peculiar beating pattern in its light curves from all-sky surveys and our own observations. Using Gaia DR3 and OGLE-IV photometry, we show that this variability arises from blending with a nearby, unrelated Mira variable (Gaia DR3 406134544052580377 = OGLE-BLG-LPV-241930). Analysis of VPHAS+ and Pan-STARRS imaging, combined with optical and infrared spectroscopy from the Southern African Large Telescope and ESO New Technology Telescope, further reveals that the symbiotic star has been misidentified in the literature. We identify the correct counterpart as Gaia DR3 4061345440488592896 (=OGLE-BLG-LPV-241932), a Mira with a 161-d period. Its infrared spectrum displays prominent emission lines and is remarkably similar to those of other symbiotic Miras. Based on our data and previous studies, Terz V 2513 likely experienced a symbiotic nova outburst in the past. This study highlights the importance of careful analysis of survey light curves in crowded fields and demonstrates how combining multiwavelength photometry, spectroscopy, and high-precision Gaia data can disentangle blended sources and accurately determine their nature.