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A research team led by Ph.D. candidate Wang Haozhi under the supervision of Prof. Ali Esamdin at the Xinjiang Astronomical Observatory (XAO) of the Chinese Academy of Sciences (CAS) has revealed the genuine source of the pulsating star KOI-1755 transit signal using the Kepler space telescope. Their are published in The Astronomical Journal.

Although KOI-1755 shows periodic dimming in Kepler photometric data, the true origin of this signal had long been uncertain. By analyzing Kepler's Target Pixel Files (TPFs), the researchers revealed that the signal actually originates from a background eclipsing binary star system located to the left of KOI-1755.

To reach this conclusion, they applied pixel-level photometric modeling, centroid-shift measurements, and cross-matching with Gaia DR3 data. Through refined modeling and contamination removal, they isolated the uncontaminated light curve of this background star directly from the TPF data, confirming it as an eclipsing binary system composed of two dwarf stars with an orbital period of about 6.14 days.

Compared with existing batch-processing methods, the proposed pixel-level modeling strategy significantly improves the quality of light curves. By incorporating Gaia DR3 parameters into the modeling process, it effectively avoids systematic errors caused by unaccounted contamination from nearby bright stars, resulting in a deviation of less than 3% between the system's mean flux and the theoretical value derived from Gaia DR3 parameters.

Further analysis revealed that, in addition to clear eclipses, the binary system exhibits periodic modulations caused by starspots and differential rotation. The primary star's rotation frequency is about 13% lower than the orbital frequency, consistent with patterns observed in other short-period binaries.

This study not only clarifies the true source of KOI-1755's transit-like signal but also demonstrates that Kepler archival data still contain a wealth of undiscovered variable-star information. The pixel-level photometric modeling method developed in this study holds great potential for broader application to Kepler, K2, and TESS high-precision survey data, significantly enhancing the accuracy of faint variable star light-curve extraction and promoting a new stage of "second discovery" from archival data.