The Transit Signal of KOI-1755 Originates from a Background Eclipsing Binary Star—Extracting the Light Curve of a Faint Background Star from Kepler Target Pixel File Data

Abstract KOI-1755 (KIC 5302006) was initially identified by the Kepler mission as a candidate exoplanet host but subsequently classified as a false positive due to suspected background contamination. The target star itself exhibits intrinsic stellar pulsations, accompanied by transit-like dimming events, complicating a straightforward identification of the signal source. In this study, we carried out a detailed pixel-level reanalysis of KOI-1755 using the Kepler Target Pixel Files (TPFs) to clarify the origin of these transit-like signals. Through careful pixel-level flux modeling, centroid shift measurements, and cross-matching with the Gaia DR3 catalog, we conclusively determined that the dimming signals originate from a faint background eclipsing binary (EB), rather than KOI-1755 itself. We then developed a specialized photometric method to effectively remove contamination from nearby stars, allowing us to reliably extract the EB's uncontaminated light curve directly from the TPFs data. Analysis of this extracted light curve confirmed the contaminating source to be an EB system composed of two dwarf stars with a clear eclipse period of approximately 6.14 days. Our study provides a concrete example of how background EBs can mimic planetary transit signals, highlighting the importance of detailed pixel-level analyses for correctly identifying astrophysical false positives. Furthermore, our method demonstrates significant potential for uncovering previously hidden variable-star information within archival Kepler data, thus emphasizing the continuing scientific value of mining and reanalyzing existing data sets.

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