Six New Circumbinary Disk Occultation (CBO) Candidates from the Zwicky Transient Facility

TL;DR

This study addresses the scarcity of circumbinary disk occultation (CBO) systems with known orbital periods by performing a systematic search of ZTF photometry to identify CBO candidates. Six new CBO candidates, ZTF-CBO-1 through ZTF-CBO-6, are identified with orbital periods spanning about $30$ to $530$ days and occultation duty cycles of roughly 32% to 77% of the orbit. Infrared excess is detected in the spectral energy distributions of ZTF-CBO-1 and ZTF-CBO-2, while TESS observations of ZTF-CBO-1 show no hours- to days-timescale variability during ingress and egress, indicating a smooth disk edge. Together these results nearly double the known CBO sample, enabling population-level studies of circumbinary disk geometry and dynamics and guiding future follow-up observations.

Abstract

Circumbinary disk occultation (CBO) systems, in which a misaligned circumbinary disk periodically obscures the central binary, provide unique probes of disk structure and dynamics. However, fewer than ten candidates with measured orbital periods were previously known. In this work, we identify six new CBO candidates, designated ZTF-CBO-1 through ZTF-CBO-6, through a systematic search of Zwicky Transient Facility (ZTF) photometry. These systems exhibit deep ($\gtrsim$1 mag) periodic dimming events with orbital periods ranging from $\sim$30 to $\sim$530 days and occultation durations spanning 32%-77% of their orbital periods. Such large duty cycles rule out the interpretation of circum-companion material occultation. Spectral energy distributions of ZTF-CBO-1 and ZTF-CBO-2 reveal infrared excess indicative of a dust component. TESS observations of ZTF-CBO-1 show no hours- to days-timescale variability during ingress and egress, indicating a smooth disk edge. These discoveries nearly double the known CBO sample, enabling meaningful population-level studies.