Photometric Modulations on Intermediate Timescales in the Symbiotic Binaries

TL;DR

This study analyzes multi-year, multi-band data of three symbiotic binaries, revealing complex variability patterns on intermediate and short timescales driven by pulsations, accretion, and rotation, providing new insights into their activity cycles.

Contribution

It is the first comprehensive multi-band, multi-timescale analysis of symbiotic binaries combining ground and space data over 14 years to identify diverse variability sources.

Findings

Detection of dominant pulsation periods in all systems.

Identification of short-period signals indicating rapid activity.

Observation of variability linked to pulsation, circumstellar activity, and rotation.

Abstract

We present a multi-band study of three symbiotic binaries using combined ground- and space-based monitoring that spans up to 14 years. These datasets enable a systematic investigation of variability on intermediate timescales (tens of days) and the detection of shorter-period signals. All systems display coherent photometric modulations that are distinct from the orbital cycles. In AX Per, a dominant 75-day signal and its 37-day harmonic are identified, which we interpret as pulsations of the cool giant. CI Cyg exhibits a stable modulation between 70 and 74 days, which likely arises from a combination of pulsation and circumstellar or disk-related variability. For Z And, we confirm a persistent modulation between 55 and 60 days, consistent with semiregular pulsations of the cool component. Additionally, space-based data reveal further short-period variability, including coherent signals at 26.7 and 66.6 minutes in Z And and CI Cyg, respectively, and a quasi-periodic modulation near 0.95 days in AX Per. These detections suggest the presence of rapid activity driven by accretion or rotation, superposed on the intermediate timescale behavior. Our results show that the observed variability in these symbiotic binaries reflects the combined effects of cool giant pulsation, circumstellar or disk activity, and possible rotation of the hot component. The multi-timescale behavior revealed here offers new constraints on mass transfer and activity cycles in interacting binaries.