Physical origin of apparently long-period YSO variability

Determine the physical origin of apparently robust 100–500-day variability in pre-main-sequence stars that is unlikely to arise from stellar rotation, including whether it is caused by periodic disk occultation, unresolved-binary orbital motion, or another long-timescale process.

Background

The paper evaluates its period-based classification against an external sample of emission-line young stellar objects. Some external YSOs are assigned apparently robust long periods after stricter false-alarm-probability and search-boundary cuts are applied.

Because rotational periods of approximately 100–500 days are considered physically unlikely for pre-main-sequence stars, these objects may be exhibiting variability from mechanisms other than stellar rotation. The source light curves are not publicly available, so the paper cannot resolve the origin of the variability and identifies possibilities such as periodic occultation by disk substructures or orbital motion in unresolved binaries.

References

Since the Borissova et al. (2025) light curves are not publicly available, we cannot determine the physical origin of these apparently robust long periods and we speculate that they may instead trace longer timescale physical processes (e.g., periodic occultation by disk substructures, orbital motion in an unresolved binary) rather than stellar rotation.

— Near-infrared periodicity in the SPICY catalog. True young stellar objects versus contaminants  (2609.37779 - Ordenes-Huanca et al., 29 Sep 2026) in Appendix D, Validation with other LPV and YSO catalogs