Determine the true nature of GJJC 1 and its association with NGC 6656

Determine whether the planetary nebula GJJC 1 is genuinely a planetary nebula physically associated with the globular cluster NGC 6656, including whether its peculiar properties are attributable to binary evolution.

Background

GJJC 1 has been reported as physically associated with the globular cluster NGC 6656, but its unusual properties have prompted doubts about both the nebular classification and the evolutionary interpretation. The paper notes that binary evolution could explain the inferred low progenitor mass and other peculiar characteristics.

The effective temperature of the central star remains poorly constrained because of large interstellar-extinction uncertainties, and the object is classified only as a likely planetary nebula. Consequently, the physical nature of GJJC 1 and the validity of its proposed cluster association remain unresolved.

References

Since the status of this object is still debated and we use updated CS and cluster parameters, we kept this pair in our analysis to try to shed light on its true nature.

— Planetary Nebula Central Stars as Tracers of Planetary Nebula-Star Cluster Associations in the Galaxy  (2609.09618 - Fragkou et al., 9 Sep 2026) in Section 5.1.7, “PN GJJC 1 - GC NGC 6656 (CS_ID=2312)”

For PNe K~3-48 and MPAJ1559-5552, the estimated initial and final CS masses present a small overlap within their large assigned errors according to stellar evolution models, and thus we cannot exclude them without more precise measurements.

— Planetary Nebula Central Stars as Tracers of Planetary Nebula-Star Cluster Associations in the Galaxy  (2609.09618 - Fragkou et al., 9 Sep 2026) in Section 5, paragraph discussing borderline initial and final central-star masses