Functional form of the FUV dependence of inferred disk lifetime

Determine whether the inferred disk lifetime decreases gradually with increasing far-ultraviolet irradiation or instead undergoes an abrupt transition above a threshold FUV field strength.

Background

The comparison of Orion A, Lupus, the Orion Nebula Cluster, and σ Orionis suggests a tentative population-level decrease in inferred disk lifetime toward stronger FUV environments. However, the relation is dominated by large intrinsic scatter and by the limited number of systems with both accretion-rate and disk-mass measurements at intermediate and high irradiation levels. Consequently, the available sample cannot distinguish a continuous dependence from a threshold-like transition, which is important for assessing whether external photoevaporation drives disk dispersal in a gradual or switch-like manner.

References

Whether this reflects a gradual strengthening of the FUV dependence or a more abrupt transition (a ``switch'') above some threshold field strength cannot be determined with the present sample.

— X-shooter survey Across Regions and Ages to probe Disk Evolution (ARADE): Accretion properties in Orion A and their relation with disk masses  (2609.00938 - Piscarreta et al., 1 Sep 2026) in Section 4.3, Environmental dependences

Indeed, protoplanetary discs dissipate faster as the stellar mass increases, although the underlying processes are not fully understood.

— Signatures of rocky debris accretion in AF-Type planet hosts  (2609.04790 - Maldonado et al., 4 Sep 2026) in Section 4, subsection “A differential chemical fingerprint: Iron-peak, volatiles and α-elements”