Origin of the mid-infrared excess of HD 253659

Determine whether the mid-infrared excess emission of HD 253659 originates from warm circumstellar dust or from a remnant Be-star decretion disk.

Background

The spectral energy distributions of PY Gem and HD 253659 show infrared excesses that the authors model with warm components. For HD 253659, the excess becomes visible at wavelengths longer than 3 μm and is represented by a blackbody temperature of approximately 550 K.

The authors favor warm dust because HD 253659 is expected to lack a free–free-emitting disk during quiescence, but the available WISE observations do not include the W3 and W4 bands during a quiescent interval. Consequently, distinguishing compact warm dust from residual disk emission remains unresolved.

References

We propose this excess emission to be due to warm dust, because in quiescence the star should not have a disk emitting free-free emission, but we cannot exclude that the mid-infrared emission might emerge from a disk remnant.

— Central stars of newly discovered infrared nebulae: eruptive Be stars PY Gem and HD253659  (2609.28889 - Maryeva et al., 24 Sep 2026) in Section 3.1, Stellar parameters