Origin of the infrared excess in V745 Sco

Determine whether the observed WISE-band infrared excess in V745 Sco originates from a dusty circumstellar component or from the outer layers of an extended accretion disk.

Background

V745 Sco exhibits an infrared excess that can be modeled using either thermal emission from circumstellar dust or emission from sufficiently cool outer regions of an extended accretion disk. The disk model considered in the paper fails to reproduce the observed spectral energy distribution without also producing excessive predicted 2MASS fluxes and requires an unexpectedly large outer radius of approximately 170 solar radii.

The authors therefore regard a dusty circumstellar component as a more natural explanation, while acknowledging that the mismatch may result from the simplicity of the flat, thin disk model. Distinguishing between these alternatives requires resolving the physical origin of the infrared emission and accounting for effects omitted from the current disk treatment, such as disk irradiation and non-flat structure.

References

Although a sufficiently extended accretion disk can in principle reach temperatures capable of producing WISE-band excess emission, we were unable to reproduce the observed SED without simultaneously introducing excess to predicted 2MASS fluxes. Such attempts also find the outer radius of the accretion disk to extend to unexpectedly large $r_\mathrm{out}\sim170\ R_\odot$. This may indicate that a dusty circumstellar component provides a more natural explanation for the observed infrared excess, however, such a mismatch alone could also be attributed to the simplicity of our model.

— The quiescent states of V745 Sco and V3890 Sgr: VLT/X-shooter and Swift/XRT+UVOT observations  (2609.01388 - Jamnik et al., 1 Sep 2026) in Section “Source of IR excess in V745 Sco”