We present multi-instrument observations of the disc around the Herbig Ae star, HD 145718, employing geometric and Monte Carlo radiative transfer models to explore the disc orientation, the vertical and radial extent of the near-infrared (NIR) scattering surface, and the properties of the dust in the disc surface and sublimation rim. The disc appears inclined at 67–71°, with position angle, PA = −1.0 to 0.6°, consistent with previous estimates. The NIR scattering surface extends out to ${\sim}75\,$ au and we infer an aspect ratio, hscat(r)/r ∼ 0.24 in J band; ∼0.22 in H band. Our Gemini Planet Imager images and VLTI + CHARA NIR interferometry suggest that the disc surface layers are populated by grains ≳λ/2π in size, indicating these grains are aerodynamically supported against settling and/or the density of smaller grains is relatively low. We demonstrate that our geometric analysis provides a reasonable assessment of the height of the NIR scattering surface at the outer edge of the disc and, if the inclination can be independently constrained, has the potential to probe the flaring exponent of the scattering surface in similarly inclined (i ≳ 70°) discs. In re-evaluating HD 145718’s stellar properties, we found that the object’s dimming events – previously characterized as UX Or and dipper variability – are consistent with dust occultation by grains larger, on average, than found in the ISM. This occulting dust likely originates close to the inferred dust sublimation radius at $0.17\,$ au.
The cool hypergiant star RW Cephei is currently in a deep photometric minimum that began several years ago. This event bears a strong similarity to the Great Dimming of the red supergiant Betelgeuse that occurred in 2019–2020. We present the first resolved images of RW Cephei that we obtained with the CHARA Array interferometer. The angular diameter and Gaia distance estimates indicate a stellar radius of 900–1760
- NSF-PAR ID:
- 10436953
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astronomical Journal
- Volume:
- 166
- Issue:
- 2
- ISSN:
- 0004-6256
- Page Range / eLocation ID:
- Article No. 78
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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