Kavli Affiliate: Gregory J. Herczeg
| First 5 Authors: Yifan Zhou, Brendan P. Bowler, Haifeng Yang, Aniket Sanghi, Gregory J. Herczeg
| Summary:
The proposed protoplanet AB Aur b is a spatially concentrated emission source
imaged in the mm-wavelength disk gap of the Herbig Ae/Be star AB Aur. Its
near-infrared spectrum and absence of strong polarized light have been
interpreted as evidence supporting the protoplanet interpretation. However, the
complex scattered light structures in the AB Aur disk pose challenges in
resolving the emission source and interpreting the true nature of AB Aur b. We
present new images of the AB Aur system obtained using the Hubble Space
Telescope Wide Field Camera 3 in the ultraviolet (UV) and optical bands. AB Aur
b and the known disk spirals are recovered in the F336W, F410M, and F645N
bands. The spectral energy distribution of AB Aur b shows absorption in the
Balmer jump, mimicking those of early-type stars. By comparing the colors of AB
Aur b to those of the host star, the disk spirals, and predictions from
scattered light and self-luminous models, we find that the emission from AB Aur
b is inconsistent with planetary photospheric or accretion shock models.
Instead, it is consistent with those measured in the circumstellar disks that
trace scattered light. We conclude that the UV and visible emission from AB Aur
b does not necessitate the presence of a protoplanet. We synthesize
observational constraints on AB Aur b and discuss inconsistent interpretations
of AB Aur b among different datasets. Considering the significance of the AB
Aur b discovery, we advocate for further observational evidence to verify its
planetary nature.
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