Direct Imaging Detection of the Protoplanet AB Aurigae b at Wavelengths Covering Pa$\beta$: Rebuttal to Biddle et al. (2024)

TL;DR

This paper reanalyzes data claiming non-detection of AB Aurigae b, demonstrating it was actually imaged with better quality data, and discusses the limitations of Paβ imaging for detecting accretion signatures.

Contribution

The paper provides a reprocessing of existing data showing AB Aur b was detected, and critiques previous non-detection claims based on image quality and modeling inaccuracies.

Findings

AB Aur b was decisively imaged with high-quality data.

Previous non-detection was due to poorer image quality and modeling errors.

Paβ imaging alone is insufficient for confirming accretion; Hα spectroscopy is recommended.

Abstract

Recently, Biddle et al. (2024) claimed a non-detection of the protoplanet AB Aurigae b in Keck/NIRC2 Pa$\beta$ imaging. I reprocess these newly-public data and compare them to data from the extreme AO platform (SCExAO/CHARIS) used to discover AB Aur b. AB Aur b is decisively imaged with SCExAO/CHARIS at wavelengths covering Pa$\beta$. The Biddle et al. non detection of AB Aur b results from a far poorer image quality that is non competitive with SCExAO/CHARIS. Their contrast limits and thus constraints on accretion are overestimated due to an inaccurate AB Aur b source model. Consequentially, the revised Pa$\beta$ 2-$\sigma$ upper limit from these data is about three times higher than previously reported. Irrespective of image quality, single-band Pa$\beta$ imaging is ill suited to conclusively identifying accretion onto AB Aur b. Instead, high-resolution H$\alpha$ spectroscopy may provide accretion signatures. Aside from PDS 70, AB Aurigae remains the system with the strongest evidence for having a directly-imaged protoplanet.