TOP: Other MUSE reductions showing the detection of AB Aur b from OB4. (left, middle) 6558.88 Aand 6560.13 Afrom the reduction shown in Figure 1. Average of the 6558.88 Aand 6560.13 Aslices from a classical SDI reduction (right). In each panel, we mask the field out to a separation affected by horizontal striping and saturation BOTTWO: Detection of AB Aur b from OB2 (left, middle panels) and weaker detection from OB1 in blue-shifted Hα (right). — astro-ph.EP
We analyze high-contrast, medium-spectral-resolution Hα observations of the star AB Aurigae using the Very Large Telescope’s Multi Unit Spectroscopic Explorer (MUSE).
In multiple epochs, MUSE detects the AB Aur b protoplanet discovered from Subaru/SCExAO data in emission at wavelengths slightly blue-shifted from the Hα line center (i.e. at 6558.88–6560.13 Å; ∼ -100 km s−1) and in absorption at redshifted wavelengths (6562.8–6565.1 Å; ∼ 75 km s−1).
AB Aur b’s Hα spectrum is inconsistent with that of the host star or the average residual disk spectrum and is dissimilar to that of PDS 70 b and c. Instead, the spectrum’s shape resembles that of an inverse P Cygni profile seen in some accreting T Tauri stars and interpreted as evidence of infalling cold gas from accretion, although we cannot formally rule out all other nonaccretion origins for AB Aur b’s MUSE detection.
AB Aurigae hosts only the second protoplanetary system detected in Hα thus far and the first with a source showing a spectrum resembling an inverse P Cygni profile. Future modeling and new optical data will be needed to assess how much of AB Aur b’s emission source(s) originates from protoplanet accretion reprocessed by the disk, a localized scattered-light feature with a unique Hα profile, or another mechanism.
Thayne Currie, Jun Hashimoto, Yuhiko Aoyama, Ruobing Dong, Misato Fukagawa, Takayuki Muto, Erica Dykes, Mona El Morsy, Motohide Tamura
Comments: 23 pages, 16 figures, 3 tables; ApJ Letters in press
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2508.18351 [astro-ph.EP] (or arXiv:2508.18351v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2508.18351
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Submission history
From: Thayne Currie
[v1] Mon, 25 Aug 2025 18:00:02 UTC (1,915 KB)
https://arxiv.org/abs/2508.18351
Astrobiology
