Near-infrared Accretion Signatures from the Circumbinary Planetary-mass Companion Delorme 1 (AB)b*
Abstract

Accretion signatures from bound brown dwarf and protoplanetary companions provide evidence for ongoing planet formation, and accreting substellar objects have enabled new avenues to study the astrophysical mechanisms controlling the formation and accretion processes. Delorme 1 (AB)b, a ∼30–45 Myr circumbinary planetary-mass companion, was recently discovered to exhibit strong Hαemission. This suggests ongoing accretion from a circumplanetary disk, somewhat surprising given canonical gas disk dispersal timescales of 5–10 Myr. Here, we present the first NIR detection of accretion from the companion in Paβ, Paγ, and Brγemission lines from SOAR/TripleSpec 4.1, confirming and further informing its accreting nature. The companion shows strong line emission, withLline≈ 1–6 × 10−8Lacross lines and epochs, while the binary host system shows no NIR hydrogen line emission (Lline< 0.32–11 × 10−7L). Observed NIR hydrogen line ratios are more consistent with a planetary accretion shock than with local line excitation models commonly used to interpret stellar magnetospheric accretion. Using planetary accretion shock models, we derive mass accretion rate estimates of$Ṁpla∼3$–4 × 10−8MJyr−1, somewhat higher than expected under the standard star formation paradigm. Delorme 1 (AB)b’s high accretion rate is perhaps more consistent with formation via disk fragmentation. Delorme 1 (AB)b is the more »

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Award ID(s):
Publication Date:
NSF-PAR ID:
10369935
Journal Name:
The Astrophysical Journal Letters
Volume:
935
Issue:
1
Page Range or eLocation-ID:
Article No. L18
ISSN:
2041-8205
Publisher:
DOI PREFIX: 10.3847
National Science Foundation
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