Detection Of Hydrocarbons In The Disk Around An Actively-Accreting Planetary-Mass Object
We present the 0.6–12-micron spectrum of Cha 1107-7626, a 6-10 Jupiter-mass free-floating object in the ∼2 Myr-old Chamaeleon-I star-forming region, from observations with the NIRSpec and MIRI instruments onboard the James Webb Space Telescope.
We confirm that Cha 1107-7626 is one of the lowest-mass objects known to harbor a dusty disk with infrared excess emission at wavelengths beyond 4 microns. Our NIRSpec data, and prior ground-based observations, provide strong evidence for ongoing accretion through Hydrogen recombination lines.
In the mid-infrared spectrum, we detect unambiguously emission lines caused by methane (CH4) and ethylene (C2H4) in its circum-substellar disk. Our findings mean that Cha 1107-7626 is by far the lowest-mass object with hydrocarbons observed in its disk.
The spectrum of the disk looks remarkably similar to that of ISO-ChaI 147, a very low mass star with a carbon-rich disk that is 10 to 20 times more massive than Cha 1107- 7626. The hydrocarbon lines can be accounted for with a model assuming gas temperatures of a few hundred Kelvin in the inner disk.
The obvious similarities between the spectra of a low-mass star and a planetary-mass object indicate that the conditions in the inner disks can be similar across a wide range of central object masses.
Laura Flagg, Aleks Scholz, V. Almendros-Abad, Ray Jayawardhana, Belinda Damian, Koraljka Muzic, Antonella Natta, Paola Pinilla, Leonardo Testi
Comments: accepted to ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2505.13714 [astro-ph.EP] (or arXiv:2505.13714v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2505.13714
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Submission history
From: Laura Flagg
[v1] Mon, 19 May 2025 20:24:33 UTC (3,738 KB)
https://arxiv.org/abs/2505.13714
Astrobiology, Astrochemistry,
