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Constraining nitrogen partitioning into N2 in Wolf 1130C

Ascertain the disequilibrium abundance of molecular nitrogen (N2) in the atmosphere of the brown dwarf Wolf 1130C under vertical mixing, to determine nitrogen partitioning between N2 and NH3 and enable a complete elemental nitrogen budget.

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Background

The retrieval analysis robustly constrains several molecular abundances (H2O, CH4, CO, NH3, H2S, PH3) in Wolf 1130C, but the authors note that nitrogen locked in N2 is not directly retrievable and therefore the total nitrogen abundance remains uncertain.

Because vertical mixing drives disequilibrium chemistry, N2 can be a significant reservoir for nitrogen in cool atmospheres, yet its abundance is typically hard to constrain spectroscopically. The inability to measure N2 prevents a full accounting of the elemental nitrogen budget.

References

For nitrogen, our abundance estimate is a lower limit because we cannot constrain the disequilibrium abundance of nitrogen locked up in N$_2$ due to vertical mixing .

— Observation of undepleted phosphine in the atmosphere of a low-temperature brown dwarf (2510.03916 - Burgasser et al., 4 Oct 2025) in Supplementary Materials, Subsection "Retrieval Modeling"