Determine whether the MIRI LRS ramp affects the long-wavelength spectral feature

Determine whether the observed 10–12 μm emission feature of LHS 3844 b is influenced by the wavelength-dependent exponential ramp shape associated with the MIRI LRS shadowed-region effect.

Background

The spectrum of LHS 3844 b shows a tentative feature between 10 and 12 μm, but MIRI LRS observations can exhibit wavelength-dependent changes in the exponential detector ramp at wavelengths longer than approximately 10.5 μm. Because exponential ramps can bias retrieved eclipse depths and the ramp behavior depends on the detector’s preceding illumination history, the feature could be instrumental rather than astrophysical.

The authors separate observations by ramp amplitude and compare the resulting spectra, but the available data are too noisy to determine whether the feature is affected by the ramp. Resolving this issue requires additional MIRI LRS observations designed to mitigate or characterize the ramp effect, such as observations using newer subarrays or a detector pre-flash strategy.

References

We conclude that the current data are too noisy to diagnose whether the observed feature is influenced by the exponential ramp shape.

— Improved Constraints on the Surface of LHS 3844 b from its Mid-Infrared Spectrum  (2609.37982 - Paragas et al., 29 Sep 2026) in Section “Can the Feature Be Explained by Residual Ramp Effects?”