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Incoming links: The Transit Light Source Effect by Benjamin V. Rackham and others
Benjamin V. Rackham 2026-11-05
Benjamin V. Rackham studies how stellar surface inhomogeneity can contaminate exoplanet transmission spectra. His coauthored transit-light-source work shows that different spectra along the transit chord and across the whole star can mimic atmospheric features. This makes the illuminating star part of the inference problem.[ref]
The Transit Light Source Effect by Benjamin V. Rackham and others. author list and the described study’s abstract or introductory account
Stellar contamination of a transmission spectrum Created 2026-10-20 Updated 2026-11-05
Stellar contamination of a transmission spectrum arises when the spectrum behind a transiting planet differs from the spectrum averaged over the whole stellar disc. For a small opaque planet, neglecting limb darkening, the approximate depth isHere is specific intensity. Unocculted cool starspots change the denominator in a wavelength-dependent way, creating apparent planetary features even if is constant. Crossing a starspot changes the numerator and can produce a visible anomaly in the light curve.[ref]
The Transit Light Source Effect by Benjamin V. Rackham and others. Abstract: spectral mismatch between the illuminating chord and disc-integrated stellar spectrum
Repeated exoplanet transits, monitoring of the host star, and joint stellar and planetary modelling help test this effect. Small rotational variability alone does not establish that the stellar surface is uniform.