Orateur
Description
We investigate the origin of dipole features observed in some Rubin alert light curves, as identified in the Fink alert broker stream. These dipoles, notably present in cross-matched sources such as Gaia counterparts, are characterized by a dipole angle and an angular separation provided at the alert level.
Our analysis reveals a strong angular dependence of these features, suggestive of a systematic effect rather than an astrophysical signal. In particular, the observed behavior is consistent with expectations from parallactic effects induced by atmospheric refraction, which can introduce chromatic centroid shifts depending on observing geometry.
We test this hypothesis by comparing the measured dipole orientations and amplitudes to the expected parallactic angle and its associated scaling with observational parameters. We present the current status of this study, including quantitative comparisons and limitations of the available alert-level information. Finally, we discuss the implications for alert stream analysis and broker-level filtering, as well as perspectives for improving the modeling and mitigation of such effects in Rubin data products.