The 1D cross-correlation function after stacking all exposures in all orders of all datasets. Top panel: entire cross-correlation function between ± 1600 km s⁻¹, bottom panel: zoom-in around ± 100 km s⁻¹ for clarity. The red and black lines represent the injected and non-injected data, respectively. The gold line is the difference between the two, and the dashed horizontal line is 3σ away fromthe mean of cross-correlation (which is around zero). The model was injected at a strength of 2 × 10⁻⁵ Φ(α), and is retrieved at a level of 4.6σ. The corresponding 3σ upper limit of ϵ is 1.5 × 10⁻⁵, taking into account a factor 0.87 to correct for the efficiency at which the PHOENIX template correlates with the stellar spectrum (see Sect. 3.2).