10^{5}$GHz) on-board the *Swift* satellite [@2008MNRAS.383..627P], observed the source 15 times during the MAGIC campaign, out of which eight were simultaneous to the *XRT* data taking[^7]. An iterative data calibration procedure was used to calculate the Galactic extinction[^8], the effective frequency, and the flux conversion factor for each filter.

Optical
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### Light-curve (KVA, KAIT, and Catalina)

S2 0109+22 was added to the Tuorla blazar monitoring program[^9] when HE activity was reported in 2015 July. The monitoring observations were performed in optical R-band using a 35cm Celestron telescope coupled to the KVA (Kunglinga Vetenskapsakademi) telescope located at La Palma. Data analysis was performed using a semi-automatic pipeline for differential photometry assuming the comparison star magnitudes in . The magnitudes were corrected for Galactic extinction using values from @2011ApJ...737..103S.

In order to study the long-term optical behaviour of S2 0109+22, its optical LC is retrieved from the publicly available online database of 76-cm Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory[^10]. The LC from KAIT is produced through a pipeline that utilizes aperture photometry and performs brightness calibrations using USNO B1.0 catalogue stars in the source field. The long-term optical LC is extended back to 2005 by including available online data 