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tokens: as Giles et al. (2018) . A pipeline was built for the CORALIE spectra based on iSpec 1 ( Blanco-Cuaresma et al. 2014a ). All observations were aligned and co-added to increase the signal-to-noise ratio (S/N), were reduced and spectrally fitted using the code SPECTRUM ( Gray Corbally 1994 ) as the radiative transfer code. Atomic data were obtained from the Gaia -ESO Survey line list ( Heiter et al. 2015b ). We selected the line based on an R ~ 47 000 solar spectrum ( Blanco-Cuaresma et al. 2016 , 2017 ), and we used MARCS model atmospheres ( Gustafsson et al. 2008 ). The resulting errors were increased by quadratically adding the dispersions found when analysing the Gaia benchmark stars ( Heiter et al. 2015a ; Jofré et al. 2014 ; Blanco-Cuaresma et al. 2014b ) with the same pipeline. This resulted in an effective temperature of 4877 ± 68 K, a log g of 3.41 ± 0.07 dex, and [Fe/H] = −0.24 ± 0.04 dex. In the second data release of Gaia ( Gaia Collaboration 2018 ), EPIC248847494 has a measured parallax (see Table 2 ) based on which we can determine an independent stellar radius using bolometric absolute magnitudes and the spectroscopically determined effective temperature for EPIC248847494 following the method detailed in Fulton Petigura (2018) . We took the K -band apparent magnitude ( Skrutskie et al. 2006 ), the Gaia distance, and a bolometric correction (BC K , from Houdashelt et al. 2000 ) of 1.91 ± 0.05, which was interpolated from the range within the coarse grid. We chose not to include an extinction correction as this only introduces an uncertainty of 0.5% ( Fulton Petigura 2018 ). This gave a radius of 2.70 ± 0.12 R sol . Table 2. Properties of the EPIC248847494 system. Notes. (a) Huber et al. (2016) , (b) APASS: Henden Munari (2014) , (c) 2MASS: Skrutskie et al. (2006) , (d) Gaia Collaboration (2018) , (†) This Work. Taking the spectrally determined metallicity and effective temperature and the measured radius as observational constraints, we input them into the Geneva stellar evolution code ( Eggenberger et al. 2008 ). This resulted in a stellar mass of 0.9 ± 0.09 M sol . These values of mass and radius would therefore indicate a log g of 3.52 dex. When we fixed the iSpec analysis to this log g , the metallicity and effective temperature were very similar to the initial results (see Table 2 ). Log g is not well constrained spectroscopically, and changes have a very limited effect on other parameters. Therefore we adopt the parameters based on log g = 3.52. 3.2. Eliminating the photometric systematics of K2 The possibility for false positives is high in monotransits. We therefore endeavored to eliminate all causes for false positives. All objects listed as “stars” with K2 light curves within 25 arcmin were checked for similar artefacts. Of the 61 objects, none showed odd behaviour at the same epoch as the monotransit. Additionally, the location of EPIC248847494 was not near the edge of the CCD, which suggests that no near-edge effects