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tokens: also provide viable explanations. In any case, the transit of a more extended cloud of material, whether associated with a planet or not, might be more easily detectable. About 20 ks into the XMM-Newton observation (Fig. 2 ), the soft-band count rate drops by ≈35% for ≈800 s, i.e., two data points. This timescale is consistent with the occultation of a point-like source by the hypothesized planetary body of CVSO 30 b. However, the lack of an associated depression in the hard-band light curve makes an eclipse by a solid planetary disk unlikely. A temporary elevation in the absorption column by 10 21 cm −2 (e.g., caused by the transit of an extended planetary atmosphere) produces a count rate drop of 60% in the soft band with only a 10% drop in the hard band. Such a scenario would thus be compatible with the observation. By means of a Student’s t-test, we find that the mean of the two data points in question differs from that of the sample consisting of the two preceding and following points at the 2% significance level. As the ephemerides are uncertain, however, we count about ten similar opportunities during the flare where such an occultation may have happened and be interpreted in the same way. Therefore, the chance to obtain such a result by chance is about 20%, and we conclude that the data remain insufficient to produce a significant result. The hard-band light curve shows an apparent depression about 25 ks into the XMM-Newton observation (Fig. 2 ). This variation has no counterpart in the soft-band light curve, however, and might be more easily explained by the superposition of two flares or secondary heating rather than absorption or occultation of flaring material. 3.4. Planetary irradiation and mass loss Having measured the stellar X-ray flux, we now estimate the expected mass-loss rate of the candidate hot Jupiter CVSO 30 b to see whether such a configuration is physically plausible. A number of values have been proposed for the mass of CVSO 30 b (e.g., Barnes et al. 2013 ; Ciardi et al. 2015 , or Johns-Krull et al. 2016 ). These range from approximately one to seven Jovian masses. We assume here a stellar mass of 0.44 M ⊙ , a planetary mass of 3.9 M J , and a planetary radius of 1.61 R J . These values are based on those given in Table 1 . To remain on the conservative side regarding the planetary mass-loss rate, we increased the nominal mass estimate in Table 1 by its uncertainty and decreased the radius likewise. Both choices increase the assumed planetary density and inhibit mass loss. Kepler’s third law then demands a semimajor axis, a , of 0.00874 AU. The resulting Roche-lobe geometry is shown in Fig. 4 . The shape of the planetary candidate CVSO 30 b is determined by an equipotential surface, the level of which is given by the radius derived from transit modeling. The result clearly demonstrates the expected deviation from spherical geometry. Fig. 4. Roche lobe (solid line) and extent (blue shade) of planetary candidate CVSO