J/A+A/689/L8ivo://CDS.VizieR/J/A+A/689/L8doi:10.26093/cds/vizier.36899008CDSLillo-Box J.Latham D.W.Collins K.A.Armstrong D.J.Gandolfi D.,Jensen E.L.N.Castro-Gonzalez A.Balsalobre-Ruza O.Montesinos B.,Sousa S.G.Aceituno J.Schwarz R.P.Narita N.Fukui A.Cabrera J.,Hadjigeorghiou A.Kuzuhara M.Hirano T.Fridlund M.Hatzes A.P.,Barragan O.Batalha N.M.2025-02-24T20:01:16Z2024-09-17T12:27:38ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frmultiple-starsradial-velocityvisible-astronomyThe transit technique has been very efficient in detecting planet candidate signals over the past decades. The so-called statistical validation approach has become a popular way of verifying a candidate's planetary nature. However, the incomplete consideration of false positive scenarios and data quality can lead to the misinterpretation of the results. In this work we revise the planetary status of K2-399 b, a validated planet with an estimated false positive probability of 0.078% located in the middle of the so-called Neptunian desert, and hence a potential key target for atmospheric prospects. We use radial velocity data from the CARMENES, HARPS and TRES spectrographs, as well as ground-based multi-band transit photometry LCOGT MuSCAT3 and broad band photometry to test the planetary scenario. Our analysis of the available data does not support the existence of this (otherwise key) planet, and instead points to a scenario composed of an early G-dwarf orbited in a 846.62^+0.22^_-0.28_days period by a pair of eclipsing M-dwarfs (hence a hierarchical eclipsing binary) likely in the mid-type domain. We thus demote K2-399 b as a planet. We conclude that the validation process, while very useful to prioritise follow-up efforts, must always be conducted with careful attention to data quality while ensuring that all possible scenarios have been properly tested to get reliable results. We also encourage developers of validation algorithms to ensure the accuracy of a priori probabilities for different stellar scenarios that can lead to this kind of false validation. We further encourage the use of follow-up observations when possible (such as radial velocity and/or multi-band light curves) to confirm the planetary nature of detected transiting signals rather than only relying on validation tools.2024A&A...689L...8Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/689/L8CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/AJ/156/89 : K2-24 system RVs & predicted transit-times (Petigura+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/689/L8https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/689/L8http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/689/L8https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/689/L8https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/689/L8http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/689/L8GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/A+A/689/L8/tablec1Radial velocity measurements of EPIC 248472140recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDBarycentric Julian date (TBD)dtime.epochdoubleRVRadial velocitykm/sphys.veloc;pos.heliocentricdoublee_RVRadial velocity uncertaintykm/sstat.errordoubleInstInstrument (1)meta.id;instrchar