geosciences

Article A Quantitative Comparison of Exoplanet Catalogs

Dolev Bashi 1,*, Ravit Helled 2 ID and Shay Zucker 1 1 School of Geosciences, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, 6997801 Tel Aviv, Israel; [email protected] 2 Institute for Computational Science, Center for Theoretical Astrophysics and Cosmology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland; [email protected] * Correspondence: [email protected]; Tel.: +972-54-7365-965



Received: 30 July 2018; Accepted: 25 August 2018; Published: 29 August 2018


Abstract: In this study, we investigated the differences between four commonly-used exoplanet catalogs (exoplanet.eu; exoplanetarchive.ipac.caltech.edu; openexoplanetcatalogue.com; exoplanets.org) using a Kolmogorov–Smirnov (KS) test. We found a relatively good agreement in terms of the planetary parameters (mass, radius, period) and stellar properties (mass, temperature, metallicity), although a more careful analysis of the overlap and unique parts of each catalog revealed some differences. We quantified the statistical impact of these differences and their potential cause. We concluded that although statistical studies are unlikely to be significantly affected by the choice of catalog, it would be desirable to have one consistent catalog accepted by the general exoplanet community as a base for exoplanet statistics and comparison with theoretical predictions.

Keywords: methods: statistical; astronomical data bases: miscellaneous; catalogs; planetary systems; stars: statistics

1. Introduction Since the detection of ‘51 Peg b’, the first exoplanet around a main sequence star [1], many more planets around other stars have been discovered. Currently, more than 3500 exoplanets have been detected in our galaxy. The diversity of these exoplanets in terms of orbital and physical properties is overwhelming. This diversity challenges planet formation and evolution theories, which were tuned originally to explain the planets in our Solar System [2,3]. Several groups took it upon themselves to label and classify the known exoplanets, and compile catalogs to provide the scientific community with a comprehensive working tool to access the data and perform statistical studies of the exoplanet sample (hereafter, exostatistics). These databases include information about the physical properties of the planets, as well as their host stars. Analysis of this information is constantly improving our understanding of planet formation mechanisms [4], protoplanetary disks [5], and planetary composition and internal structure [6,7]. At the moment, several exoplanet catalogs are available and are used by the community (see [8]). arXiv:1808.10236v1 [astro-ph.EP] 30 Aug 2018 The most widely-used exoplanet catalogs are: 1. The Extrasolar Planets Encyclopaedia, www.exoplanet.eu([9]; hereafter, EU). 2. The NASA Exoplanet Archive, https://exoplanetarchive.ipac.caltech.edu ([10]; hereafter, ARCHIVE). 3. The Open Exoplanet Catalogue, www.openexoplanetcatalogue.com/ (hereafter, OPEN). 4. The Exoplanet Data Explorer, www.exoplanets.org([11]; hereafter, ORG). These catalogs include data from ground-based observations as well as space missions such as CoRoT, Kepler, and K2. The available data in these catalogs are comprehensive and include the physical properties of the host star, available information on the planetary physical properties, and the referenced confirmation paper or other mentioned source.

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The different teams of each catalog use different criteria to include a planet, which are usually based on the physical properties of the planet or statistical thresholds (see Table1). Furthermore, each catalog has a different approach to displaying the database. For example, ARCHIVE designates a set of default parameters for each planet. This set is extracted from a single published reference to ensure internal consistency. Additional values published in other papers can only be found by viewing the pages dedicated to individual planets, where multiple sets of parameters are displayed. As a result, the ARCHIVE table provides a self-consistent set of parameters for any system, with missing values when the information is unavailable. On the other hand, EU uses a table displaying information on specific planet extracted from different sources, thus making for a more complete parameter set, though not necessarily self-consistent. Many exostatistics papers use one of these catalogs as their source of observational data. Nevertheless, so far, the different catalogs have not been compared in terms of their possible differences and potential biases and selection effects that might affect inferred results and conclusions.

Table 1. The exoplanets catalogs inclusion criteria.

Catalog Object Mass Criterion Reference Criteria Published or submitted to peer-reviewed journals or EU <60M ± 1σ J announced in conferences by professional astronomers. ARCHIVE <30MJ Accepted, refereed paper. OPEN Not listed Open-source. ORG <24MJ Carefully vetted, peer-reviewed journal papers.

In this work, we present a simple statistical comparison between the different exoplanet catalogs. We mainly focus on the EU, ARCHIVE and OPEN catalogs. The database of the ORG catalog contains a single and reliable set of parameters for each planet. However, since it has not been updated for a couple of years now (see website and discussion in Reference [8]), we perform only a coarse comparison. As discussed in Reference [8], there are plans to restart regular updates in the near future.

2. Methods We have downloaded lists of confirmed planets from the following four catalogs: EU, ARCHIVE, OPEN and ORG on 3 April 2018. As discussed previously, because of the different planetary mass criteria of each catalog (see Table1), we set 10MJ as an upper bound for the planetary mass, to strictly exclude any potential brown dwarfs. Thus, we avoided any biases that might emerge from the different mass cutoffs the catalogs use. The parameters we use in order to compare the catalogs are the stellar mass (M∗), surface temperature (Te f f ) and metallicity ([Fe/H]), and planetary mass (Mp), radius (Rp) and orbital period (Period). We chose this set of six parameters because they are the fundamental parameters that are most easily available from current photometric and spectroscopic detection methods [12]. Physically, these parameters provide basic, broad information about the planetary system [6]. The process of deriving the stellar properties involves a collection of literature values for atmospheric properties (temperature, surface gravity, and metallicity) derived from different observational techniques (photometry, spectroscopy, asteroseismology, and exoplanet transits), and then fitting them to stellar isochrones (e.g., References [13,14]). The stellar properties are then used in the derivation of almost all planet properties from radial velocities (RV), transits or transit timing variation (TTV) data. Thus, a reliable estimate of these parameters is crucial for the quality of the planet properties estimate (e.g., Reference [15]). In the framework of this analysis, we compared separately (and in combination) the planetary properties of the confirmed planets from the listed catalogs. In addition, we performed a comparison between planetary systems by examining the distributions of stellar and planetary properties of the main star and each system’s first detected planet. By doing so, we were able to find the biases Geosciences 2018, 8, 325 3 of 22 of the planet properties emerging from the stellar properties. There was no sense in comparing the stellar parameters of all the confirmed planets since it is possible to unintentionally give more weight to multi-planetary systems when performing the analysis. Table2 lists the total number of confirmed planets and systems of each catalog as a function of the different stellar and planet properties. The significant variability of those numbers raised the following questions: Does the catalog with the largest number of planets include all the listed objects of the other catalogs? How different is the distribution of planets from two different catalogs?

Table 2. The total number of listed planets with different stellar and planet properties for each exoplanet catalog.

Number of Objects EU ARCHIVE OPEN ORG All planets 3757 3708 3524 2950 With planetary mass 1327 1276 1275 2917 With planetary radius 2807 2912 2731 2438 With planetary orbital period 3505 3564 3371 2920 With planetary mass, radius and orbital period 655 576 558 2436 All systems 2652 2693 2556 2200 With stellar mass M∗ 2465 2571 2476 1929 With stellar metallicity [Fe/H] 2444 2581 2088 1877 With stellar surface temperature Te f f 2503 2424 2469 2162

Most of the statistical work in this analysis is based on comparing the different sets using a two-sample Kolmogorov–Smirnov test (hereafter, KS test, [16]). Broadly speaking, the p-value of the KS test indicates to what extent two samples can be considered to be drawn from the same distribution—a high p-value indicates a good agreement. It is sensitive to differences in both shape and location of the empirical distribution functions of the two samples. A KS test comparison between two catalogs would compare the distributions of all available estimates of one of the planetary properties mentioned above. If a specific object’s quantity is unavailable, we excluded the object from the comparison pertaining to this property. In cases where only lower/upper bounds were available, we set it to the listed value instead of excluding it. Thus, there were some cases in which two catalogs agreed on the planetary nature of a specific object, yet, since one of the catalogs had a missing value for some property, we excluded this planet from the test. For each pair of catalogs, ‘A’ and ‘B’, we compiled three subsets: (1) The overlap subset, including all objects listed in both catalogs; (2) the unique ‘A’ subset, including only the planets that are unique to catalog ‘A’ and not listed in catalog ‘B’; and (3) the unique ‘B’ subset, including only the planets that are unique to catalog ‘B’ and not listed in catalog ‘A’. We then applied the KS test to compare the three subsets. We performed this analysis for each one of the six parameters separately, as well as a comparison of subsets that include information about the planetary mass, radius and orbital period. Figure1 describes the methodology applied to compare the different catalogs. Geosciences 2018, 8, 325 4 of 22 Geosciences 2018, 8, x FOR PEER REVIEW 4 of 22

Figure 1. Venn diagram describing the different compared subsets. Catalogs ‘A’, ‘B’ represents two Figure 1. Venn diagram describing the different compared subsets. Catalogs ‘A’, ‘B’ represents two out out of the three compared catalogs. For each planet or stellar property we used a Kolmogorov– of the three compared catalogs. For each planet or stellar property we used a Kolmogorov–Smirnov Smirnov (KS) test to compare two out of the three derived subsets: ‘Overlap’, ‘unique A’ and ‘unique B’. (KS) test to compare two out of the three derived subsets: ‘Overlap’, ‘unique A’ and ‘unique B’. A problem we often encountered in our analysis is the possibility of different planet names and aliasesA problemlisted in we each often of encountered the catalogs. in our The analysis differences is the possibilityare typically of different caused planet by spaces, names uppercase/lowercaseand aliases listed in mix-up, each ofand the numbers catalogs. or unique The differences symbols that are are typically used in causedspelling bythe spaces,stellar anduppercase/lowercase planet names. Yet, mix-up, in most and cases, numbers we found or unique a given symbols object to that have are two used different in spelling names the in stellar two differentand planet catalogs. names. To Yet, overcome in most this cases, difficulty, we found wea first given cross-matched object to have the two different different objects names according in two todifferent their stellar catalogs. names To overcomeusing the SIMBAD this difficulty, database, we first and cross-matched then identified the the different different objects planetary according names to thattheir populate stellar names each using system. the SIMBADThis practice database, imparted and thenus with identified the following the different unfortunate planetary conclusion: names that Currently,populate each there system. is no consensus This practice on impartedan unambiguous us with themethod following to mark unfortunate a specific conclusion:planet and to Currently, find its aliasesthere is in no a consensusconvenient on way. an unambiguousTherefore, there method is no reliable to mark way a specific to cross-match planet and two to findplanetary its aliases tables. in a convenient way. Therefore, there is no reliable way to cross-match two planetary tables. 3. Results 3. Results In general, we found the distributions of planets and systems from the different catalogs to be In general, we found the distributions of planets and systems from the different catalogs to be quite similar. An exception was the ORG catalog, where its missing planetary mass values were quite similar. An exception was the ORG catalog, where its missing planetary mass values were derived derived from some theoretical mass–radius (M–R) relation. See Appendix A for the detailed and from some theoretical mass–radius (M–R) relation. See AppendixA for the detailed and complete complete analysis with the quantitative results (Tables A1 and A8; Figures A1 and A7). To infer the analysis with the quantitative results (Tables A1 and A8; Figures A1 and A7). To infer the differences differences between the catalogs, we compared the derived populations of the overlap and unique between the catalogs, we compared the derived populations of the overlap and unique subsets for two subsets for two catalogs at a time, as discussed above. We found the distributions of the overlapping catalogs at a time, as discussed above. We found the distributions of the overlapping planets between planets between the different catalogs to be similar. However, there were significant differences the different catalogs to be similar. However, there were significant differences between the overlap between the overlap and unique subsets. In Figure 2, a kernel density estimation (KDE) [17] for the and unique subsets. In Figure2, a kernel density estimation (KDE) [ 17] for the probability density probability density functions (PDF) of the mass, radius and orbital period for the different subsets is functions (PDF) of the mass, radius and orbital period for the different subsets is given. The solid given. The solid blue curves represent the three overlap subsets when comparing each pair of the blue curves represent the three overlap subsets when comparing each pair of the EU-ARCHIVE-OPEN EU-ARCHIVE-OPEN catalogs. The brown curves represent the unique subsets, where the dashed, catalogs. The brown curves represent the unique subsets, where the dashed, dashed-dotted and dotted dashed-dotted and dotted curves correspond to the unique EU, ARCHIVE and OPEN subsets, curves correspond to the unique EU, ARCHIVE and OPEN subsets, respectively. Evidently, the overlap respectively. Evidently, the overlap and unique subsets seem to have very different distributions for and unique subsets seem to have very different distributions for the three planet properties. Table3 the three planet properties. Table 3 presents the KS tests p-values for the different comparisons presents the KS tests p-values for the different comparisons between KS tests. We found a low p-value between KS tests. We found a low p-value for most comparison tests. for most comparison tests.

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Figure 2. Each catalogs’ subsets probability density functions (PDFs) of planetary mass, radius and orbitalFigure period 2. Each properties, catalogs’ subsets using probability the kernel density density functions estimation (PDFs) (KDE), of planetary where overlapmass, radiusis represented and by orbital period properties, using the kernel density estimation (KDE), where overlap is represented by blue curves and unique by brown curves. In each plot three overlap subsets and six unique subsets may blue curves and unique by brown curves. In each plot three overlap subsets and six unique subsets may be noted (see text for further details). be noted (see text for further details).

AsAs for for thethe propertyproperty of of planetary planetary mass, mass, we wenote notedd that thata higher a higher density density of small of mass small planets mass planets ( ~10 ⊕) populate the unique subsets. We found most of these planets to be TTV planets, ( Mp ∼ 10M⊕) populate the unique subsets. We found most of these planets to be TTV planets, detecteddetected in in multi-planetarymulti-planetary systems. systems. Usually, Usually, the themass mass of a ofplanet a planet detected detected through through TTV is TTVnot is not resolved directly, and in practice, is degenerate with the planet’s eccentric orbit [18]. As a result, we resolved directly, and in practice, is degenerate with the planet’s eccentric orbit [18]. As a result, we have many small TTV planets with an upper mass limit, rather than a nominal value. However, have many small TTV planets with an upper mass limit, rather than a nominal value. However, there there is no uniform approach to displaying this mass limit. At times, the catalogs choose to omit the isvalue no uniform altogether, approach while at to other displaying times it this is displayed mass limit. as Atan times,upper thelimit. catalogs However, choose in many to omit cases, the value altogether,especially whilewith the at otherEU catalog, times the it is mass displayed limit is asreported an upper as a limit. valid However,nominal estimate. in many Due cases, to this especially withdifference the EU in catalog, the mass the property mass limit criteria, is reported we found as many a valid small nominal mass planets estimate. biasing Due the to thisunique difference insubset the mass towards property smaller criteria, masses. we found many small mass planets biasing the unique subset towards smallerFor masses. the planet radii and orbital period distributions, we found the EU and OPEN unique subsetsFor theto have planet a relative radii andhigher orbital density period of planets distributions, in radii values we found of ~1 the EU, and and periods OPEN of unique ~1000 days. Examining the planets that comprise these subsets suggests the reason for this subsets to have a relative higher density of planets in radii values of Rp ∼ 1RJ, and periods of Perioddifference∼ 1000 is probably days. Examining related to the the different planets inclus thation comprise criteria thesethe catalogs subsets use. suggests Some examples the reason are: for this Listed planets where the confirmation paper has used some theoretical M–R relations to infer the difference is probably related to the different inclusion criteria the catalogs use. Some examples are: planetary radius (or mass), some unusual large radii planets suffering strong tidal forces due to their Listedproximity planets to the where parent the stars confirmation (in short periods), paper hasplanets used with some ‘strange theoretical’ transiting M–R light relations curves that to infer the planetarymake the radius planetary (or detection mass), some more unusual controversial, large etc. radii As planets for the sufferinghigher consis strongtency, tidal in terms forces ofdue the to their proximityoverlap and to theunique parent parts stars of (inthe short ARCHIVE periods), catalog, planets we with found ‘strange’ it to be transiting somewhat light artificial. curves By that make theexamining planetary the detection ARCHIVE more unique controversial, planets, we found etc. As ov forer 75% the higherof them consistency,to be K2 planets, in terms suggesting of the overlap andthe unique reason partsfor the of good the ARCHIVEagreement with catalog, the overlap we found subsets it to related be somewhat to the simple artificial. fact: Most By examining of the the ARCHIVEoverlap planets unique are transiting planets, weplanets found (Kepler over and 75% K2), of with them similar to be properties K2 planets, as the suggesting K2 planets. the reason for the good agreement with the overlap subsets related to the simple fact: Most of the overlap planets are Table 3. The p-values from KS tests wherein the distributions of the overlap vs. unique subsets of transiting planets (Kepler and K2), with similar properties as the K2 planets. planetary mass, radius and orbital period properties are compared. The three numbers in brackets in

each cell represent the p-value according to this order: (,,). Table 3. The p-values from KS tests wherein the distributions of the overlap vs. unique subsets of Overlap planetary mass, radius and orbital period propertiesOverlap are compared. EU-OPEN The Overlap three numbers ARCHIVE-EU in brackets in OPEN-ARCHIVE each cell represent the p-value according to this order: (MP, RP, Period). Unique EU --- (<10−10, <10‒10, <10‒10) (<10‒10, <10‒10, <10‒10) ‒8 ‒3 Unique ARCHIVE Overlap(3 × 10 ,OPEN-ARCHIVE 0.03, 2 × 10 ) Overlap --- EU-OPEN (0.69,Overlap 0.01, 0.02)ARCHIVE-EU Unique OPEN (<10‒10, <10‒10, 10‒9) (0.034, 0.74, 4 × 10‒8) --- Unique EU — (<10−10, <10−10, <10−10) (<10−10, <10−10, <10−10) Unique ARCHIVE (3 × 10−8, 0.03, 2 × 10−3) — (0.69, 0.01, 0.02) Performing a similar analysis for the subset of planets in which all three properties of planetary Unique OPEN (<10−10, <10−−10, 10−9) (0.034, 0.74, 4 × 10−8) — mass, radius and orbital period were available, we found the unique and overlap subsets were different again (Figure 3), although having slightly higher p-values (Table 4) than the individual propertyPerforming comparisons a similar presented analysis above. for the subset of planets in which all three properties of planetary mass, radius and orbital period were available, we found the unique and overlap subsets were different again (Figure3), although having slightly higher p-values (Table4) than the individual property comparisons presented above. Geosciences 2018, 8, 325 6 of 22

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Figure 3. Same as Figure 2, but for the subset of planets in which all three properties of planetary Figure 3. Same as Figure2, but for the subset of planets in which all three properties of planetary mass, mass, radius and orbital period were available. radius and orbital period were available. In this case, most of the overlap planets had large masses and radii, with short periods. This in itselfIn is this a bias, case, caused most by of the the combinedoverlap planets sensitivity had of large the RV masses and transit and radii,detection with methods shortperiods. [19]. As This in itselffor the is adistributions bias, caused of by the the unique combined subsets, sensitivity we found them of the to RV be compromised and transit detection by a higher methods number [ 19of ]. As for theTTV-detected distributions planets, of the causingunique thesubsets, distributions we found to be almost them uniform to be compromised in the regime of by both a higher small and number of large planets. Another interesting aspect we observed about these unique subsets was their relative TTV-detected planets, causing the distributions to be almost uniform in the regime of both small and similarity between each other, as displayed quantitative in Table A10 displaying the unique subsets large planets. Another interesting aspect we observed about these unique subsets was their relative p-values. In spite of this relative similarity, these subsets populate different planets, causing this similarityresemblance between to be a eachproduct other, of the as TTV displayed biases in quantitative the catalogs inplanet Table mass A10 inclusion displaying criteria. the unique subsets p-values. In spite of this relative similarity, these subsets populate different planets, causing this resemblanceTable 4. toSame be as a Table product 3, but of for the the TTV subset biases of planets inthe in which catalogs all three planet properties mass of inclusion planetary mass, criteria. radius and orbital period are available. Table 4. Same as Table3, but for the subset of planets in which all three properties of planetary mass, Overlap OPEN-ARCHIVE Overlap EU-OPEN Overlap ARCHIVE-EU radiusUnique and EU orbital period are available.--- (2 × 10‒8, <10‒10, 8 × 10‒6) (3 × 10‒7, 8 × 10‒7, 0.23) Unique ARCHIVE (3 × 10‒5, <10‒10, 3 × 10‒11) --- (0.02, 3 × 10‒7, 8 × 10‒4) Unique OPEN (6Overlap × 10‒5, 7OPEN-ARCHIVE × 10‒5, 6 × 10‒4) (6 × 10Overlap‒3, 2 × 10‒EU-OPEN7, 10‒3) Overlap--- ARCHIVE-EU Unique EU — (2 × 10−8, <10−10, 8 × 10−6) (3 × 10−7, 8 × 10−7, 0.23) − − − − − UniqueAfterARCHIVE examining the(3 ×planetary10 5, <10 systems10, 3 × 10 accordin11) g to the stellar— properties,(0.02, we again 3 × 10 found7, 8 × 10 4) −5 −5 −4 −3 −7 −3 similarityUnique betweenOPEN the (6overlap× 10 ,subsets 7 × 10 and, 6 × significant10 ) (6 ×differences10 , 2 × 10 between, 10 ) the unique to —overlap subsets (Figure 4). We noted that the unique distributions of stellar mass and surface temperature wereAfter biased examining towards smaller the planetary mass and systemslower temper accordingature stars to (K, the M-stars). stellar properties,Spectroscopy we of small again found similaritystars (especially between M-stars) the overlap is challengingsubsets andbecause significant of their intrinsic differences faintness between and thehighunique activityto [20].overlap As subsets a result, detection of planets around these stars is purportedly more difficult and somewhat (Figure4). We noted that the unique distributions of stellar mass and surface temperature were controversial, thus explaining why we found a higher relative number of these objects in the unique biased towards smaller mass and lower temperature stars (K, M-stars). Spectroscopy of small stars subsets. As for the stellar metallicity, we found it to be an unreliable property when analyzing (especiallypossible biases M-stars) in the is challenging catalog comparison. because ofAlthough their intrinsic the metallicity faintness andis an high important activity property, [20]. As a result, detectionproviding of an planets early record around of these the chemical stars is purportedlycomposition moreof the difficultinitial protoplanetary and somewhat disk controversial, [21], the thus explainingplanetary detection why we methods found a do higher not rely relative on this number property of directly. these objectsThe catalogs in the usuallyunique reportedsubsets. thisAs for the stellarproperty metallicity, with high we relative found errors, it to beprobably an unreliable linked to property the imprecise when derivation analyzing that possible is used biases to in the catalogdetermine comparison. the metallicity Although value. Adding the metallicity to this the isfa anct that important each catalog property, referred providing to different an stellar early record ofsurvey the chemical sources, compositionwe found the highest of theinitial inconsistency protoplanetary between catalogs disk [21 to], be the in planetary this parameter detection (when methods docompared not rely with on this the other property stellar directly. and planetary The catalogs properties). usually Nevertheless, reported we this still property found the with following high relative trends: The unique subsets that included larger planets, especially in terms of the OPEN catalog, was errors, probably linked to the imprecise derivation that is used to determine the metallicity value. biased towards higher metallicity values, as expected from previous studies [22,23]. On the other Adding to this the fact that each catalog referred to different stellar survey sources, we found the hand, small planets, especially listed in the unique ARCHIVE catalog, had a wider distribution of highestmetallicities inconsistency [24]. As before, between the catalogsp-values for to bethe in different this parameter KS tests of (when stellar compared properties within the the overlap other stellar andvs. planetaryunique subsets properties). are provided Nevertheless, in Table 5. we The still seemingly found the improved following mean trends: p-value The resultsunique of subsetsthe that includedOPEN catalog larger are planets, caused especially by its relative in terms smaller of thenumber OPEN of listed catalog, stellar was property biased towardsobjects. higher metallicity values, as expected from previous studies [22,23]. On the other hand, small planets, especially listed in the unique ARCHIVE catalog, had a wider distribution of metallicities [24]. As before, the p-values for the different KS tests of stellar properties in the overlap vs. unique subsets are provided in Table5. Geosciences 2018, 8, 325 7 of 22

The seemingly improved mean p-value results of the OPEN catalog are caused by its relative smaller numberGeosciences of 2018 listed, 8, x FOR stellar PEER property REVIEW objects. 7 of 22

FigureFigure 4.4. Catalogs’Catalogs’ subsets PDF’s of of stellar mass, mass, me metallicitytallicity and and surface surface temperature temperature properties properties using KDE,using where:KDE, where:overlap overlapis given is given in blue in blue and andunique uniqueis givenis given in in brown. brown. In In each each plot,plot, threethree overlapoverlap subsets andsubsets six uniqueand six subsetsunique subsets may be may noted be noted (see text(see text for furtherfor further details). details).

TableTable 5.5. TheThe p-values-values obtained obtained from from KS KStests tests comparing comparing the distributions the distributions of the overlap of the vs.overlap uniquevs. unique subsetssubsets ofof stellar mass, mass, metallicity metallicity and and surface surface temp temperatureerature properties. properties. The three The numbers three numbers in brackets in brackets of each cell represent the p-value according to this order: ( ,[/],). of each cell represent the p-value according to this order:∗ (M∗, [Fe/∗ H], T∗). Overlap OPEN-ARCHIVE Overlap EU-OPEN Overlap ARCHIVE-EU Unique EU Overlap OPEN-ARCHIVE--- (<10Overlap‒10, <10‒10EU-OPEN, 9 × 10‒10) (5 × Overlap10‒7, 0.19,ARCHIVE-EU 0.02) ‒10 ‒10 ‒10 ‒6 ‒5 ‒4 UniqueUnique ARCHIVEEU (<10 , <10— , <10 ) (<10−10, <10---− 10, 9 × 10−10)(2 × 10 , (52 × ×1010−, 72, × 0.19,10 0.02)) ‒4 UniqueUniqueARCHIVE OPEN (<10−(0.12,10, <10 0.02,−10 0.09), <10 −10) (0.06, 0.04, —9 × 10 ) (2 × 10−---6, 2 × 10−5, 2 × 10−4) Unique OPEN (0.12, 0.02, 0.09) (0.06, 0.04, 9 × 10−4) — Although it would be reasonable to detect most biases in the exoplanets catalogs in the extreme ends of the examined distributions, the analysis we have presented used a quantitative approach to Although it would be reasonable to detect most biases in the exoplanets catalogs in the extreme study the biases the catalogs possess. We conclude that the biases in the catalogs are caused by: endsSome of missing the examined or obsolete distributions, information about the analysis a planets’ we properties have presented (e.g., the usedsystem a quantitativeof ‘Kepler 53 b,c approach’ is to studylabeled the in biases the ARCHIVE the catalogs catalog possess. with main We conclude planetary that masses the biasesof in< 18 the catalogs and are < 15 caused, for by: Some missingplanets or‘b’, obsolete ‘c’ respectively information [25], however about a planets’a later paper properties [26] finds (e.g., the the masses system to of be ‘Kepler much 53smaller b,c’ is labeled in the~0.18 ARCHIVE, ~0.11 catalog, withrespectively, main planetary as listed in masses both EU of andMP OPEN);< 18 M modelJ and dependentMP < 15 M planetaryJ, for planets ‘b’, ‘c’information respectively based [25 ],on however some theoretical a later paperassumption [26] finds and not the a masses direct measurement to be much smaller(e.g., ‘Kepler-446MP ∼ 0.18 MJ, Mb,c,dP ∼’: Both0.11 MEUJ ,and respectively, OPEN display as listed their in mass both proper EU andty, however, OPEN); model according dependent to the reference planetary article information based[27], onthe somegiven theoretical value is assumptiononly a coarse and estima not atedirect for the measurement planets’ masses (e.g., ‘andKepler-446 expected b,c,d RV’: Both EU andsemi-amplitude OPEN display signatures their mass using property, recent however, empi accordingrically-measured to the referencedata); roughly article[ 27estimated], the given value measurements, which is especially relevant for stellar parameters; or approximated upper limits as is only a coarse estimate for the planets’ masses and expected RV semi-amplitude signatures using the nominal value (e.g., ‘Kepler-114 c’ is a TTV detected mass planet. The EU catalog displays its mass recent empirically-measured data); roughly estimated measurements, which is especially relevant to be ~40⊕ [26]. However, since this measurement is an upper limit, we find it to be for stellar parameters; or approximated upper limits as the nominal value (e.g., ‘Kepler-114 c’ is a inconsistent with the nominal measurement the ARCHIVE displays of ~2.8⊕ [28], while the TTVOPEN detected catalog massdoes not planet. include The this EU planet). catalog displays its mass to be Mp ∼ 40M⊕ [26]. However, since this measurement is an upper limit, we find it to be inconsistent with the nominal measurement the ARCHIVE4. Summary displays & Discussion of Mp ∼ 2.8M⊕ [28], while the OPEN catalog does not include this planet). Our analysis suggests that, although the main exoplanet catalogs overlap significantly, which 4.results Summary in similar & Discussion distributions for most astrophysical parameters, the small discrepancies between the subsetsOur analysis highlight suggests some of that,the catalogs’ although biases. the mainThese exoplanetbiases can best catalogs be seen overlap in the extreme significantly, ends which resultsof the inexamined similar distributions distributions of for small most mass, astrophysical long orbital parameters,period planets the or smallsmall discrepanciesstars (less than betweenour the sun). These biases do not only result from different numbers of confirmed planets in each catalog, subsets highlight some of the catalogs’ biases. These biases can best be seen in the extreme ends of the but mainly from contributing factors, related to the data collection policy of each catalog, such as: examinedThe process distributions each catalog ofuses small to present mass, and long collect orbital the period properties planets of a specific or small planet, stars the (less decision than our sun). Thesewhether biases to include do not a only controversial result from object different as a plan numberset, or the of confirmedroutine maintenance planets in each each catalog catalog, team but mainly fromperforms contributing to its current factors, listed related planets. to the data collection policy of each catalog, such as: The process each catalog uses to present and collect the properties of a specific planet, the decision whether to

Geosciences 2018, 8, 325 8 of 22 include a controversial object as a planet, or the routine maintenance each catalog team performs to its current listed planets. Furthermore, in our analysis, we excluded planets with masses larger than Mp > 10MJ. However the different catalogs use different mass boundaries, which also adds to their different biases. Unfortunately, most of the biases we found are due to the use of various subjective criteria in compiling and maintaining the database. Although all catalogs usually include in their database planets announced in peer-reviewed publications, this should not be the only criterion for a confirmed planet. We suggest that the explosive growth in the known planet population in recent years once again highlights the need for a more rigorous and objective mechanism to tag planets as confirmed. The differences among the catalogs demonstrate that there are conflicting views in the community regarding such criteria. The International Astronomical Union (IAU) is an objective and well-accepted authority by the community, and we therefore suggest that a central catalog could be maintained by Division F (Planetary Systems and Bio-astronomy) of the IAU, and specifically its Commission F2 (Exoplanets and the Solar Systems). Discussions within the commission should resolve the various differences and arrive at a system that can be agreed upon. After performing this analysis and scrutinizing the different calculated biases, we can carefully make the following statements:

• The ARCHIVE catalog is the most up-to-date catalog, with recent Kepler and K2 planet discoveries. It is also the least biased catalog in terms of the interpretation of the mass upper limit, being the true value or the adoption of a model-based value instead of a genuine measurement. Another interesting feature the catalog has is a list of “removed targets” displaying objects that had been listed in the catalog but were removed, suggesting a more rigorous process applied by the ARCHIVE team. • The EU catalog is less restrictive when listing the planetary properties, and therefore could include imprecise estimates. The EU catalog differs the most with the overlap subsets, probably due to its more permissive acceptance criteria and the use of mixed sources of information. However, it has the most wide and large coverage of planets. • The OPEN catalog is somewhere in the middle, between ARCHIVE and EU. In some cases, we find that it resembles the EU subsets, while in others the ARCHIVE. This might not be surprising, given that this catalog is an open-source catalog which is managed and updated by the astronomical community. Although its interface is elegant and user friendly, it has its drawbacks, especially the lack of detection reference and a smaller planet population.

Finally, while each catalog suffers biases, for an exostatistics work, there should not be too much difference among the databases, since the planet population (especially the one compared in this work) is large enough to wash out the small biases and discrepancies. Nevertheless, we find the fusion of catalogs (the overlap subset) a powerful tool as a starting point for increasing the reliability of exostatistics research. A promising platform seems to be the Data & Analysis Center for Exoplanets (DACE) database (https://dace.unige.ch), which includes a linked table to commonly-used exoplanet catalogs. DACE offers an accessible option to check the properties of a specific planet listed in different catalogs, and to compare its properties as they are displayed on the catalogs. Besides a careful and detailed inspection of each exoplanet related paper confirmation, other useful techniques that can be used to increase the confidence of some exoplanet databases is to check other related parameters such as: Discovery date and update times, which can solve issues of “catch-up” times between catalogs and the rate by which they upload new exoplanets; a measure of the velocity semi-amplitude K parameter can suggest the mass measurement is truly deduced from a RV measurement and not derived from some theoretical model; a TTV flag with reported eccentricity parameter can suggest the reported mass measurement is probably not an upper limit, but some nominal value. Geosciences 2018, 8, 325 9 of 22

Author Contributions: Formal analysis, D.B.; Investigation, D.B., R.H. and S.Z.; Methodology, D.B., R.H. and S.Z.; GeosciencesSupervision, 2018 R.H., 8, x andFOR S.Z.;PEER Validation, REVIEW D.B., R.H. and S.Z.; Writing–original draft, D.B.; Writing–review & editing,9 of 22 D.B., R.H. and S.Z. Acknowledgments:Funding: This research We wasthank supported the anonymous by the Ministry referees offo Science,r valuable Technology comments and and Space, suggestions. Israel. This research hasAcknowledgments: made use of the WeNASA thank Exoplanet the anonymous Archive, referees which for is valuableoperated comments by the California and suggestions. Institute This of Technology, research has undermade usecontract of the with NASA the Exoplanet National Archive,Aeronautics which and is operatedSpace Administration by the California under Institute the Exoplanet of Technology, Exploration under Program.contract with This the research National has Aeronautics made use andof the Space Exoplane Administrationt Orbit Database under the and Exoplanet the Exoplanet Exploration Data Program. Explorer This at exoplanets.org.research has made use of the Exoplanet Orbit Database and the Exoplanet Data Explorer at exoplanets.org. Conflicts of Interest: The authors declare no conflict of interest. Conflicts of Interest: The authors declare no conflict of interest. Appendix Details of the Comparison Appendix A. Details of the Comparison

AppendixAppendix A.1. A.1 ComparisonComparison ofof PlanetaryPlanetary PropertiesProperties

We first compared the different catalogs using a KS test for the planet properties of mass (MP), We first compared the different catalogs using a KS test for the planet properties of mass (), radius (RP) and orbital period (Period). Table2 summarizes the number of available objects in radius () and orbital period (). Table 2 summarizes the number of available objects in each catalogeach catalog for the for different the different properties. properties. We Wepresent present in Table in Table A1 A1 and and Figure Figure A1 A1 the the pp-values-values of of the the correspondingcorresponding KSKS teststests and and relevant relevant empirical empirical cumulative cumulative distribution distribution functions functions (CDF) (CDF) of each of subset each subsetrespectively. respectively. The distributions The distributions of the of planetary the planet propertiesary properties from thefrom different the different catalogs catalogs were foundwere foundto be veryto be similar, very similar, apart fromapart thefrom ORG the ORG catalog, cata whichlog, which bases bases its missing its missing planetary planetary mass mass values values on a ontheoretical a theoretical mass-radius mass-radius relation. relation. Table A1. p-values of the different catalogs’ KS test for various planetary properties. Table A1. p-values of the different catalogs’ KS test for various planetary properties.

PlanetPlanet Property Property EU-ORG EU-ORG EU-ARCHIVE EU-ARCHIVE ARCH ARCHIVE-ORGIVE-ORG EU-OPEN EU-OPEN OPEN-ARCHIVE OPEN-ARCHIVE OPEN-ORG OPEN-ORG ‒10−10 ‒−1010 −‒1010 MP <10<10 0.120.12 <10<10 0.300.30 0.99 0.99 <10 <10 ‒4−4 −‒44 RP 6 6×× 1010 0.210.21 0.18 0.18 0.82 0.82 0.03 0.03 3 3 ×× 10 Period 0.320.32 0.37 0.37 0.96 0.96 0.99 0.99 0.74 0.74 0.73 0.73

FigureFigure A1. CumulativeCumulativedistribution distribution functions functions (CDFs) (CDFs) of theof planetarythe planetary mass, mass, radius radius and orbital and orbital period. period.The different The different colors correspond colors corre to thespond different to the catalogs: different Blue: catalogs: The Extrasolar Blue: The Planets Extrasolar Encyclopaedia Planets Encyclopaedia(EU), red: NASA (EU), Exoplanet red: NASA Archive Exoplanet (ARCHIVE), Archive orange:(ARCHIVE), Open orange: Exoplanet Open Catalogue Exoplanet (OPEN), Catalogue and (OPEN),purple:Exoplanet and purple: Data Exoplanet Explorer Data (ORG). Explorer (ORG).

Although the catalogs seemed similar in this comparison, to reveal their true differences, we Although the catalogs seemed similar in this comparison, to reveal their true differences, we applied the analysis discussed in Section 2 to compare the overlap and unique subsets between each applied the analysis discussed in Section2 to compare the overlap and unique subsets between each pair of the EU-ARCHIVE-OPEN catalogs. In all the comparisons we also investigated whether there pair of the EU-ARCHIVE-OPEN catalogs. In all the comparisons we also investigated whether there was any difference between the properties of the overlap parts listed in catalog ‘A’ or ‘B’. In all cases, was any difference between the properties of the overlap parts listed in catalog ‘A’ or ‘B’. In all cases, the p-values were nearly one, suggesting that the two catalogs are comparable. In the following the p-values were nearly one, suggesting that the two catalogs are comparable. In the following subsections we present the comparison for the different planetary properties. subsections we present the comparison for the different planetary properties. Appendix A.1.1. Planetary Mass We summarize the results of the planetary mass comparisons in Tables A2 and A3. In these tables (and the following tables), each row represents two catalogs we compare, where the columns represent the number of planets in that subset (Table A2) or the p-values of the comparison between each two subsets (Table A3). We abbreviate by ‘UA’ and ‘UB’ the unique subsets ‘A’ and ‘B’ respectively. For instance, the first row in Table A3 represents (by column order from left to right):

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Appendix A.1.1 Planetary Mass We summarize the results of the planetary mass comparisons in Tables A2 and A3. In these tables (and the following tables), each row represents two catalogs we compare, where the columns represent the number of planets in that subset (Table A2) or the p-values of the comparison between each two subsets (Table A3). We abbreviate by ‘UA’ and ‘UB’ the unique subsets ‘A’ and ‘B’ respectively. Geosciences 2018, 8, x FOR PEER REVIEW 10 of 22 For instance, the first row in Table A3 represents (by column order from left to right): The p-value of Thethe p-value comparison of the betweencomparison the overlapbetweenof the the overlap EU and of OPEN the EU catalogs and OPEN with catalogs the unique withpart the of unique EU catalog; part ofthe EUp catalog;-value of the the p comparison-value of the between comparison the overlap betweenof the the EU overlap and OPENof the catalogsEU and OPEN with the catalogsunique partwithof theOPEN unique catalog; part of and OPEN the p -valuecatalog; of and the comparisonthe p-value betweenof the comparison the unique EU between and OPEN the unique subsets EU (see and also OPENFigure subsets1, for a (see graphic also explanation).Figure 1, for a graphic explanation). TheThe CDFs CDFs of of the the different different subsets subsets is is shown shown in in Figure Figure A2.A2. We We found that thethe numbernumber ofof planetsplanets in inthe theoverlap overlapsubsets subsets was was large, large, yet yet the populationthe population of the ofunique the uniquesubsets subsets (in this (in section this section and the and following the followingto come) to were come) non-negligible. were non-negligible. Moreover, Moreover, although thealthough number the of number planets inof each planets catalog in each was catalog different, wasthere different, was no there single was catalog no single that includedcatalog that all theincluded objects all from the theobjects other from catalog. the other We found catalog. that We the foundunique thatsubsets the unique were subsets different were from different the overlap from subsetsthe overlap with subsets the exception with the ofexception the unique of theARCHIVE unique ARCHIVEand OPEN and subsets, OPEN when subsets, comparing when them comparing with the themoverlap withsubset the of overlap the EU. subset Correspondingly, of the EU. we Correspondingly,also found the unique we alsoparts found of the the ARCHIVE unique parts and OPENof the ARCHIVE to be very similarand OPEN based to on be the very comparison similar basedbetween on the these comparison two catalogs. between these two catalogs.

Table A2. Catalogs’ subsets total number of planets with listed planetary mass. Table A2. Catalogs’ subsets total number of planets with listed planetary mass.

CatalogCatalog OverlapOverlap UAUA UB UB EU-OPENEU-OPEN 11881188 239239 87 87 OPEN-ARCHIVEOPEN-ARCHIVE 10891089 187187 186 186 ARCHIVE-EU 11751175 101101 252 252

TableTable A3. A3. p-valuesp-values of ofthe the different different catalogs’ catalogs’ KS KS test test for for the the planetary planetary mass mass property. property.

CatalogCatalog OverlapOverlap vs. UAvs. UA Overlap Overlap vs.vs. UBUB UA vs. UBUB ‒10 7 × ‒3 EU-OPENEU-OPEN <10<10 −10 0.0340.034 7 × 1010−3 OPEN-ARCHIVEOPEN-ARCHIVE <10<10‒10 −10 3 3×× 1010‒8− 8 0.42 ARCHIVE-EUARCHIVE-EU 0.69 0.69 <10<10‒10− 10 3.53.5× ×10 10−‒44

FigureFigure A2. A2. CDF ofof the the planetary planetary mass propertymass property for different for subsets.different (a ) EU-OPEN;subsets. (a (b) )EU-OPEN; OPEN-ARCHIVE; (b) OPEN-ARCHIVE;(c) ARCHIVE-EU ( blue:c) ARCHIVE-EUOverlap, red: UAblue:, yellow: OverlapUB, red:. UA, yellow: UB.

We found that most of the disagreement between the overlap and unique subsets to be We found that most of the disagreement between the overlap and unique subsets to be concentrated concentrated in the region of lower-mass planets. At present, most planets with masses < 10⊕, are in the region of lower-mass planets. At present, most planets with masses < 10M⊕, are estimated from estimated from TTVs in multi-planetary systems. Usually, the mass of a planet detected through TTVs in multi-planetary systems. Usually, the mass of a planet detected through TTV is not resolved TTV is not resolved directly, and in practice, is degenerate with the planet’s eccentric orbit [18], following knowledge on an upper mass limit, rather than a nominal value. Consequently, we found the catalogs use different inclusion criteria for these kinds of planets with no uniform approach to displaying this mass limit. Sometimes the catalogs chose to omit the value altogether, sometimes to display it as an upper limit, but in many cases, the mass limit was reported as a legitimate nominal estimate. The derived CDF presented in Figure A2 suggest the EU catalog, as opposed to the ARCHIVE and OPEN, displays many of its TTV planets’ mass as the reported upper limit value given from their confirmation paper without any strict filtering. The modest agreement we found

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directly, and in practice, is degenerate with the planet’s eccentric orbit [18], following knowledge on an upper mass limit, rather than a nominal value. Consequently, we found the catalogs use different inclusion criteria for these kinds of planets with no uniform approach to displaying this mass limit. Sometimes the catalogs chose to omit the value altogether, sometimes to display it as an upper limit, but in many cases, the mass limit was reported as a legitimate nominal estimate. The derived CDF Geosciencespresented 2018, in8, x Figure FOR PEER A2 suggestREVIEW the EU catalog, as opposed to the ARCHIVE and OPEN, displays11 of many 22 of its TTV planets’ mass as the reported upper limit value given from their confirmation paper without betweenany strict the OPEN filtering. and The ARCHIVE modest agreementunique parts we was found artificial, between driven the fr OPENom the and similar ARCHIVE numberunique of TTVparts planetswas artificial,the two catalogs driven fromchoose the to similar include. number of TTV planets the two catalogs choose to include.

AppendixAppendix A.1.2. A.1.2 Planetary Planetary Radius Radius and and Orbital Orbital Period Period AlthoughAlthough we we inspected inspected the the properties properties of of planet planetaryary radiusradius andand orbital orbital period period separately, separately, we we found foundthe resultthe result of the of comparison the comparison analysis analysis between between their overlap their overlapand unique and subsetsunique subsets to be similar. to be Wesimilar. present Wethe present number the ofnumber planets of withplanets reported with reported radii, calculated radii, calculatedp-values p and-values CDFs and of CDFs the different of the different subsets in subsetsTables in A4 Tables and A4A5 and FigureA5 and A3 Figure, respectively. A3, respec Wetively. present We the present number the ofnumber planetary of planetary orbital periods orbital and periodscalculated and calculatedp-values and p-values CDFs and of the CDFs different of the subsets different in Tables subsets A6 in and Tables A7 and A6 Figureand A7 A4 and, respectively. Figure A4, respectively. Table A4. Catalogs’ subsets total number of planets with listed planetary radius. Table A4. Catalogs’ subsets total number of planets with listed planetary radius. Catalog Overlap UA UB Catalog Overlap UA UB EU-OPENEU-OPEN 2691 2691 116 40 40 OPEN-ARCHIVE 2667 64 244 OPEN-ARCHIVEARCHIVE-EU 2703 2667 208 64 244 104 ARCHIVE-EU 2703 208 104 Table A5. p-values of the different catalogs’ KS test for the planetary radius property. Table A5. p-values of the different catalogs’ KS test for the planetary radius property.

CatalogCatalog OverlapOverlap vs.vs. UAUA Overlap Overlap vs.vs. UBUB UA UA vs.vs. UBUB EU-OPENEU-OPEN <10<10‒10− 10 0.740.74 0.02 0.02 −10 −10 OPEN-ARCHIVEOPEN-ARCHIVE <10<10‒10 0.030.03 <10<10‒10 ARCHIVE-EU 0.01 <10−10 <10−10 ARCHIVE-EU 0.01 <10‒10 <10‒10

FigureFigure A3. A3. CDFCDF of thethe planetary planetary radius radius property property for different for different subsets.( a)subsets. EU-OPEN; (a) (bEU-OPEN;) OPEN-ARCHIVE; (b) OPEN-ARCHIVE;(c) ARCHIVE-EU (c) blue: ARCHIVE-EUOverlap, red: blue:UA, Overlap yellow:,UB red:. UA, yellow: UB.

Table A6. Catalogs’ subsets total number of planets with listed planetary orbital period.

Catalog Overlap UA UB EU-OPEN 3303 202 77 OPEN-ARCHIVE 3245 135 317 ARCHIVE-EU 3313 249 192

Table A7. p-values of the different catalogs’ KS test for the planetary orbital period property.

Catalog Overlap vs. UA Overlap vs. UB UA vs. UB EU-OPEN <10‒10 4 × 10‒8 0.31 OPEN-ARCHIVE 10‒9 2 × 10‒3 5 × 10‒10 ARCHIVE-EU 0.02 <10‒10 <10‒10

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Table A6. Catalogs’ subsets total number of planets with listed planetary orbital period.

Catalog Overlap UA UB EU-OPEN 3303 202 77 OPEN-ARCHIVE 3245 135 317 ARCHIVE-EU 3313 249 192

Table A7. p-values of the different catalogs’ KS test for the planetary orbital period property.

Catalog Overlap vs. UA Overlap vs. UB UA vs. UB EU-OPEN <10−10 4 × 10−8 0.31 OPEN-ARCHIVE 10−9 2 × 10−3 5 × 10−10 ARCHIVE-EU 0.02 <10−10 <10−10 Geosciences 2018, 8, x FOR PEER REVIEW 12 of 22

Figure A4. CDF of the planetary orbital period property for different subsets. (a) EU-OPEN; (b) Figure A4. CDF of the planetary orbital period property for different subsets. (a) EU-OPEN; (b) OPEN-ARCHIVE; (c) ARCHIVE-EU blue: Overlap, red: UA, yellow: UB. OPEN-ARCHIVE; (c) ARCHIVE-EU blue: Overlap, red: UA, yellow: UB.

In the analysis of both properties, we found relative similarity between the overlap and unique In the analysis of both properties, we found relative similarity between the overlap and unique subsets of the ARCHIVE catalog and a large difference with the EU and OPEN subsets. It seems that subsets of the ARCHIVE catalog and a large difference with the EU and OPEN subsets. It seems that the OPEN and EU unique parts are shifted towards larger radii ( >1) or longer orbital periods. the OPEN and EU unique parts are shifted towards larger radii (R > 1R ) or longer orbital periods. However, when we examined the list of ARCHIVE unique planets weP foundJ over 75% of them to be However, when we examined the list of ARCHIVE unique planets we found over 75% of them to be K2 K2 planets. We found also a similar ratio of Kepler and K2 planets that populate the overlap planets. We found also a similar ratio of Kepler and K2 planets that populate the overlap ARCHIVE ARCHIVE subset. These two facts together suggest the reason for the good agreement we found subset. These two facts together suggest the reason for the good agreement we found between the between the ARCHIVE overlap and unique subsets related to the similar properties and biases that ARCHIVE overlap and unique subsets related to the similar properties and biases that emerged from the emerged from the transiting detected Kepler and K2 planets: Relative small radii ( <4⊕) and transiting detected Kepler and K2 planets: Relative small radii (R < 4R ) and short orbital period short orbital period ( < 100 ) [29]. Other differences we foundP between⊕ the listed subsets (Period < 100 days) [29]. Other differences we found between the listed subsets are: Listed planets are: Listed planets where the confirmation paper has used some theoretical M–R relations to infer where the confirmation paper has used some theoretical M–R relations to infer the planetary radius the planetary radius (or mass), some unusual large radii planets suffering strong tidal forces due to (or mass), some unusual large radii planets suffering strong tidal forces due to their proximity to the their proximity to the parent stars (in short periods), planets with a ‘strange’ transiting light curves parent stars (in short periods), planets with a ‘strange’ transiting light curves that make the planetary that make the planetary detection more controversial, etc. detection more controversial, etc. We conclude that the reason for the disagreement between the catalogs radii and orbital period We conclude that the reason for the disagreement between the catalogs radii and orbital period distributions is derived from: (1) Different criteria for including planets in the catalogs that do not distributions is derived from: (1) Different criteria for including planets in the catalogs that do not emerge directly from the criteria presented in Table 1; (2) Different update and confirmation emerge directly from the criteria presented in Table1; (2) Different update and confirmation processes processes for new candidates. for new candidates. Appendix A.1.3. Planetary Mass-Radius-Period (MRP) Appendix A.1.3 Planetary Mass-Radius-Period (MRP) In this subsection we compare the total number of planets in each catalog for a subset in which In this subsection we compare the total number of planets in each catalog for a subset in which all all three properties of planetary mass, radius and orbital period are available. Information of these three properties of planetary mass, radius and orbital period are available. Information of these three three physical properties can provide important constraints for planetary characterization and physical properties can provide important constraints for planetary characterization and formation formation models [7]. Most of the current MRP planets were detected with both RV and transit methods while, as of today, most confirmed mass-radius planets are not TTV detected [30]. Consequently, we expect to detect especially large mass-radius, close orbit planets (Hot-Jupiters) around bright solar-like stars. As before, we started by analyzing the MRP distributions of the different catalogs (including the ORG catalog). We present in Table A8 and Figure A5 the p-values of the corresponding KS tests and relevant empirical cumulative distribution functions (CDF) of each subset respectively.

Table A8. Same as Table A1, but for planets with combined information of planetary properties.

Planet EU-ORG EU-ARCHIVE ARCHIVE-ORG EU-OPEN OPEN-ARCHIVE OPEN-ORG Property ‒10 ‒10 ‒10 <10 0.73 <10 0.69 0.92 <10 ‒10 ‒10 ‒10 <10 0.98 <10 0.21 0.24 <10 <10‒10 0.99 <10‒10 0.81 0.58 <10‒10

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models [7]. Most of the current MRP planets were detected with both RV and transit methods while, as of today, most confirmed mass-radius planets are not TTV detected [30]. Consequently, we expect to detect especially large mass-radius, close orbit planets (Hot-Jupiters) around bright solar-like stars. As before, we started by analyzing the MRP distributions of the different catalogs (including the ORG catalog). We present in Table A8 and Figure A5 the p-values of the corresponding KS tests and relevant empirical cumulative distribution functions (CDF) of each subset respectively.

Table A8. Same as Table A1, but for planets with combined information of planetary properties.

Planet Property EU-ORG EU-ARCHIVE ARCHIVE-ORG EU-OPEN OPEN-ARCHIVE OPEN-ORG −10 −10 −10 MP <10 0.73 <10 0.69 0.92 <10 −10 −10 −10 RP <10 0.98 <10 0.21 0.24 <10 Period <10−10 0.99 <10−10 0.81 0.58 <10−10 Geosciences 2018, 8, x FOR PEER REVIEW 13 of 22

Figure A5. Same as Figure A1, but for planets with combined information of planetary properties. Figure A5. Same as Figure A1, but for planets with combined information of planetary properties. Similar with the overall catalogs comparison, excluding the ORG catalog with its added theoreticalSimilar supplement, with the overall all three catalogs other comparison, catalogs ag excludingreed on thetheir ORG distributions. catalog with We its addednoted theoreticalthat as expected,supplement, the distributions all three other were catalogs different agreed than on those their distributions.displayed for Wethe notedseparate that properties as expected, (see the Figuredistributions A1), with were indeed different a higher than number those displayed of planets for in the the separate large mass-radius properties (see and Figure small A1period), with regimes.indeed a higher number of planets in the large mass-radius and small period regimes. ByBy comparing comparing the the total total numbers, numbers, p-valuesp-values and and distributions distributions of ofthe the catalogs catalogs subsets subsets (Tables (Tables A9 A9 andand A10 A10 and and Figure Figure A6), A6 we), we found found most most of ofthe the disagreements disagreements between between the the overlapoverlap andand uniqueunique subsetssubsets to tobe be evident evident in inthe the small small planetary planetary regime regime of ofTTVs’ TTVs’ detected detected planets. planets. We We found found the the uniqueunique subsets,subsets, andand especially especially the the planetary planetary masses masses distributions, distributions, to tobe besimilar similar between between the the catalogs, catalogs, although although the the listedlisted planets planets are are different. different. We We conclude conclude that mostmost ofof the the disagreement disagreement with with the the planets planets of listedof listed MRP MRPcomes comes especially especially from from the different the different approaches approa eachches catalog each usescatalog for uses the confirmed for the confirmed TTV planets. TTV planets. Table A9. Catalogs’ subsets total number of planets with listed mass-radius-period (MRP) properties. Table A9. Catalogs’ subsets total number of planets with listed mass-radius-period (MRP) Catalog Overlap UA UB properties. EU-OPEN 520 135 36 OPEN-ARCHIVECatalog Overlap465 91UA UB 110 ARCHIVE-EUEU-OPEN 528520 47135 36 127 OPEN-ARCHIVE 465 91 110 ARCHIVE-EU 528 47 127

Table A10. p-values of the different catalogs’ KS test for the planetary MRP properties.

Catalog Planetary Property Overlap vs. UA Overlap vs. UB UA vs. UB ‒8 ‒3 2 × 10 6 × 10 0.49 ‒10 ‒7 EU-OPEN <10 2 × 10 0.46 8 × 10‒6 10‒3 0.23 ‒5 ‒5 6 × 10 3 × 10 0.34 ‒5 ‒10 ‒3 OPEN-ARCHIVE 7 × 10 <10 2 × 10 6 × 10‒4 3 × 10‒11 0.05 ‒7 0.02 3 × 10 0.51 ‒7 ‒7 ARCHIVE-EU 3 × 10 8 × 10 0.02 8 × 10‒4 0.23 0.05

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Table A10. p-values of the different catalogs’ KS test for the planetary MRP properties.

Catalog Planetary Property Overlap vs. UA Overlap vs. UB UA vs. UB −8 −3 MP 2 × 10 6 × 10 0.49 −10 −7 EU-OPEN RP <10 2 × 10 0.46 Period 8 × 10−6 10−3 0.23 −5 −5 MP 6 × 10 3 × 10 0.34 −5 −10 −3 OPEN-ARCHIVE RP 7 × 10 <10 2 × 10 Period 6 × 10−4 3 × 10−11 0.05 −7 MP 0.02 3 × 10 0.51 −7 −7 ARCHIVE-EU RP 3 × 10 8 × 10 0.02 Period 8 × 10−4 0.23 0.05 Geosciences 2018, 8, x FOR PEER REVIEW 14 of 22

Figure A6. CDF of the MRP properties for different subsets. ( a) EU-OPEN; ( (b)) OPEN-ARCHIVE; ( (cc)) ARCHIVE-EU blue: Overlap, red: UA, yellow: UB.

Appendix A.2. Planetary Systems We first compared the different catalogs by using a KS test for the stellar properties of the planetary systems of mass (∗ ), metallicity ([/]) and surface temperature ( ). Table 2 summarizes the number of available objects in each catalog for the different properties. We present in Table A11 and Figure A7 the p-values of the corresponding KS tests and relevant empirical CDFs of each subset respectively. We found the distributions to be very similar between all catalogs. The slightly lower metallicity p-values we found was caused by the large error that follows the metallicity property measurement and does not relate to any different distribution between the catalogs.

Table A11. p-values of the different catalogs’ KS test for various stellar properties.

Stellar EU-ORG EU-ARCHIVE ARCHIVE-ORG EU-OPEN OPEN-ARCHIVE OPEN-ORG Property

M∗ 0.77 0.59 0.56 0.76 0.33 0.93 [/] 0.08 0.99 0.03 0.07 0.01 0.28 0.55 0.99 0.74 0.94 0.89 0.99

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Appendix A.2 Planetary Systems We first compared the different catalogs by using a KS test for the stellar properties of the planetary systems of mass (M∗), metallicity ([Fe/H]) and surface temperature (Te f f ). Table2 summarizes the number of available objects in each catalog for the different properties. We present in Table A11 and Figure A7 the p-values of the corresponding KS tests and relevant empirical CDFs of each subset respectively. We found the distributions to be very similar between all catalogs. The slightly lower metallicity p-values we found was caused by the large error that follows the metallicity property measurement and does not relate to any different distribution between the catalogs.

Table A11. p-values of the different catalogs’ KS test for various stellar properties.

Stellar Property EU-ORG EU-ARCHIVE ARCHIVE-ORG EU-OPEN OPEN-ARCHIVE OPEN-ORG

M∗ 0.77 0.59 0.56 0.76 0.33 0.93 [Fe/H] 0.08 0.99 0.03 0.07 0.01 0.28 Te f f 0.55 0.99 0.74 0.94 0.89 0.99 Geosciences 2018, 8, x FOR PEER REVIEW 15 of 22

Figure A7. CDFsCDFs of of the stellar mass, metallicity and surfacesurface temperature.temperature. The The different colors correspond to the different catalogs: blue: EU, red: ARCHIVE, orange: OPEN OPEN purple: ORG.

Similar withwith the the planetary planetary properties, properties, we nextwe comparednext compared the overlap the andoverlapunique andstellar unique properties stellar propertiessubsets between subsets each between pair of theeach EU-ARCHIVE-OPEN pair of the EU-ARCHIVE-OPEN catalogs. We performed catalogs. the We following performed analysis the followingfor the stars analysis of each for planetary the stars system. of each As mentionedplanetary insystem. Section As2, wementioned also compared in Section the distributions 2, we also comparedof the first the detect distributions planet in each of the system first detect to better plan understandet in each system the reasons to better for the understand possible differences.the reasons for the possible differences. Appendix A.2.1 Stellar Mass and Surface Temperature Appendix A.2.1. Stellar Mass and Surface Temperature Finding the stellar mass is an important prior when assessing a planet’s mass by the RV methodFinding [31]. the We stellar expected mass to is detect an important most of our prioroverlap whenplanets assessing around a planet’s F, G and mass K starsby the since RV method most of [31].the planetary We expected detection to detect projects most and of efforts our overlap as of today planets have around been dedicatedF, G and towardsK stars since searching most planets of the planetaryaround a solar detection mass star.projects We presentand efforts the numberas of today of objects have withbeen reporteddedicated stellar towards mass searching (and first planet’splanets aroundplanetary a properties),solar mass calculatedstar. We presentp-values the and number CDFs ofof the objects different with subsets reported in Tables stellar A12 mass and (and A13 firstand planet’sFigures A8planetary and A9 prop, respectively.erties), calculated We found p-values the unique andvs CDFsoverlap of thesubsets different to be subsets different, in withTables higher A12 anddisagreement A13 and Figures in the regimeA8 and of A9, small-mass respectively. stars We (especially found the K unique and M-stars). vs overlap The subsets spectrum to be of different, M-stars withpresents higher a difficulty disagreement for measuring, in the regime due of to small-mass its intrinsic stars faintness (especia andlly high K and activity M-stars). [20]. Consequently,The spectrum ofdetection M-stars of presents planets arounda difficulty these for stars measuring, is supposed due toto be its more intrinsic difficult faintness and somewhat and high controversial,activity [20]. Consequently,thus explaining detection why we found of planets a higher around relative thes numbere stars of theseis supposed objects into the beunique moresubsets. difficult and somewhat controversial, thus explaining why we found a higher relative number of these objects in the unique subsets.

Table A12. Catalogs’ subsets total number of objects with listed stellar mass and planetary properties fractions.

Catalog Stellar/Planet Property Overlap UA UB

∗ 2306 185 157 EU-OPEN 904 122 60 1867 105 129 2268 159 157

∗ 2290 173 282 OPEN-ARCHIVE 877 73 101 1833 141 218 2253 171 263

∗ 2348 224 143 ARCHIVE-EU 1876 175 72 894 84 113 2307 209 119

Table A13. Stellar mass and planet properties KS test p-values for the different catalogs.

Catalog Stellar/Planet Property Overlap vs. UA Overlap vs. UB UA vs. UB ‒10 ‒4 ∗ <10 0.06 8 × 10 ‒3 EU-OPEN 6 × 10 0.11 0.77

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Table A12. Catalogs’ subsets total number of objects with listed stellar mass and planetary properties fractions.

Catalog Stellar/Planet Property Overlap UA UB

M∗ 2306 185 157 M 904 122 60 EU-OPEN P RP 1867 105 129 Period 2268 159 157

M∗ 2290 173 282 M 877 73 101 OPEN-ARCHIVE P RP 1833 141 218 Period 2253 171 263

M∗ 2348 224 143 M 1876 175 72 ARCHIVE-EU P RP 894 84 113 Period 2307 209 119

Table A13. Stellar mass and planet properties KS test p-values for the different catalogs.

Catalog Stellar/Planet Property Overlap vs. UA Overlap vs. UB UA vs. UB Geosciences 2018, 8, x FOR PEER REVIEW 16 of 22 −10 −4 M∗ <10 0.06 8 × 10 −3 M 6 × 10‒3 0.11‒3 0.77‒5 EU-OPEN P 2 × 10 9 × 10 1 × 10 R 2 × 10−3 9 × 10−3 1 × 10−5 P 0.02 2 × 10‒8 8 × 10‒6 Period 0.02 2 × 10−8 8 × 10−6 ‒10 ∗ 0.12 <10 0.01 −10 M∗ 0.12 <10 0.01 OPEN-ARCHIVE 0.44 0.16 0.46 MP 0.44 0.16 0.46 OPEN-ARCHIVE 0.11 0.19 0.05 RP 0.11 0.19 0.05 Period 0.0140.014 0.04 0.04 0.36 0.36 ‒6 ‒7 2 × 10 −6 5 × 10 −7 0.05 ∗M∗ 2 × 10 5 × 10 0.05 ARCHIVE-EU M P 0.310.31 0.14 0.14 0.99 0.99 ARCHIVE-EU ‒10−10 ‒10 −10 R P 0.220.22 <10<10 <10<10 −3 −8 −6 Period 2 ×2 ×1010‒3 2 2× ×1010‒8 8 ×8 10×‒106

Figure A8. CDF of the stellar mass property for different subsets. (a) EU-OPEN; (b) Figure A8. CDF of the stellar mass property for different subsets. (a) EU-OPEN; (b) OPEN-ARCHIVE; OPEN-ARCHIVE; (c) ARCHIVE-EU blue: Overlap, red: UA, yellow: UB. (c) ARCHIVE-EU blue: Overlap, red: UA, yellow: UB.

When comparing the planetary properties of the first detected planets in these systems, we observedWhen a bias comparing towards small the planetaryplanets that properties were probably of the easier first detected to detect planets around inlower these mass systems, stars. we Weobserved also found a a bias small towards fraction small of long planets orbital that period were planets probably (~1000 days easier to detect around) derived lower from mass direct stars. ∼ imagingWe also of foundlarge, high a small mass, fraction semi-major of long axis orbital objects period around planets a small ( Period mass 1000star ordays brown) derived dwarf from (especiallydirect imaging evident of inlarge, the EU high subsets). mass, semi-major axis objects around a small mass star or brown dwarf (especiallyExamining evident the stellar in the surface EU subsets). temperature (not displayed here), we found the unique vs. overlap subsets analysis to be analogous to that of the stellar mass analysis. This was no surprise, especially because of the well-known correlation the two properties possess according to some mass– luminosity relation [32]. For this reason, we have chosen not to elaborate about it here.

Geosciences 2018, 8, 325 17 of 22

Examining the stellar surface temperature (not displayed here), we found the unique vs. overlap subsets analysis to be analogous to that of the stellar mass analysis. This was no surprise, especially because of the well-known correlation the two properties possess according to some mass–luminosity relationGeosciences [32]. 2018 For, 8 this, x FOR reason, PEER REVIEW we have chosen not to elaborate about it here. 17 of 22

Figure A9. CDF of the planetary properties for different subsets of the first detected planet systems Figure A9. CDF of the planetary properties for different subsets of the first detected planet systems with reported stellar mass property. (a) EU-OPEN; (b) OPEN-ARCHIVE; (c) ARCHIVE-EU blue: a b c withOverlap reported, red: stellar UA, yellow: mass UB property.. ( ) EU-OPEN; ( ) OPEN-ARCHIVE; ( ) ARCHIVE-EU blue: Overlap, red: UA, yellow: UB. Appendix A.2.2. Stellar Metallicity AppendixWe A.2.2 found Stellar the catalogs Metallicity usually reported the metallicity property with high relative errors, probablyWe found linked the catalogs to imprecise usually derivation reported that the is metallicity used to determine property the with metallicity high relative value. errors,Combined probably linkedwith to imprecisethe different derivation survey sources that is the used exoplanet to determine catalogs the choose metallicity to present value. in Combinedtheir sites, withwe the consequently found the highest inconsistency between catalogs to be with this parameter (as different survey sources the exoplanet catalogs choose to present in their sites, we consequently found compared with the other stellar and planetary properties). We present the number of objects with the highest inconsistency between catalogs to be with this parameter (as compared with the other reported stellar metallicity (and first planet’s planetary properties), calculated p-values and CDFs of stellarthe and different planetary subsets properties). in Tables A14 We and present A15 and the numberFigures A10 of objectsand A11, with respectively. reported We stellar found metallicity the (andunique firstplanet’s vs. overlap planetary subsets to properties),be yet again different. calculated Whilep-values the overlap and subsets CDFs have ofthe a clear different peak around subsets in Tablessolar A14 metallicity, and A15 and the Figuresunique A10subsets and haveA11 , respectively.a wider range We of found metallicities the unique values.vs. overlapCombiningsubsets to be yetinformation again different. we acquired While from the theoverlap system’ssubsets firsthave detected a clear planet, peak we around noted the solar unique metallicity, OPEN subset the unique subsetsto be have populate a wider withrange a relatively of metallicities low number values. of small Combiningplanets: The informationOPEN catalog welists acquired fewer Kepler from the system’splanets first with detected their stellar planet, metallicity, we noted and the uniquehence they OPEN automatically subset to bemove populate to the withopposite a relatively unique low subset. We found the unique subsets of the ARCHIVE catalog to be especially distributed with a wide variance coming from its population of many K2 and Kepler small radii planets [24].

Geosciences 2018, 8, 325 18 of 22

number of small planets: The OPEN catalog lists fewer Kepler planets with their stellar metallicity, Geosciencesand hence2018, 8, theyx FORautomatically PEER REVIEW move to the opposite unique subset. We found the unique subsets18 of 22 of the ARCHIVE catalog to be especially distributed with a wide variance coming from its population of manyTable K2A14. and Catalogs’ Kepler subsets small radiitotal planetsnumber [of24 ].objects with listed stellar metallicity and planetary properties fractions. Table A14. Catalogs’ subsets total number of objects with listed stellar metallicity and planetary Catalog Stellar/Planet Property Overlap UA UB properties fractions. [/] 2035 409 53 EU-OPENCatalog Stellar/Planet Property Overlap798 97 UA 48 UB 1654 103 24 [Fe /H] 2035 409 53 M 2034798 407 97 52 48 EU-OPEN P [/]RP 19371654 151 103 487 24 Period 2034 407 52 OPEN-ARCHIVE 691 137 108 [Fe /H] 15541937 103 151 450 487 M 691 137 108 OPEN-ARCHIVE P 1936 150 486 RP 1554 103 450 [/]Period 22661936 158 150 178 486 ARCHIVE-EU [Fe /H] 7322266 67 158 144 178 M 1871732 133 67 134 144 ARCHIVE-EU P RP 22641871 158 133 176 134 Period 2264 158 176 Table A15. Stellar metallicity and planet properties KS test p-values for the different catalogs. Table A15. Stellar metallicity and planet properties KS test p-values for the different catalogs. Catalog Stellar/ Planet Property Overlap vs. UA Overlap vs. UB UA vs. UB Catalog Stellar/[/] Planet Property Overlap<10‒10 vs. UA Overlap0.04 vs. UB9 UA× 10vs.‒4 UB ‒5 EU-OPEN [ Fe/H] 5 × 10<10− 10 0.240.04 0.119 × 10 −4 ‒6 −5 ‒4 ‒6 MP 2 ×5 10× 10 8 × 0.2410 3 × 10 0.11 EU-OPEN −6 −4 −6 R P <102 ×‒10 10 2 8×× 1010‒3 103 ×‒510 Period <10−10 2 × 10−3 10−5 [/] 0.02 <10‒10 3 × 10‒9 −10 −9 [Fe/H] 0.02 <10 ‒5 3 × 10‒4 OPEN-ARCHIVE 0.13 2 × 10 3 × 10 M 0.13 2 × 10−5 3 × 10−4 P ‒10 ‒6 ‒10 OPEN-ARCHIVE <10 −10 1 × 10 − 6 < 10 − 10 RP <10 1 × 10 < 10 Period 3 ×3 10×‒107 −7 <10<10‒10− 10 7 ×7 ×1010‒5 −5 [/] ‒5 ‒3 [Fe /H] 2 ×2 10× 10 −5 0.190.19 1010 −3 ARCHIVE-EU M 0.480.48 0.12 0.12 0.33 0.33 ARCHIVE-EU P ‒10−10 ‒10−10 RP 0.890.89 <10<10 <10<10 × −6 × −3 Period 0.050.05 3 3× 1010‒6 3 ×3 1010‒3

FigureFigure A10. A10.CDF ofCDF the ofstellar the stellarmetallicity metallicity property property for different for different subsets. subsets. (a) EU-OPEN; (a) EU-OPEN; (b) OPEN-ARCHIVE;(b) OPEN-ARCHIVE; (c) ARCHIVE-EU (c) ARCHIVE-EU blue: Overlap blue:, Overlapred: UA,, red:yellow:UA, UB. yellow: UB.

Geosciences 2018, 8, 325 19 of 22 Geosciences 2018, 8, x FOR PEER REVIEW 19 of 22

FigureFigure A11. A11. CDFCDF of the of theplanetary planetary properties properties for fordifferent different subsets subsets of the of thefirst first detected detected planet planet systems systems withwith reported reported stellar stellar metallicity metallicity property. property. ( (aa)) EU-OPEN; ((bb)) OPEN-ARCHIVE;OPEN-ARCHIVE; ( c()c ARCHIVE-EU) ARCHIVE-EU blue: blue:Overlap Overlap, red:, red:UA UA, yellow:, yellow:UB. UB.

AppendixAppendix A.3. A.3 Specific Specific Examples Examples of ofDifferences Differences between between the the Catalogs Catalogs Below,Below, we we present present some some of thethe examples examples we we have ha comeve come across across during during this analysis. this analysis. These examplesThese examplesemphasize emphasize some of some the differences of the differences between thebetw catalogseen the reported catalogs planetary reported andplanetary stellar properties:and stellar properties: (I) Planetary mass inconsistency: ‘Kepler-114 c’ is a TTV detected mass planet. The EU catalog (I) Planetary mass inconsistency: ‘Kepler-114 c’ is a TTV detected mass planet. The EU catalog displays its mass to be Mp ∼ 40 M⊕ [26]. However, since this measurement is an upper displays its mass to be ~40 [26]. However, since this measurement is an upper limit, we limit, we found it to be inconsistent⊕ with the nominal measurement the ARCHIVE displays found it to be inconsistent with the nominal measurement the ARCHIVE displays of of Mp ∼ 2.8M⊕ [28], while the OPEN catalog does not include this planet; The system of ~2.8⊕ [28], while the OPEN catalog does not include this planet; The system of ‘Kepler 53 ‘Kepler 53 b,c’ is labeled in the ARCHIVE catalog with main planetary mass of MP < 18 MJ and b,c’ is labeled in the ARCHIVE catalog with main planetary mass of < 18 and < MP < 15 MJ, for planets ‘b’, ‘c’ respectively [25], however a later paper [26] reports the masses 15 , for planets ‘b’, ‘c’ respectively [25], however a later paper [26] reports the masses to be to be much smaller, MP ∼ 0.18 MJ, MP ∼ 0.11 MJ, respectively, as listed in both EU and much smaller, ~0.18 , ~0.11 , respectively, as listed in both EU and OPEN. Both OPEN. Both EU and OPEN display the mass properties of ‘Kepler-446 b,c,d’, however according EU toand the OPEN reference display article the [27 mass], the properties given value of is‘Kepler-446 only a coarse b,c,d’ estimate, however for according the planets to masses the referenceand expected article semi-amplitudes[27], the given value radial is velocities only a coarse signatures estimate using for recent the planets empirically-measured; masses and expected semi-amplitudes radial velocities signatures using recent empirically-measured; ‘Hd181720 b’ is an object that is listed in the OPEN unique with a mass of Mp ∼ 0.37 MJ. On the ‘Hd181720 b’ is an object that is listed in the OPEN unique with a mass of ~0.37 . On the other hand, the EU catalog lists its mass to be Mp ∼ 12.12 MJ (and because of a planet mass other hand, the EU catalog lists its mass to be ~12.12 (and because of a planet mass larger than our 10 cutoff, dropped from our analysis). The explanation for this difference is

Geosciences 2018, 8, 325 20 of 22

larger than our 10 MJ cutoff, dropped from our analysis). The explanation for this difference is referred in EU to be related with the planetary inclination, measured by astrometry, to be small ◦ (i ∼ 1.75 ,[33]), resulting indeed with a MP·sini ∼ 0.37 MJ that was set to be the planet mass in the OPEN catalog.

(II) Planetary radius inconsistency: ‘CoRoT-21 b’ is a Rp ∼ 1.3RJ planet in short orbit ( Period ∼ 2.7 days) which exchanges extreme tidal forces with its parent star [34], and is listed in the EU and OPEN catalogs only; On the other hand, the radius of ‘HD 219134 d’ with a bottom radius limit > 1.6R⊕ [35] is listed only on the ARCHIVE catalog. (III) Planetary orbital period inconsistency: ‘51 Eri b’ is an imaged astrometric giant planet with an assumed orbital period of period~14965 days (41 years) listed on both the EU and OPEN catalogs [36], but with missing information in the ARCHIVE, displaying only the semi-major axis measurement [37]. Another difference between the catalogs for this planet is with its reported planetary mass: Mp ∼ 2 MJ (OPEN and ARCHIVE) Mp ∼ 9 MJ (EU); ’Kepler-37 e’ is a TTV detected planet reported only on the ARCHIVE and OPEN catalogs with no extra reported information except to each period of period~51.19 days [26]. (IV) Stellar mass inconsistency: ‘HIP 57050 b’[38] is listed in all three catalogs but with a missing stellar mass measurement ( M∗ ∼ 0.34M) in the ARCHIVE catalog; ‘OGLE-2014-BLG-1722 b’ is a Mp ∼ 55.3M⊕ planet detected by the Microlensing method around a M∗ ∼ 0.4M star (two-planet system), listed only on the EU catalog [39].

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