{"schema":"https://ver.cy/schemas/card/1.0.0","id":"vr.tr.r-coronae-borealis-variable","code":"thing-q920941","url":"https://ver.cy/models/thing/q920941/","name":"R Coronae Borealis variable","alternateNames":["DY Persei variable"],"kind":"thing","status":"published","version":"0.2.0-wave.1","language":"en","classifiers":{"family":"Thing Registry","category":"Physical world and living systems","entryKind":"thing","plane":"PHY","domain":["PHY.SPC"],"industry":[],"navPath":"","tags":[],"facets":{}},"whatItIs":"A rare class of hydrogen-deficient, carbon-rich supergiant stars that unpredictably fade by several magnitudes when clouds of carbon dust form near the star, then slowly recover; the prototype is R Coronae Borealis, cooler relatives are DY Persei variables, and many may result from mergers of two white dwarfs.","purpose":"Let an agent explain R Coronae Borealis variables by properties, fading mechanism, origin models and observation data, attributing hypotheses.","scope":{"in":[],"out":[],"boundaries":[]},"distinguishingFeatures":["Irregular deep fades","Carbon dust formation","Hydrogen-deficient","Rare"],"structure":{"bundles":[{"id":"properties","name":"Properties","description":"What they are.","layers":[{"id":"star","name":"Star","description":"Stellar properties.","findings":[{"id":"star-finding","name":"Star","description":"Stellar properties.","questions":[{"text":"What are the temperature, luminosity and composition of this star?","kind":"measurement"},{"text":"How is hydrogen deficiency measured?","kind":"definition"}]}]},{"id":"class","name":"Class","description":"Membership.","findings":[{"id":"class-finding","name":"Class","description":"Class membership.","questions":[{"text":"Is the star a confirmed RCB variable or a candidate?","kind":"provenance"},{"text":"Which catalogue lists it?","kind":"provenance"}]}]}]},{"id":"fading","name":"Fading","description":"Dust events.","layers":[{"id":"mechanism","name":"Mechanism","description":"Carbon dust.","findings":[{"id":"mechanism-finding","name":"Mechanism","description":"Fading mechanism.","questions":[{"text":"How does carbon dust formation cause the fades?","kind":"definition"},{"text":"How long do recoveries take?","kind":"measurement"}]}]},{"id":"predict","name":"Predict","description":"Unpredictability.","findings":[{"id":"predict-finding","name":"Predict","description":"Predictability.","questions":[{"text":"Can fades be predicted?","kind":"boundary"},{"text":"What monitoring catches them early?","kind":"provenance"}]}]}]},{"id":"origin","name":"Origin","description":"Formation.","layers":[{"id":"merger","name":"Merger","description":"White dwarf mergers.","findings":[{"id":"merger-finding","name":"Merger","description":"Merger hypothesis.","questions":[{"text":"What evidence supports the white dwarf merger origin, according to astronomers?","kind":"provenance"},{"text":"What alternatives exist?","kind":"provenance"}]}]},{"id":"rarity","name":"Rarity","description":"Numbers.","findings":[{"id":"rarity-finding","name":"Rarity","description":"Numbers.","questions":[{"text":"How many RCB stars are known in our galaxy and nearby galaxies?","kind":"provenance"},{"text":"Why are they rare?","kind":"definition"}]}]}]},{"id":"observing","name":"Observing","description":"Data.","layers":[{"id":"data","name":"Data","description":"Light curves.","findings":[{"id":"data-finding","name":"Data","description":"Light curves.","questions":[{"text":"Where can long-term light curves of R CrB be found?","kind":"provenance"},{"text":"Which surveys observe RCB stars?","kind":"provenance"}]}]},{"id":"amateur","name":"Amateur","description":"Observing programmes.","findings":[{"id":"amateur-finding","name":"Amateur","description":"Amateur observing.","questions":[{"text":"How can amateurs monitor RCB stars and report fades?","kind":"action"},{"text":"Which organisations coordinate observations?","kind":"provenance"}]}]}]}]},"agentConduct":{"may":["Describe R Coronae Borealis variables and their fading behaviour from published data.","Report brightness observations to variable star databases with their source."],"mustNot":["Submit fabricated or unchecked observations to variable star databases.","Misclassify a star as an R Coronae Borealis variable without evidence.","Fail to credit observers whose data are used."],"requiresHuman":["Publishing a new classification of a star."]},"ethics":{"considerations":["Variable star science relies on volunteer observers who deserve credit and accurate records."],"affectedParties":["Amateur and professional astronomers","Readers"]},"owners":{"steward":"Nobody: natural objects held in common; astronomers catalogue them.","roles":[],"masterSystems":["Variable star catalogues and observation databases"]},"relations":[{"target":"Q1362543","type":"parent","note":"registry parent class"},{"target":"eruptive variable star","type":"related","note":"category"},{"target":"R Coronae Borealis","type":"related","note":"prototype"},{"target":"white dwarf merger","type":"related","note":"hypothesis"},{"target":"Beta Cephei variable","type":"related","note":"other variable class"}],"interaction":{"identity":{"applicability":"required","items":["Vercy registry: vr.tr.r-coronae-borealis-variable","Wikidata: Q920941 (https://www.wikidata.org/wiki/Q920941)","GCVS type: RCB variable star type"]},"properties":{"applicability":"required","items":["Effective temperature:  K - Temperature is estimated from stellar spectra and atmosphere models, with substantial variation across the class.","Fading amplitude:  mag - Amplitude is measured as the difference between maximum-light and fading-event magnitudes in a specified photometric band.","Recovery duration:  day - Duration is measured from a light curve using a stated criterion for return toward the pre-fading brightness.","Hydrogen abundance:  dimensionless number ratio - Abundance is inferred from spectral modelling and reported relative to a specified reference element."]},"recognition":{"applicability":"required","items":["Sudden deep fades","Carbon-rich, hydrogen-poor spectra","Eclipsing binaries fade periodically","Yellowish supergiant stars that suddenly fade and slowly return to normal brightness."]},"capabilities":{"applicability":"required","items":["describe RCB star properties","explain dust-formation fading","summarise origin hypotheses","find light curves and observing programmes"]},"hazards":{"applicability":"required","items":["Presenting origin hypotheses as settled","Confusing fades with eclipses"]},"interfaces":{"applicability":"required","items":["General Catalogue of Variable Stars classification"]},"context":{"applicability":"required","items":["Stellar astrophysics and variable star observing.","classical RCB stars","DY Persei variables","hot RCB stars","extreme helium stars (related)"]}},"sources":[{"title":"Wikidata item Q920941: R Coronae Borealis variable","url":"https://www.wikidata.org/wiki/Q920941","note":"identity and sense of the item"},{"title":"Wikipedia: R Coronae Borealis variable","url":"https://en.wikipedia.org/wiki/R_Coronae_Borealis_variable","note":"general description of the item"}],"openQuestions":["Should each RCB star be a separate entry?","How should light curve archives be linked?","How should DY Persei stars be linked?"],"resources":{"spec":"/models/things/publications/thing-q920941/spec.json"},"provenance":{"origin":"thing registry research (pass 2)","builtFrom":["models/things/publications/thing-q920941/spec.json"],"providers":["Claude"],"researchStatus":"unreviewed","generatedAt":"2026-09-11T13:55:32Z","builder":"tools/build_cards.py@1.0.0"},"completeness":{"sections":{"classifiers":"filled","whatItIs":"filled","purpose":"filled","distinguishingFeatures":"filled","structure":"filled","agentConduct":"filled","ethics":"filled","owners":"filled","relations":"filled","interaction.identity":"filled","interaction.properties":"filled","interaction.recognition":"filled","interaction.capabilities":"filled","interaction.hazards":"filled","interaction.interfaces":"filled","interaction.context":"filled","sources":"filled"},"notes":{"_gate":"Published through the thing publication gate 1.0 on 2026-10-07T10:10:33+00:00: completeness 1.00; sense: Wikidata description; 2 live sources; review by codex: pass"},"score":1.0}}