{"schema":"https://ver.cy/schemas/card/1.0.0","id":"vr.tr.bl-herculis-variable","code":"thing-q14557003","url":"https://ver.cy/models/thing/q14557003/","name":"BL Herculis variable","alternateNames":[],"kind":"thing","status":"published","version":"0.2.0-wave.2","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 class of Type II Cepheid variable stars with pulsation periods of about one to four days, named after the prototype BL Herculis, which are old, low-mass, metal-poor stars often showing a bump on the light curve; they are the short-period counterparts of W Virginis variables and are used as distance indicators.","purpose":"Let an agent explain BL Herculis variables by properties, relation to other Type II Cepheids and classical Cepheids, use in distance measurement, and observation data.","scope":{"in":[],"out":[],"boundaries":[]},"distinguishingFeatures":["Type II Cepheid","Short periods","Old, metal-poor stars","Distance indicators"],"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 period, luminosity and metallicity of this star?","kind":"measurement"},{"text":"Which population does it belong to?","kind":"provenance"}]}]},{"id":"classify","name":"Classify","description":"Type II subclasses.","findings":[{"id":"classify-finding","name":"Classify","description":"Subclass.","questions":[{"text":"Is the star a BL Herculis, W Virginis or RV Tauri variable, or an RR Lyrae star?","kind":"definition"},{"text":"Which criteria decide?","kind":"definition"}]}]}]},{"id":"physics","name":"Physics","description":"Pulsation.","layers":[{"id":"mechanism","name":"Mechanism","description":"Pulsation mechanism.","findings":[{"id":"mechanism-finding","name":"Mechanism","description":"Mechanism.","questions":[{"text":"What drives the pulsation of BL Herculis stars?","kind":"definition"},{"text":"What causes the bump on the light curve?","kind":"provenance"}]}]},{"id":"evolution","name":"Evolution","description":"Evolutionary state.","findings":[{"id":"evolution-finding","name":"Evolution","description":"Evolutionary state.","questions":[{"text":"What evolutionary stage are these stars in?","kind":"provenance"},{"text":"How do they differ from classical Cepheids in origin?","kind":"definition"}]}]}]},{"id":"distances","name":"Distances","description":"Standard candles.","layers":[{"id":"relation","name":"Relation","description":"Period-luminosity.","findings":[{"id":"relation-finding","name":"Relation","description":"Period-luminosity relation.","questions":[{"text":"What period-luminosity relation applies to BL Herculis stars?","kind":"provenance"},{"text":"How is it calibrated?","kind":"provenance"}]}]},{"id":"use","name":"Use","description":"Applications.","findings":[{"id":"use-finding","name":"Use","description":"Applications.","questions":[{"text":"How are they used to measure distances to clusters and the Galactic bulge?","kind":"definition"},{"text":"What uncertainties apply?","kind":"boundary"}]}]}]},{"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 light curves and catalogue entries be found?","kind":"provenance"},{"text":"Which surveys observe them?","kind":"provenance"}]}]},{"id":"amateur","name":"Amateur","description":"Observing.","findings":[{"id":"amateur-finding","name":"Amateur","description":"Amateur observing.","questions":[{"text":"Can this star be observed by amateurs?","kind":"boundary"},{"text":"How can observations be reported?","kind":"action"}]}]}]}]},"agentConduct":{"may":["Report known BL Herculis variables and their properties from astronomical catalogues.","Explain how they differ from classical Cepheids and their use as distance indicators."],"mustNot":["Classify a star as a BL Herculis variable without a published study.","Present distances derived from them without stated uncertainty.","Attribute observations to observers or surveys that did not make them."],"requiresHuman":["Submitting a classification to a variable star catalogue."]},"ethics":{"considerations":["Shared catalogues depend on honest, sourced classifications.","Amateur and professional observers deserve credit for their data."],"affectedParties":["Astronomers using the catalogues","Amateur observers"]},"owners":{"steward":"Nobody: natural objects held in common; variable star catalogues maintain classifications.","roles":[],"masterSystems":["General Catalogue of Variable Stars","Variable star databases"]},"relations":[{"target":"Q1393939","type":"parent","note":"registry parent class"},{"target":"Type II Cepheid","type":"related","note":"category"},{"target":"BL Herculis","type":"related","note":"prototype"},{"target":"W Virginis variable","type":"related","note":"related class"},{"target":"classical Cepheid","type":"related","note":"related class"}],"interaction":{"identity":{"applicability":"required","items":["Vercy registry: vr.tr.bl-herculis-variable","Wikidata: Q14557003 (https://www.wikidata.org/wiki/Q14557003)","GCVS type: CWB variable star type"]},"properties":{"applicability":"required","items":["pulsation period: about 1-4 days - typical"]},"recognition":{"applicability":"required","items":["Periods of about 1-4 days","Found in globular clusters and the halo","W Virginis stars have longer periods","Pulsating stars with regular light curves and short periods, in old stellar populations."]},"capabilities":{"applicability":"required","items":["describe BL Herculis star properties","distinguish them from other Cepheid types","explain their period-luminosity relation","find light curves and catalogues"]},"hazards":{"applicability":"required","items":["Confusing with classical Cepheids or RR Lyrae stars","Misclassifying by period alone"]},"interfaces":{"applicability":"required","items":["General Catalogue of Variable Stars classification"]},"context":{"applicability":"required","items":["Stellar astrophysics and distance measurement.","BL Herculis stars","W Virginis stars (longer periods)","RV Tauri stars (longest periods)"]}},"sources":[{"title":"Wikidata item Q14557003: BL Herculis variable","url":"https://www.wikidata.org/wiki/Q14557003","note":"identity and sense of the item"},{"title":"Wikipedia: BL Herculis variable","url":"https://en.wikipedia.org/wiki/BL_Herculis_variable","note":"general description of the item"}],"openQuestions":["Should Type II Cepheids be a single entry?","How should catalogues be linked?","How should distance calibrations be recorded?"],"resources":{"spec":"/models/things/publications/thing-q14557003/spec.json"},"provenance":{"origin":"thing registry research (pass 2)","builtFrom":["models/things/publications/thing-q14557003/spec.json"],"providers":["Claude"],"researchStatus":"unreviewed","generatedAt":"2026-09-11T19:32:26Z","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 2026-10-06T19:51:54+00:00: completeness 1.00; sense: Wikidata description; 2 live sources; review by codex: pass"},"score":1.0}}