RR Lyrae variable
Let an agent describe RR Lyrae variables by subtype, period, amplitude and use as distance indicators, with sourced data.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
written by Claude from model knowledge without web access - no source was read, every claim is a lead to verify
Researched by: Claude
Purpose and description
Let an agent describe RR Lyrae variables by subtype, period, amplitude and use as distance indicators, with sourced data.
A pulsating variable star, typically an old horizontal-branch star of low mass, with periods of about 0.2 to 1 day and amplitudes up to about 1 magnitude; used as standard candles to measure distances in the Milky Way and nearby galaxies.
What it is for: Distance measurement and studying old stellar populations.
It can be look up periods and subtypes; explain use as standard candles; find survey light curves; relate to globular clusters.
Distinguishing features
Short-period radial pulsators
Old, low-mass stars
Nearly uniform luminosity
Common in globular clusters
What it looks like
White to yellow-white stars varying over hours with a characteristic light curve.
Physical character
period: about 0.2-1 days
absolute visual magnitude: about +0.6 mag - approximate
How it is recognised
GCVS types RRAB, RRC, RRD
Periods under a day
Cepheids are brighter with longer periods
Related models
is a kind of - category
is used as - distance indicator
is found in - location
is contrasted with - other standard candle
In practice
Families and kinds
RRab (asymmetric light curves)
RRc (nearly symmetric)
RRd (double-mode)
Identifiers
GCVS type RRAB, RRC, RRD variable star type
Standards and regulation
IAU variable star nomenclature
Failure modes and hazards
Ignoring metallicity in distance estimates
Misclassifying subtypes
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 4 bundles · 8 layers · 8 findings · 16 questions.
Identity Which star.
Catalogues identify.
Designation
Name.
Designation
Designation.
- Which star is meant and what is its subtype? provenance
- Which catalogue lists it? provenance
Host
Population.
Host
Host population.
- Is it in the field, a globular cluster or another galaxy? provenance
- What is its metallicity? measurement
Variability Light curve.
Light curves characterise it.
Period
Timescale.
Period
Period.
- What is its period? measurement
- Does it show the Blazhko effect? provenance
Amplitude
Range.
Amplitude
Amplitude.
- What is its amplitude? measurement
- In which band? definition
Distance Standard candle.
Distances need calibration.
Method
Calibration.
Method
Distance method.
- What distance does its luminosity imply? measurement
- Which calibration was used? provenance
Uncertainty
Errors.
Uncertainty
Uncertainty.
- What uncertainties affect the distance? boundary
- How does extinction matter? definition
Observing Contributing.
Amateurs contribute.
Visibility
Equipment.
Visibility
Visibility.
- Can it be observed with amateur equipment? boundary
- When is it best placed? measurement
Submit
Databases.
Submit
Submitting data.
- How can timings or photometry be submitted? action
- Which organisation collects them? provenance
What the second pass must settle
- Should subtypes be separate entries?
- How should survey data be linked?
- How should calibrations be recorded?