# EF Hydrae

> RR Lyrae variable star in the constellation Hydra

**Wikidata**: [Q86337360](https://www.wikidata.org/wiki/Q86337360)  
**Source**: https://4ort.xyz/entity/ef-hydrae


## References

1. SIMBAD
2. Gaia Data Release 3
3. Gaia Data Release 2
4. Discovery of ~9,000 new RR Lyrae in the southern Catalina surveys
5. The University of New South Wales Extrasolar Planet Search: a catalogue of variable stars from fields observed between 2004 and 2007
6. VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
7. Gaia Early Data Release 3
8. On the Use of Field RR Lyrae as Galactic Probes. III. The α-element Abundances
9. On the Use of Field RR Lyrae as Galactic Probes. II. A New ΔS Calibration to Estimate Their Metallicity