About the Project

Cepheid variable stars play a fundamental role in astronomy because they are standard candles in calibrating the cosmic distance scale via the period-luminosity relationship. As of June 2022, Cepheids have been discovered in galaxies beyond the Milky Way. The total number of known Cepheid variable stars exceeds 20,000 (not counting the ones announced in Gaia DR2).

The aim of the online database maintained at the Konkoly Observatory is to provide easy access to the available photometric data on individual extragalactic Cepheids and to facilitate statistical studies on Cepheid variables known in external galaxies. Stars belonging to any type of Cepheid variables (classical, anomalous, Type II) have been included in this database. Suspected variables and ambiguously identifiable Cepheids have remained, however, out of consideration.

The construction of the database is in progress and has not been finished yet. Data on variables in galaxies hosting the largest numbers of known Cepheids (Small Magellanic Cloud, Large Magellanic Cloud, M31, etc.) will be uploaded at a later phase of the project. Until now we have Cepheids in galaxies.

The Structure of this Website

The table in the Statistics menu lists the number of known Cepheids in the individual galaxies. The detailed data on Cepheids are accessible by clicking on the name of the host galaxy. The Database menu offers the list of the galaxies hosting Cepheids. Selecting a given galaxy, then clicking on the OK button, a table listing the relevant information (coordinates, pulsation period, mean magnitudes in various photometric bands, remarks) is shown.

The name of the galaxy at the upper right corner is linked to the NASA/IPAC Extragalactic Database. Clicking on the ID of the Cepheid brings the SIMBAD web-page of the given star on screen. A list of research papers publishing photometric data on the Cepheids in the given galaxy is found below the table. This bibliographic list is linked to the ADS.

Remarks and suggestions are welcome in order to improve the structure and information content. Contact address: szabados at konkoly.hu.

Acknowledgments

Technical help from Nikolett Szalai, András Holl and Mihály Varadi is gratefully acknowledged. Construction and maintenance of this database has been supported by the ESTEC Contract No.4000106398/12/NL/KML.