Lawrence Short presents his previous work on Friday March 26, 10:30, via webex - see the details below.
Investigating the Cepheid Period-Age Relation with Young, Massive Stellar Clusters in the Large Magellanic Cloud
Cepheid variable stars have long been used as distance indicators due to their strong period-luminosity relation, but this is not the only way in which Cepheids are useful tools for Astronomy. There also exists a Period-Age (PA) relation which we derive here empirically using Cepheids that are hosted by stellar clusters whose ages have be determined by isochrone fitting.
We use observations from 6 stellar clusters in the Large Magellanic Cloud (LMC). To find Cepheids, image subtraction techniques are used and their periods are determined via a Phase Dispersion Minimisation (PDM) algorithm. The PA relation we derive shows a steeper gradient than those produced by models caused by a spread in Cepheid periods in each individual cluster. The period spread increases inversely with cluster age. This could be caused by the stars used in our sample having different initial rotation rates. Cepheids whose progenitors have faster initial rotation rates will show longer periods than those with slower initial rotation rates at the same age. This affects the PA relation by causing an increase in the spread of periods observed in Cepheids from a single cluster, as observed. Therefore, rotation rates should be considered when using the PA relation. Having a robust Cepheid PA relation means that once the period of any Cepheid is found, its age can be immediately determined.
This means that the star formation history of any region that contains Cepheids can be studied simply.
Meeting link: https://observatory.webex.com/observatory/j.php?MTID=m9f66477fcaecede83a64c2c82ec60d89
