Three classical Cepheid variable stars in the nuclear bulge of the Milky Way

TL;DR

This paper reports the discovery of three classical Cepheid stars near the Milky Way's center, providing insights into recent star formation history within the nuclear bulge over the past 25 million years.

Contribution

It identifies three Cepheids in the nuclear bulge and uses their periods to infer recent star formation activity, a novel approach in this region.

Findings

Three Cepheids found within 40 parsecs of the galactic center

Star formation increased approximately 25 million years ago

No Cepheids with significantly different periods detected

Abstract

The nuclear bulge is a region with a radius of about 200 parsecs around the centre of the Milky Way. It contains stars with ages ranging from a few million years to over a billion years, yet its star-formation history and the triggering process for star formation remain to be resolved. Recently, episodic star formation, powered by changes in the gas content, has been suggested. Classical Cepheid variable stars have pulsation periods that decrease with increasing age, so it is possible to probe the star-formation history on the basis of the distribution of their periods. Here we report the presence of three classical Cepheids in the nuclear bulge with pulsation periods of approximately 20 days, within 40 parsecs (projected distance) of the central black hole. No Cepheids with longer or shorter periods were found. We infer that there was a period about 25 million years ago, and possibly lasting until recently, in which star formation increased relative to the period of 30-70 million years ago.