Timing data for the classical Cepheid l Car

Understanding the properties of this star will also constrain the physics and evolution of massive (M>=8M_{sun}_) Cepheids. The challenge, however, is precisely measuring the star's pulsation period and its rate of period change.

The former is important for calibrating the Leavitt Law and the latter for stellar evolution modeling. In this work, we combine previous time-series observations spanning more than a century with new observations to remeasure the pulsation period and compute the rate of period change. We compare our new rate of period change with stellar evolution models to measure the properties of l Car, but find models and observations are, at best, marginally consistent.