The temporal changes of the pulsational periods of the pre-white dwarf PG 1159-035

TL;DR

This study measures the changes in pulsation periods of the pre-white dwarf PG 1159-035 to directly estimate its cooling, contraction, and rotational rates, providing insights into stellar evolution models.

Contribution

It provides the first detailed measurement of period change rates and their second derivatives for multiple pulsation modes in PG 1159-035, refining stellar evolutionary parameters.

Findings

Measured 27 pulsation period changes with rates between 1 and 100 ms/yr.

Achieved a 2% uncertainty in the period change rate for the dominant mode.

Estimated the star's cooling rate, contraction rate, and rotational period change.

Abstract

PG 1159-035, a pre-white dwarf with T=140000 K, is the prototype of the PG1159 spectroscopic class and the DOV pulsating class. Changes in the star cause variations in its oscillation periods. The measurement of temporal change in the oscillation periods, dP/dt, allows us to estimate directly rates of stellar evolutionary changes, such as the cooling rate and the envelope contraction rate, providing a way to test and refine evolutionary models for pre-white dwarf pulsating stars. We measured 27 pulsation modes period changes. The periods varied at rates of between 1 and 100 ms/yr, and several can be directly measured with a relative standard uncertainty below 10%. For the 516.0 s mode (the highest in amplitude) in particular, not only the value of dP/dt can be measured directly with a relative standard uncertainty of 2%, but the second order period change, d(dP/dt)/dt, can also be calculated reliably. By using the (O-C) method we refined the dP/dt and estimated the d(dP/dt)/dt for six other pulsation periods. As a first application, we calculated the change in the PG 1559-035 rotation period, dP_rot/dt = -2.13*10^{-6} s/s, the envelope contraction rate dR/dt = -2.2*10^{-13} solar radius/s, and the cooling rante dT/dt = -1.42*10^{-3} K/s.