Researchers Determine Evolutionary Stages of Pre-main Sequence Delta Scuti Stars with Asteroseismology----Chinese Academy of Sciences

Researchers Determine Evolutionary Stages of Pre-main Sequence Delta Scuti Stars with Asteroseismology

Feb 22, 2019

Recently, researchers from Yunnan Observatories of Chinese Academy of Sciences determined precisely the evolutionary stage of the pre-main-sequence delta Scuti stars HIP 80088 and IP Per with asteroseismology for the first time. The two studies were published in The Astrophysical Journal.

The δ Scuti pulsating stars are a class of A-and F-type stars situated at the position where the main sequence overlaps with the classical instability strip. They are mainly in the evolutionary stage of the main sequence and post-main sequence, and in the pre-main-sequence stage. Obtaining reliable masses and ages of the pre-main-sequence stars is essential for investigating the initial mass function and its possible dependence on the features of the parent cloud.

HIP 80088 and IP Per are two delta Scuti pulsators in the Upper Scorpius association and the Perseus OB2 association. Twelve and nine oscillation frequencies are detected for HIP 80088 and IP Per, respectively. Due to invalid of the asymptotic theory of nonradial oscillations for low-order modes, mode identifications are very difficult.

Two common methods of mode identifications are the spectroscopic method and the photometric method. Besides, the rotational splitting and sequence search are two recently developed methods.

Based on the method of the rotational splitting, researchers found that frequency spectra of HIP 80088 and IP Per can be well identified. In particularly, two sets of multiplets are identified for HIP 80088, including one complete triplet and four components of one quintuplet.

Moreover, they found that HIP 80088 and IP Per are two pre-main-sequence stars where the carbon nitrogen (CN) cycle have not reached the equilibrium state. The present percentages of C12 and N14 in the metal composition are determined precisely, i.e., 28% of C12 have been turned into N14 for HIP 80088, and 14% of C12 have been turned into N14 for IP Per.

The studies were funded by the National Natural Science Foundation of China, key Laboratory for the Structure and Evolution of Celestial Objects of Chinese Academy of Sciences, and Light of West China Program.