Unexpected series of regular frequency spacing of delta Scuti stars in the non-asymptotic regime -- II. Sample -- echelle diagrams and rotation

TL;DR

This study analyzes regular frequency spacings in 90 delta Scuti stars observed by CoRoT, using a new sequence search method and echelle diagrams to explore stellar rotation and internal structure.

Contribution

The paper introduces a combined visual and algorithmic approach for identifying regular frequency spacings in delta Scuti stars, including detailed data treatment and analysis of rotational effects.

Findings

Identification of at least one regular frequency sequence in 77 stars.

Detection of rotationally split multiplets in 31 stars.

Distribution of large separations aligns with stellar models' density relations.

Abstract

A sequence search method was developed for searching for regular frequency spacing in delta Scuti stars by visual inspection and algorithmic search. The sample contains 90 delta Scuti stars observed by CoRoT. An example is given to represent the visual inspection. The algorithm (SSA) is described in detail. The data treatment of the CoRoT light curves, the criteria for frequency filtering and the spacings derived by two methods (three approaches: VI, SSA and FT) are given for each target. Echelle diagrams are presented for 77 targets, for which at least one sequence of regular spacing was identified. Comparing the spacing and the shifts between pairs of echelle ridges revealed that at least one pair of echelle ridges is shifted to midway between the spacing for 22 stars. The estimated rotational frequencies compared to the shifts revealed rotationally split doublets, triplets and multiplets not only for single frequencies, but for the complete echelle ridges in 31 delta Scuti stars. Using several possible assumptions for the origin of the spacings, we derived the large separation ($\Delta\nu$), which are distributed along the mean density versus large separations relation derived from stellar models Suarez 2014.