# KIC 10001893: A pulsating sdB star with multiple trapped modes

## TL;DR

This paper analyzes the pulsation modes of the sdB star KIC 10001893 using Kepler data, identifying trapped modes that offer new insights into the star's internal structure and composition.

## Contribution

First detection of three trapped modes in a pulsating sdB star, providing key constraints for stellar modeling and understanding of internal structure.

## Key findings

- Identified 110 pulsation frequencies, including 32 dipole and 18 quadrupole modes.
- Detected three trapped modes, first in an sdB star, aiding interior modeling.
- No multiplets observed, suggesting a pole-on orientation.

## Abstract

KIC 10001893 is a V1093 Her type pulsating subdwarf-B star, which was observed extensively by the Kepler spacecraft. It was a part of the survey searching for compact pulsators in the Kepler field of view. An amplitude spectrum of the star demonstrates a rich content of g-modes between 102 and 496 {\mu}Hz as well as a few p-modes above 2000 {\mu}Hz. In total, we found 110 frequencies. The g-mode region contains 104 frequencies, while the p-mode region contains just six, altogether indicating the hybrid nature of KIC 10001893. The main goal of our analysis was to identify the detected modes and to find some features, which will significantly help modeling of the star. We found no multiplets, which points at a pole-on orientation, however, we defined modal degrees and relative radial orders using asymptotic period spacing. Eventually, we assigned 32 dipole l = 1 and 18 quadrupole l = 2 modes. The most remarkable feature we found are trapped modes, which are clearly seen in a reduce period diagram. It is the first time that three trapped modes are detected in one pulsating sdB star. Since the more trapped modes we find, the better sounding of the stellar interior we can do, this feature provides important constraints on the physical structure of the star. Mode trapping is likely caused by the He-H transition region and therefore it provides crucial constraints for making realistic theoretical models of hot subdwarfs.