Photometry and spectroscopy of massive stars observed during K2 Campaign 8

TL;DR

This study combines spectroscopic and photometric data to analyze eight massive stars observed during K2 Campaign 8, revealing stellar parameters, periodicities, and classifications, including a peculiar giant star and a delta Scuti variable.

Contribution

It provides detailed stellar parameters and variability analysis for a set of massive stars observed by K2, including the identification of a peculiar evolved giant and a delta Scuti star, expanding understanding of massive star behavior.

Findings

Three stars show significant periodicity.

One star identified as a delta Scuti variable.

A peculiar giant star with silicon lines was characterized.

Abstract

We report in this paper spectroscopic and photometric analysis of eight massive stars observed during Campaign 8 of the Kepler/K2 mission from January to March 2016. Spectroscopic data were obtained on these stars at OPD/LNA, Brazil, and their stellar parameters determined using SME. Periodic analyses of the light curves were performed through CLEANEST and PERIOD04 algorithms. Mass, luminosity, and radius of our stars were estimated employing CESAM+POSC grids. Three of our stars show significant periodicity. K2 ID 220679442 and K2 ID 220532854 have periods linked to the stellar rotation. K2 ID 220532854 has prominent silicon lines (Si II 4128-4131), a characteristic presented in the peculiar class of Ap magnetic main sequence stars. However, in our spectral analysis, this object was found to be an evolved, luminous giant star. K2 ID 220466722 was revealed to be a $\delta$ Scuti variable, and 40 individual frequencies were determined for this star. No significant periodicity was found in the light curves for the remaining stars analyzed in this work, besides the instrumental one.