Photometry and spectroscopy of massive stars observed during K2 Campaign 8

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.

arXiv commentaccepted in MNRAS, 11 pages, 13 figures

References in corpus (20)

• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• The SIMBAD astronomical database
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• Kepler Mission Design, Realized Photometric Performance, and Early Science
• Observation of Electron Neutrino Appearance in a Muon Neutrino Beam
• The K2 Ecliptic Plane Input Catalog (EPIC) and Stellar Classifications of 138,600 Targets in Campaigns 1-8
• Revised Stellar Properties of Kepler Targets for the Q1-17 (DR25) Transit Detection Run
• Rotational velocities of A-type stars IV. Evolution of rotational velocities
• K2SC: Flexible systematics correction and detrending of K2 light curves using Gaussian Process regression
• Rotation Periods, Variability Properties and Ages for Kepler Exoplanet Candidate Host Stars
• Kepler observations of variability in B-type stars
• A unifying explanation of complex frequency spectra of gamma Dor, SPB and Be stars: combination frequencies and highly non-sinusoidal light curves
• Characterising the observational properties of δ Sct stars in the era of space photometry from the Kepler mission
• Spectroscopic survey of Kepler stars. I. HERMES/Mercator observations of A- and F-type stars
• The main-sequence rotation-colour relation in the Coma Berenices open cluster
• Beyond the Kepler/K2 bright limit: variability in the seven brightest members of the Pleiades
• Measuring mean densities of delta Scuti stars with asteroseismology. Theoretical properties of large separations using TOUCAN
• The Classificiation of Kepler B star Variables
• Grids of stellar evolution models for asteroseismology (CESAM + POSC)