Confirmation of simultaneous p and g mode excitation in HD 8801 and Gamma Peg from time-resolved multicolour photometry of six candidate "hybrid" pulsators

Abstract

We carried out a multi-colour time-series photometric study of six stars claimed as "hybrid" p and g mode pulsators in the literature. Gamma Peg was confirmed to show short-period oscillations of the Beta Cep type and simultaneous long-period pulsations typical of Slowly Pulsating B (SPB) stars. From the measured amplitude ratios in the Stromgren uvy passbands, the stronger of the two short period pulsation modes was identified as radial; the second is l=1. Three of the four SPB-type modes are most likely l=1 or 2. Comparison with theoretical model calculations suggests that Gamma Peg is either an 8.5 solar mass radial fundamental mode pulsator or a 9.6 solar mass first radial overtone pulsator. HD 8801 was corroborated as a "hybrid" Delta Sct Gamma Dor star; four pulsation modes of the Gamma Dor type were detected, and two modes of the Delta Sct type were confirmed. Two pulsational signals between the frequency domains of these two known classes of variables were confirmed and another was newly detected. These are either previously unknown types of pulsation, or do not originate from HD 8801. The O-type star HD 13745 showed small-amplitude slow variability on a time scale of 3.2 days. This object may be related to the suspected new type of supergiant SPB stars, but a rotational origin of its light variations cannot be ruled out at this point. 53 Psc is an SPB star for which two pulsation frequencies were determined and identified with low spherical degree. The behaviour of 53 Ari and Iota Her is consistent with non-variability during our observations, and we could not confirm light variations of the comparison star 34 Psc previously suspected. The use of signal-to-noise criteria in the analysis of data sets with strong aliasing is critically discussed.

14 pages, 10 figures, accepted by MNRAS

References in corpus (7)

• Abundance analysis of prime B-type targets for asteroseismology I. Nitrogen excess in slowly-rotating beta Cephei stars
• Most Detects G- and P-Modes in the B Supergiant HD 163899 (B2Ib/II)
• Instability strips of SPB and beta Cephei stars: the effect of the updated OP opacities and of the metal mixture
• The two hybrid B-type pulsators: Nu Eridani and 12 Lacertae
• Excitation and visibility of slow modes in rotating B-type stars
• The planet-hosting subdwarf B star V391 Pegasi is a hybrid pulsator
• Discovery of hybrid $\gamma$ Dor and $\delta$ Sct pulsations in BD+18 4914 through MOST spacebased photometry

Cited by in corpus (31)

• The Kepler characterization of the variability among A- and F-type stars. I. General overview
• Hybrid gamma Doradus - delta Scuti pulsators: New insights into the physics of the oscillations from Kepler observations
• Kepler observations of variability in B-type stars
• Characterising the observational properties of δ Sct stars in the era of space photometry from the Kepler mission
• Forward asteroseismic modeling of stars with a convective core from gravity-mode oscillations: parameter estimation and stellar model selection
• Results of a Search for gamma Dor and delta Sct Stars with the Kepler Spacecraft
• WASP-33: The first delta Scuti exoplanet host star
• The excitation of solar-like oscillations in a delta Scuti star by efficient envelope convection
• KIC 4142768: An Evolved Gamma Doradus/Delta Scuti Hybrid Pulsating Eclipsing Binary with Tidally Excited Oscillations
• Asteroseismology of hybrid pulsators made possible: simultaneous MOST space photometry and ground-based spectroscopy of Gamma Peg
• Atmospheric parameters and pulsational properties for a sample of $\delta$\,Sct, $\gamma$\,Dor, and hybrid {\it Kepler} targets
• Periodic variable A-F spectral type stars in the northern TESS continuous viewing zone
• Strong interactions between g- and p-modes in the hybrid gamma Doradus-delta Scuti CoRoT star ID105733033
• The $\beta$ Cep/SPB star 12 Lacertae: extended mode identification and complex seismic modelling
• Asteroseismology of hybrid $\delta$ Scuti--$\gamma$ Doradus pulsating stars
• Delta Scuti Variables
• CoRoT high-precision photometry of the B0.5 IV star HD 51756
• The hybrid B-type pulsator $\gamma$ Pegasi: mode identification and complex seismic modelling
• TIC 308396022: a $\delta$ Scuti--$\gamma$ Doradus hybrid with large-amplitude radial fundamental mode and regular g-mode period spacing
• Frequency analysis of Delta Scuti stars towards the Galactic bulge
• Unveiling $\delta$ Scuti and $\gamma$ Doradus Hybrid Pulsation of HD 53166 and HD 53349 Plus Rich Frequencies in HD 52788 -- Catalogs of 70552 $\delta$ Sct and 8080 $\gamma$ Dor
• Spectroscopy of hot Gamma Doradus and A-F hybrid Kepler candidates close to the hot border of the Delta Scuti instability strip
• A search for weak or complex magnetic fields in the the B3V star iota Herculis
• Modeling of multimode radially pulsating High-Amplitude Delta Scuti stars from the OGLE Galactic bulge sample
• Polarimetric detection of nonradial oscillation modes in the beta Cephei star beta Crucis
• Period change and stellar evolution of $\beta$ Cephei stars
• A study of Pulsation & Rotation in a sample of A-K type stars in the Kepler field
• Discovery and Characterization of a Rare Magnetic Hybrid $\beta$ Cephei Slowly Pulsating B-type Star in an Eclipsing Binary in the Young Open Cluster NGC 6193
• Complex asteroseismology of the hybrid B-type pulsator $\gamma$ Pegasi: a test of stellar opacities
• Abundance analysis of the Gamma Doradus - Delta Scuti hybrid metallic line (Am) star HD 8801
• KIC 3868420: A high-amplitude $\delta$ Scuti-$\gamma$ Dor hybrid star crossing the Hertzsprung gap