MOST detects SPBe pulsations in HD 127756 & HD 217543: Asteroseismic rotation rates independent of vsini

Abstract

The MOST (Microvariability and Oscillations of Stars) satellite has discovered SPBe (Slowly Pulsating Be) oscillations in the stars HD 127756 (B1/B2 Vne) and HD 217543 (B3 Vpe). For HD 127756, 30 significant frequencies are identified from 31 days of nearly continuous photometry; for HD 217543, up to 40 significant frequencies from 26 days of data. In both cases, the oscillations fall into three distinct frequency ranges, consistent with models of the stars. The variations are caused by nonradial g-modes (and possibly r-modes) distorted by rapid rotation and excited by the opacity mechanism near the iron opacity bump. A comparison of pulsation models and observed frequency groups yields a rotation frequency for each star, independently of vsini. The rotation rates of these stars, as well as those of the SPBe stars previously discovered by MOST, HD 163868 and $\beta$ CMi, are all close to their critical values.

36 pages, 16 figures, 3 tables, accepted for publication in ApJ

References in corpus (13)

• Up-dated opacities from the Opacity Project
• Be-star rotation: how close to critical?
• A Statistical Study of Threshold Rotation Rates for the Formation of Disks around Be Stars
• A heuristic derivation of the uncertainty of the frequency determination in time series data
• 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
• Gravity-mode pulsations in subdwarf B stars: a critical test of stellar opacity
• On the evolutionary status of Be stars. I. Field Be stars near the Sun
• MOST Detects g-Modes in the Late-Type be Star beta CMi (B8Ve)
• Excitation and visibility of slow modes in rotating B-type stars
• Non-radial oscillations of the rapidly rotating Be star HD 163868
• MOST Photometry of the roAp Star HD 134214
• Multiperiodicity in the newly discovered mid-late Be star V2104 Cygni

Cited by in corpus (22)

• Classical Be Stars: Rapidly Rotating B Stars with Viscous Keplerian Decretion Disks
• Probing the interior physics of stars through asteroseismology
• Kepler observations of variability in B-type stars
• A new asteroseismic diagnostic for internal rotation in $\gamma$ Doradus stars
• Forward asteroseismic modeling of stars with a convective core from gravity-mode oscillations: parameter estimation and stellar model selection
• Beyond the Kepler/K2 bright limit: variability in the seven brightest members of the Pleiades
• An astrophysical interpretation of the remarkable g-mode frequency groups of the rapidly rotating $\gamma$ Dor star, KIC 5608334
• Rotationally-modulated g-modes in the rapidly-rotating delta Scuti star Rasalhague (alpha Ophiuchi)
• Short-term variability and mass loss in Be stars II. Physical taxonomy of photometric variability observed by the Kepler spacecraft
• TESS observations of Be stars: a new interpretation
• TESS lightcurves of gamma-Cas stars
• Short-term variability and mass loss in Be stars IV. Two groups of closely spaced, approximately equidistant frequencies in three decades of space photometry of $\nu$ Puppis (B7-8 IIIe)
• Amplitudes of low frequency modes in rotating B type stars
• Rotational Splitting of Pulsational Modes
• High-precision CoRoT space photometry and fundamental parameter determination of the B2.5V star HD 48977
• Stability of g-modes in rotating B-type stars
• Let there be more variability in two gamma Cas stars
• Period-luminosity relations of fast-rotating B-type stars in the young open cluster NGC3766
• Massive Star Asteroseismology in Action
• Prospects for asteroseismology of rapidly rotating B-type stars
• Internal rapid rotation and its implications for stellar structure and pulsations
• Driving mechanism in massive B-type pulsators