Amplitude and frequency variations in PG~0101+039 from K2 photometry -- A pulsating hot B subdwarf star in an unsynchronized binary system

Abstract

K2 photometry is suitable for the exploitation of mode variability on short timescales in hot B subdwarf stars, which is important to constrain nonlinear quantities addressed by the stellar theory of high-order perturbation in the future. We analyze the $\sim 80$~d high-quality K2 data collected on PG~0101+039 and extract the frequency content of oscillation. We then determine its rotational and orbital properties, as well as characterize the dynamics of amplitude and frequency. The frequencies are extracted from light curves via a standard prewhitening technique. The binary information is obtained from variations both in brightness and radial velocities. Amplitude and frequency modulation of oscillation modes are measured by piece-wise light curves and characterized by EMCMC method. We have extracted 137 independent frequencies in PG~0101+039 and derived period spacing of ~252s and 144s for the dipole and quadruple modes, respectively. We derive a rotation rate of 8.81+-0.06d and ~8.60+-0.16d based on g- and p-mode multiplets, implying a marginally differential rotation with a probability of ~ 60%. We find that the rotation period is much shorter than the orbital period of ~0.57d, indicating that this system is not synchronized. Amplitude and frequency modulation are measurable for 44 frequencies with high enough amplitude, including 12 rotational components. We characterize their modulating patterns and find a clear correlation between amplitude and frequency variation, which is linked to nonlinear resonant couplings. In general, the modulating scale and timescale are on an order of a few dozen of nano hertz and a few tens of days, respectively, whose values are important constraints to future calculations of nonlinear amplitude equations.

arXiv comment16 pages, 9 figures, accepted

References in corpus (34)

• emcee: The MCMC Hammer
• The Transiting Exoplanet Survey Satellite
• The K2 Mission: Characterization and Early results
• The Origin of Subdwarf B Star (I): the Formation Channels
• A Technique for Extracting Highly Precise Photometry for the Two-Wheeled Kepler Mission
• Spin down of the core rotation in red giants
• Hot subluminous stars
• The binary fraction of extreme horizontal branch stars
• The Potential of Asteroseismology for Hot, Subdwarf B Stars: A New Class of Pulsating Stars?
• Gaia Data Release 2: Properties and validation of the radial velocities
• Self-consistent Stellar Radial Velocities from LAMOST Medium-Resolution Survey (MRS) DR7
• HS0702+6043: A star showing both short-period p-mode and long-period g-mode oscillations
• Photometry of four binary subdwarf B stars and the nature of their unseen companion stars
• Overview of the LAMOST survey in the first decade
• Population of hot subdwarf stars studied with Gaia III. Catalogue of known hot subdwarf stars: Data Release 2
• Amplitude and frequency variations of oscillation modes in the pulsating DB white dwarf star KIC~08626021: The likely signature of nonlinear resonant mode coupling
• The orbits of subdwarf-B + main-sequence binaries. II. Three eccentric systems; BD+29 3070, BD +34 1543 and Feige 87
• First Kepler results on compact pulsators VIII: Mode identifications via period spacings in $g-$mode pulsating Subdwarf B stars
• Phase II of the LAMOST-Kepler/K2 survey. I. Time series of medium-resolution spectroscopic observations
• Asteroseismology revealing trapped modes in KIC 10553698A
• Signatures of nonlinear mode interactions in the pulsating hot B subdwarf star KIC 10139564
• KIC7668647: a 14 day beaming sdB+WD binary with a pulsating subdwarf
• The discovery of differential radial rotation in the pulsating subdwarf B star KIC 3527751
• TESS first look at evolved compact pulsators : Discovery and asteroseismic probing of the g-mode hot B subdwarf pulsator EC 21494-7018
• A transit survey to search for planets around hot subdwarfs: I. methods and performance tests on light curves from Kepler, K2, TESS, and CHEOPS
• Hot subdwarfs in close binaries observed from space II: Analysis of the light curves
• Mode identification in three pulsating hot subdwarfs observed with TESS satellite
• A pulsation analysis of K2 observations of the subdwarf B star PG1142-037 during Campaign 1: A subsynchronously rotating ellipsoidal variable
• Filling the gap between synchronized and non-synchronized sdBs in short-period sdBV+dM binaries with TESS: TIC 137608661, a new system with a well defined rotational splitting
• The sdB pulsating star V391 Peg and its putative giant planet revisited after 13 years of time-series photometric data
• EPIC 228782059: Asteroseismology of what could be the coolest pulsating helium-atmosphere white dwarf (DBV) known?
• High-degree gravity modes in the single sdB star HD4539
• K2 photometry on oscillation mode variability: the new pulsating hot B subdwarf star EPIC 220422705
• The Properties and Evolutions of Starspots on Three Detached Eclipsing Binaries in the LAMOST-Kepler survey

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