Planetary influences on photometric variations of the extreme helium subdwarf KIC 10449976

Bear, Ealeal; Soker, Noam

doi:10.1093/mnras/stt1968

Cited by 10 publications

(12 citation statements)

References 43 publications

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“…Radial-velocity measurements over a 5 d time-scale show an upper variability limit of ≈ 50 ± 20 km s −1 . The origin of this modulation remains to be confirmed; Bear & Soker (2014) argue for reflection from a weather-affected planet but fail to show how such a model can lose phase coherence over an interval of 160 or more orbits. Follow-up observations are yet to be carried out.…”

Section: Variabilitymentioning

confidence: 97%

Discovery of a variable lead-rich hot subdwarf: UVO 0825+15

Jeffery

Baran

Behara

et al. 2016

Mon. Not. R. Astron. Soc.

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UVO 0825+15 is a hot bright helium-rich subdwarf which lies in K2 Field 5 and in a sample of intermediate helium-rich subdwarfs observed with Subaru/HDS. The K2 light curve shows low-amplitude variations, whilst the Subaru spectrum shows Pbiv absorption lines, indicative of a very high lead overabundance. UVO 0825+15 also has a high proper motion with kinematics typical for a thick disk star. Analyses of ultraviolet and intermediate dispersion optical spectra rule out a short-period binary companion, and provide fundamental atmospheric parameters of T eff = 38 900±270 K, log g/cm s −2 = 5.97 ± 0.11, log n He /n H = −0.57 ± 0.01, E B−V ≈ 0.03, and angular radius θ = 1.062±0.006×10−11 radians (formal errors). The high-resolution spectrum shows that carbon is > 2 dex subsolar, iron is approximately solar and all other elements heavier than argon are at least 2 -4 dex overabundant, including germanium, yttrium and lead. Approximately 150 lines in the blue-optical spectrum remain unidentified. The chemical structure of the photosphere is presumed to be determined by radiatively-dominated diffusion. The K2 light curve shows a dominant period around 10.8 h, with a variable amplitude, its first harmonic, and another period at 13.3 h. The preferred explanation is multi-periodic non-radial oscillation due to g-modes with very high radial order, although this presents difficulties for pulsation theory. Alternative explanations fail for lack of radial-velocity evidence. UVO 0825+15 represents the fourth member of a group of hot subdwarfs having helium-enriched photospheres and 3-4 dex overabundances of trans-iron elements, and is the first lead-rich subdwarf to show evidence of pulsations.

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Section: Variabilitymentioning

confidence: 97%

Discovery of a variable lead-rich hot subdwarf: UVO 0825+15

Jeffery

Baran

Behara

et al. 2016

Mon. Not. R. Astron. Soc.

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“…The mechanisms that are responsible for the amplitude variations may be attributed to either intrinsic or external reasons. The latter includes the tidal effect due to a component star, like an interesting example given by Bear & Soker (2014). In this assumption, amplitude variations should be synchronized with the orbital motion.…”

Section: Amplitude Variationsmentioning

confidence: 99%

Pulsations and period variations of the δ Scuti star AN Lyncis in a possible three-body system

Li¹,

Fu²,

Su³

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Observations for the δ Scuti star AN Lyn have been made between 2008 and 2016 with the 85-cm telescope at Xinglong station of National Astronomical Observatories of China, the 84-cm telescope at SPM Observatory of Mexico and the Nanshan One meter Wide field Telescope of Xinjiang Observatory of China. Data in V in 50 nights and in R in 34 nights are obtained in total. The bi-site observations from both Xinglong Station and SPM Observatory in 2014 are analyzed with Fourier Decomposition to detect pulsation frequencies. Two independent frequencies are resolved, including one non-radial mode. A number of stellar model tracks are constructed with the MESA code and the fit of frequencies leads to the best-fit model with the stellar mass of M = 1.70 ± 0.05 M ⊙ , the metallicity abundance of Z = 0.020 ± 0.001, the age of 1.33 ± 0.01 billion years and the period change rate 1/P · dP/dt = 1.06 × 10 −9 yr −1 , locating the star at the evolutionary stage close to the terminal age main sequence (TAMS). The O-C diagram provides the period change rate of 1/P · dP/dt = 4.5(8) × 10 −7 yr −1 . However, the period change rate calculated from the models is smaller in two orders than the one derived from the O-C diagram. Together with the sinusoidal function signature, the period variations are regarded to be dominated by the lighttravel time effect of the orbital motion of a three-body system with two low-luminosity components, rather than the stellar evolutionary effect.

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“…Amplitude and/or frequency variations have been found among nearly all types of nonstochastically excited pulsating variables: δ Sct (Breger et al 2012, Breger & Pamyatnykh 2006, Bowman & Kurtz 2014; γ Dor (Rostopchina et al 2013); β Cep (Pigulski & Pojmanski 2008), roAp (Balona et al 2013, Medupe et al 2015; classical pulsators such as high-amplitude δ Sct stars (Zhou & Jiang 2011, Khokhuntod et al 2011, Cepheids (Engle 2015), RR Lyrae (Chadid & Preston 2013), Miras and yellow supergiants (Percy & Yook 2014, Percy & Khatu 2014; white dwarfs (DBV; Handler et al 2003 and DAV;Bell et al 2015); GW Vir stars (Vauclair et al 2012), sdB stars (Kilkenny 2010, Langfellner et al 2012), and an extreme helium subdwarf (Bear & Soker 2014).…”

Section: Causes Of Amplitude/frequency Variationsmentioning

confidence: 99%

Amplitude variability in γ Dor and δ Sct stars observed by the Kepler spacecraft

Guzik¹,

Kosak

Bradley³

et al. 2015

Proc. IAU

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The NASA Kepler spacecraft data revealed a large number of multimode nonradially pulsating γ Dor and δ Sct variable star candidates. The Kepler high precision long time-series photometry makes it possible to study amplitude variations of the frequencies. We summarize recent literature on amplitude and frequency variations in pulsating variables. We are searching for amplitude variability in several dozen faint γ Doradus or δ Scuti variable-star candidates observed as part of the Kepler Guest Observer program. We apply several methods, including a Matlab-script wavelet analysis developed by J. Jackiewicz, and the wavelet technique of the VSTAR software (http://www.aavso.org/vstar-overview). Here we show results for two stars, KIC 2167444 and KIC 2301163. We discuss the magnitude and timescale of the amplitude variations, and the presence or absence of correlations between amplitude variations for different frequencies of a given star. Amplitude variations may be detectable using Kepler data even for stars with Kepler magnitude >14 with low-amplitude frequencies (∼100 ppm) using only one or a few quarters of long-cadence data. We discuss proposed causes of amplitude spectrum variability that will require further investigation.

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Planetary influences on photometric variations of the extreme helium subdwarf KIC 10449976

Cited by 10 publications

References 43 publications

Discovery of a variable lead-rich hot subdwarf: UVO 0825+15

Discovery of a variable lead-rich hot subdwarf: UVO 0825+15

Pulsations and period variations of the δ Scuti star AN Lyncis in a possible three-body system

Amplitude variability in γ Dor and δ Sct stars observed by the Kepler spacecraft

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