KIC 10001893: a pulsating sdB star with multiple trapped modes

Uzundag, Murat; Baran, A.; Østensen, R. H.; Reed, M. D.; Telting, J. H.; Quick, Breanna

doi:10.1093/mnras/stx2011

Cited by 16 publications

(17 citation statements)

References 31 publications

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“…The planets Silvotti et al find orbiting KIC 10001893 are similar to the two Charpinet et al (2011a) find orbiting KPD 1943 + 4058. Uzundag et al (2017) provide a pulsation mode analysis for KIC 10001893, using the same Kepler time-series as Silvotti et al (2014). The amplitude spectrum shows 104 g-mode frequencies between 102 and 496 μHz, as well as six p-modes above 2000 μHz.…”

Section: Kepler Observationsmentioning

confidence: 99%

Asteroseismic Observations of Hot Subdwarfs

Lynas-Gray¹

2021

Front. Astron. Space Sci.

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There are a number of reasons for studying hot subdwarf pulsation; the most obvious being that these stars remain a poorly understood late-stage of stellar evolution and knowledge of their interior structure, which pulsation studies reveal, constrains evolution models. Of particular interest are the red giant progenitors as in looking at a hot subdwarf we are seeing a stripped-down red giant as it would have been just before the Helium Flash. Moreover, hot subdwarfs may have formed through the merger of two helium white dwarfs and their study gives insight into how such a merger may have happened. A less obvious reason for studying pulsation in hot subdwarfs is that they provide a critical test of stellar envelope opacities and the atomic physics upon which they depend.

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Section: Kepler Observationsmentioning

confidence: 99%

Asteroseismic Observations of Hot Subdwarfs

Lynas-Gray¹

2021

Front. Astron. Space Sci.

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“…Unfortunately, short-period modulations are difficult to measure based on the data we have. For data from Uzundag et al (2017), we could not find any reasonable case of amplitude modulation.…”

Section: Frequency Combinationsmentioning

confidence: 65%

“…By restricting the pulsating modes to those with amplitudes above 30 ppm, which is the ∼5 σ detection threshold of LC data (calculated within the 60-450 µHz FT range of the prewhitened light curve), we found that in some cases, the dif- ferences can reach nearly 0.01 µHz. However, the average value of all frequency differences between our data sets and those of Uzundag et al (2017) is lower, approximately 0.005 µHz, and this value is taken as an error of a single frequency in our further considerations. For two combined frequencies, the error of a combination frequency therefore is ±0.007 µHz and determines the maximum distance of the combined frequency to a low FT signal.…”

Section: Frequency Combinationsmentioning

confidence: 83%

“…This high-amplitude l = 1 pulsation g mode ( f 55 as identified by Uzundag et al 2017) would correspond to the third harmonic of k 1 . We found, however, that a 158.08 µHz l = 1 g mode ( f 35 in Uzundag et al 2017, a few times lower in amplitude than f 55 ), fits k 1 better as a second harmonic. We do not observe any unusual amplitude amplification in f 55 or f 35 , as we would expect from tidally powered modes.…”

Section: Discussionmentioning

confidence: 93%

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Analysis of putative exoplanetary signatures found in light curves of two sdBV stars observed by Kepler

Blokesz

Krzesinski

Kedziora-Chudczer

2019

A&A

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Context. We investigate the validity of the claim that invokes two extreme exoplanetary system candidates around the pulsating B-type subdwarfs KIC 10001893 and KIC 5807616 from the primary Kepler field. Aims. Our goal was to find characteristics and the source of weak signals that are observed in these subdwarf light curves. Methods. To achieve this, we analyzed short-and long-cadence Kepler data of the two stars by means of a Fourier transform and compared the results to Fourier transforms of simulated light curves to which we added exoplanetary signals. The long-cadence data of KIC 10001893 were extracted from CCD images of a nearby star, KIC 10001898, using a point spread function reduction technique.Results. It appears that the amplitudes of the Fourier transform signals that were found in the low-frequency region depend on the methods that are used to extract and prepare Kepler data. We demonstrate that using a comparison star for space telescope data can significantly reduce artifacts. Our simulations also show that a weak signal of constant amplitude and frequency, added to a stellar light curve, conserves its frequency in Fourier transform amplitude spectra to within 0.03 µHz. Conclusions. Based on our simulations, we conclude that the two low-frequency Fourier transform signals found in KIC 5807616 are likely the combined frequencies of the lower amplitude pulsating modes of the star. In the case of KIC 10001893, the signal amplitudes that are visible in the light curve depend on the data set and reduction methods. The strongest signal decreases significantly in amplitude when KIC 10001898 is used as a comparison star. Finally, we recommend that the signal detection threshold is increased to 5 σ (or higher) for a Fourier transform analysis of Kepler data in low-frequency regions.

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“…Similar analysis was performed for the second candidate for extreme exoplanetary system around KIC 10001893 where three signals were found in the low FT frequency region at k 1 = 52.683, k 2 = 35.578 and k 3 = 14.261 μHz (Silvotti et al 2014). Using the newest list of pulsation frequencies identified by Uzundag et al (2017), as well as, frequencies prewhitened by us from pure SC (Q3.2, Q6-Q7) and LC (Q1-Q17) data, we performed analysis of pulsation frequency combinations. It appears, that allowing for n and m natural numbers > 1 in n • f i − m • f k frequency combinations we can match all three low FT frequency signals with one or more combination frequencies.…”

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confidence: 78%

Problems with exoplanets around sdBV and sdO stars from primary Kepler field

et al. 2018

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The existence of exoplanets around evolved objects is one of the most interesting subjects from the viewpoint of planetary system evolution and its fate. What happens to the exoplanets engulfed in the host star envelope during red giant branch (RGB) phase? Can planets survive this evolutionary stage of the host star? Here, we are showing that at least some of the exoplanetary candidates recently found around a couple of sdBV stars, KIC 5807616 and KIC 10001893, might not be exoplanets after all. One “exoplanetary signal” visible in the light curve FT of KIC 10001893 can be just a frequency combination of stellar pulsation modes, while others are likely artifacts. Similarly, low frequency signals found in KIC 5807616 light curve FT, are beating frequencies of stellar oscillations, rather than resulting from the exoplanetary radiation. We also analyzed frequency and amplitude changes of the signal around 0.256 c/d (∼3.9 day) visible in the light curve FT of the KIC 10449976 sdO star. Our simulations show that it is difficult to reproduce the observed signal frequency variations by the weather changes in the exoplanet atmosphere.

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KIC 10001893: a pulsating sdB star with multiple trapped modes

Cited by 16 publications

References 31 publications

Asteroseismic Observations of Hot Subdwarfs

Asteroseismic Observations of Hot Subdwarfs

Analysis of putative exoplanetary signatures found in light curves of two sdBV stars observed by Kepler

Problems with exoplanets around sdBV and sdO stars from primary Kepler field

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