Long term light curve variations of the<i>Kepler</i>Cepheid V 1154 Cyg

Kanev, E.; Саванов, И. С.; Sachkov, Mikhail

doi:10.1051/epjconf/201510106036

Cited by 8 publications

(7 citation statements)

References 5 publications

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“…3.1). Our findings agree with the period calculated from smoothed Fourier parameters by Kanev, Savanov & Sachkov (2015). The frequency spectrum of R21 is shown in the top panel of Fig.…”

Section: Fourier Parameterssupporting

confidence: 90%

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TheKeplerCepheid V1154 Cyg revisited: light curve modulation and detection of granulation

Derekas

Plachy

Molnár

et al. 2016

Mon. Not. R. Astron. Soc.

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We present a detailed analysis of the bright Cepheid-type variable star V1154 Cygni using 4 years of continuous observations by the Kepler space telescope. We detected 28 frequencies using standard Fourier transform method. We identified modulation of the main pulsation frequency and its harmonics with a period of ∼159 d. This modulation is also present in the Fourier parameters of the light curve and the O-C diagram. We detected another modulation with a period of about 1160 d. The star also shows significant power in the low-frequency region that we identified as granulation noise. The effective timescale of the granulation agrees with the extrapolated scalings of red giant stars. Non-detection of solar-like oscillations indicates that the pulsation inhibits other oscillations. We obtained new radial velocity observations which are in a perfect agreement with previous years data, suggesting that there is no high mass star companion of V1154 Cygni. Finally, we discuss the possible origin of the detected frequency modulations.

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“…3.1). Our findings agree with the period calculated from smoothed Fourier parameters by Kanev, Savanov & Sachkov (2015). The frequency spectrum of R21 is shown in the top panel of Fig.…”

Section: Fourier Parameterssupporting

confidence: 90%

“…The latest study of V1154 Cyg was performed by Kanev, Savanov & Sachkov (2015) using the 4 years of long cadence Kepler data and studied the light curve by using Fourier decomposition technique. They found that the Fourier parameters R21 and R31 (see in Sect.…”

Section: Introductionmentioning

confidence: 99%

TheKeplerCepheid V1154 Cyg revisited: light curve modulation and detection of granulation

Derekas

Plachy

Molnár

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Such single periodicity may be due to contamination, but may also indicate a possible modulation. We note that periodic modulation was detected in V1154 Cyg, fundamental mode Cepheid (P0 ≈ 4.925 d) observed with Kepler/K2 (Kanev, Savanov & Sachkov 2015;Derekas et al 2017). Modulation period is Pm ≈ 159 d, but amplitudes of the modulation side peaks are nearly an order of magnitude lower than reported here; the highest side peak, at ν0 − νm, has an amplitude of 0.55 mmag.…”

Section: Discussioncontrasting

confidence: 43%

Unstable standard candles. Periodic light-curve modulation in fundamental mode classical Cepheids

Smolec¹

2017

Monthly Notices of the Royal Astronomical Society

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We report the discovery of periodic modulation of pulsation in 51 fundamental mode classical Cepheids of the Magellanic Clouds observed by the Optical Gravitational Lensing Experiment. Although the overall incidence rate is very low, about 1 per cent in each of the Magellanic Clouds, in the case of the SMC and pulsation periods between 12 and 16 d the incidence rate is nearly 40 per cent. On the other hand, in the LMC the highest incidence rate is 5 per cent for pulsation periods between 8 and 14 d, and the overall amplitude of the effect is smaller. It indicates that the phenomenon is metallicity dependent. Typical modulation periods are between 70 and 300 d. In nearly all stars the mean brightness is modulated, which, in principle, may influence the use of classical Cepheids for distance determination. Fortunately, the modulation of mean brightness does not exceed 0.01 mag in all but one star. Also, the effect averages out in typical observations spanning a long time base. Consequently, the effect of modulation on the determination of the distance moduli is negligible. The relative modulation amplitude of the fundamental mode is also low and, with one exception, it does not exceed 6 per cent. The origin of the modulation is unknown. We draw a hypothesis that the modulation is caused by the 2:1 resonance between the fundamental mode and the second overtone that shapes the famous Hertzsprung bump progression.

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“…An early example of this was V473 Lyr, which exhibits periodic variations of its light and radial velocity amplitude, similar to RR Lyrae stars exhibiting the Blazhko effect (Burki et al 1982;Molnár et al 2013). Space-based photometry obtained with the Kepler, MOST, and BRITE satellites has revealed a host of variations in the fundamentalmode Cepheid V1154 Cyg (Derekas et al 2012;Kanev et al 2015;Derekas et al 2017), found long-period modulation in T Vul (Smolec et al 2016a) and suggested a greater degree of irregularity exhibited by first-overtone (FO) Cepheids (Evans et al 2015). Smolec (2017) detected strictly periodic modulations in the pulsation periods of 51 Magellanic Cloud Cepheids using OGLE data.…”

Section: Introductionmentioning

confidence: 98%

Investigating light-curve modulation via kernel smoothing – II. New additional modes in single-mode OGLE classical Cepheids

Süveges

Anderson

2018

Monthly Notices of the Royal Astronomical Society

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Detailed knowledge of the variability of classical Cepheids, in particular their modulations and mode composition, provides crucial insight into stellar structure and pulsation. However, tiny modulations of the dominant radial-mode pulsation were recently found to be very frequent, possibly ubiquitous in Cepheids, which makes secondary modes difficult to detect and analyse, since these modulations can easily mask the potentially weak secondary modes. The aim of this study is to re-investigate the secondary mode content in the sample of OGLE-III and -IV single-mode classical Cepheids using kernel regression with adaptive kernel width for pre-whitening, instead of using a constant-parameter model. This leads to a more precise removal of the modulated dominant pulsation, and enables a more complete survey of secondary modes with frequencies outside a narrow range around the primary. Our analysis reveals that significant secondary modes occur more frequently among first overtone Cepheids than previously thought. The mode composition appears significantly different in the Large and Small Magellanic Clouds, suggesting a possible dependence on chemical composition. In addition to the formerly identified non-radial mode at P 2 ≈ 0.6 . . . 0.65P 1 (0.62-mode), and a cluster of modes with near-primary frequency, we find two more candidate non-radial modes. One is a numerous group of secondary modes with P 2 ≈ 1.25P 1 , which may represent the fundamental of the 0.62-mode, supposed to be the first harmonic of an l ∈ {7, 8, 9} non-radial mode. The other new mode is at P 2 ≈ 1.46P 1 , possibly analogous to a similar, rare mode recently discovered among first overtone RR Lyrae stars.

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Long term light curve variations of theKeplerCepheid V 1154 Cyg

Cited by 8 publications

References 5 publications

TheKeplerCepheid V1154 Cyg revisited: light curve modulation and detection of granulation

TheKeplerCepheid V1154 Cyg revisited: light curve modulation and detection of granulation

Unstable standard candles. Periodic light-curve modulation in fundamental mode classical Cepheids

Investigating light-curve modulation via kernel smoothing – II. New additional modes in single-mode OGLE classical Cepheids

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