Activity time series of old stars from late F to early K

Meunier, N.; Lagrange, Anne-Marie; Boulet, T.; Borgniet, S.

doi:10.1051/0004-6361/201834796

Cited by 31 publications

(19 citation statements)

References 99 publications

(171 reference statements)

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“…The main advantages conferred by this model are a better statistical significance as several samples can be generated, better noise effect estimation as Ca II time-series are noise-free, and eventually the possibility to look at better temporal sampling. These simulations take the impact of inclination into account, in particular in the construction of the chromospheric emission time-series: Meunier et al (2019b) showed that inclination has an impact on the average level (also found later by Sowmya et al 2021), and also impacts the amplitude of the LT variability. These effects are therefore included in our reconstructions.…”

Section: Appendix B: Correction Of Hα Dependence On B-vmentioning

confidence: 81%

“…We first constituted a sample of synthetic time-series similar to the observed ones from the simulations performed in Meunier et al (2019b). Those simulations of complex activity patterns are designed to reproduce a realistic behaviour of F-G-K old main sequence stars, more specifically in the F6-K4 range.…”

Section: Appendix B: Correction Of Hα Dependence On B-vmentioning

confidence: 99%

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Relationship between Ca and Hα chromospheric emission in F-G-K stars: Indication of stellar filaments?

Meunier¹,

Kretzschmar

Gravet

et al. 2022

A&A

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Context. Different relationships between the Hα and Ca II chromospheric emissions have been reported in solar-type stars. In particular, the time-series of emissions in these two lines are clearly anti-correlated for a few percent of the stars, contrary to what is observed on the Sun. Aims. Our objective is to characterise these relationships in more detail using complementary criteria, and to constrain the properties of filaments and plages that are necessary to explain the observations. Methods. We analysed the average level and variability of the Hα and Ca II emission for 441 F-G-K stars, paying particular attention to their (anti-)correlations on both short and long timescales. We also computed synthetic Hα and Ca II time-series for different assumptions of plage and filament properties and compared them with the observations. Results. We were not able to find plage properties that, alone, are sufficient to reproduce the observations at all timescales simultaneously, even when allowing different Hα and Ca II emission relationships for different stars. We also specified the complex and surprising relationship between the average activity levels of both indexes, in particular for low-activity stars. Conclusions. We conclude that plages alone are unlikely to explain the observed variety of relationships between Ca II and Hα emission, and that the presence of other phenomena like filaments may help to reconcile the models with observations.

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Section: Appendix B: Correction Of Hα Dependence On B-vmentioning

confidence: 81%

Section: Appendix B: Correction Of Hα Dependence On B-vmentioning

confidence: 99%

Relationship between Ca and Hα chromospheric emission in F-G-K stars: Indication of stellar filaments?

Meunier¹,

Kretzschmar

Gravet

et al. 2022

A&A

Self Cite

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“…Similarly, Keplerian orbits can be added to the simulated RVs to study the effect of 'red noise' on the planet mass measurements (Gilbertson et al 2020;Meunier & Lagrange 2020). Meunier et al (2019) (2011,2016). Our methods differ from the above work in that we directly use the photometric calibrated granulation and oscillation amplitudes and explicitly show the scaling relations.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…Rotational modulation can appear as a dominant frequency peak at the rotation period, as well as several lower-amplitude peaks at orbital harmonic frequencies. As the amplitude of magnetic activity in the form of rotationally modulated variability is more difficult to model, we do not consider these effects here (see However, Meunier et al 2019).…”

Section: Stellar Granulation and Oscillations In The Fourier Spacementioning

confidence: 99%

Modeling Stellar Oscillations and Granulation in Radial Velocity Time Series: A Fourier-based Method

Guo¹,

Stello²,

Luhn³

et al. 2022

Preprint

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Tens of thousands of solar-like oscillating stars have been observed by space missions. Their photometric variability in the Fourier domain can be parameterized by a sum of two super-Lorentizian functions for granulation and a Gaussian-shaped power excess for oscillation. The photometric granulation/oscillation parameters scale with stellar parameters and they can also make predictions for corresponding parameters in radial velocity measurements. Based on scaling relations, we simulate realistic radial velocity time series and examine how the root-mean-square scatter of radial velocity measurements varies with stellar parameters and different observation strategies such as the length of integration time and gaps in the time series. Using stars with extensive spectroscopic observations from the spectrographs (SONG and HARPS), we measure the granulation amplitude and timescale from the power spectrum of the radial velocity time series. We compare these measurements with literature values based on Kepler photometry. We find that the granulation amplitude in radial velocity can be well predicted from the photometry and scaling relations. Both granulation timescales in radial velocity agree with those predicted from photometry for giants and sub-giants. However, for main-sequence stars, only one granulation timescale in radial velocity is in agreement with the photometric-based values, while the other timescale generally lies at lower frequencies compared to the result of photometry. In conclusion, we show the photometric scaling relations from Kepler photometry and the scaling relationship to Doppler observations can be very useful for predicting the photometric and radial velocity stellar variabilities due to stellar granulation and oscillation.

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“…Recently, Morris et al (2018) developed a simple model to show that the precision of Gaia astrometry is insufficient to detect starspot-induced jitter from stars with near-solar activity levels, though it is sufficient to detect jitter of nearby active stars. Meunier et al (2019) proposed a model to simulate astrometric time series for solar-type stars. Using these simulated time series, Meunier et al (2020) quantified the effect of stellar activity on astrometric measurements, and its impact on the search for Earth-mass planets in the habitable zones of old main-sequence solar-type stars.…”

Section: Introductionmentioning

confidence: 99%

Predictions of Astrometric Jitter for Sun-like Stars. II. Dependence on Inclination, Metallicity, and Active-Region Nesting

Sowmya,

Nèmec,

Shapiro

et al. 2021

Preprint

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Ultra-precise astrometry from the Gaia mission is expected to lead to astrometric detections of more than 20,000 exoplanets in our Galaxy. One of the factors that could hamper such detections is the astrometric jitter caused by the magnetic activity of the planet host stars. In our previous study, we modeled astrometric jitter for the Sun observed equator-on. In this work, we generalize our model and calculate the photocenter jitter as it would be measured by the Gaia and Small-JASMINE missions for stars with solar rotation rate and effective temperature, but with various values of the inclination angle of the stellar rotation axis. In addition, we consider the effect of metallicity and of nesting of active regions (i.e. the tendency of active regions to emerge in the vicinity of each other). We find that, while the jitter of stars observed equator-on does not have any long-term trends and can be easily filtered out, the photocenters of stars observed out of their equatorial planes experience systematic shifts over the course of the activity cycle. Such trends allow the jitter to be detected with continuous measurements, in which case it can interfere with planet detectability. An increase in the metallicity is found to increase the jitter caused by stellar activity. Active-region nesting can further enhance the peak-to-peak amplitude of the photocenter jitter to a level that could be detected by Gaia.

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Activity time series of old stars from late F to early K

Cited by 31 publications

References 99 publications

Relationship between Ca and Hα chromospheric emission in F-G-K stars: Indication of stellar filaments?

Relationship between Ca and Hα chromospheric emission in F-G-K stars: Indication of stellar filaments?

Modeling Stellar Oscillations and Granulation in Radial Velocity Time Series: A Fourier-based Method

Predictions of Astrometric Jitter for Sun-like Stars. II. Dependence on Inclination, Metallicity, and Active-Region Nesting

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