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

Meunier, N.; Lagrange, Anne-Marie

doi:10.1051/0004-6361/201935347

Cited by 26 publications

(26 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Lindegren & Dravins (2003) further estimate the effects of stellar activity such as oscillation, granulation, meridional flow, long-term magnetic cycle, surface magnetic activity and rotation, gravitational redshift and many more on the RV measurement. Meunier & Lagrange (2019) then try to model the effect of this kind of activity signal on RV data of mature stars. With our data probing activity timescales of days to years, we are mainly probing the combined effect of stellar rotation, reconfiguration of active regions, and long-term magnetic cycles.…”

Section: Introductionmentioning

confidence: 99%

Radial-velocity jitter of stars as a function of observational timescale and stellar age

Brems

Kürster

Trifonov

et al. 2019

A&A

View full text Add to dashboard Cite

Context. Stars show various amounts of radial-velocity (RV) jitter due to varying stellar activity levels. The typical amount of RV jitter as a function of stellar age and observational timescale has not yet been systematically quantified, although it is often larger than the instrumental precision of modern high-resolution spectrographs used for Doppler planet detection and characterization. Aims. We aim to empirically determine the intrinsic stellar RV variation for mostly G and K dwarf stars on different timescales and for different stellar ages independently of stellar models. We also focus on young stars (≲30 Myr), where the RV variation is known to be large. Methods. We use archival FEROS and HARPS RV data of stars which were observed at least 30 times spread over at least two years. We then apply the pooled variance (PV) technique to these data sets to identify the periods and amplitudes of underlying, quasiperiodic signals. We show that the PV is a powerful tool to identify quasiperiodic signals in highly irregularly sampled data sets. Results. We derive activity-lag functions for 20 putative single stars, where lag is the timescale on which the stellar jitter is measured. Since the ages of all stars are known, we also use this to formulate an activity–age–lag relation which can be used to predict the expected RV jitter of a star given its age and the timescale to be probed. The maximum RV jitter on timescales of decades decreases from over 500 m s−1 for 5 Myr-old stars to 2.3 m s−1 for stars with ages of around 5 Gyr. The decrease in RV jitter when considering a timescale of only 1 d instead of 1 yr is smaller by roughly a factor of 4 for stars with an age of about 5 Myr, and a factor of 1.5 for stars with an age of 5 Gyr. The rate at which the RV jitter increases with lag strongly depends on stellar age and reaches 99% of the maximum RV jitter over a timescale of a few days for stars that are a few million years old, up to presumably decades or longer for stars with an age of a few gigayears.

show abstract

Section: Introductionmentioning

confidence: 99%

Radial-velocity jitter of stars as a function of observational timescale and stellar age

Brems

Kürster

Trifonov

et al. 2019

A&A

View full text Add to dashboard Cite

show abstract

“…This approach also allowed us to produce radial velocities (RV; Meunier & Lagrange 2019), astrometric variations, filling factors, and chromospheric emission (see also Herrero et al 2016). It is important to understand the effect of activity on exoplanet detectability, especially in RV (Meunier & Lagrange 2019;Meunier et al 2019b). In this paper, we focus on the analysis of the complex brightness variations from the same simulations, which cover old main-sequence stars A&A 629, A42 (2019) with spectral types F6-K4.…”

Section: Introductionmentioning

confidence: 99%

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

Meunier

Lagrange

2019

A&A

Self Cite

View full text Add to dashboard Cite

Context. A number of high-precision time series have recently become available for many stars as a result of data from CoRoT, Kepler, and TESS. These data have been widely used to study stellar activity. Photometry provides information that is integrated over the stellar disk. Therefore, there are many degeneracies between spots and plages or sizes and contrasts. In addition, it is important to relate activity indicators, derived from photometric light curves, to other indicators (Log R′HK and radial velocities). Aims. Our aim is to understand how to relate photometric variability to physical parameters in order to help the interpretation of these observations. Methods. We used a large number of synthetic time series of brightness variations for old main sequence stars within the F6-K4 range. Simultaneously, we computed using consistent modeling for radial velocity, astrometry, and chromospheric emission. We analyzed these time series to study the effect of the star spectral type on brightness variability, the relationship between brightness variability and chromospheric emission, and the interpretation of brightness variability as a function of spot and plage properties. We then studied spot-dominated or plage-dominated regimes. Results. We find that within our range of activity levels, the brightness variability increases toward low-mass stars, as suggested by Kepler results. However, many elements can create an interpretation bias. Brightness variability roughly correlates to Log R′HK level. There is, however, a large dispersion in this relationship, mostly caused by spot contrast and inclination. It is also directly related to the number of structures, and we show that it can not be interpreted solely in terms of spot sizes. Finally, a detailed analysis of its relation with Log R′HK shows that in the activity range of old main-sequence stars, we can obtain both spot or plage dominated regimes, as was shown by observations in previous works. The same star can also be observed in both regimes depending on inclination. Furthermore, only strong correlations between chromospheric emission and brightness variability are significant. Conclusions. Our realistic time series proves to be extremely useful when interpreting observations and understanding their limitations, most notably in terms of activity interpretation. Inclination is crucial and affects many properties, such as amplitudes and the respective role of spots and plages.

show abstract

“…For several 1000 points, covering full stellar cycles and an excellent sampling, values below 1 M Earth can be reached, but only in a few cases: for K stars, edge-on configurations and excellent samplings. This illustrates the challenge we are facing to detect or even characterize (for example for a transit follow-up in RV) the mass of an Earth mass planet in RV in the habitable zone around such stars (Meunier & Lagrange 2019).…”

Section: Resultsmentioning

confidence: 99%

“…3 vs. B-V (left-hand side panel) and log R HK (right-hand side panel). The color code corresponds to stellar inclination, from pole-on in yellow to edge-on in green/blue, fromMeunier & Lagrange (2019). Only one point out of 5 is shown for clarity.…”

mentioning

confidence: 99%

From the Sun to solar-type stars: radial velocity, photometry, astrometry and logR′_HK time series for late-F to early-K old stars

Meunier¹,

Lagrange²

2019

Proc. IAU

View full text Add to dashboard Cite

Solar simulations and observations showed that the detection of Earth twins around Sun-like stars is difficult in radial velocities with current methods techniques. The Sun has proved to be very useful to test processes, models, and analysis methods. The convective blueshift effect, dominating for the Sun, decreases towards lower mass stars, providing more suitable conditions to detect low mass planets. We describe the basic processes at work and how we extended a realistic solar model of radial velocity, photometry, astrometry and LogR′HK variability, using a coherent grid of stellar parameters covering a large range in mass and average activity levels. We present selected results concerning the impact of magnetic activity on Earth-mass planet detectability as a function of stellar type. We show how such realistic simulations can help characterizing the effect of stellar activity on RV and astrometric exoplanet detection.

show abstract

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

Cited by 26 publications

References 46 publications

Radial-velocity jitter of stars as a function of observational timescale and stellar age

Radial-velocity jitter of stars as a function of observational timescale and stellar age

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

From the Sun to solar-type stars: radial velocity, photometry, astrometry and logR′_HK time series for late-F to early-K old stars

Contact Info

Product

Resources

About

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

Cited by 26 publications

References 46 publications

Radial-velocity jitter of stars as a function of observational timescale and stellar age

Radial-velocity jitter of stars as a function of observational timescale and stellar age

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

From the Sun to solar-type stars: radial velocity, photometry, astrometry and logR′HK time series for late-F to early-K old stars

Contact Info

Product

Resources

About

From the Sun to solar-type stars: radial velocity, photometry, astrometry and logR′_HK time series for late-F to early-K old stars