Binarity, activity and metallicity among late-type stars

Dall, T. H.; Bruntt, H.; Strassméier, K. G.

doi:10.1051/0004-6361:20053539

Cited by 20 publications

(25 citation statements)

References 42 publications

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“…However, a positive correlation would also be observed for BiGauss and V span meanwhile here we do find a negative correlation for those two line profile indicators. Another case for a positive correlation between BIS and RV was found for the active K giant EK Eri (Dall et al 2005) which later was reported to have a strong cool spot by Aurière et al (2011) using the Zeeman-Doppler imaging method.…”

Section: Stellar Activity and Line Profile Analysismentioning

confidence: 90%

Planets around evolved intermediate-mass stars

Mena

Santos

Silva

et al. 2018

A&A

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Aims. The aim of this work is to search for planets around intermediate-mass stars in open clusters by using data from an extensive survey with more than 15 years of observations. Methods. We obtain high-precision radial velocities (RV) with the HARPS spectrograph for a sample of 142 giant stars in 17 open clusters. We fit Keplerian orbits when a significant periodic signal is detected. We also study the variation of stellar activity indicators and line-profile variations to discard stellar-induced signals.Results. We present the discovery of a periodic RV signal compatible with the presence of a planet candidate in the 1.15 Gyr open cluster IC4651 orbiting the 2.06 M star No. 9122. If confirmed, the planet candidate would have a minimum mass of 7.2M J and a period of 747 days. However, we also find that the FWHM of the CCF varies with a period close to the RV, casting doubts on the planetary nature of the signal. We also provide refined parameters for the previously discovered planet around NGC2423 No. 3 but show evidence that the BIS of the CCF is correlated with the RV during some of the observing periods. This fact advises us that this might not be a real planet and that the RV variations could be caused by stellar activity and/or pulsations. Finally, we show that the previously reported signal by a brown dwarf around NGC4349 No. 127 is presumably produced by stellar activity modulation. Conclusions. The long-term monitoring of several red giants in open clusters has allowed us to find periodic RV variations in several stars. However, we also show that the follow-up of this kind of stars should last more than one orbital period to detect long-term signals of stellar origin. This work warns that although it is possible to detect planets around red giants, large-amplitude, long-period RV modulations do exist in such stars that can mimic the presence of an orbiting planetary body. Therefore, we need to better understand how such RV modulations behave as stars evolve along the Red Giant Branch and perform a detailed study of all the possible stellar-induced signals (e.g. spots, pulsations, granulation) to comprehend the origin of RV variations.

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Section: Stellar Activity and Line Profile Analysismentioning

confidence: 90%

Planets around evolved intermediate-mass stars

Mena

Santos

Silva

et al. 2018

A&A

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“…HIP 37923/18,HIP 44817,and HIP 70386) show abundance differences larger than 0.03 dex (formally significant at more than 2σ level only for HIP 37923/18). A strong magnetic activity and correlated phenomena may cause spurious abundance differences between the components of young, active pairs for several reasons: -the adopted magnitude difference may be affected by photometric variability; -the presence of spots may anomalously alter the strength of the vanadium lines (Dall et al 2005), which are used to derive effective temperatures;…”

Section: Individual Objectsmentioning

confidence: 99%

Abundance difference between components of wide binaries

Desidera¹,

Gratton²,

Lucatello³

et al. 2006

A&A

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Aims. We present high-precision iron abundance differences for 33 wide binaries with similar components. They were observed with the FEROS spectrograph at ESO, looking for abundance anomalies due to the ingestion of metal rich material of a planetary origin.Methods. An optimized data analysis technique and the high quality of the spectra allowed us to achieve an error of about 0.02 dex for pairs with small temperaure differences. Results. We found one case (HIP 64030 = HD 113984) with a large (0.27 dex) abundance difference. The primary of this binary appears to be a blue straggler, and the abundance difference might be due to the peculiar evolution of the star. A few other pairs show small abundance differences (≤0.09 dex). In a few cases these differences suggest the ingestion of a small amount of metal rich material, but in others they are likely spurious, because of the large temperature difference, high level of magnetic activity, or different evolutionary phases between the components. Some cases of abundance differences involving pairs with warm (T eff ≥ 6000 K) primaries might be due to the diffusion of heavy elements; dedicated theoretical models for the stellar parameters of the targets would be welcome. Conclusions. This study confirms our preliminary result based on analysis of 23 pairs (Desidera et al. 2004) that the occurrence of large alterations in stellar abundances caused by the ingestion of metal rich, rocky material is not a common event. For at least 65% of the pairs with components warmer than 5500 K, the limits on the amount of rocky material accreted by the program stars are comparable to the estimates of rocky material accreted by the Sun during its main-sequence lifetime.Key words. stars: abundances -stars: planetary systems -stars: binaries: visual -techniques: spectroscopic IntroductionWide visual binaries with similar components are ideal targets for high-precision differential abundance measurements. Gratton et al. (2001) and Desidera et al. (2004, hereafter Paper I) showed that errors in estimating the difference of iron content between the two components that are lower than 0.02 dex can be achieved for pairs with temperature differences smaller than 300−400 K and components with effective temperatures in the range 5300−6300 K. This opens possibilities for a detailed and quantitative study of chemical alterations in the external convective layer, which is caused by the accretion of metal-rich planetary material occurring during the main-sequence lifetime of the stars. In fact, the engulfment of 1 M ⊕ of iron (about 5 M ⊕ of meteoritic material) corresponds to an iron abundance difference of about 0.01 dex for a solar type main sequence star.Accretion phenomena have been suggested to explain the correlation between the presence of giant planets and the high metallicity of their parent stars (Gonzalez 1997). The most recent studies (Santos et al. 2004;Fischer & Valenti 2005) Based on observations collected at the European Southern Observatory, Chile, using FEROS spectrograp...

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“…Latham et al (2002) and Carney et al (2005) reported a lower binarity for stars on retrograde Galactic orbits compared to stars on prograde Galactic orbits, but found no dependence between binarity and metallicity within those two kinematic groups. Dall et al (2005) speculated that the frequency of host stars with stellar companions may be correlated with metallicity in the same way that host stars with planets are.…”

Section: Introductionmentioning

confidence: 99%

The Metallicity of Stars with Close Companions

Grether¹,

Lineweaver²

2007

ApJ

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We examine the relationship between the frequency of close companions (stellar and planetary companions with orbital periods <5 yr) and the metallicity of their Sun-like ($FGK ) hosts. We confirm and quantify a $4 positive correlation between host metallicity and planetary companions. We find little or no dependence on spectral type or distance in this correlation. In contrast to the metallicity dependence of planetary companions, stellar companions tend to be more abundant around low-metallicity hosts. At the $2 level, we find an anticorrelation between host metallicity and the presence of a stellar companion. After dividing our sample into FG and K subsamples, we find a negligible anticorrelation in the FG subsample and a $3 anticorrelation in the K subsample. A kinematic analysis suggests that this anticorrelation is produced by a combination of low-metallicity, high-binarity thick-disk stars and higher metallicity, lower binarity thin-disk stars.

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Binarity, activity and metallicity among late-type stars

Cited by 20 publications

References 42 publications

Planets around evolved intermediate-mass stars

Planets around evolved intermediate-mass stars

Abundance difference between components of wide binaries

The Metallicity of Stars with Close Companions

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