Discovery of an activity cycle in the solar analog HD 45184

Flores, M.; González, J. F.; Arancibia, M. Jaque; Buccino, A. P.; Saffe, C.

doi:10.1051/0004-6361/201628145

Cited by 25 publications

(27 citation statements)

References 54 publications

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“…Both stars are younger than the Sun: 18 Sco is 3.8 ± 0.5 Gyr old (Nissen 2015) and HD 30495 is 0.97 ± 0.12 Gyr old (Egeland et al 2015). In addition, we found a cycle of only ∼5.1 yr in the solar-analogue HD 45184 (Flores et al 2016), while in the ζ Ret binary system, the components simultaneously show erratic (ζ 1 Ret) and cyclic activity patterns (ζ 2 ∼ 10 yr) (Flores et al 2018); both stars are similar to the Sun (Saffe et al 2016).…”

Section: Introductionmentioning

confidence: 56%

“…For our studies, we mainly use the extensive data base of the High Accuracy Radial velocity Planet Searcher (HARPS) spectra, which are occasionally complemented with CASLEO observations. Some recent findings of our new programme can be found in Flores et al (2016Flores et al ( , 2017Flores et al ( , 2018.…”

Section: Introductionmentioning

confidence: 97%

“…In this way, HD 38858 constitutes an excellent laboratory for performing a comparative study of their chromospheric patterns (e.g. mean activity level, cycle length, and cycle amplitude), which has been done for only a few stars, such as 18 Sco (Hall et al 2007) and HD 45184 (Flores et al 2016).…”

Section: Introductionmentioning

confidence: 99%

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HD 38858: a solar-type star with an activity cycle of ∼10.8 yr

Flores

González

Arancibia

et al. 2018

A&A

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Context. The detection of chromospheric activity cycles in solar-analogue and twin stars can be used to place the solar cycle in a wider context. However, relatively few of these stars with activity cycles have been detected. It is well known that the cores of the Ca II H&K lines are modulated by stellar activity. The behaviour of the Balmer and other optical lines with stellar activity is not yet completely understood. Aims. We search for variations in the Ca II H&K, Balmer, and Fe II lines modulated by stellar activity. In particular, we apply a novel strategy to detect possible shape variations in the Hα line. Methods. We analysed activity signatures in HD 38858 using HARPS and CASLEO spectra obtained between 2003 and 2017. We calculated the Mount Wilson index (SMW), log(R′HK), and the statistical moments of the Ca II H&K, Balmer, and other optical lines. We searched for periodicities using the generalized Lomb-Scargle periodogram. Results. We detect a long-term activity cycle of 10.8 yr in Ca II H&K and Hα in the solar-analogue star HD 38858. In contrast, this cycle is marginally detected in the Fe II lines. We also detect a noticeable variation in radial velocity that seems to be produced by stellar activity. Conclusions. HD 38858 is the second solar-analogue star where we find a clear activity cycle that is replicated in the Balmer lines. Spectral indexes based on the shape of Hα line seem to be more reliable than the fluxes in the same line for detecting activity variations. The cyclic modulation we detected gives place to a variation in radial velocity that previously has been associated with a super-Earth planet. Finally, due to the similarity of HD 38858 with the Sun, we recommend to continue monitoring this star.

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Section: Introductionmentioning

confidence: 56%

Section: Introductionmentioning

confidence: 97%

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HD 38858: a solar-type star with an activity cycle of ∼10.8 yr

Flores

González

Arancibia

et al. 2018

A&A

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“…Flores et al (2016) have discovered that one of the solar twins included in Paper I, HD 45184, has a 5.14 yr activity cycle over which the equivalent widths of strong Fe ii lines change with an amplitude of about ±1 mÅ, and Reddy & Lambert (2017) Table 1. For each star, the age is calculated as the mean of the results from the seven different analyses of the available seismic data.…”

Section: D Effects and Systematic Errorsmentioning

confidence: 99%

High-precision abundances of elements inKeplerLEGACY stars

Nissen

Aguirre

Christensen‐Dalsgaard

et al. 2017

A&A

100

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Context. A previous study of solar twin stars has revealed the existence of correlations between some abundance ratios and stellar age providing new knowledge about nucleosynthesis and Galactic chemical evolution. Aims. High-precision abundances of elements are determined for stars with asteroseismic ages in order to test the solar twin relations. Methods. HARPS-N spectra with signal-to-noise ratios S /N > ∼ 250 and MARCS model atmospheres were used to derive abundances of C, O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, and Y in ten stars from the Kepler LEGACY sample (including the binary pair 16 Cyg A and B) selected to have metallicities in the range −0.15 < [Fe/H] < +0.15 and ages between 1 and 7 Gyr. Stellar gravities were obtained from seismic data and effective temperatures were determined by comparing non-LTE iron abundances derived from Fe i and Fe ii lines. Available non-LTE corrections were also applied when deriving abundances of the other elements.

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“…These activity cycles have been found in main sequence and even post main sequence stars with spectral types ranging from F to M (Baliunas et al 1998), including solar analogue/twins and stars with planets (e.g. Flores et al 2016). In addition, several stars seem to have multiple activity cycles (e.g.…”

Section: Introductionmentioning

confidence: 97%

ζ1 + ζ2 Reticuli binary system: a puzzling chromospheric activity pattern

Flores

Saffe

Buccino

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We perform, for the first time, a detailed long-term activity study of the binary system ζ Ret. We use all available HARPS spectra obtained between the years 2003 and 2016. We built a time series of the Mount Wilson S index for both stars, then we analyse these series by using Lomb-Scargle periodograms. The components ζ 1 Ret and ζ 2 Ret that belong to this binary system are physically very similar to each other and also similar to our Sun, which makes it a remarkable system. We detect in the solaranalogue star ζ 2 Ret a long-term activity cycle with a period of ∼10 yr, similar to the solar one (∼11 yr). It is worthwhile to mention that this object satisfies previous criteria for a flat star and for a cycling star simultaneously. Another interesting feature of this binary system, is a high ∼0.220 dex difference between the averages log(R ′ HK ) activity levels of both stars. Our study clearly shows that ζ 1 Ret is significantly more active than ζ 2 Ret. In addition, ζ 1 Ret shows an erratic variability in its stellar activity. In this work, we explore different scenarios trying to explain this rare behaviour in a pair of coeval stars, which could help to explain the difference in this and other binary systems. From these results, we also warn that for the development of activity-age calibrations (which commonly use binary systems and/or stellar clusters as calibrators) it should be taken into account the whole history of activity available of the stars involved.

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Discovery of an activity cycle in the solar analog HD 45184

Cited by 25 publications

References 54 publications

HD 38858: a solar-type star with an activity cycle of ∼10.8 yr

HD 38858: a solar-type star with an activity cycle of ∼10.8 yr

High-precision abundances of elements inKeplerLEGACY stars

ζ1 + ζ2 Reticuli binary system: a puzzling chromospheric activity pattern

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