Correlation Between Sunspot Number and Ca ii K Emission Index

Bertello, L.; Pevtsov, Alexei A.; Tlatov, A. G.; Singh, Jagdev

doi:10.1007/s11207-016-0927-9

Cited by 53 publications

(61 citation statements)

References 30 publications

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“…In this way, before the stellar cycle that we are now observing (∼10 yr), perhaps the mean stellar activity of 10 The sunspot number, a key indicator of solar activity, has a strong correlation with the Ca ii H&K chromospheric activity proxy (e.g. Bertello et al 2016). 11 As previously indicated, these individual observations were taken at different dates ζ 2 Ret was even lower.…”

Section: Possible Scenarios To Explain the Activity Differences In Bimentioning

confidence: 68%

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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Section: Possible Scenarios To Explain the Activity Differences In Bimentioning

confidence: 68%

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 extend the S-index record back to cycle 20 using the composite K time series of Bertello et al (2016), which is available online (Pevtsov 2016). This composite calibrates the NSO/SP data to K-line observations by the successor program at NSO, the Synoptic Optical Long-term Investigations of the Sun (SOLIS) Integrated Sunlight Spectrometer (ISS) (Bertello et al 2011).…”

Section: Kodaikanal Observatory Ca K Spectroheliogramsmentioning

confidence: 99%

“…This composite calibrates the NSO/SP data to K-line observations by the successor program at NSO, the Synoptic Optical Long-term Investigations of the Sun (SOLIS) Integrated Sunlight Spectrometer (ISS) (Bertello et al 2011). The calibration used in Bertello et al (2016) is: Bertello et al (2016) calibrated the synoptic Ca ii K plage index from spectroheliograms from the Kodaikanal (KKL) Observatory in India to the ISS flux scale using the overlapping portion NSO/SP data, resulting in a time 9 ftp://ftp.nso.edu/idl/cak.parameters series of Ca ii K emission from 1907 to the present. We transform this composite timeseries from the ISS flux scale to the NSO/SP flux scale by applying the inverse of equation (5):…”

Section: Kodaikanal Observatory Ca K Spectroheliogramsmentioning

confidence: 99%

The Mount Wilson Observatory S-Index of the Sun

Egeland

Soon

Baliunas³

et al. 2017

ApJ

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104

118

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The most commonly used index of stellar magnetic activity is the instrumental flux scale of singlyionized calcium H & K line core emission, S, developed by the Mount Wilson Observatory (MWO) HK Project, or the derivative index R HK . Accurately placing the Sun on the S scale is important for comparing solar activity to that of the Sun-like stars. We present previously unpublished measurements of the reflected sunlight from the Moon using the second-generation MWO HK photometer during solar cycle 23 and determine cycle minimum S 23,min = 0.1634 ± 0.0008, amplitude ∆S 23 = 0.0143 ± 0.0012, and mean S 23 = 0.1701 ± 0.0005. By establishing a proxy relationship with the closely related National Solar Observatory Sacramento Peak calcium K emission index, itself well-correlated with the Kodaikanal Observatory plage index, we extend the MWO S time series to cover cycles 15-24 and find on average S min = 0.1621 ± 0.0008, ∆S cyc = 0.0145 ± 0.0012, S cyc = 0.1694 ± 0.0005. Our measurements represent an improvement over previous estimates which relied on stellar measurements or solar proxies with non-overlapping time series. We find good agreement from these results with measurements by the Solar-Stellar Spectrograph at Lowell Observatory, an independently calibrated instrument, which gives us additional confidence that we have accurately placed the Sun on the S-index flux scale.

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“…The Kodaikanal data is in Integrated Sunlight Spectrometer (ISS) flux scale, calibrated by Bertello et al (2016) using the synoptic Ca II K plage index from spectroheliograms from the Kodaikanal (KKL) Observatory in India. This time series data of Ca II K emission is first transformed to the Ca II H & K measurement scale of Sacramento Peak National Observatory (NSO/SP) flux scale by applying following equation.…”

Section: Checking the Waldmeier Effect In Solar S-indexmentioning

confidence: 99%

Waldmeier Effect in Stellar Cycles

Garg

Karak

Egeland

et al. 2019

ApJ

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One of the most robust features of the solar magnetic cycle is that the stronger cycles rise faster than the weaker ones. This is popularly known as the Waldmeier Effect, which is known for more than 80 years. This fundamental feature of the solar cycle has not only practical implications, e,g., in predicting the solar cycle, but also implications in understanding the solar dynamo. Here we ask the question whether the Waldmeier Effect exists in other Sun-like stars. To answer this question, we analyze the Ca II H & K S-index from Mount Wilson Observatory for 21 Sun-like G-K stars. We specifically check two aspects of Waldmeier Effect, namely, WE1: the anti-correlation between the rise times and the peaks and WE2: the positive correlation between rise rates and amplitudes. We show that except HD 16160, HD 81809, HD 155886 and HD 161239, all stars considered in the analysis show WE2. While WE1 is found to be present only in some of the stars studied. Further, the WE1 correlation is weaker than the WE2. Both WE1 and WE2 exist in the solar S-index as well. Similar to the solar cycles, the magnetic cycles of many stars are asymmetric about their maxima. The existence of the Waldmeier Effect and asymmetric cycles in Sun-like stars suggests that the dynamo mechanism which operates in the Sun is also operating in other stars.

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Correlation Between Sunspot Number and Ca ii K Emission Index

Cited by 53 publications

References 30 publications

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

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

The Mount Wilson Observatory S-Index of the Sun

Waldmeier Effect in Stellar Cycles

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