12 years of stellar activity observations in Argentina

Mauas, P. J. D.; Buccino, A. P.; Díaz, R. F.; Vieytes, M.; Petrucci, R.; Jofré, E.; Abrevaya, Ximena C.; Luoni, M. L.; Valenzuela, P.

doi:10.1017/s1743921312005029

Cited by 3 publications

(2 citation statements)

References 15 publications

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“…As the Lowell series is the longest among the recent measurements, we used these observations to rescale the other data to the MWO system. The southern survey at CASLEO includes measurements of ǫ Eri from 2001-2011 (Mauas et al 2012). Additional published data between 2002-2010 are available from the California Planet Search (CPS; Isaacson & Fischer 2010), and between 2004-2008 from the HARPS spectrograph (Anglada-Escudé & Butler 2012).…”

Section: Observations and Archival Datamentioning

confidence: 99%

Magnetic Activity Cycles in the Exoplanet Host Star Ε Eridani

Metcalfe

Buccino

Brown

et al. 2013

ApJ

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The active K2 dwarf ǫ Eri has been extensively characterized, both as a young solar analog and more recently as an exoplanet host star. As one of the nearest and brightest stars in the sky, it provides an unparalleled opportunity to constrain stellar dynamo theory beyond the Sun. We confirm and document the 3 year magnetic activity cycle in ǫ Eri originally reported by Hatzes and coworkers, and we examine the archival data from previous observations spanning 45 years. The data show coexisting 3 year and 13 year periods leading into a broad activity minimum that resembles a Maunder minimum-like state, followed by the resurgence of a coherent 3 year cycle. The nearly continuous activity record suggests the simultaneous operation of two stellar dynamos with cycle periods of 2.95 ± 0.03 years and 12.7 ± 0.3 years, which by analogy with the solar case suggests a revised identification of the dynamo mechanisms that are responsible for the so-called "active" and "inactive" sequences as proposed by Böhm-Vitense. Finally, based on the observed properties of ǫ Eri we argue that the rotational history of the Sun is what makes it an outlier in the context of magnetic cycles observed in other stars (as also suggested by its Li depletion), and that a Jovian-mass companion cannot be the universal explanation for the solar peculiarities.

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Section: Observations and Archival Datamentioning

confidence: 99%

Magnetic Activity Cycles in the Exoplanet Host Star Ε Eridani

Metcalfe

Buccino

Brown

et al. 2013

ApJ

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121

114

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“…Recent efforts are being carried out in order to extend the baseline of observations and increase the sample of identified cycles (e.g. Hall et al 2007, Mauas et al 2012, and to place the solar chromosphere in the general stellar context (e.g. Metcalfe et al 2016.…”

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confidence: 99%

Far beyond the Sun – I. The beating magnetic heart in Horologium

Alvarado‐Gómez

Hussain

Drake

et al. 2017

Monthly Notices of the Royal Astronomical Society

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A former member of the Hyades cluster, ι Horologii (ι Hor) is a planet-hosting Sun-like star which displays the shortest coronal activity cycle known to date (P cyc ∼ 1.6 yr). With an age of ∼625 Myr, ι Hor is also the youngest star with a detected activity cycle. The study of its magnetic properties holds the potential to provide fundamental information to understand the origin of cyclic activity and stellar magnetism in latetype stars. In this series of articles, we present the results of a comprehensive project aimed at studying the evolving magnetic field in this star and how this evolution influences its circumstellar environment. This paper summarizes the first stage of this investigation, with results from a long-term observing campaign of ι Hor using groundbased high-resolution spectropolarimetry. The analysis includes precise measurements of the magnetic activity and radial velocity of the star, and their multiple time-scales of variability. In combination with values reported in the literature, we show that the long-term chromospheric activity evolution of ι Hor follows a beating pattern, caused by the superposition of two periodic signals of similar amplitude at P 1 1.97 ± 0.02 yr and P 2 1.41 ± 0.01 yr. Additionally, using the most recent parameters for ι Hor b in combination with our activity and radial velocity measurements, we find that stellar activity dominates the radial velocity residuals, making the detection of additional planets in this system challenging. Finally, we report here the first measurements of the surface longitudinal magnetic field strength of ι Hor, which displays varying amplitudes within ±4 G and served to estimate the rotation period of the star (P rot = 7.70 +0.18 −0.67 d).

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The HARPS search for southern extra-solar planets

Díaz

Ségransan

Udry

et al. 2016

A&A

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We present the analysis of the entire HARPS observations of three stars that host planetary systems: HD 1461, HD 40307, and HD 204313. The data set spans eight years and contains more than 200 nightly averaged velocity measurements for each star. This means that it is sensitive to both long-period and low-mass planets and also to the effects induced by stellar activity cycles. We modelled the data using Keplerian functions that correspond to planetary candidates and included the short-and long-term effects of magnetic activity. A Bayesian approach was taken both for the data modelling, which allowed us to include information from activity proxies such as log (R HK ) in the velocity modelling, and for the model selection, which permitted determining the number of significant signals in the system. The Bayesian model comparison overcomes the limitations inherent to the traditional periodogram analysis. We report an additional super-Earth planet in the HD 1461 system. Four out of the six planets previously reported for HD 40307 are confirmed and characterised. We discuss the remaining two proposed signals. In particular, we show that when the systematic uncertainty associated with the techniques for estimating model probabilities are taken into account, the current data are not conclusive concerning the existence of the habitable-zone candidate HD 40307 g. We also fully characterise the Neptune-mass planet that orbits HD 204313 in 34.9 days.

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12 years of stellar activity observations in Argentina

Cited by 3 publications

References 15 publications

Magnetic Activity Cycles in the Exoplanet Host Star Ε Eridani

Magnetic Activity Cycles in the Exoplanet Host Star Ε Eridani

Far beyond the Sun – I. The beating magnetic heart in Horologium

The HARPS search for southern extra-solar planets

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