J/ApJ/763/L26 SMARTS observations of eps Eridani (Metcalfe+, 2013)
Magnetic activity cycles in the exoplanet host star ε Eridani.
Metcalfe T.S., Buccino A.P., Brown B.P., Mathur S., Soderblom D.R.,
Henry T.J., Mauas P.J.D., Petrucci R., Hall J.C., Basu S.
<Astrophys. J., 763, L26 (2013)>
=2013ApJ...763L..26M 2013ApJ...763L..26M
ADC_Keywords: Stars, K-type ; Stars, double and multiple ; Stars, nearby
Keywords: stars: activity; stars: chromospheres; stars: individual: HD 22049;
surveys
Abstract:
The active K2 dwarf ε 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 ε Eri originally reported by Hatzes and
coworkers (2000ApJ...544L.145H 2000ApJ...544L.145H), 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±0.03yr 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
(2007ApJ...657..486B 2007ApJ...657..486B). Finally, based on the observed properties of
ε 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.
Description:
Since 2007 August, we have used the RC Spec instrument on the SMARTS
1.5m telescope to obtain 141 low-resolution spectra (R∼2500) of
ε Eri on 69 distinct epochs.
We used additional observations of ε Eri from previously
published surveys to corroborate our recent SMARTS measurements and to
extend the time baseline of our analysis (see section 2).
Objects:
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RA (ICRS) DE Designation(s)
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03 32 55.84 -09 27 29.7 ε Eri = HD 22049
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 45 141 Journal of SMARTS Observations for ε Eri
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See also:
III/185 : Search for Jupiter-Mass Companions (Walker+, 1995)
III/159 : Ca II H and K Measurements Made at MWO (Duncan+ 1991)
J/A+A/552/A27 : Stellar activity and kinematics of FGK stars (Murgas+, 2013)
J/A+A/551/L8 : Chromospheric activity of field stars (Pace, 2013)
J/A+A/537/A147 : Optimizing exoplanet transit searches (Herrero+, 2012)
J/ApJS/200/15 : HARPS-TERRA project. I. (Anglada-Escude+, 2012)
J/ApJ/756/46 : Lithium abundances in HIP stars (Ramirez+, 2012)
J/ApJ/744/138 : Calibrated visibilities of ε Eri (Baines+, 2012)
J/AZh/88/1217 : Solar-like activity of low-mass stars (Kasova+, 2011)
J/ApJ/725/875 : Chromospheric activity for CPS stars (Isaacson+, 2010)
J/ApJ/724/154 : Lithium abundances in stars with planets (Ghezzi+, 2010)
J/MNRAS/403/1368 : Li abundances for star-planet systems (Gonzalez+, 2010)
J/A+A/483/903 : Mount Wilson index for F-K stars (Buccino+, 2008)
J/A+A/469/309 : Late-type stars chromospheric activity (Cincunegui+, 2007)
J/ApJ/640/1051 : 25pc sample of Sun-like stars (Grether+, 2006)
J/MNRAS/372/163 : Activity indices for southern stars (Jenkins+, 2006)
J/MNRAS/361/1102 : Spectrum of ε Eri (Sim+, 2005)
J/PASJ/57/45 : Lithium abundances of F-K stars (Takeda+, 2005)
J/ApJS/152/261 : Chromospheric Ca II emission in nearby stars (Wright+, 2004)
J/A+A/416/281 : X-ray spectra of 4 cool stars (Sanz-Forcada+, 2004)
J/A+A/409/251 : Li abundances & velocities in F and G stars (Mallik+, 2003)
J/AJ/111/439 : Chromospheric emission in late-type stars. (Henry+ 1996)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 "YYYY/MMM/DD" Obs.date Date of the observation (UT)
13- 20 A8 "h:m:s" Obs.time UT time of the observation
22- 31 F10.5 d BJD Barycentric Julian Date of observation;
BJD+2450000
33- 38 F6.4 --- S(MWO) [0.39/0.64] Measured Mount Wilson S-index
40- 45 F6.4 --- e_S(MWO) Uncertainty in S(MWO)
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 21-Oct-2014