CDS

2011A&A...534A.139A

Query : 2011A&A...534A.139A

2011A&A...534A.139A - Astronomy and Astrophysics, volume 534A, 139-139 (2011/10-1)

A dominant magnetic dipole for the evolved Ap star candidate EK Eridani.

AURIERE M., KONSTANTINOVA-ANTOVA R., PETIT P., ROUDIER T., DONATI J.-F., CHARBONNEL C., DINTRANS B., LIGNIERES F., WADE G.A., MORGENTHALER A. and TSVETKOVA S.

Abstract (from CDS):

EK Eri is one of the most slowly rotating active giants known, and has been proposed to be the descendant of a strongly magnetic Ap star. We have performed a spectropolarimetric study of EK Eri over 4 photometric periods with the aim of inferring the topology of its magnetic field. We used the NARVAL spectropolarimeter at the Bernard Lyot telescope at the Pic du Midi Observatory, along with the least-squares deconvolution method, to extract high signal-to-noise ratio Stokes V profiles from a timeseries of 28 polarisation spectra. We have derived the surface-averaged longitudinal magnetic field Bl. We fit the Stokes V profiles with a model of the large-scale magnetic field and obtained Zeeman Doppler images of the surface magnetic strength and geometry. We studied the classical activity indicators, the Ca ii H and K lines, the Ca ii infrared triplet, and Hα line, as well as the stellar radial velocity. Bl variations of up to about 80G are observed without any reversal of its sign, and which are in phase with photometric ephemeris. The activity indicators are shown to vary smoothly on a timescale compatible with the rotational period inferred from photometry (308.8d), however large deviations can occur from one rotation to another. The surface magnetic field variations of EK Eri appear to be dominated by a strong magnetic spot (of negative polarity) which is phased with the dark (cool) photometric spot. Our modeling shows that the large-scale magnetic field of EK Eri is strongly poloidal. For a rotational axis inclination of i=60°, we obtain a model that is almost purely dipolar. In the dipolar model, the strong magnetic/photometric spot corresponds to the negative pole of the dipole, which could be the remnant of that of an Ap star progenitor of EK Eri. Our observations and modeling conceptually support this hypothesis, suggesting an explanation of the outstanding magnetic properties of EK Eri as the result of interaction between deep convection and the remnant of an Ap star magnetic dipole. Nevertheless, the longitudinal magnetic field curve clearly shows changes from one rotation to the next, indicating that the surface magnetic topology is not static as in an Ap star.

Abstract Copyright: ∼

Journal keyword(s): stars: individual: EK Eridani - stars: magnetic field - stars: late-type

Simbad objects: 1

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Number of rows : 1
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023 		#notes
1 V* EK Eri BY* 04 20 38.6418121776 -06 14 45.577773096   7.036 6.154     K0III 120 0

Query : 2011A&A...534A.139A

Basic data :
V* EK Eri -- BY Dra Variable
Origin of the objects types :

(Ref) Object type as listed in the reference "Ref"
(acronym) Object type linked to the acronym according to the original reference
() Anterior to 2007, before we can link the objet type to a reference, or given by the CDS team in some particular cases

Other object types: 		* (HD,BD,...), X (2E,RBS,...), V* (NSV,V*), UV (EUVE,TD1), BY* (2017ARep), PM* (2016ApJS), NIR (2MASS), MIR (WISEA), IR (IRAS)
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
ICRS coord. (ep=J2000) : 		04 20 38.6418121776 -06 14 45.577773096 (Optical) [ 0.0160 0.0123 90 ] A 2020yCat.1350....0G
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
FK4 coord. (ep=B1950 eq=1950) : 		04 18 11.2747844396 -06 21 48.781265769 [ 0.0160 0.0123 90 ]
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
Gal coord. (ep=J2000) : 		200.0173322107482 -36.2004647510466 [ 0.0160 0.0123 90 ]
Syntax of proper motions is : "pm-ra pm-dec [error ellipse] quality bibcode"
  • pm-ra : mu-ra*cos(dec) (expressed in the ICRS system in mas/yr)
  • pm-dec : mu-dec (expressed in the ICRS system in mas/yr)
  • [error ellipse] : error major axis and minor axis (in mas), orientation angle (in deg)
  • quality : flag of quality (A=best quality -> E=worst quality, {� } =unknown quality)
  • bibcode : bibcode of the proper motion reference
Proper motions mas/yr : 		92.020 -55.192 [0.021 0.016 90] A 2020yCat.1350....0G
Syntax of radial velocity (or/and redshift) is : "value [error] (wavelength) quality bibcode"
  • value : radial velocity or/and redshift (Heliocentric frame) according to your Output Options
    (redshift may be not displayed if the data value is <0 and the database inside value is a radial velocity)
  • [error] : error of the corresponding value displayed before
  • (wavelength) : wavelength range of the measurement : Rad, mm, IR, Opt, UV, Xray, Gam or  '∼'(unknown)
  • quality : flag of quality ( A=best quality -> E=worst quality, {� } =unknown quality)
  • bibcode : bibcode of the value's origin
Radial velocity / Redshift / cz : 		V(km/s) 6.866 [0.0002] / z(spectroscopic) 0.000023 [0.000000] / cz 6.87 [0.00]
   (Opt) A 2018A&A...616A...7S
Syntax of parallax is : 'value quality [error] bibcode'
  • value : parallax value
  • quality : flag of quality (A=best quality -> E=worst quality, {� } =unknown quality)
  • [error] : mean error
  • bibcode : bibcode of the parallax reference
Parallaxes (mas): 		15.6213 [0.0236] A 2020yCat.1350....0G
Spectral type is made of 3 parts: %coding is composed of 4 parts :
  • the spectral type, which is made of a temperature class, eventually a luminosity class (roman number) and/or spectral peculiarities;
  • a quality letter: A=best quality→E=worst quality, {� } =unknown quality %
  • a quality letter: A=best quality -> E=worst quality, {� } =unknown quality
  • bibcode : bibcode of the spectral type reference
Spectral type: 		K0III C 1999MSS...C05....0H
Syntax of fluxes (or magnitudes) is : "filter-name (System) flux-value [error] quality MultVarFlags bibcode"
  • filter-name : U, B, V, R, I, G, J, H, K, u, g, r, i, z
  • (System) : may be AB (default is Vega)
  • flux-value : value of flux or magnitude
  • [error] : error value
  • quality : flag of quality of the flux value ( A=best quality -> E=worst quality, {� } =unknown quality)
  • MultVarFlags : Mult is zero or one char (J) for joined photometry ; Var can be zero or two chars (V[0-4])
  • bibcode : bibcode of the flux reference
Fluxes (6) :
B 7.036 [0.015] D 2000A&A...355L..27H
V 6.154 [0.010] D 2000A&A...355L..27H
G 6.083227 [0.003112] C 2020yCat.1350....0G
J 5.083 [0.260] D 2003yCat.2246....0C
H 4.44 [0.22] D 2003yCat.2246....0C
K 4.175 [0.036] C 2003yCat.2246....0C
SIMBAD within arcmin
', {sourceSize:12, color:'#30a090'})); aladin.on('objectClicked', function(object) { var objName=object.data.MAIN_ID; aladin.showPopup(object.ra,object.dec,'',''+ objName+''); });" title="Show Simbad objects"> Overlay Simbad points in this preview
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within arcsec The VizieR photometry tool allows for easy visualization of photometry points extracted around the Simbad position from photometry-enabled catalogues in VizieR.
The search radius has to be specified by the user. It is currently limited to a maximum of 30 arcsec. It depends mostly on the precision or quality of the coordinates (SIMBAD and VizieR catalogs), the resolution of the images from which the sources were extracted, source extent, and source crowding.
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The link on the acronym of the identifiers give access to the information for this acronym in the dictionary of nomenclature.
Identifiers (34) :
An access of full data is available using the icon Vizier near the identifier of the catalogue

HD 27536 HERZ 11371 RX J0420.6-0614 uvby98 100027536
BD-06 875 HIC 20263 1RXS J042038.4-061443 V* EK Eri
2E 980 HIP 20263 SAO 131129 WISEA J042038.72-061446.1
2E 0418.1-0621 HR 1362 SKY# 6661 YZ 96 1077
EUVE J0420-06.2 IRAS 04181-0621 TD1 3069 Gaia DR2 3202223888145435136
GC 5264 2MASS J04203863-0614455 TIC 37778297 Gaia DR3 3202223888145435136
GCRV 26073 NSV 1563 TYC 4733-2188-1 Gaia DR1 3202223883847807360
GEN# +1.00027536 PPM 186813 UBV 4205
GSC 04733-02188 RBS 535 UBV M 10094

References (120 between 1850 and 2023) (Total 120)
Simbad bibliographic survey began in 1850 for stars (at least bright stars) and in 1983 for all other objects (outside the solar system).
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Collections of Measurements


velocities : 5    V* : 2    distance : 2    ROT : 1    Fe_H : 1    PLX : 5    PM : 6    MK : 2   

   

Observing logs


herschel : 2    IUE : 2   

   

External archives :

Archive data at HEASARC - High-Energy Astrophysics Science Archive Research Center

Data at NED - NASA/IPAC Extragalactic Database : V* EK Eri

Link by name to the catalogue in VizieR :

HD 27536 BD-06 875 2E 980 EUVE J0420-06.2 GSC 04733-02188
HIC 20263 HIP 20263 HR 1362 IRAS 04181-0621 2MASS J04203863-0614455
NSV 1563 PPM 186813 1RXS J042038.4-061443 SAO 131129 TD1 3069
TYC 4733-2188-1 uvby98 100027536 V* EK Eri WISEA J042038.72-061446.1 Gaia DR2 3202223888145435136
Gaia DR3 3202223888145435136 Gaia DR1 3202223883847807360

Search by coordinates in Vizier (radius: 5 arcsec)

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2023.10.04-22:56:49

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