The corona of V390 Aurigae (HD 33798)

Gondoin, P.

doi:10.1051/0004-6361:20030482

Cited by 13 publications

(29 citation statements)

References 70 publications

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“…We checked that this solution also easily and correctly fits other spectral regions throughout the NARVAL wavelength range. Our T eff value perfectly agrees with that derived by Gondoin (2003) and Bell & Gustafsson (1989) value of 5000 K obtained by Fekel & Balachandran (1993). We determined a lithium abundance N Li = 1.6 ± 0.15 dex.…”

Section: Evolutionary Considerations and Dynamo Operation In V390 Aursupporting

confidence: 91%

“…Temperature polar spots were reported for giants in RS CVn systems and for FK Com-type stars by Strassmeier (1997), Korhonen et al (2002), andStrassmeier (2002). This surface structure with close magnetic spots might explain the flare activity properties of the star reported in optical and X-ray (Konstantinova-Antova et al 2000;Gondoin 2003;Konstantinova-Antova et al 2005), such as the groups of optical flares and the "continuous flare activity" in the corona.…”

Section: Discussionmentioning

confidence: 69%

“…It has been classified as a chromospherically active giant by Fekel & Marshall (1991) on the basis of its CaII K emission and fast rotation (v sin i = 29 km s −1 ). Later, enhanced X-ray emission (Hünsch et al 1998;Gondoin 1999Gondoin , 2003 and optical flares (Konstantinova-Antova et al 2000 were detected for this star. Recently, Konstantinova-Antova et al (2008) reported the direct detection of magnetic field using the spectropolarimeter NARVAL at the 2 m Bernard Lyot Telescope at Pic du Midi Observatory, France.…”

Section: Introductionmentioning

confidence: 81%

“…For the Zeeman analysis, the least-squares deconvolution analysis (LSD, ) was applied to all observations. We used a mask calculated for an effective temperature of 5000 K, log g = 3.0 and a microturbulence of 2.0 km s −1 , consistent with physical parameters given by Gondoin (2003). For the case of V390 Aur, the method enabled us to average about 12 300 lines and to obtain the Stokes I and Stokes V profiles with a significantly improved signal-to-noise ratio (S/N).…”

Section: Observations and Data Processingmentioning

confidence: 99%

“…According to the literature V390 Aur has a mass of about 1.8-2 M and is evolving along the base of the red giant branch (RGB) (Gondoin 2003;Konstantinova-Antova et al 2009). It is the primary of a wide multiple physical system, ADS 3812, Based on data obtained using the Bernard Lyot Telescope at Observatoire du Pic du Midi, CNRS and Université Paul Sabatier, France.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic field structure in single late-type giants: the effectively single giant V390 Aurigae

Konstantinova-Antova

Aurière

Petit

et al. 2012

A&A

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Aims. We have studied the active giant V390 Aur using spectropolarimetry to obtain direct and simultaneous measurements of the magnetic field and the activity indicators to obtain a precise insight of its activity. Methods. We used the spectropolarimeter NARVAL at the Bernard Lyot Telescope (Observatoire du Pic du Midi, France) to obtain a series of Stokes I and Stokes V profiles. Using the least-squares deconvolution (LSD) technique we were able to detect the Zeeman signature of the magnetic field in each of our 13 observations and to measure its longitudinal component. Using the wide wavelength range of the spectra we were able to monitor the CaII K&H and IR triplet, as well as the H α lines, which are activity indicators. To reconstruct the magnetic field geometry of V390 Aur on the basis of modelling the Stokes V profiles, we applied the Zeeman Doppler imaging (ZDI) inversion method and present a map for the magnetic field. Based on the obtained spectra, we also refined the fundamental parameters of the star and the Li abundance using MARCS model atmospheres. Results. The ZDI revealed a structure in the radial magnetic field consisting of a polar magnetic spot of positive polarity and several negative spots at lower latitude. A high latitude belt is present on the azimuthal field map, indicative of a toroidal field close to the surface. Similar features are observed in some RS CVn and FK Com -type stars. It was found that the photometric period cannot fit the behaviour of the activity indicators formed in the chromosphere. Their behaviour suggests slower rotation compared to the photosphere, but our dataset is too short for us to be able to estimate their exact periods. All these results can be explained in terms of an α−ω dynamo operation, taking into account the stellar structure and rotation properties of V390 Aur that we studied with up-to-date stellar models computed at solar metallicity with the code STAREVOL. The calculated Rossby number also points to a very efficient dynamo.

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Section: Evolutionary Considerations and Dynamo Operation In V390 Aursupporting

confidence: 91%

Section: Discussionmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 81%

Section: Observations and Data Processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Magnetic field structure in single late-type giants: the effectively single giant V390 Aurigae

Konstantinova-Antova

Aurière

Petit

et al. 2012

A&A

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The flare activity of V390 Aur: First results of an international collaboration

Konstantinova-Antova¹,

Antov

Zhilyaev

et al. 2005

Astron. Nachr.

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Abstract. V390 Aur is classified as a G8 spectral class active single giant by Fekel and Marshall (1991). Multi-site cooperative high-speed photoelectric monitoring was carried out for it in the period 1998-2003 as part of a program developed in Bulgaria recently to study chromospherically active evolved stars. Astronomers from Greece and Ukraine joined the flare activity study of V390 Aur in 2000. As a result, several flares with a duration from seconds to minutes were detected on this star at 3 observatories. Taking into account all the events detected, the flare rate of the star is estimated to 0.205 flares per hour. Comparison with the active dwarfs AD Leo and EV Lac indicates that the flare rate of V390 Aur is lower than that of AD Leo but comparable with the well-known flare star EV Lac.

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The corona of HD 223460 (HR 9024)

Gondoin

2003

A&A

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Abstract. HD 223460 (HR 9024), a chromospherically active late−type giant with a high X-ray luminosity, was observed by the XMM-Newton space observatory. Series of lines of highly ionized Fe and several Lyman lines of hydrogen-like ions and triplet lines of helium-like ions are visible in the reflection grating spectra, most notably from O and Ne. Analysis results suggest a scenario where the corona of HD 223460 is dominated by large magnetic structures similar in size to interconnecting loops between solar active regions but significantly hotter. The surface area coverage of these active regions may approach up to 30%. A hypothesis is that the interaction of these structures themselves induces a flaring activity on a small scale not visible in the EPIC light curves that is responsible for heating HD 223460 plasma to coronal temperatures of T ≥ 10 7 K. The intense X-ray activity of HD 223460 is related to its evolutionary position at the bottom of the red giant branch. It is anticipated that its rotation will spin down in the future with the effect of decreasing its helicity-related, dynamo-driven activity and suppressing large-scale magnetic structures in its corona.Key words. stars: individual: HD 223460 -stars: activity -stars: coronae -stars: evolution -stars: late-type -X-rays: stars IntroductionHD 223460 (HR 9024) is a chromospherically active late−type giant. Cowley & Bidelman (1979) indicate that the Ca II emission in this star is moderately strong while Bopp (1984) notes that the H and K emission fluxes are quite high, comparable to what is observed in FK Comae. Feldman (1982) detected HD 223460 as a radio source and initially suggested that HD 223460, which apparently exhibits no detectable velocity variation, is an FK Comae type star. Cowley & Bidelman (1979) classified HD 223460 as a G1 III star but its B − V color is too large for the assigned MK type which suggests unusual reddening for the distance (Ayres et al. 1998) our understanding of the magnetic activity on HD 223460 by investigating the origin of its high X-ray luminosity and the structure of its X-ray corona.This paper is organized as follows. Section 2 provides the stellar parameters of HD 223460 and compares the evolution status of this star with those of nearby single field giants in light of Hipparcos parallaxes (ESA 1997). Section 3 describes the Xray observations of HD 223460 and the data reduction procedures. Section 4 then presents the integrated flux measurements and their temporal behavior during the observations. Section 5 describes the spectral analysis of the datasets obtained with the European Photon Imaging Camera (EPIC) and the Reflection Grating Spectrometer (RGS) on board XMM-Newton. Finally, a physical interpretation of the analysis results is proposed in Sect. 6. In this last section, the structure of HD 223460 corona and its possible evolution is discussed within the frame of stellar activity evolution across the Hertzsprung gap. HD 223460 stellar parametersA differential UBV photometry study performed by Strassmeier &...

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The corona of V390 Aurigae (HD 33798)

Cited by 13 publications

References 70 publications

Magnetic field structure in single late-type giants: the effectively single giant V390 Aurigae

Magnetic field structure in single late-type giants: the effectively single giant V390 Aurigae

The flare activity of V390 Aur: First results of an international collaboration

The corona of HD 223460 (HR 9024)

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