Element Abundances in the Upper Atmospheres of the Sun and Stars: Update of Observational Results

Feldman, U.; Laming, J. M.

doi:10.1238/physica.regular.061a00222

Cited by 188 publications

(206 citation statements)

References 145 publications

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“…We note, however, that such abundance variations might not be unreasonable in the light of a recent survey of coronal densities by Testa et al (2004) that clearly demonstrates that the cooler T $ 10 6 K corona resides in quite different structures to the hotter, T $ 10 7 K plasma that appears to be universally characterized by much higher pressures. Feldman & Laming (2000) found that for the solar corona the FIP effect is larger at T $ 10 5:9 K than at T $ 10 6:15 K.…”

Section: Temperature Structurementioning

confidence: 90%

“…The resulting ratio of measured line fluxes then yields directly the ratio of the abundances of the relevant elements, independently of the atmospheric temperature structure. A similar, although less sophisticated, method has been previously used in solar coronal observations (see, e.g., Feldman 1992;Feldman & Laming 2000) and in stellar EUVE observations (Drake et al , 1997.…”

Section: Element Abundancesmentioning

confidence: 99%

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The Coronae of AB Doradus and V471 Tauri: Primordial Angular Momentum versus Tidal Spin‐up

García-Álvarez

Drake

Lin

et al. 2005

ApJ

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The zero-age main-sequence star AB Dor and the K dwarf component of the V471 Tau close binary have essentially identical rotation rates and spectral types. An analysis of their high-resolution Chandra X-ray spectra reveals remarkably similar coronal characteristics in terms of both temperature structure and element abundances. Both stars show depletions of low first ionization potential (FIP) elements by factors of $3, with higher FIP elements showing more mild depletions. No evidence for enhancements of very low FIP (<7 eV) elements, such as Na, Al, and Ca, as compared to other low-FIP elements, was found. The abundance anomaly pattern for AB Dor and V471 Tau is similar to, although less extreme than, the abundance anomalies exhibited by active RS CVn-type binaries. While we find statistically significant structure in the underlying differential emission measure distributions of these stars over narrow temperature intervals, this structure is strongly dependent on the lines used in the analysis and is probably spurious. On the basis of their X-ray similarities, we conclude that the exact evolutionary state of a star has little effect on coronal characteristics and that the parameters that dominate coronal structure and composition are simply the rotation rate and spectral type.

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Section: Temperature Structurementioning

confidence: 90%

Section: Element Abundancesmentioning

confidence: 99%

The Coronae of AB Doradus and V471 Tauri: Primordial Angular Momentum versus Tidal Spin‐up

García-Álvarez

Drake

Lin

et al. 2005

ApJ

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“…However, from shortly after and for the duration of the observations the abundance ratio continued to change until it reached a factor of ≈9 after five to six days. For review papers describing the recent findings that relate to the composition of the solar atmosphere see Feldman (1992), Saba (1995), Fludra et al (1999b), Feldman and Laming (2000), and Feldman and Widing (2003). Ko et al (2006) used in situ data from the Solar Wind Ion Composition Spectrometer (SWICS) on board the Advanced Composition Explorer (ACE) spacecraft at ≈1 ua in combination with spectroscopic data from UVCS measured at 1.64 R to investigate the coronal origin of the solar wind.…”

Section: Composition Of the Coronamentioning

confidence: 99%

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

et al. 2007

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In Part I of this review, the concepts of solar vacuum-ultraviolet (VUV) observations were outlined together with a discussion of the space instrumentation used for the investigations. A section on spectroradiometry provided some quantitative results on the solar VUV radiation without considering any details of the solar phenomena leading to the radiation. Here, in Part II, we present solar VUV observations over the last decades and their interpretations in terms of the plasma processes and the parameters of the solar atmosphere, with emphasis on the spatial and thermal structures of the chromosphere, transition region and corona of the quiet Sun. In addition, observations of active regions, solar flares and prominences are included as well as of small-scale events. Special sections are devoted to the elemental composition of the solar atmosphere and theoretical considerations on the heating of the corona and the generation of the solar wind.

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“…Solar abundances have been derived both from optical/UV/X-ray spectroscopy and from composition measurements of solar wind particles or meteorites (Feldman & Laming 2000), but the most recent and sophisticated results are in stark conflict with models of the solar interior tuned with helioseismology data (Asplund et al 2009). A second problematic point is the finding that photospheres of stars hosting close-in giant planets are known to be metal-rich, which can possibly be explained by a higher probability of planet formation in highmetallicity birth clouds (Gonzalez 2006).…”

Section: Introductionmentioning

confidence: 99%

“…In this respect, stellar X-ray spectroscopy is a fundamental tool for the chemical analysis of stellar outer atmospheres, and the only method to determine the abundances of noble gases, like argon and neon, with no optical lines in photospheric spectra. For the solar corona, and in particular in long-lived coronal structures, the composition of the plasma appears enriched with elements having low first ionization potentials (FIP < 10 eV) by about a factor 4, on average, with respect to photospheric values (Feldman & Laming 2000). In other stars a more complex behavior has been observed (Güdel & Nazé 2009), with a tendency for the low-FIP elements (including iron) to become depleted with respect to the high-FIP elements (neon in particular) in extremely active RS CVn-type and Algol-type binaries.…”

Section: Introductionmentioning

confidence: 99%

Photospheric and coronal abundances in solar-type stars: the peculiar case ofτ Bootis

Maggio

Sanz-Forcada

2011

A&A

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Aims. Chemical abundances in solar-type stars are still a much debated topic in many respects. In particular, planet-hosting stars are known to be metal-rich, but whether or not this peculiarity applies also to the chemical composition of the outer stellar atmospheres is still to be clarified. More in general, coronal and photospheric abundances in late-type stars appear to be different in many cases, but understanding how chemical stratification effects work in stellar atmospheres requires an observational base larger than currently available. Methods. We obtained XMM-Newton high-resolution X-ray spectra of τ Bootis, a well known nearby star with a Jovian-mass close-in planet. We analyzed these data with the aim to perform a detailed line-based emission measure analysis and derive the abundances of individual elements in the corona with two different methods applied independently. We compared the coronal abundances of τ Bootis with published photospheric abundances based on high-resolution optical spectra and with those of other late-type stars with different magnetic activity levels, including the Sun. Results. We find that the two methods provide consistent results within the statistical uncertainties for both the emission measure distribution of the hot plasma and for the coronal abundances, with discrepancies at the 2σ level limited to the amount of plasma at temperatures of 3-4 MK and to the O and Ni abundances. In both cases, the elements for which both coronal and photospheric measurements are available (C, N, O, Si, Fe, and Ni) result systematically less abundant in the corona by a factor 3 or more, with the exception of the coronal Ni abundance which is similar to the photospheric value. Comparison with other late-type stars of similar activity level shows that these coronal/photospheric abundance ratios are peculiar to τ Bootis and possibly related to the characteristic over-metallicity of this planet-hosting star.

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Element Abundances in the Upper Atmospheres of the Sun and Stars: Update of Observational Results

Cited by 188 publications

References 145 publications

The Coronae of AB Doradus and V471 Tauri: Primordial Angular Momentum versus Tidal Spin‐up

The Coronae of AB Doradus and V471 Tauri: Primordial Angular Momentum versus Tidal Spin‐up

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

Photospheric and coronal abundances in solar-type stars: the peculiar case ofτ Bootis

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