Investigations of stellar coronae with XMM-Newton

Audard, M.

doi:10.1016/s0273-1177(03)00294-1

Cited by 4 publications

(4 citation statements)

References 50 publications

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“…Since we see in this study good evidence for a trend of decreasing Mg XI R ratio with increasing L X /L bol , the correlation of Ne X/Mg XI line strength with Mg XI R ratio would be expected if the Ne/Mg abundance ratio increased with L X /L bol . While the Ne/Mg abundance ratio remains to be investigated thoroughly in the stars of our sample, the evidence from analyses to date summarised by Drake (2003) and Audard (2003) does suggest that the relative Ne enhancement increases with stellar activity.…”

Section: Density Correlated With Ne/mg?mentioning

confidence: 82%

The Density of Coronal Plasma in Active Stellar Coronae

Testa

Drake

Peres

2004

ApJ

116

135

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We have analyzed high-resolution X-ray spectra of a sample of 22 active stars observed with the High Energy Transmission Grating Spectrometer on {\em Chandra} in order to investigate their coronal plasma density. Densities where investigated using the lines of the He-like ions O VII, Mg XI, and Si XIII. While Si XIII lines in all stars of the sample are compatible with the low-density limit, Mg XI lines betray the presence of high plasma densities ($> 10^{12}$ cm$^{-3}$) for most of the sources with higher X-ray luminosity ($> 10^{30}$ erg/s); stars with higher $L_X$ and $L_X/L_{bol}$ tend to have higher densities at high temperatures. Ratios of O VII lines yield much lower densities of a few $10^{10}$ cm$^{-3}$, indicating that the ``hot'' and ``cool'' plasma resides in physically different structures. Our findings imply remarkably compact coronal structures, especially for the hotter plasma emitting the Mg XI lines characterized by coronal surface filling factor, $f_{MgXI}$, ranging from $10^{-4}$ to $10^{-1}$, while we find $f_{OVII}$ values from a few $10^{-3}$ up to $\sim 1$ for the cooler plasma emitting the O VII lines. We find that $f_{OVII}$ approaches unity at the same stellar surface X-ray flux level as solar active regions, suggesting that these stars become completely covered by active regions. At the same surface flux level, $f_{MgXI}$ is seen to increase more sharply with increasing surface flux. These results appear to support earlier suggestions that hot $10^7$ K plasma in active coronae arises from flaring activity, and that this flaring activity increases markedly once the stellar surface becomes covered with active regions.Comment: 53 pages, 19 figures, accepted for publication in Astrophysical Journal. A version of the paper with higher quality figures is available from http://www.astropa.unipa.it/Library/preprint.htm

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Section: Density Correlated With Ne/mg?mentioning

confidence: 82%

The Density of Coronal Plasma in Active Stellar Coronae

Testa

Drake

Peres

2004

ApJ

116

135

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“…Emission lines have been recorded by several solar missions, such as Skylab (Dere 1978). In the recent years, high-resolution XUV spectroscopic observations by Chandra and XMM-Newton satellites, have also shown that a vast number of astrophysical sources produce emission lines from Be-like ions, such as Fe XXIII (Audard 2003).…”

Section: Introductionmentioning

confidence: 99%

“…Because of their importance to astrophysics, extensive IC R-matrix calculations for Be-like iron and nickel were carried out by Chidichimo et al (2005;2003) within the Iron Project, following an early distorted wave study by Bhatia & Mason (1981). In Chidichimo et al (2005), collision strengths and effective collision strength were obtained for Be-like Fe for the configurations n = 2, 3, 4, including a total of 98 fine-structure levels in the basis set.…”

Section: Introductionmentioning

confidence: 99%

R-matrix electron-impact excitation data for the Be-like iso-electronic sequence

Fernández-Menchero

Zanna

Badnell

2014

A&A

162

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Aims. Emission lines from ions in the Be-like isoelectronic sequence can be used for reliable diagnostics of temperature and density of astrophysical and fusion plasmas over a wide range of temperatures. Surprisingly, interpolated data is all that is available for a number of astrophysically important ions. Methods. We have carried out intermediate coupling frame transformation R-matrix calculations which include a total of 238 finestructure levels in both the configuration interaction target and close-coupling collision expansions. These arise from the configurations 1s 2 2{s, p} nl with n = 3−7, and l = 0−4 for n ≤ 5 and l = 0−2 for n = 6, 7. Results. We obtain ordinary collision strengths and Maxwell-averaged effective collision strengths for the electron-impact excitation of all the ions of the Be-like sequence, from B + to Zn 26+ . We compare with previous R-matrix calculations and interpolated values for some benchmark ions. We find good agreement for transitions n = 2−2 with previous R-matrix calculations but some disagreements with interpolated values. We also find good agreement for the most intense transitions n = 2−3 which contribute via cascade to the (n = 2) diagnostic radiating levels.

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“…They are ideal targets for X-ray spectroscopy since they display a wealth of bright emission lines of various elements. Recent reviews summarize results obtained in the first years after the launch of Chandra and XMM-Newton (e.g., Audard 2003, Linsky 2003. In particular, patterns in coronal abundances have been recognized in which elements with a first ionization potential (FIP) < 10 eV are underabundant with respect to the high-FIP elements when observed in very active stars; this is opposite to the solar FIP effect in which low-FIP elements are overabundant whereas high-FIP elements are of photospheric composition.…”

Section: Introductionmentioning

confidence: 99%

Coronae of Cool Stars

Audard¹,

Drake²,

Güdel

et al. 2004

Symp. - Int. Astron. Union

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Abstract. We present preliminary results of grating observations ofYY Mensae and V824 Arae by Chandra and XMM-Newton. Spectral features are presented in the context of the emission measure distributions, the coronal abundances, and plasma electron densities. In particular, we observe a coronal N/ C enhancement in YY Men believed to reflect the photospheric composition (CN cycle). Finally, we interpret line broadening in YY Men as Doppler thermal broadening in its very hot corona.

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Investigations of stellar coronae with XMM-Newton

Cited by 4 publications

References 50 publications

The Density of Coronal Plasma in Active Stellar Coronae

The Density of Coronal Plasma in Active Stellar Coronae

R-matrix electron-impact excitation data for the Be-like iso-electronic sequence

Coronae of Cool Stars

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