Variability of a stellar corona on a time scale of days

Nordon, R.; Behar, E.; Drake, S. A.

doi:10.1051/0004-6361/201220491

Cited by 6 publications

(3 citation statements)

References 34 publications

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“…Moreover, as is the case on the Sun, different parts of a single corona may exhibit different abundances (Sanz-Forcada et al 2004;Nordon et al 2013). Wood & Linsky (2006) found that even though two stars may have very similar properties and activity levels (and being visual binary companions), 70 Oph A and 70 Oph B did not exhibit the same coronal abundance patterns.…”

Section: Introductionmentioning

confidence: 99%

“…In particular, the influence of stellar metallicity on stellar coronal properties is still unclear, since most of the stars with wellstudied X-ray spectra have photospheric abundances similar (or assumed to be) to the solar photospheric values. Moreover, as is the case on the Sun, different parts of a single corona may exhibit different abundances (Sanz-Forcada et al 2004;Nordon et al 2013). Wood & Linsky (2006) found that even though two stars may have very similar properties and activity levels (and being visual binary companions), 70 Oph A and 70 Oph B did not exhibit the same coronal abundance patterns.…”

Section: Introductionmentioning

confidence: 99%

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Coronae of stars with supersolar elemental abundances

Peretz

Behar

Drake

2015

A&A

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Coronal elemental abundances are known to deviate from the photospheric values of their parent star, with the degree of deviation depending on the first ionization potential (FIP). This study focuses on the coronal composition of stars with supersolar photospheric abundances. We present the coronal abundances of six such stars: 11 LMi, ι Hor, HR 7291, τ Boo, and α Cen A and B. These stars all have high-statistics X-ray spectra, three of which are presented for the first time. The abundances we measured were obtained using the line-resolved spectra of the Reflection Grating Spectrometer (RGS) in conjunction with the higher throughput EPIC-pn camera spectra onboard the XMM-Newton observatory. A collisionally ionized plasma model with two or three temperature components is found to represent the spectra well. All elements are found to be consistently depleted in the coronae compared to their respective photospheres. For 11 LMi and τ Boo no FIP effect is present, while ι Hor, HR 7291, and α Cen A and B show a clear FIP trend. These conclusions hold whether the comparison is made with solar abundances or the individual stellar abundances. Unlike the solar corona, where low-FIP elements are enriched, in these stars the FIP effect is consistently due to a depletion of high-FIP elements with respect to actual photospheric abundances. A comparison with solar (instead of stellar) abundances yields the same fractionation trend as on the Sun. In both cases, a similar FIP bias is inferred, but different fractionation mechanisms need to be invoked.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Coronae of stars with supersolar elemental abundances

Peretz

Behar

Drake

2015

A&A

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“…However, its precise role is difficult to establish because measuring the attenuation curve for individual galaxies represents a major challenge (e.g., Kriek & Conroy 2013;Salmon et al 2016;Leja et al 2017;Salim et al 2018;Buat et al 2018. IR observations from Spitzer allowed the study of the IRXβ relation to be carried out out to z 1, for IR luminous galaxies Reddy et al 2010;Murphy et al 2011;Buat et al 2012) and strongly lensed sources (Siana et al 2009;Pope et al 2017), again suggesting a large spread in the IRX-β plane. These redshifts were subsequently explored at longer wavelengths with Herschel (Nordon et al 2013). At even higher redshifts (z 3), some studies using Herschel and ALMA suggest a stronger evolution in the IRXβ relation (Capak et al 2015;Bouwens et al 2016;Barisic et al 2017), but the question of how IR luminosity is measured start to arise as well (Lee et al 2012;Faisst et al 2017;Cullen et al 2017;Ferrara et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Diversity of Galaxy Dust Attenuation Curves Drives the Scatter in the IRX–β Relation

Salim

Boquien

2019

ApJ

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We study the drivers of the scatter in the IRX-β relation using 23,000 low-redshift galaxies from the GALEX-SDSS-WISE Legacy Catalog 2 (GSWLC-2). For each galaxy we derive, using CIGALE and the SED+LIR fitting technique, the slope of the dust attenuation curve and the strength of the UV bump, plus many other galaxy parameters. We find that the IRX-β scatter is driven entirely by a wide range of attenuation curvesprimarily their slopes. Once the slope and the UV bump are fixed, the scatter in the IRX-β vanishes. The question of the IRX-β scatter is the direct manifestation of a more fundamental question of the diversity of dust attenuation curves. The predominant role of the attenuation curve is the consequence of a narrow range of intrinsic UV slopes of star-forming galaxies. Galaxies with different specific SFRs or population ages do not show strong trends in the IRX-β diagram because their attenuation curves are, on average, similar. Similarly, there is no shift in the IRX-β locus between starbursts and normal star-forming galaxies, both types having, on average, steep attenuation curves. Optical opacity is identified as the strongest determinant of the attenuation curve slope, and consequently the IRX-β diversity. Despite the scatter, the use of an average IRX-β relation is justified to correct SFRs, adding a random error of 0.15 dex. The form of the local correspondence between IRX-β and attenuation curves is maintained at high redshift as long as the evolution of the intrinsic UV slopes stays within a few tenths.

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A Solar cycle correlation of coronal element abundances in Sun-as-a-star observations

et al. 2017

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The elemental composition in the coronae of low-activity solar-like stars appears to be related to fundamental stellar properties such as rotation, surface gravity, and spectral type. Here we use full-Sun observations from the Solar Dynamics Observatory, to show that when the Sun is observed as a star, the variation of coronal composition is highly correlated with a proxy for solar activity, the F10.7 cm radio flux, and therefore with the solar cycle phase. Similar cyclic variations should therefore be detectable spectroscopically in X-ray observations of solar analogs. The plasma composition in full-disk observations of the Sun is related to the evolution of coronal magnetic field activity. Our observations therefore introduce an uncertainty into the nature of any relationship between coronal composition and fixed stellar properties. The results highlight the importance of systematic full-cycle observations for understanding the elemental composition of solar-like stellar coronae.

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Variability of a stellar corona on a time scale of days

Cited by 6 publications

References 34 publications

Coronae of stars with supersolar elemental abundances

Coronae of stars with supersolar elemental abundances

Diversity of Galaxy Dust Attenuation Curves Drives the Scatter in the IRX–β Relation

A Solar cycle correlation of coronal element abundances in Sun-as-a-star observations

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