Coronal Evolution of the Sun in Time: High-Resolution X-Ray Spectroscopy of Solar Analogs with Different Ages

By A. Telleschi, M. Gudel, K. Briggs, M. Audard, J.-U. Ness, S. Skinner. 2005

138 citations recorded by the source corpus.

We investigate the long-term evolution of X-ray coronae of solar analogs based on high-resolution X-ray spectroscopy and photometry with XMM-Newton. Six nearby main-sequence G stars with ages between ≈0.1 and ≈1.6 Gyr and rotation periods between ≈1 and 12.4 days have been observed. We use the X-ray spectra to derive coronal element abundances of C, N, O, Ne, Mg, Si, S, and Fe and the coronal emission measure distribution (EMD). We find that the abundances change from an inverse first ionization potential (FIP) distribution in stars with ages around 0.1 Gyr to a solar-type FIP distribution in stars at ages of 0.3 Gyr and beyond. This transformation is coincident with a steep decline of nonthermal radio emission. The results are in qualitative agreement with a simple model in which the stream of electrons in magnetic fields suppresses diffusion of low-FIP ions from the chromosphere into the corona. The coronal emission measure distributions show shapes characterized by power laws on each side of the EMD peak. The latter shifts from temperatures of about 10 MK in the most rapidly rotating, young stars to temperatures around 4 MK in the oldest target considered here. The power-law index on the cooler side of the EMD exceeds expected slopes for static loops, with typical values being 1.5-3. We interpret this slope with a model in which the coronal emission is due to a superposition of stochastically occurring flares, with an occurrence rate that is distributed in radiated energy E as a power law, dN/dE ∝ E-α, as previously found for solar and stellar flares. We obtain the relevant power-law index α from the slope of the high-temperature tail of the EMD. Our EMDs indicate α ≈ 2.2-2.8, in excellent agreement with values previously derived from light curves of magnetically active stars. Modulation with timescales reminiscent of flares is found in the light curves of all our targets. Several strong flares are also observed. We use our α-values to simulate light curves and compare them with the observed light curves. We thus derive the range of flare energies required to explain the light-curve modulation. More active stars require a larger range of flare energies than less active stars within the framework of this simplistic model. In an overall scenario, we propose that flaring activity plays a larger role in more active stars. In this model, the higher flare rate is responsible both for the higher average coronal temperature and the high coronal X-ray luminosity, two parameters that are indeed found to be correlated.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/4f8e5e1c887d6c9da43ffc4e62c793b4006ace20

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In Astronomy and Astrophysics

1. M. Gudel
2. J. Drake
3. N. Wright
4. Y. Nazé
5. J. Laming
6. G. Henry
7. Eric Mamajek
8. Colin P. Johnstone

Citations in the corpus

• X-ray emission from T Tauri stars and the role of accretion: inferences from the XMM-Newton extended survey of the Taurus molecular cloud (2006, methodology): “Solar analogs decrease in LX by three orders of magnitude from the zero-age main sequence to the end of the main-sequence life (Güdel et al. 1997; Telleschi et al. 2005).”
• Stellar winds on the main-sequence - II. The evolution of rotation and winds (2015, background): “Observations of the coronae of young solar analogues show that coronal temperatures decay with magnetic activity as stars spin down (Güdel et al. 1997; Telleschi et al. 2005), which suggests that the solar wind temperatures, and therefore speeds, were higher at young ages.”
• Coronal Loops: Observations and Modeling of Confined Plasma (2010, unknown): “The level of activity is ruled by several factors, but, first of all, the age of the star is important: young fast-rotating stars are more active (e.g., Telleschi et al., 2005).”
• THE STELLAR-ACTIVITY–ROTATION RELATIONSHIP AND THE EVOLUTION OF STELLAR DYNAMOS (2011, methodology): “The temperature of the thermal spectrum for the conversion was chosen based on the activity level of the star, LX/Lbol, and the observed correlation between activity level and plasma temperature (see e.g. Telleschi et al. 2005; Güdel & Nazé 2009)5.”
• X-ray spectroscopy of stars (2009, methodology): “…identified in nearby stars with well-measured near-solar photospheric abundances such as AB Dor or several solar analogs (Sanz-Forcada et al, 2003; Telleschi et al, 2005; Garcı́a-Alvarez et al, 2005); further, the similarity of the FIP or IFIP effects in stars with similar activity levels, or the…”
• The FIP and Inverse FIP Effects in Solar and Stellar Coronae (2015, methodology): “Observational evidence of low-lying reconnection producing jets and transverse waves of similar frequencies and amplitudes has been reported (Nishizuka et al., 2008; He et al., 2009; Vasheghani Farahani et al., 2009).”
• The Sun in Time: Activity and Environment (2007, methodology): “From full spectral interpretation, a tight correlation has indeed been found between the characteristic coronal temperature and the normalized coronal luminosity LX/Lbol: Stars at higher activity levels support hotter coronae (Vaiana, 1983; Schrijver et al., 1984; Stern et al., 1986; Schmitt et al.,”