Serendipitous discovery of the faint solar twin Inti 1

Abstract

Context. Solar twins are increasingly the subject of many studies owing to their wide range of applications from testing stellar evolution models to the calibration of fundamental observables; these stars are also of interest because high precision abundances could be achieved that are key to investigating the chemical anomalies imprinted by planet formation. Furthermore, the advent of photometric surveys with large telescopes motivates the identification of faint solar twins in order to set the zero point of fundamental calibrations. Aims. We intend to perform a detailed line-by-line differential analysis to verify whether 2MASS J23263267-0239363 (designated here as Inti 1) is indeed a solar twin. Methods. We determine the atmospheric parameters and differential abundances using high-resolution (R ≈ 50 000), high signal-to-noise (S/N ≈ 110–240 per pixel) Keck/HIRES spectra for our solar twin candidate, the previously known solar twin HD 45184, and the Sun (using reflected light from the asteroid Vesta). Results. For the bright solar twin HD 45184, we found T_(eff) = 5864 ± 9 K, log g = 4.45 ± 0.03 dex, v_t = 1.11 ± 0.02 km s^(-1), and [Fe/H] = 0.04 ± 0.01 dex, which are in good agreement with previous works. Our abundances are in excellent agreement with a recent high-precision work, with an element-to-element scatter of only 0.01 dex. The star Inti 1 has atmospheric parameters T_(eff) = 5837 ± 11 K, log g = 4.42 ± 0.03 dex, v_t = 1.04 ± 0.02 km s^(-1), and [Fe/H] = 0.07 ± 0.01 dex that are higher than solar. The age and mass of the solar twin HD 45184 (3 Gyr and 1.05 M⊙) and the faint solar twin Inti 1 (4 Gyr and 1.04 M⊙) were estimated using isochrones. The differential analysis shows that HD 45184 presents an abundance pattern that is similar to typical nearby solar twins; this means this star has an enhanced refractory relative to volatile elements, while Inti 1 has an abundance pattern closer to solar, albeit somewhat enhanced in refractories. The abundance pattern of HD 45184 and Inti 1 could be reproduced by adding ≈3.5 M⊕ and ≈1.5 M⊕ of Earth-like material to the convective zone of the Sun. Conclusions. The star Inti 1 is a faint solar twin, therefore, it could be used to calibrate the zero points of different photometric systems. The distant solar twin Inti 1 has an abundance pattern similar to the Sun with only a minor enhancement in the refractory elements. It would be important to analyze other distant solar twins to verify whether they share the Sun's abundance pattern or if they are enhanced in refractories, as is the case in the majority of nearby solar twins.

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