THE FUTURE OF THE SUN: AN EVOLVED SOLAR TWIN REVEALED BY CoRoT

Abstract

The question of whether the Sun is peculiar within the class of solar-type stars has been the subject of active investigation over the past three decades. Although several solar twins have been found with stellar parameters similar to those of the Sun (albeit in a range of Li abundances and with somewhat different compositions), their rotation periods are unknown, except for 18 Sco, which is younger than the Sun and with a rotation period shorter than solar. It is difficult to obtain rotation periods for stars of solar age from ground-based observations, as a low-activity level implies a shallow rotational modulation of their light curves. CoRoT has provided space-based long time series from which the rotation periods of solar twins as old as the Sun could be estimated. Based on high-signal-to-noise, high-resolution spectroscopic observations gathered at the Subaru Telescope, we show that the star CoRoT ID 102684698 is a somewhat evolved solar twin with a low Li abundance. Its rotation period is 29 ± 5 days, compatible with its age (6.7 Gyr) and low lithium content, A Li 0.85 dex. Interestingly, our CoRoT solar twin seems to have enhanced abundances of the refractory elements with respect to the Sun, a typical characteristic of most nearby twins. With a magnitude V 14.1, ID 102684698 is the first solar twin revealed by CoRoT, the farthest field solar twin so far known, and the only solar twin older than the Sun for which a rotation period has been determined.

Serendipitous discovery of the faint solar twin Inti 1

“…In Table 1 we showed that the colors of Inti 1 are identical to the Sun within errors. Thus our faint solar solar twin and the distant solar twin found by do Nascimento et al (2013) could be used to calibrate different photometric surveys.…”

“…The mass and age of HD 45184 are in excellent agreement with the weighted mean value found in the literature ( Table 2). The Yonsei-Yale grids of stellar models do not include nonstandard physics such as those included in studies of lithium depletion (Do Nascimento et al 2009;Denissenkov 2010;Li et al 2012). We tested our method for the star 18 Sco, which was analyzed using nonstandard models by Li et al (2012), and found the same mass and age.…”

“…In the last few years, the number of solar twins have increased to about 100 (Pasquini et al 2008;Meléndez et al 2009Meléndez et al , 2014bRamírez et al 2009Ramírez et al , 2014Takeda & Tajitsu 2009;Baumann et al 2010;Önehag et al 2011;Datson et al 2012;do Nascimento et al 2013;Porto de Mello et al 2014). Solar twins could be a useful source for astronomical tests and applications.…”

“…For example, they could set the zero point of fundamental calibrations (Holmberg et al 2006;Casagrande et al 2010;Datson et al 2014), and they are used to subtract the Sun's reflected light on asteroids to study their mineralogy (e.g., Lazzaro et al 2004;Jasmim et al 2013). Solar twins are also useful for testing stellar interior and evolution models (e.g., Tucci Maia et al 2015), investigating the chemical evolution of the Galactic disk (Nissen 2015;Spina et al 2016), studying the rotational evolution of the Sun (do Nascimento et al 2013Nascimento et al , 2014, and measuring distances using spectroscopically identified solar twins (Jofré et al 2015). anomalies that are correlated with the condensation temperature, T C , (Lodders 2003).…”

Magnetic variability in the young solar analog KIC 10644253

“…Following do Nascimento et al (2013), the lithium abundance of KIC 10644253 was derived from the Li I resonance transition at 670.7 nm by producing and comparing a synthetic spectrum to the observed HERMES spectrum for the set of atmospheric parameters given in Table 5, to match a single-line equivalent width. This procedure requires an atmosphere model and physical parameters of a list of absorption lines to compute atomic chemical abundances.…”