High-precision analysis of the solar twin HIP 100963

¹ Universidade de São Paulo, IAGDepartamento de Astronomia, Rua do Matão 1226, São Paulo, 05509-900 SP, Brasil
e-mail: ramstojh@usp.br
² University of Texas at Austin, McDonald Observatory and Department of Astronomy, 2515 Speedway, Austin, TX 78712-1205, USA
³ Australian National University, Research School of Astronomy and Astrophysics, Mt. Stromlo Observatory, via Cotter Rd., Weston, ACT 2611, Australia

Received: 7 December 2015
Accepted: 24 February 2016

Abstract

Context. HIP 100963 was one of the first solar twins identified. Although some high-precision analyses are available, a comprehensive high-precision study of chemical elements from different nucleosynthetic sources is still lacking from which to obtain potential new insights on planets, stellar evolution, and Galactic chemical evolution (GCE).

Aims. We analyze and investigate the origin of the abundance pattern of HIP 100963 in detail, in particular the pattern of the light element Li, the volatile and refractory elements, and heavy elements from the s- and r-processes.

Methods. We used the HIRES spectrograph on the Keck I telescope to acquire high-resolution (R ≈ 70 000) spectra with a high signal-to-noise ratio (S/N ≈ 400–650 per pixel) of HIP 100963 and the Sun for a differential abundance analysis. We measured the equivalent widths (EWs) of iron lines to determine the stellar parameters by employing the differential spectroscopic equilibrium. We determined the composition of volatile, refractory, and neutron-capture elements through a differential abundance analysis with respect to the Sun.

Results. The stellar parameters we found are T_eff = 5818 ± 4 K, log g = 4.49 ± 0.01 dex, v_t = 1.03 ± 0.01km s^-1, and [Fe/H] = −0.003 ± 0.004 dex. These low errors allow us to compute a precise mass (1.03^+0.02_-0.01 M_⊙) and age (2.0 ± 0.4 Gyr), obtained using Yonsei-Yale isochrones. Using our [Y/Mg] ratio, we have determined an age of 2.1 ± 0.4 Gyr, in agreement with the age computed using isochrones. Our isochronal age also agrees with the age determined from stellar activity (2.4 ± 0.3 Gyr). We study the abundance pattern with condensation temperature (T_cond) taking corrections by the GCE into account. We show that the enhancements of neutron-capture elements are explained by contributions from both the s- and r-process. The lithium abundance follows the tight Li-age correlation seen in other solar twins.

Conclusions. We confirm that HIP 100963 is a solar twin and demonstrate that its abundance pattern is about solar after corrections for GCE. The star also shows enrichment in s- and r-process elements, as well as depletion in lithium that is caused by stellar evolution.