Survey for Distant Solar Twins (SDST) - III. Identification of new solar twin and solar analogue stars
Abstract
The Survey for Distant Solar Twins aims to find stars very similar to the Sun at distances of 1-$4\, {\rm kpc}$, several times more distant than any currently known solar twins and analogues. The goal is to identify the best stars with which to test whether the fine-structure constant, α, varies with dark matter density in our Galaxy. Here, we use EPIC, our line-by-line differential technique, to measure the stellar parameters - effective temperature Teff, surface gravity log g, and metallicity [Fe/H] - from moderate-resolution (R ≲ 32 000) spectra of 877 solar twin and analogue candidates (547 at 1-$4\, {\rm kpc}$) observed with the High Efficiency and Resolution Multi-Element Spectrograph (HERMES) on the Anglo-Australian Telescope. These are consistent with expectations for Teff and log g from photometry, and for [Fe/H] from the Besançon stellar population model. EPIC provides small enough uncertainties ($\sim 90\, {\rm K}$, $0.08\, {\rm dex}$, and $0.05\, {\rm dex}$, respectively), even at the low signal-to-noise ratios available (${\rm S/N}\gtrsim$ 25 per pixel), to identify 299 new solar analogues ($\ge 90~{{\ \rm per\ cent}}$ confidence) and 20 solar twins (≥50 per cent confidence), 206 and 12 of which are at 1-$4\, {\rm kpc}$. By extending EPIC to measure line broadening and lithium abundance from HERMES spectra, and with ages derived from isochrone fitting with our stellar parameters, we identify 174 solar analogues at 1-$4\, {\rm kpc}$ that are relatively inactive, slowly rotating, and with no evidence of spectroscopic binarity. These are the preferred targets for follow-up spectroscopy to measure α.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- May 2023
- DOI:
- 10.1093/mnras/stad381
- arXiv:
- arXiv:2302.00399
- Bibcode:
- 2023MNRAS.521..148L
- Keywords:
-
- instrumentation: spectrographs;
- methods: data analysis;
- techniques: spectroscopic;
- stars: fundamental parameters;
- stars: solar-type;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 12 pages, 12 figures. Accepted by MNRAS. The full table of stars used in this work can be found at https://doi.org/10.5281/zenodo.7332606