Pre-main-sequence isochrones -- III. The Cluster Collaboration isochrone server

TL;DR

This paper introduces an accessible isochrone server providing semi-empirical pre-main-sequence models across multiple photometric systems, integrating empirical data to improve stellar age and distance estimations for young clusters.

Contribution

The authors developed a semi-empirical isochrone server using empirical cluster data to refine stellar models and provide updated parameters for Pleiades and Praesepe clusters.

Findings

New cluster parameters for Pleiades and Praesepe with improved age and distance estimates.

Creation of semi-empirical bolometric corrections for multiple photometric systems.

An accessible online tool for stellar age and distance determination using semi-empirical isochrones.

Abstract

We present an isochrone server for semi-empirical pre-main-sequence model isochrones in the following systems: Johnson-Cousins, Sloan Digital Sky Survey, Two-Micron All-Sky Survey, Isaac Newton Telescope (INT) Wide-Field Camera, and INT Photometric H$\alpha$ Survey (IPHAS)/UV-Excess Survey (UVEX). The server can be accessed via the Cluster Collaboration webpage {http://www.astro.ex.ac.uk/people/timn/isochrones/}. To achieve this we have used the observed colours of member stars in young clusters with well-established age, distance and reddening to create fiducial loci in the colour-magnitude diagram. These empirical sequences have been used to quantify the discrepancy between the models and data arising from uncertainties in both the interior and atmospheric models, resulting in tables of semi-empirical bolometric corrections (BCs) in the various photometric systems. The model isochrones made available through the server are based on existing stellar interior models coupled with our newly derived semi-empirical BCs. As part of this analysis we also present new cluster parameters for both the Pleiades and Praesepe, yielding ages of $135^{+20}_{-11}$ and $665^{+14}_{-7}\,\rm{Myr}$ as well as distances of $132 \pm 2$ and $184 \pm 2\,\rm{pc}$ respectively (statistical uncertainty only).