This page contains an overview of some of the global population properties in the MOCA database.
Currently, MOCAdb contains [...] adopted stellar associations with [...] age measurements compiled. MOCAdb also contains [...] astrophysical bodies (stars, brown dwarfs, planemos, exoplanets, white dwarfs, etc.), [...] of which are assigned as candidate members to at least one coeval association and therefore benefit from an age constraint.
A large fraction of the database objects consist in relatively young (10-100 Myr) M dwarfs as seen in the figure below; this is not unexpected given the shape of the initial mass function and the ages of the nearest known young associations and open clusters.
We are attempting to include all stellar associations at distances up to 500 pc from the Sun in MOCAdb, but we have also included some open clusters that are further away:
Most of the masses in MOCAdb are estimated from the spectral type of the star and empirical sequences (shown below) explained in the MOCA paper reference. While this is not the most precise method to estimate masses, it suffers from less biases from unresolved binaries and is not subject to systematic errors that are still present in evolutionary models (in the case of stars earlier than M6). The semi-empirical sequences shown below are stored as a 3D grid in the table data_astro_sequences with the unique sequence identifier moca_seqid='sptn_msun_age'.
The stellar and substellar radii in MOCAdb are estimated in a similar manner, except that the radii of young G to M dwarfs are a much stronger function of age because this is a period where stars are still contracting onto the main sequence. The semi-empirical sequences shown below are stored as a 3D grid in the table data_astro_sequences with the unique sequence identifier moca_seqid='sptn_rsun_age'.
MOCAdb also contains a large number of substellar objects: [...] spectroscopically confirmed brown dwarfs and planemos with spectral types L0 or later; and [...] if we add the young M6 dwarfs or later to this count.