  We present an extensive catalogue of BY Draconis (BY Dra)-type variables and
their stellar parameters. BY Dra are main-sequence FGKM-type stars. They
exhibit inhomogeneous starspots and bright faculae in their photospheres. These
features are caused by stellar magnetic fields, which are carried along with
the stellar disc through rotation and which produce gradual modulations in
their light curves (LCs). Our main objective is to characterise the properties
of BY Dra variables over a wide range of stellar masses, temperatures and
rotation periods. A recent study categorised 84,697 BY Dra variables from Data
Release 2 of the Zwicky Transient Facility based on their LCs. We have
collected additional photometric data from multiple surveys and performed
broad-band spectral energy distribution fits to estimate stellar parameters. We
found that more than half of our sample objects are of K spectral type,
covering an extensive range of stellar parameters in the low-mass regime
(0.1-1.3 M$_{\odot}$ ). Compared with previous studies, most of the sources in
our catalogue are rapid rotators, and so most of them must be young stars for
which a spin-down has not yet occurred. We subdivided our catalogue based on
convection zone depth and found that the photospheric activity index, $S_{\rm
ph}$, is lower for higher effective temperatures, i.e., for thinner convective
envelopes. We observe a broad range of photospheric magnetic activity for
different spectral classes owing to the presence of stellar populations of
different ages. We found a higher magnetically active fraction for K- than
M-type stars.
