  Compact stars (CS) are stellar remnants of massive stars. Inside CSs the
density is so high that matter is in subatomic form composed of nucleons. With
increase of density of matter towards the centre of the objects other degrees
of freedom like hyperons, heavier non-strange baryons, meson condensates may
appear. Not only that at higher densities, the nucleons may get decomposed into
quarks and form deconfined strange quark matter (SQM). If it is so then CSs may
contain SQM in the core surrounded by nucleonic matter forming hybrid stars
(HSs). However, the nature and composition of matter inside CSs can only be
inferred from the astrophysical observations of these CSs. Recent astrophysical
observations in terms of CS mass-radius (M-R) relation and gravitational wave
(GW) observation indicate that the matter should be soft in the intermediate
density range and stiff enough at higher density range to attain the maximum
possible mass above $2~M_\odot$ which is not compatible with pure hadronic
equation of states (EOSs). Consequently, we study the HS properties with
different models of SQM and find that within vector bag model considering
density dependent bag parameter, the model goes well with the astrophysical
observations so far.
