| dc.description.abstract | We have identified stellar and substellar members in the nearby star cluster Coma Berenices,
using photometry, proper motions, and distances of a combination of 2MASS, UKIDSS, URAT1,
and {it Gaia} DR,2 data. Those with {it Gaia} DR,2 parallax measurements provide the most
reliable sample to constrain the distance, averaging 86.7~pc with a dispersion 7.1~pc, and the
age $sim800$~Myr, of the cluster. This age is older than the 400--600~Myr commonly adopted
in the literature. Our analysis, complete within $5degr$ of the cluster radius, leads to identification
of 192 candidates, among which, after field contamination is considered, about 148 are true members.
The members have $Jsim3$~mag to $sim17.5$~mag, corresponding to stellar masses 2.3--0.06~M$_sun$.
Our list contains nine substellar members, including three new discoveries of an M8, an L1 and an L4
brown dwarfs, extending from the previously known coolest members of late-M types to even cooler types. \
We also report the discovery of tidal structures around the Coma Berenices by only using the {it Gaia} DR,2
parallax and proper motion data on searching the spatial and kinematic grouping signature with a clustering
analysis tool, extsc{StarGO}. A leading and a trailing tails, each with an extension of $sim50$~pc are revealed
for the first time around this disrupting star cluster. The cluster members,
totaling to $sim112^{+5}_{-3},
m{M_sun}$, are clearly mass segregated, and exhibit a flat mass function with
$alpha sim 0.79pm0.16$, in the sense of $dN/dm = m^{-alpha}$, where $N$ is the number of member stars
and $m$ is stellar mass, in the mass range of $m=0.25$--$2.51~{
m M_sun}$. Within the tidal radius of
$sim$6.9~pc, there are 77 member candidates with an average position, i.e., as the cluster center, of
R.A.= 186.8110~deg, and decl.= 25.8112~deg, and an average distance of 85.8~pc. Additional 120 member
candidates reside in the tidal structures, i.e., outnumbering those in the cluster core.
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