44 research outputs found
A detection of the layered structure of nearby open clusters
We applied the newly developed rose diagram overlay method to detect the
layered structure of 88 nearby open clusters (500~pc) on the three
projections after the distance correction of their member stars, based on the
catalog in literature. The results show that with the rose diagram overlay
method, a total of 74 clusters in our sample have a layered structure, while
the remaining clusters are without a clear layered structure. We for the first
time defined the layered structure parameters for the sample clusters.
Meanwhile, we found that the layered circle core area () has a strong
positive correlation with the number of cluster members, while the kernel
instability index () has a strong negative correlation with the number of
cluster members. Our study provides a novel perspective for the detection of
the layered structure of open clusters.Comment: 11 pages, 9 figures, 6 tables, accepted for publication in A&
X-ray emission of contact binary variables within 1 kpc
By assembling the largest sample to date of X-ray emitting EW-type binaries
(EWXs), we carried out correlation analyses for the X-ray luminosity
log, and X-ray activity level
log(/) versus the orbital period and
effective temperature . We find strong -log and
-log(/) correlations for EWXs with <
0.44 days and we provide the linear parametrizations for these relations, on
the basis of which the orbital period can be treated as a good predictor for
log and log(/). The
aforementioned binary stellar parameters are all correlated with
log, while only exhibits a strong correlation
with log(/). Then, EWXs with higher
temperature show lower X-ray activity level, which could indicate the thinning
of the convective area related to the magnetic dynamo mechanism. The total
X-ray luminosity of an EWX is essentially consistent with that of an X-ray
saturated main sequence star with the same mass as its primary, which may imply
that the primary star dominates the X-ray emission. The monotonically
decreasing -log(/) relation and the short
orbital periods indicate that EWXs could all be in the X-ray saturated state,
and they may inherit the changing trend of the saturated X-ray luminosities
along with the mass shown by single stars. For EWXs, the orbital period, mass,
and effective temperature increase in concordance. We demonstrate that the
period days corresponds to the primary mass of ,
beyond which the saturated X-ray luminosity of single stars will not continue
to increase with mass. This explains the break in the positive
-log relation for EWXs with days.Comment: 16 pages, 7 figures and 8 tables; accepted for publication in A&
Variable stars detection in the field of open cluster NGC 188
This work presents the charge-coupled device (CCD) photometric survey of the
old open cluster NGC 188. Time-series V-band photometric observations were
conducted for ten nights in January 2017 using the Nanshan One-meter Wide-field
Telescope (NOWT) to search for variable stars in the field of the cluster
field. A total of 25 variable stars, including one new variable star, were
detected in the target field. Among the detected variables, 16 are cluster
member stars, and the others are identified as field stars. The periods, radial
velocities, effective temperatures, and classifications of the detected
variables are discussed in this work. Most of the stars' effective temperatures
are between 4200 K and 6600 K, indicating their spectral types are G or K. The
newly discovered variable is probably a W UMa system. In this study, a known
cluster variable star (V21 = V0769 Cep) is classified as an EA-type variable
star based on the presence of an 0.5 magnitude eclipse in its light curve