Study of 26 Galactic Open Clusters with Extended Main-sequence Turnoffs

Recent studies indicate that some Galactic open clusters(OCs)exhibit extended main-sequence turnoff(eMSTO)in their color–magnitude diagrams(CMDs).However,the number of Galactic OCs with eMSTO structures detected so far is limited,and the reasons for their formation are still unclear.This work identifies 26 Galactic OCs with undiscovered eMSTOs and investigates the causes of these features.Stellar population types and fundamental parameters of cluster samples are acquired using CMD fitting methods.Among them,the results of 11 OCs are reliable as the observed CMDs are well-reproduced.We propose the crucial role of stellar binarity and confirm the importance of stellar rotation in reproducing eMSTO morphologies.The results also show that the impact of age spread is important,as it can adequately explain the structure of young OCs and fit the observed CMDs of intermediate-age OCs better.

The fractions of post-binary-interaction stars and evolved blue straggler stars on the red giant branch of globular clusters

The red giant branch(RGB)of globular clusters(GCs)is home to some exotic stars,which may provide clues on the formation of multiple stellar populations in GCs.It is well known that binary interactions are responsible for many exotic stars.Thus,it is important to understand what fraction of stars on the RGB of GCs is the result of binary interactions.In this paper,we performed a binary population synthesis study to track the number of post-binary-interaction(post-BI)stars that appear on the RGB,with particular emphasis on the evolved blue straggler stars(E-BSSs).Assuming an initial binary fraction of nearly 50%,we find that about half of the objects on the RGB(called giants)underwent the binary interactions,and that E-BSSs account for around 10%of the giants in our standard simulation.We also compare the properties of post-BI giants that evolved from different channels.We find that the initial orbital period and mass ratio distributions significantly affect the fraction of post-BI giants.Our results imply that the non-standard stars from binary interactions provide a non-negligible contribution to the RGB stars in GCs,which should be considered in future investigations of the origin of multiple stellar populations.

Fractions of Compact Object Binaries in Star Clusters:Theoretical Predictions

The binary population in field stars and star clusters contributes to the formation of gravitational wave(GW)sources.However,the fraction of compact-object binaries(CBs),which is an important feature parameter of binary populations,is still difficult to measure and very uncertain.This paper predicts the fractions of important CBs and semi-compact object binaries(SCBs) making use of an advanced stellar population synthesis technique.A comparison with the result of N-body simulation is also presented.It is found that most CBs are formed within about 500 Myr after the starburst.The fractions of CBs and SCBs are demonstrated to correlate with stellar metallicity.The higher the metallicity becomes,the smaller the fraction of black hole binaries(BHBs),neutron star binaries(NSBs) and SCBs.This suggests that the GW sources of BHBs and NSBs are more likely to form in metal-poor environments.However,the fraction of black hole-neutron star binaries is shown to be larger for metalrich populations on average.

Unsupervised Binary Protocol Clustering Based on Maximum Sequential Patterns

With the rapid development of the Internet,a large number of private protocols emerge on the network.However,some of them are constructed by attackers to avoid being analyzed,posing a threat to computer network security.The blockchain uses the P2P protocol to implement various functions across the network.Furthermore,the P2P protocol format of blockchain may differ from the standard format specification,which leads to sniffing tools such as Wireshark and Fiddler not being able to recognize them.Therefore,the ability to distinguish different types of unknown network protocols is vital for network security.In this paper,we propose an unsupervised clustering algorithm based on maximum frequent sequences for binary protocols,which can distinguish various unknown protocols to provide support for analyzing unknown protocol formats.We mine the maximum frequent sequences of protocolmessage sets in bytes.Andwe calculate the fuzzymembership of the protocolmessage to each maximum frequent sequence,which is based on fuzzy set theory.Then we construct the fuzzy membership vector for each protocol message.Finally,we adopt K-means++to split different types of protocol messages into several clusters and evaluate the performance by calculating homogeneity,integrity,and Fowlkes and Mallows Index(FMI).Besides,the clustering algorithms based onNeedleman–Wunsch and the fixed-length prefix are compared with the algorithm presented in this paper.Compared with these traditional clustering methods,we demonstrate a certain improvement in the clustering performance of our work.

Binary star detection in the open cluster King 1 field

A rarely studied open cluster,King 1 is observed using the 1.3-m telescope equipped with a 2 k×4 k CCD at Vainu Bappu Observatory,India.We analyze the photometric data obtained from CCD observations in both B and V bands.Out of 132 detected stars in the open cluster King 1 field,we have identified four stellar variables,and two among them are reported as newly detected binary systems.The parallax values from Gaia DR2 suggest that the open cluster King 1 is in the background of these two detected binary systems,falling along the same line of sight,giving rise to different parallax values.Periodogram analysis was carried out using Phase Dispersion Minimization(PDM)and the Lomb-Scargle(LS)method for all the detected variables.PHysics Of Eclipsing Binari Es(PHOEBE)is extensively employed to model various stellar parameters of both the detected binary systems.Based on the modeling results obtained from this work,one of the binary systems is reported for the first time as an Eclipsing Detached(ED)and the other as an Eclipsing Contact(EC)binary of W-type W UMa.

Two particular EA-type binaries in the globular cluster ω Centauri

We analyzed the B and V light curves of two EA-type binaries V211 and NV358 for the first time using the Wilson-Devinney code. Our analysis shows that V211 is a typical Algol-type binary and NV358 is a well detached binary system. As the two binaries are definite members of ω Centauri due to their proper motion, we estimated their physical parameters, obtaining M1 = 1.13 4±0.03 M⊙, R1 = 0.98±0.01 R⊙, M2 = 0.33 ±0.01 M⊙ and R2 = 0.92 ±0.01 R⊙ forV211; M1 = 1.304-0.05 M⊙, R1 = 1.03±0.01 R⊙, M2 = 0.58±0.02 M⊙ and R2 = 0.78±0.01 R⊙ for NV358. On the color-magnitude diagram of ω Centauri, V211 is located in the faint blue straggler region and its primary component is more massive than a star at the main-sequence turnoff. Therefore, V211 is a blue straggler and was formed by mass transfer from the secondary component to the primary. The age of NV358 is less than 1.93 Gyr, indicating that it is much younger than the first generation of stars in ω Centaufi. Like NV364 in ω Centaufi, NV358 should be a second-generation binary.

Melting properties of mixed Ni(13-x)Alx(x=0 to 13) clusters

Starting from the configuration full optimized by Genetic Algorithm (GA), the melting behaviors of Binary Ni 13-xAl x(x=0 to 13) clusters have been investigated by Monte Carlo (MC) simulations with Metropolis algorithm with a n-body Gupta potential. In contrast to bulk, these clusters have smeared first order transitions occurring over a range of temperature. The melting temperature T m calculated from Lindemann’s criterion vary drastically with concentrations x. For most clusters studied, the average energy per atom E, the relative root-mean-square (rms) bond length fluchuation δ and the heat capacity C per atom related to the energy fluctuation of the system change with temperature in the transition region in manners differing from LJ and alkali metal clusters. For Ni 12Al, Ni 7Al 6, Ni 6Al 7, Ni 5Al 8 clusters, there are behaviors characteristic of magic number in C, which do not exist in the pure TM clusters.

Estimation of Attributable Risk from Clustered Binary Data: The Case of Cross-Sectional and Cohort Studies

Effect sizes are estimated from several study designs when the subjects are individually sampled. When the samples are the aggregate cluster of individuals, the within cluster correlation must be accounted for to construct correct confidence intervals, and to conduct valid statistical inference. The purpose of this article is to propose and evaluate statistical procedures for the estimation of the variance of the estimated attributable risk in parallel groups of clusters, and in a design dividing each of k clusters into two segments creating multiple sub-clusters. The estimated variance is the first order approximation and is obtained by the delta method. We apply the methodology and propose a Wald type confidence interval on the difference between two correlated attributable risks. We also construct a test on the hypothesis of equality of two correlated attributable risks. We evaluate the power of the proposed test via Monte-Carlo simulations.

Variable Stars in the 50BiN Open Cluster Survey.Ⅲ.NGC 884

Open clusters are the basic building blocks that serve as a laboratory for the study of young stellar populations in the Milky Way.Variable stars in open clusters provide a unique way to accurately probe the internal structure,temporal and dynamical evolutionary stages of individual stars and the host cluster.The most powerful tool for such studies is time-domain photometric observations.This paper follows the route of our previous work,concentrating on a photometric search for variable stars in NGC 884.The target cluster is the companion of NGC869,forming the well-known double cluster system that is gravitationally bound.From the observation run in 2016 November,a total of 9247 B-band CCD images and 8218Ⅴ-band CCD images were obtained.We detected a total of 15 stars with variability in visual brightness,including five Be stars,three eclipsing binaries,and seven of unknown types.Two new variable stars were discovered in this work.We also compared the variable star content of NGC 884 with its companion NGC 869.

Binary-Positive下的并行化CURE算法

当CURE算法在处理不均匀的海量数据时,针对随机抽样不具有代表性的问题,提出了一种健壮的并行化改进算法。该算法使用Binary-Positive算法得到原始数据的有效属性,并利用MapReduce并行框架对有效数据进行层次聚类,从而实现了正确率与效率的一种权衡。实验分析表明,改进后的CURE算法具有更高的执行效率,且聚类效果良好。

基于粗集与聚类投票机制的光谱双星特征分析

光谱双星通常是指光谱中呈现双主导成分特征,由于该双成分复杂多样,其成因也多种多样,同时光谱信噪比相对比较低,现有许多分析方法将双成分系统光谱分离成两条光谱进行分析,而分离方法无法保证光谱的准确性,现有聚类方法的单次聚类可靠性比较低。提出一种基于粗集与聚类投票机制的光谱双星分析与评估方法,采用多次聚类和投票思想,给出每条光谱属于相应类别的梯度可靠性。该方法包含两个部分:(1)采用不同思想的聚类算法,将光谱双星数据集进行重构,将每种聚类算法标签采用匈牙利算法将聚类标签对齐作为光谱属性,从而重构数据集。(2)利用投票机制,得票数反映聚类结果的一致程度,获得每条光谱的类别,定义粗集示踪每类光谱特征,采用上/下近似集给出每条光谱所归类别的可靠性。选择郭守敬望远镜(LAMOST)DR10发布光谱双星集作为分析对象,采用基于划分的K-means、基于模型的GMM(Gaussian mixture model)、谱聚类(spectral clustering)和层次聚类(agglomerative clustering)四种聚类算法重构光谱数据集,选择得票数下界μ为2,通过投票得到1、0.75、0.5为可靠性梯度的聚类结果。其中大约1/3的样本可靠性为1,说明这批样本的四种聚类结果完全一致;对每类光谱和投票数的信噪比进行统计分析,投票数低的样本的信噪比相对较低,是它们被不同的聚类算法划分到不同类别的原因之一;对可靠性为1的6类光谱样本进行了物理成因的分析,其中以双星、河内星云+目标恒星两种为主,聚类标签的差异可能由于两种成分流量差异或拼接、定标等数据处理所导致。也有可能由于光谱质量较低导致pipeline误判的因素,其天区位置分布与低质量数据分布特征的研究基本一致。

Hybridization of Fuzzy and Hard Semi-Supervised Clustering Algorithms Tuned with Ant Lion Optimizer Applied to Higgs Boson Search

This paper focuses on the unsupervised detection of the Higgs boson particle using the most informative features and variables which characterize the“Higgs machine learning challenge 2014”data set.This unsupervised detection goes in this paper analysis through 4 steps:(1)selection of the most informative features from the considered data;(2)definition of the number of clusters based on the elbow criterion.The experimental results showed that the optimal number of clusters that group the considered data in an unsupervised manner corresponds to 2 clusters;(3)proposition of a new approach for hybridization of both hard and fuzzy clustering tuned with Ant Lion Optimization(ALO);(4)comparison with some existing metaheuristic optimizations such as Genetic Algorithm(GA)and Particle Swarm Optimization(PSO).By employing a multi-angle analysis based on the cluster validation indices,the confusion matrix,the efficiencies and purities rates,the average cost variation,the computational time and the Sammon mapping visualization,the results highlight the effectiveness of the improved Gustafson-Kessel algorithm optimized withALO(ALOGK)to validate the proposed approach.Even if the paper gives a complete clustering analysis,its novel contribution concerns only the Steps(1)and(3)considered above.The first contribution lies in the method used for Step(1)to select the most informative features and variables.We used the t-Statistic technique to rank them.Afterwards,a feature mapping is applied using Self-Organizing Map(SOM)to identify the level of correlation between them.Then,Particle Swarm Optimization(PSO),a metaheuristic optimization technique,is used to reduce the data set dimension.The second contribution of thiswork concern the third step,where each one of the clustering algorithms as K-means(KM),Global K-means(GlobalKM),Partitioning AroundMedoids(PAM),Fuzzy C-means(FCM),Gustafson-Kessel(GK)and Gath-Geva(GG)is optimized and tuned with ALO.

Photometric study of an eclipsing binary in Praesepe

We present CCD photometric observations of an eclipsing binary in the direction of the open cluster Praesepe using the 2 m telescope at IUCAA Girawali Observatory, India. Though the system was classified as an eclipsing binary by Pepper et al., detailed investigations have been lacking. The photometric solutions using the Wilson-Devinney code suggest that it is a W-type W UMa system and, interestingly, the system parameters are similar to another contact binary system SW Lac.

Photometric solution and period analysis of the contact binary system AH Cnc

Photometric observations of AH Cnc, a W UMa-type system in the open cluster M67, were car- fled out by using the 50BIN telescope. About 100h of time-series/3- and V-band data were taken, based on which eight new times of light minima were determined. By applying the Wilson-Devinney method, the light curves were modeled and a revised photometric solution of the binary system was derived. We con- firmed that AH Cnc is a deep contact （f = 51%）, low mass-ratio （q - 0.156） system. Adopting the distance modulus derived from study of the host cluster, we have re-calculated the physical parameters of the binary system, namely the masses and radii. The masses and radii of the two components were estimated to be respectively 1.188（4-0.061） Me, 1.332（4-0.063） RQ for the primary component and 0.185（4-0.032） Me, 0.592（4-0.051） Re for the secondary. By adding the newly derived minimum timings to all the available data, the period variations of AH Cnc were studied. This shows that the orbital period of the binary is con- tinuously increasing at a rate of dp/dt = 4.29 x 10-10 d yr-1. In addition to the long-term period increase, a cyclic variation with a period of 35.26 yr was determined, which could be attributed to an unresolved tertiary component of the system.

Variable stars in the open cluster NGC 2141

We report the results of a search for variable stars in the open cluster NGC 2141. Ten variable stars are detected, among which nine are new variable stars and they are classified as three short-period W UMa-type eclipsing binaries, two EA- type eclipsing binaries, one EB-type eclipsing binary, one very short-period RS CVn- type eclipsing binary, one d-type RR Lyrae variable star, and one unknown type of variable star. The membership and physical properties are discussed, based on their light curves, positions in the color magnitude diagrams, spatial locations and periods. A known EB-type eclipsing binary is also identified as a blue straggler candidate in the cluster. Furthermore, we find that all eclipsing contact binaries have prominent asymmetric eclipses and display the O＇Connell effect, which increases with a decrease in orbital periods. This suggests that the O＇Connell effect is probably related to the evolution of the orbital period in short period eclipsing binary systems.

Multi-view recognition of fruit packing boxes based on features clustering angle

In order to realize the intelligent mechanization of the last process of the fruit industry chains,the identification of fruit packing boxes is researched.A multi-view database is established to describe the omnidirectional attitudes of the fruit packing boxes.In order to reduce the data redundancy caused by multi-view acquisition,a new binary multi-view kernel principal component analysis network(BMKPCANet) is built,and a multi-view recognition method of fruit packing boxes is proposed based on the BMKPCANet and support vector machine(SVM).The experimental results show that the recognition accuracy of proposed BMKPCANet is 12.82% higher than PCANet and3.51% higher than KPCANet on average.The time consumption of proposed BMKPCANet is 7.74%lower than PCANet and 29.01% lower than KPCANet on average.This work has laid a theoretical foundation for multi-view recognition of 3 D objects and has a good practical application value.

Variable Star 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.Timeseries V-band photometric observations were conducted for ten nights in 2017 January using the Nanshan Onemeter Wide-field Telescope to search for variable stars in the field of the cluster.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 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 mag eclipse in its light curve.

Search for variable stars in the open cluster NGC 1245

We used the Nanshan 1 m telescope of Xinjiang Astronomical Observatory to investigate variable stars in the region of NGC 1245. We detected 55 variable stars in the field of view, 42 of them are newly discovered: six binaries, 22 pulsating stars, 14 unclassified variables. We discussed the physical properties and classifications of the variable stars through their light curves. The cross-matching with the members catalog of NGC 1245 suggests that 10 variable stars are identified as probable cluster members, which including one EW type binary, eight δ Scuti stars, and an unknown type variable star. Since the difference of the members catalog of the cluster and the limitations of the instrument, there are some huge differences in the variable list of NGC 1245 compared with the previous work.

V551 Aur,an oEA binary with g-mode pulsations?

We present time-series CCD photometry of V551 Aur, an eclipsing binary located in the open cluster NGC 2126 that shows δ Scuti-like pulsations. Complete covered light curves in theBand V bands were obtained with high-precision over nine nights. Based on them, a revised orbital period and the first photometric solutions were determined. Our eclipsing light-curve synthesis reveals a detached configura- tion for the binary system with a mass-ratio of about 0.73, and the mean density of the pulsating primary component was deduced to be about （0.532±0.005）ρ. A fre- quency analysis of the eclipse-subtracted light curve yields two reliable frequencies at f1=7.727013（c/d） and f2=15.45403（c/d）, respectively. With the help of the derived mean density, mode identification was performed. The result suggests that the primary component of V551 Aur is very probably g-mode oscillations.

Discovery of high-velocity EHB stars in the globular cluster ωCentauri(NGC 5139)

Abstract We report the discovery of 45 high-velocity extreme horizontal branch （EHB） stars in the globular cluster Omega Centauri （NGC 5139）. The tangential ve- locities of these EHB stars are determined to be in the range 93-313 km s^-1, with an average uncertainty of -27 km s^-1. The central escape velocity of the cluster is determined to be in the range 60~105 km s^-1. These EHB stars are significantly more concentrated toward the cluster core compared with other cluster members. The formation mechanisms of these EHB stars are discussed. Our conclusions can be sum- marized as follows： （1） A comparison of the tangential velocities of these EHB stars to the central escape velocity of the cluster shows that most if not all of these EHB stars are unbound to the cluster; （2） These EHB stars obtained high velocities in the central cluster region no longer than - 1 Myr ago and may be subsequently ejected from the cluster in the next -1 Myr; （3） If the progenitors of these EHB stars were single stars, then they may have experienced a fast mass-loss process. If the progen- itors were in close binaries, then they may have formed through disruptions by the intermediate-mass black hole in the cluster center.