Sequential clustering of star formation in IC 1396

We present in this paper a comprehensive study of the H II region IC 1396 and its star formation activity, in which multi-wavelength data ranging from the optical to the near- and far-infrared were employed. The surface density distribution of all the 2MASS sources with certain detection toward IC 1396 indicates the existence of a compact cluster spatially consistent with the position of the exciting source of the H II region, HD 206267. The spatial distribution of the infrared excessive emission sources selected based on archived 2MASS data reveals the existence of four sub-clusters in this region. One is in association with the open cluster Trumpler 37. The other three are found to be spatially coincident with the bright rims of the H II region. All the excessive emission sources in the near infrared are cross-identified with the AKARI IRC data, an analysis of the spectral energy distributions (SEDs) of the resultant sample leads to the identification of 8 CLASS I, 15 CLASS II and 15 CLASS III sources in IC 1396. Optical identification of the sample sources with R magnitudes brighter than 17 mag corroborates the results from the SED analysis. Based on the spatial distribution of the infrared young stellar objects at different evolutionary stages, the surrounding sub-clusters located in the bright rims are believed to be younger than the central one. This is consistent with a scenario of sequential star formation in this region. Imaging data of a dark patch in IC 1396 by Herschel SPIRE, on the other hand, indicate the presence of two far-infrared cores in LDN 1111, which are likely new generation protostellar objects in formation. So we infer that the star formation process in this H II region was not continuous but episodic

Universality of competitive networks for weighted networks

In this paper, we propose a new model that allows us to investigate this competitive aspect of real networks in quantitative terms. Through theoretical analysis and numerical simulations, we find that the competitive network have the universality for a weighted network. The relation between parameters in the weighted network and the competitiveness in the competitive network is obtained. So we can use the expression of the degree distribution of the competitive model to calculate that and the strength of the weighted network directly. The analytical solution reveals that the degree distribution of the weighted network is correlated with the increment and initial value of edge weights, which is verified by numerical simulations. Moreover, the evolving pattern of a clustering coefficient along with network parameters such as the size of a network, an updating coefficient, an initial weight and the competitiveness are obtained by further simulations. Specially, it is necessary to point out that the initial weight plays equally significant role as updating coefficient in influencing the topological characteristics of the network.Comment: 18 pages, 6 figures. arXiv admin note: text overlap with arXiv:cond-mat/0406238 by other author

Probing the linear polarization of photons in ultraperipheral heavy ion collisions

We propose to measure the linear polarization of the external electromagnetic fields of a relativistic heavy ion through azimuthal asymmetries in dilepton production in ultraperipheral collisions. The asymmetries estimated with the equivalent photon approximation are shown to be sizable.Comment: The version accepted by the journal, 7 pages, 4 figure

Drama of HII regions: Clustered and Triggered Star Formation

In order to understand the star formation process under the influence of HII regions, we have carried out extensive investigations to well selected star-forming regions which all have been profoundly affected by existing massive O type stars. On the basis of multi-wavelength data from mid-infrared to millimeter collected using $Spitzer$, $Herschel$, and ground based radio telescopes, the physical status of interstellar medium and star formation in these regions have been revealed. In a relatively large infrared dust bubble, active star formation is undergoing and the shell is still expanding. Signs of compressed gas and triggered star formation have been tentatively detected in a relatively small bubble. The dense cores in the Rosette Molecular Complex detected at 1.1 mm using SMA have been speculated to have a likely triggered origin according to their spatial distribution. Although some observational results have been obtained, more efforts are necessary to reach trustworthy conclusions.Comment: Appear in IAUS 31

Studies of the hybrid star structure within 2+1 flavors NJL model

In this paper we use the equation of state (EOS) of 2+1 flavors Nambu-Jona-Lasinio (NJL) model to study the structure of compact stars. To avoid the ultraviolet divergence, we employ the proper-time regularization (PTR) with an ultraviolet cutoff. For comparison, we fix three sets of parameters, where the constraints of chemical equilibrium and electric charge neutrality conditions are taken into consideration. With a certain interpolation method in the crossover region, we construct three corresponding hybrid EOSs but find that the maximum masses of hybrid stars in the three different cases don't differ too much. It should be pointed out that, the results we get are in accordance with the recent astro-observation PSR J0348+0432, PSR J1614-2230, PSR J1946+3417

Investigation of Star Formation toward the Sharpless 155 H II region

We present a comprehensive study of star formation toward the H II region S155. Star-formation activities therein were investigated based on multi-wavelength data from optical to the far-infrared. The surface density distribution of selected 2MASS sources toward S155 indicates the existence of a compact cluster, which is spatially consistent with the position of the exciting source of the H II region, HD 217086. A sample of more than 200 excessive emission sources in the infrared were selected based on their 2MASS color indices. The spatial distribution of the sample sources reveals the existence of three young sub-clusters in this region, among which, sub-cluster A is spatially coincident with the bright rim of the H II region. In addition, photometric data from the WISE survey were used to identify and classify young stellar objects (YSOs). To further explore the evolutionary stages of the candidate YSOs, we fit the spectral energy distribution (SEDs) of 44 sources, which led to the identification of 14 Class I, 27 Class II, and 3 Class III YSOs. The spatial distribution of the classified YSOs at different evolutionary stages presents a spatio-temporal gradient, which is consistent with a scenario of sequential star formation. On the other hand, Herschel PACS observations toward the interface between S155 and the ambient molecular cloud disclose an arc-shaped dust layer, the origin of which could be attributed to the UV dissipation from the early type stars e.g. HD 217061 in S155. Four dusty cores were revealed by the Herschel data, which hints for new generations of star formation.Comment: arXiv admin note: text overlap with arXiv:1212.153

Experimental nonlocal steering of Bohmian trajectories

Interpretations of quantum mechanics (QM), or proposals for underlying theories, that attempt to present a definite realist picture, such as Bohmian mechanics, require strong non-local effects. Naively, these effects would violate causality and contradict special relativity. However if the theory agrees with QM the violation cannot be observed directly. Here, we demonstrate experimentally such an effect: we steer the velocity and trajectory of a Bohmian particle using a remote measurement. We use a pair of photons and entangle the spatial transverse position of one with the polarization of the other. The first photon is sent to a double-slit-like apparatus, where its trajectory is measured using the technique of Weak Measurements. The other photon is projected to a linear polarization state. The choice of polarization state, and the result, steer the first photon in the most intuitive sense of the word. The effect is indeed shown to be dramatic, while being easy to visualize. We discuss its strength and what are the conditions for it to occur.Comment: 10 pages, 3 figure

Impact parameter dependence of the azimuthal asymmetry in lepton pair production in heavy ion collisions

We investigate the impact parameter dependence of the $\cos 4\phi$ azimuthal asymmetry for electromagnetic lepton pair production in heavy ion collisions. The asymmetry induced by linearly polarized coherent photons exhibits strong impact parameter dependence.Comment: 6 pages, 4 figure

Cross-correlations between soft and hard light curves depending on luminosity in the transient neutron star XTE J1701-462

Using all the observations from Rossi X-ray Timing Explorer for accreting neutron star XTE J1701-462, we carry out a systematic study on the cross-correlation between its soft and hard light curves. The anti-correlations appear at the hard vertex and on the upper normal branch (NB) in the Cyg-like interval, occur on the horizontal branch (HB) and/or upper NB in the first and second Sco-like intervals, and display at the upper flaring branch (FB) in the third Sco-like interval. We suggest that the anti-correlation might evolve with luminosity, because with decreasing of luminosity, the source evolved from a Cyg-like Z source, via a Sco-like Z source, to an atoll source. In the Cyg-like interval, the positive correlations are mostly distributed on the HB, which is not consistent with that of the Cyg-like Z source GX 5-1 and Cyg X-2 whose HBs host ambiguous correlations and anti-correlations. From our spectral analyses, it is found that the ratio of the hard emission to the soft emission basically keeps unvaried from the HB to the hard vertex, which might result in the positive correlation. Additionally, we compare the spectra in the third Sco-like interval with those of atoll source 4U 1735-44 and find that their spectral evolution along the tracks in the color-color diagrams are similar, indicating that in this interval, XTE J1701-462 approaches an atoll source. Both hard time lags and soft time lags are detected and the possible origins of them are discussed

Demonstration of MultiSetting One-Way Einstein-Podolsky-Rosen Steering in Two-Qubit Systems

Einstein-Podolsky-Rosen (EPR) steering describes the ability of one party to remotely affect another's state through local measurements. One of the most distinguishable properties of EPR steering is its asymmetric aspect. Steering can work in one direction but fail in the opposite direction. This type of one-way steering, which is different from the symmetry concepts of entanglement and Bell nonlocality, has garnered much interest. However, an experimental demonstration of genuine EPR steering in the simplest scenario, i.e., one that employs two-qubit systems, is still lacking. In this work, we experimentally demonstrate one-way EPR steering with multimeasurement settings for a class of two-qubit states, which are still one-way steerable even with infinite settings. The steerability is quantified by the steering radius, which represents a necessary and sufficient steering criterion. The demonstrated one-way steering in the simplest bipartite quantum system is of fundamental interest and may provide potential applications in one-way quantum information tasks.Comment: 5 pages, 4 figure