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We present the multiwavelength studies of the H II region Sh2-311 to explore the effects of massive stars on low-mass star formation. In this study we have used optical (UBVI) data from ESO 2.2m Wide Field Imager (WFI), Near-Infrared (NIR) (JHKs) data from CTIO 4m Blanco Telescope and archival Spitzer 8μm data. Based on stellar density contours and dust distribution we have divided the complex into three regions i.e., Haffner 19 (H19), Haffner 18 (H18) and NGC 2467. Using the UBVI data we have estimated the basic parameters of these regions. We have constructed the (J - H)/(H - Ks) color-color diagram and a J/(J - H) color-magnitude diagram to identify young stellar objects (YSOs) and to estimate their masses. Spatial distribution of the YSOs indicates that most of them are distributed at the periphery of the H II region and ionizing star may be responsible for the triggering of star formation at the periphery of the H II region. [ABSTRACT FROM AUTHOR]

Unidentified emissions are observed in spectra of most comets. These separate lines and bands were not possible to be identified earlier by standard methods. A great number of narrow lines of unknown nature were tabulated [11]. For solving the problem of unidentified cometary emissions, had developed the theoretical model of frozen hydrocarbon particles of icy halos of comets and described the mechanism of FHPs photoluminescence [6]. The comparison of laboratory and observed data showed that hundreds of cometary emissions not identified earlier are the photoluminescence of frozen hydrocarbon particles. In [6] particularly suggested that the mixture of frozen polycyclic aromatic hydrocarbons and alkanes can be among the ices of cometary nuclei. These mixtures are the solid solutions of substance - solvent type; here the substance means polycyclic aromatic hydrocarbon (PAH), and the solvent - acyclic hydrocarbons. The optical properties of the solution are determined by the properties of a solvent, by the conditions of crystallization of the solution, by the existence of luminescent component, by the character of interaction between the components of the solution and by the content of additional impurities in the solution. The surface layers of icy cometary nucleus are the sources of frozen hydrocarbon particles of different sizes ejected and carried to the circumnuclear area as the comet approaches the Sun. The size of individual FHP can vary from micron to millimeter. FHP can has the characteristic color inherent in frozen mixture of PAH and acyclic hydrocarbons. Simonia assumed that the solar ultraviolet radiation excites the photoluminescence of icy particles of halo. Low albedo of particles that consist of the mentioned mixtures, and the high quantum yield of photoluminescence of PAHs make it possible to register the corresponding luminescent emissions. The quantum yield of photoluminescence of FHPs can really be rather high. In favor of this assumption speaks the results of laboratory investigations. For the case of small grains containing the frozen organic mixture obtained the quantum yield of photoluminescence in the range of 90-100% [8]. UV photons of solar origin cause the photoluminescence of cometary FHPs in the range of 3800-7000 Å. We presented in this chapter results of studies of several comets. [ABSTRACT FROM AUTHOR]

We investigated the dust properties and magnetic field orientation towards the star cluster NGC 1931. Cluster members have been identified using both optical color-color as well as QV - UV stokes plane diagrams. Thus identified probable cluster members have been used to estimate the distance to the cluster NGC 1931 which is found to be 2.3±0.3 kpc. Few young stellar objects with possible intrinsic polarization have been identified. One-dimensional surface stellar density contours suggest two clustering in the NGC 1931 region. The reddening E(B - V) is found to be variable between 0.50 to 0.90 mag. Polarimetric and photometric results indicate for the presence of slightly bigger dust grains within the intra-cluster medium. Although our previous work (Eswaraiah et al. 2011) reveals uniform dust grain alignment in the foreground medium towards the direction of NGC 1931, the polarization efficiency is found to be less than that of the general diffuse interstellar medium. This could be due to the normal extinction law in the foreground medium and anomalous reddening law in the intra-cluster medium. [ABSTRACT FROM AUTHOR]

We explore the physics of crystallization in the dense Coulomb plasma of the deep interiors of white dwarf stars using the color-magnitude diagram and luminosity function constructed from Hubble Space Telescope photometry of the globular cluster M 4 and compare it with our results for proper motion cleaned Hubble Space Telescope photometry of the globular cluster NGC 6397. We demonstrate that the data are consistent with a binary mixture of carbon and oxygen crystallizing at a value of Γ higher than the theoretical value for a One Component Plasma (OCP). We show that this result is in line with the latest Molecular Dynamics simulations for binary mixtures of C/O. We discuss implications for future work. [ABSTRACT FROM AUTHOR]

Our aim is to compile a catalog of white dwarfs within 40 parsecs of the Sun, in which newly discovered objects would significantly increase the completeness of the current census. White dwarf candidates are identified from the SUPERBLINK proper motion database ([2]), which allows us to investigate stars down to a proper motion limit as low as 40 mas yr-1. The selection criteria and distance estimates are based on a combination of color-magnitude and reduced proper motion diagrams. Candidates with distances less than 50 parsecs are selected for spectroscopic follow-up. We present our preliminary sample of spectroscopically confirmed white dwarfs, as well as their atmospheric parameters. These parameters are obtained using the spectroscopic technique developed in [8] for DA stars. DB, DQ, and DZ stars are also analyzed spectroscopically. For featureless spectra as well as those showing only Hα, we perform a detailed photometric analysis of their energy distribution. [ABSTRACT FROM AUTHOR]