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We present an improved method for the determination of membership of an open cluster using ensemble-based unsupervised machine learning techniques. The working principle of this method relies on two stages: (i) choosing a suitable range of three astrometric parameters (π, μαcos δ, μδ) using k -nearest neighbour (kNN) algorithm on the data downloaded for the cluster within a smaller search radius; (ii) application of two component Gaussian mixture modelling (GMM) on the resulting one dimensional Gaussian distribution of Mahalanobis distance (MD) of stars using the range of parameters obtained from the earlier step, but with the data downloaded within a bigger search radius. MD is calculated from the mean of each of the parameters in three dimensions. Thus the use of MD reduces the input of the GMM from the 3D parameter space into a 1D parameter space for the cluster membership determination. The method has been tested on a few clusters including those which have overlaps in some/all the parameters using the data obtained from the Gaia DR3 data base. It is found that the approach can easily separate the cluster members from the field stars. The clean colour-magnitude diagrams and similar direction of proper motions of the member stars obtained for the clusters shows that this method is very efficient and robust in segregating the cluster members from the field stars. [ABSTRACT FROM AUTHOR]

Pigments are an essential part of life on earth, ranging from microbes to plants and humans. The physiological and environmental cues induce microbes to produce a broad spectrum of pigments, giving them adaptation and survival advantages. Microbial pigments are of great interest due to their natural origin, diverse biological activities, and wide applications in the foods, Pharmaceuticals, cosmetics, and textile industries. Despite noticeable research on pigment-producing microbes, commercial successes are scarce, primarily from higher, remote, and inaccessible Himalayan niches. Therefore, substantial bioprospection integrated with advanced biotechnological strategies is required to commercialize microbial pigments successfully. The current review elaborates on pigment-producing microbes from a Himalayan perspective, offering tremendous opportunities for industrial applications. Additionally, it illustrates the ecological significance of microbial pigments and emphasizes the current status and prospects of microbial pigment production above the test tube scale. [ABSTRACT FROM AUTHOR]

This is the second of a series related to the study of geometry of the Magellanic Clouds based on multiwavelength photometry of classical Cepheids. In this paper we determine the geometrical and viewing angle parameters of the Small Magellanic Cloud (SMC) using the Leavitt law for classical Cepheids with/without a break in the law at a certain period as reported in the literature. The study utilizes photometric data for more than 3400 common classical Cepheids (Fundamental (FU) and First overtone (FO)) in optical (V, I), near-infrared (Y, J, Ks) and mid-infrared ([3.6] and [4.5]  μ m) photometric bands. We obtain statistical reddening and distance modulus free from the effect of reddening to each of the individual Cepheids with respect to the mean distance modulus and reddening of the SMC. The reddening maps of the SMC obtained from the analyses with/without breaks in the Leavitt law show good agreement with each other as well as with other maps available in the literature. The Cartesian coordinates of individual stars with respect to the galaxy plane are obtained using the information of equatorial coordinates (α, δ) as well as extinction-free distance measurements. Modelling the observed 3D distribution of the Cepheids as a triaxial ellipsoid, we obtain the geometrical and viewing angle parameters of the SMC. The weighted average yields the following values of parameters for the SMC: the geometrical axes ratios of 1.000 ± 0.001: 1.544 ± 0.002: 9.742 ± 0.030 and the viewing angle parameters having inclination angle i  = 3 |${^{\circ}_{.}}$| 465 ± 0 |${^{\circ}_{.}}$| 030 with respect to the longest axis from the line of sight and position angle of line of nodes (major axis) θlon = 63 |${^{\circ}_{.}}$| 086 ± 0 |${^{\circ}_{.}}$| 117. [ABSTRACT FROM AUTHOR]

We present a study of three-dimensional structure of the Small Magellanic Cloud (SMC). The V- and I-band light curves of the fundamental mode RR Lyrae (RRab) stars obtained by the Optical Gravitational Lensing Experiment-III project were utilized in order to comprehend the SMC structure. The [Fe/H]-P-ϕ31 relation of Jurcsik & Kovacs is exploited to obtain the metallicities. From the three-dimensional RRab distance distributions, north-east arm and main body of the galaxy are identified. Combining metallicities with spatial distribution of these tracers, no radial metallicity gradient in the SMC has been detected. Dividing the entire sample into three parts: north-eastern, central and south-western, we find that the central part has a significantly larger line of sight depth as compared to rest of the parts, indicating that the SMC may have a bulge. Results obtained from the I-band data seem to be reliable and were further substantiated using the Smolec relation. Distribution of SMC RRab stars was modelled as a triaxial ellipsoid. Errors in structural parameters of the SMC ellipsoid were obtained from Monte Carlo simulations. We estimated the axes ratios of the galaxy as 1.00 ± 0.000: 1.310 ± 0.029: 8.269 ± 0.934, the inclination of the longest axis with line of sight i = 2°.265 ± 0°.784 and the position angle of the line of nodes 6= 74?307 ± 0?509 from the variance weighted I-band determinations. [ABSTRACT FROM AUTHOR]