Abstract AstroSat/LAXPC and SXT observed the persistent neutron star low-mass X-ray binary 4U 1820-30 between 2016 and 2022. During these observations, the hardness–intensity diagram and color–color diagram (CCD) indicated that the source was in the banana state. We divided the CCD into 11 segments for spectral and timing analyses. For each segment in the CCD, we modeled the spectral data using two distinct approaches over the 0.7–20.0 keV band. A combination of a multicolor disk component with an inner disk temperature of around 0.6 keV and Comptonized emission from the boundary layer/hot corona provided the best description of the X-ray spectral data of this source. The truncation radius was found to be in the range of ∼19–40 km. The Comptonized component has an optical depth in the range of ∼7–13, with electron temperature in the range of ∼2.5–3.8 keV. The optical depth of the corona varies significantly along the position on the CCD, while ∼80% of the X-ray flux comes from the Comptonized component. We discuss possible physical scenarios to explain the relationship between the spectral evolution and motion of the source along the CCD. The timing analysis revealed kHz quasi-periodic oscillation (QPO) peaks at ∼710 and ∼740 Hz in the lower left banana branch. An energy-dependent study indicates that these QPOs are stronger in the high-energy band.

Abstract Understanding the coevolution of galaxies and active galactic nuclei (AGNs) requires accurate modeling of dust-obscured systems. Recent surveys using the Mid Infrared Instrument (MIRI) on board the James Webb Space Telescope (JWST) have uncovered a large population of dust obscured AGNs, challenging current theoretical frameworks. We present an updated version of the Simulated Infrared Extragalactic Dusty Sky (SIDES) simulation framework. Our updates include modified star-forming and starburst galaxy spectral energy distribution templates as well as quiescent and AGN templates. We also incorporate a probabilistic assignment of the fraction of the IR emission that is due to an AGN. Our simulations successfully reproduce the observed MIRI source number counts, redshift distributions, and AGN population fractions. We find that AGNs dominate at bright flux densities ( S ν ≳ 20 μ Jy) while main-sequence galaxies dominate at the faint end. We also quantify the effects of cosmic variance, showing that surveys with areas below 25 arcmin 2 suffer from ∼30% uncertainty in bright AGN counts. Finally, we provide diagnostic color–color diagrams and joint Near Infrared Camera (NIRCam) and MIRI flux distributions to aid interpretation of current and upcoming JWST surveys.

Abstract Red supergiants (RSGs) are crucial for studying the properties and evolution of massive stars. It is representative to conduct a census of RSGs across the Local Group, which spans a broad metallicity range. However, identifying RSGs in distant and metal-poor galaxies remains challenging, mainly due to contamination of foreground dwarfs and observational limitations. In this work, we perform point-spread function photometry on publicly released JWST/NIRCam images of five Local Group galaxies: NGC 6822, Sextans A, NGC 300, Wolf–Lundmark–Melotte (WLM), and IC 1613 using the DOLPHOT NIRCam module. We find an optimal color–color diagram (CCD) for metal-poor environments, that is F115W–F200W versus F356W–F444W, which clearly separates RSGs from foreground dwarfs. By using the CCD, we identify 208, 135, and 22 RSG candidates in NGC 6822, Sextans A, and NGC 300, respectively, free from contamination by foreground dwarfs and oxygen-rich asymptotic giant branch stars (O-AGBs). In addition, 40 and 14 RSG candidates are directly selected on the CMD in WLM and IC 1613, respectively. Compared with previous works, the number of RSG candidates within the same luminosity range and sky region increases significantly, demonstrating the advantages of JWST in constructing a more complete RSG sample in the Local Group thanks to its high spatial resolution and photometric quality. In addition, catalogs of O-AGBs and carbon-rich AGBs are provided as byproducts.

Abstract Ground-based observations around 1.4 μ m are normally limited by strong absorption of telluric water-vapor. However, Dome A, Antarctica has exceptionally dry conditions that offer a unique opportunity for observations in this band. We designed a new filter covering 1.34–1.48 μ m, namely W ′ , and installed it on the Antarctic Infrared Binocular Telescope (AIRBT) at Dome A in 2025. AIRBT comprises two identical 15 cm optical tube assemblies and two InGaAs cameras equipped with J and W ′ filters, respectively. With this Early Data Release (EDR), we aim to evaluate the performance of the W ′ band at Dome A to observe objects with water-vapor features. This EDR covers ∼20 deg 2 in the Galactic plane using ∼20,000 images in three nights. For 2 s exposures, the 5 σ limiting magnitude histogram peaks at J ∼ 11.5 mag (Vega) and W ′ ∼ 9.9 mag, respectively. The J − W ′ versus J − H color–color diagram distinguishes ultracool candidates with water-vapor-absorption features from reddened early type stars. Furthermore, later-type stars tend to exhibit stronger water-vapor absorption. Some sources show larger Δ W ′ than Δ J across the three nights, which we attribute to variations of their water-vapor-absorption depth. We conclude that it will be efficient to search for ultracool stars and estimate their spectral subtypes using W ′ band imaging at Dome A, where the atmospheric transmission is high and stable.

The paper presents mathematical models of functioning and numerical values of information transfer coefficients for new built-in fibre-optic TFBGs-sensors (Tilted Fiber Bragg Gratings) with tilted Bragg gratings to diagnose a complex stress-strain state inside loaded polymer composite structures. The fiber optic TFBGs sensors have the form of a continuous structured cable system, in which six unidirectional light guides with the built-in Bragg gratings are placed with a fixed mutual hexagonal arrangement in extended continuous cylindrical polymer sensor housing. Different 3D orientations of reflecting surfaces for different light guides were defined through the coordinates of non-planar normals to these surfaces. Numerical modeling of deformation fields in the elements of the fiber optic TFBGs-sensor was carried out for the calculation area composite material/built-in sensor within the linear theory of elasticity. We present color diagrams of distributions for various components of the strain field along the middle cross-section of the calculation area with corresponding simple cases of its macrostrains. Also we give numerical values of strain tensor components averaged over the area of each light guide. Further, values of strain components averaged over the light guides are used to calculate axial strains along non-planar vectors - normals to reflecting surfaces of the tilted Bragg gratings. As a result, numerical values of the desired information transfer coefficients of the fibre-optic TFBGs sensor were found taking into account given orientations of reflecting surfaces of the tilted Bragg gratings of the sensor light guides. Thus, the task of diagnosing a complex deformed state inside a loaded polymer composite structure in a local neighborhood of a built-in fiber optic TFBGs sensor is reduced to solving a system of linear algebraic equations regarding the desired six independent components of the macrodeformation tensor of this neighborhood from the measured spectra of reflections of the optical fibers of the sensor.

Abstract Observations have shown that the optical colors of Galactic cirrus clouds differ significantly from those of extragalactic sources; thus, they can be used to distinguish Galactic cirrus from extragalactic low surface brightness (LSB) features. To understand these properties, we calculate radiative transfer models in dust clouds, where photons are incident from the ambient interstellar medium (ISM). Dust clouds are modeled to mimic a turbulent medium using a fractional Brownian motion algorithm, resulting in a lognormal density distribution and a power-law power spectral density that are appropriate for the ISM. The results are compared with optical observations of cirrus clouds in the Stripe 82 region. The observed color–color ( g − r , r − i , and i − z ) diagrams of the cirrus clouds can be reproduced by scattered light if the interstellar radiation field (ISRF) of Mathis et al. (as updated by Draine) is modified, either by reducing the intensities in the i and z bands or by enhancing those in the g and r bands. Similar results can also be obtained by adjusting the scattering albedos at the corresponding wavelengths. This demonstrates that the color–color diagrams are effective not only for identifying extragalactic LSB features but also for studying the ISRF and the properties of interstellar dust.

Abstract We revisit the Quasar Main Sequence (QMS) by investigating the impact of the stellar component from the host galaxy (HG) on the emission line spectra of the active galactic nuclei (AGN). We first detect spectra with broad emission lines using a line ratio method for a sample of ∼3000 high SNR (>20) Black Hole Mapper objects (part of the fifth phase of the Sloan Digital Sky Survey). We then built the Index diagram, a novel diagnostic tool using the z-corrected spectra, model-free, designed to easily identify spectra with significant stellar HG contributions and to classify the AGN spectra into three categories based on AGN-HG dominance: HG-dominated (HGD), Intermediate (INT), and AGN-dominated (AGND) sources. A colour-z diagram was used to refine the AGN-HG classification. We subtract the stellar contributions from the HGD and INT spectra before modeling the AGN spectrum to extract the QMS parameters. Our QMS reveals that HGD galaxies predominantly occupy the Population B region with no RFeII, with outliers exhibiting RFeII > 1, likely due to HG subtraction residuals and a faint contribution of hβBC. INT and AGND spectra show similar distributions in the Population A region, while in Population B, a tail of AGND sources becomes apparent. Cross-matching with radio, infrared, and X-ray catalogs, we find that the strongest radio emitters are associated with HGD and INT groups. Strong X-ray emitters are found in INT and AGND sources, also occupying the AGN region in the WISE colour diagram.

Abstract We present analyses of the early data from Rubin Observatory’s Data Preview 1 (DP1) for the field of the globular cluster 47 Tuc. The DP1 data set for 47 Tuc includes four nights of observations from the Rubin Commissioning Camera (LSSTComCam), covering multiple bands (ugriy). We address challenges of crowding in the inner region of the cluster and toward the SMC in DP1, and demonstrate improved star–galaxy separation by fitting fifth-degree polynomials to the stellar loci in color–color diagrams and applying multidimensional sigma clipping. We compile a catalog of 3576 probable 47 Tuc member stars selected via a combination of isochrone, Gaia proper-motion, and color–color space matched filtering. We explore the sources of photometric scatter in the 47 Tuc color–color sequence, evaluating contributions from various potential sources, including differential extinction within the cluster. Finally, of the 72 well-characterized variables in the field, we recover three known variable stars, including two RR Lyrae and one eclipsing binary, in the coadd-based object catalog, and identify 62 in the difference image-based object catalog. Although the DP1 lightcurves have sparse temporal sampling, they appear to follow the patterns of densely sampled literature lightcurves well. Despite some data limitations for crowded-field stellar analysis, DP1 demonstrates the promising scientific potential for future LSST data releases.

Abstract The James Webb Space Telescope (JWST) has provided critical mid-infrared data for cold brown dwarfs. It has also provided low-resolution near-infrared spectra, and for faint sources these are the first spectra at these wavelengths. We use these data and other literature sources to synthesize near-infrared photometry on the Mauna Kea Observatories (MKO) system for 19 T and Y dwarfs, on the Euclid system for 44 T and Y dwarfs, and on the Roman systems for 48 T and Y dwarfs. We also synthesize Euclid I E magnitudes for 15 T and Y dwarfs. Using the S. A. Beiler et al. (2024) observational effective temperatures (T eff), together with ATMO 2020++ model colors, we show that the absolute 4.6 μm magnitude can be used as a proxy for T eff. We present a polynomial fit to the M W2:T eff relationship for cool dwarfs with 250 ≲ T eff K ≲ 1000. We select five Y dwarfs with 275 ≲ T eff K ≲ 400 that have a range in near- to mid-infrared colors. Comparison of the JWST spectral energy distribution to ATMO 2020++ models indicate that Y dwarfs that are bluer in J − W2 are lower gravity or more metal rich than their redder counterparts, with stronger CO and CO2 absorption at 4.2 ≲ λ μm ≲ 4.9. The near-infrared color diagrams show significant scatter, with complex dependencies on T eff, metallicity, and gravity. In order to disentangle these effects, opacity sources for cool model atmospheres need to be more complete at λ < 1 μm.

The proper motions (PMs) of M31 and M33 are key to understanding the Local Group’s dynamical evolution. However, measurement discrepancies between Gaia blue and red samples, regarding whether the transverse velocity is remarkable, introduce significant ambiguity. In this work, we remeasure the systemic PMs of M31 and M33 using massive supergiant stars from Gaia Data Release 3. Clean disk tracers are selected via color–color diagrams, with foreground contaminants removed through kinematic and astrometric cuts. We identify the discrepancy in M31’s blue and red samples as arising from systematic differences between Gaia ’s five-parameter (5p) and six-parameter (6p) astrometric solutions. The 6p solution, applied to sources lacking accurate color information, relies on a pseudo-color approximation, leading to lower precision and larger uncertainties. Two key limitations of the 6p solution are: (1) degraded astrometric accuracy for very red sources ( G BP − G RP > 2.6); (2) significant PM zero-point offsets. In our sample, red sources are dominated by the 6p solution, while blue sources include a substantial fraction of 5p sources; this mismatch drives the observed discrepancy. By excluding extreme red sources and calibrating PM zero-points separately for 5p and 6p sources using background quasars, we reduce the discrepancy, bringing blue and red measurements into agreement within 1 σ . We ultimately report the most robust Gaia -based PMs using high-quality 5p sources. For M31, we obtain ( μ α ∗ , μ δ ) M31 = (45.9±8.1, − 20.5±6.6)μas yr −1 , consistent with, but more precise than, the HST result. For M33, we find that ( μ α ∗ , μ δ ) M33 = (45.3±9.7, 26.3±7.3) μ as yr −1 , which agrees with the VLBA measurement within 1.5 σ . These results support a first infall scenario for M33.

Abstract This paper is the second in a series presenting the catalogs and properties of the largest sample to date of ∼100,000 star clusters and compact associations, in 38 spiral galaxies observed by the PHANGS-HST Treasury survey. Here, we present spectral energy distribution (SED) fitting techniques used to compute the age, mass, and reddening for each object. Our decision-tree-based strategy incorporates categorical priors on model age, reddening, and metallicity determined from additional observed parameters: localized Hα emission, source morphology, and demographic-specific locations in the UBVI color–color diagram. This approach is implemented to mitigate model degeneracies, particularly between young dusty clusters and old clusters with minimal dust, which can have identical optical colors. Results based on Hα narrowband imaging from the ground and from Hubble Space Telescope are intercompared, and contrasted with previous SED-fitting efforts. The fraction of the population that is subject to such priors is ∼14%, and of this subset, ∼63% of old globular clusters (GCs) have ages that change by a factor of 10 or more relative to unconstrained fits with single metallicity (Z ⊙) simple stellar population models. The demographics of the population are examined through age–mass and age–reddening diagrams (for individual galaxies as well as aggregated over the sample), and the GC mass function. We demonstrate relationships between cluster age–mass diagrams and properties of parent galaxies (galaxy morphology and location relative to the galaxy main sequence). We outline continuing efforts to improve the inference of physical properties, including the incorporation of JWST infrared photometry and updated synthesis models.

Abstract Split main-sequences (MSs) and extended main-sequence turn-offs (eMSTOs) have been observed in nearly all Magellanic Clouds clusters younger than 2 Gyr. More recently, Hubble Space Telescope (HST) ultraviolet photometry uncovered a puzzling new population of UV-absorbed stars, dubbed ‘UVdim’, in five Magellanic Clouds clusters aged between 40 and 200 Myr, as well as in one 1.5 Gyr-old cluster. These UVdim stars predominantly lie on the blue MS, which is composed of slow rotators, and their distinct UV properties are believed to stem from dusty circumstellar disks. Although eMSTOs are common in both Magellanic Clouds and Galactic open clusters (OCs) of comparable ages, UVdim stars have not yet been investigated in Galactic OCs. In this work, we fill that gap by combining Swift/UVOT, SkyMapper, and Gaia photometry to extend the search for UVdim stars to 35 Galactic OCs younger than 2 Gyr. By constructing colour–colour diagrams analogous to those employed with HST WFC3/UVIS, we find no evidence of UVdim-like stars in most Galactic open clusters and identify possible UVdim candidates in only five systems.The rarity of UVdim stars in young OCs suggests a potential difference between Magellanic Cloud clusters and their Milky Way counterparts, although the underlying reason remains unclear.

The pioneering study reveals the transformative power of co-doping in enhancing phosphor performance, focusing on the development of a cutting-edge white phosphor: SrCeO3:0.02Sm3+ co-doped with Y3+ (0–2 wt%) for high-CRI white LED applications. These innovative perovskites were synthesized using a low-temperature fuel-excess gel combustion technique, with citric acid as the fuel and ammonium nitrate as an additional oxidizer. By examining the impact of Y3+ sensitization on the crystalline phases, morphology, elemental composition, band gap energy, and luminescence properties, the study discovered that orthorhombic SrCeO₃:0.02Sm3+: Y3+ perovskites exhibit exceptional crystallinity and peak luminescence at 1.5 wt% Y3+. The CIE color diagram confirmed their bright white light emission across all samples. This breakthrough positions nano-perovskite SrCe0.965Sm0.02O3:1.5 wt% Y3+ as a top candidate for direct phosphor coatings on near-UV LED chips, and its practical utility promises significant advancements in energy-efficient lighting technology.

ABSTRACT We study the protoplanetary disc lifetimes using a large sample of young stellar objects in nearby clusters. To investigate the final phase of disc dissipation, we selected 32 clusters, located within 500 pc and aged between 1 and 100 Myr, with membership determined using Gaia data. The age and mass information of the sources are obtained through spectral energy distribution analysis and using evolutionary models of various ages. Using the infrared data from 2MASS and WISE catalogues, we employ three methods to identify discs across the different wavelength regimes (1.1–22 $\mu$m). We find that disc fraction consistently decreases as stellar systems age, a trend observed across all wavelengths included in this study. However, there is an increase in the time-scale of disc decay as wavelength increases, with characteristic time-scales of $\tau _{\text{short}}$ = 1.6 $\pm$ 0.1 Myr for shorter wavelengths (1.6–4.6 $\mu$m) versus $\tau _{\text{W3}}$ = 4.4 $\pm$ 0.3 Myr for 12 $\mu$m. This supports the idea that outer disc regions evolve more slowly. Notably, we detect infrared excesses at 12 and 22 $\mu$m in relatively older systems ($>$10 Myr), with some discs with estimated ages up to $\sim$100 Myr. Among these, we identify a population of full discs that persist beyond the typical dissipation time-scale. We also observe that the median mass of disc-hosting stars decreases from 0.62 to 0.27 $M_\odot$ in clusters younger and older than 40 Myr, respectively, indicating slower disc dissipation around lower mass stars. We identify 33 transitional disc candidates using various colour–colour diagrams. Using LAMOST DR8 optical spectra and H-alpha equivalent widths, we identify possible accretors and estimate their mass accretion rates, finding most are younger than 10 Myr.

Z-sources are a particular class of neutron star low-mass X-ray binaries characterized by a wide Z-like track in their hard color-soft color (or hardness-intensity) diagrams, with three branches: the horizontal (HB), the normal (NB), and the flaring branch (FB). Spectropolarimetric observations with the Imaging X-ray Polarimetry Explorer (IXPE) show that the polarization in these sources varies along the Z-track, reaching unexpectedly high values in the HB. In this work, we collected all the polarimetric results obtained so far from observations of Z-sources with IXPE, using a model-independent analysis with IXPEOBSSIM. We first performed a detailed characterization of the spectral state of each source along the Z-track using IXPE, along with the Nuclear Spectroscopic Telescope Array (NuSTAR) and the Neutron Star Interior Composition Explorer (NICER) data and then estimated the polarization for each branch. Although we confirm that the average polarization in the 2–8 keV band decreases moving from the HB to the NB for all three Z-sources observed in these branches, we also observe a qualitatively increasing trend from the NB to the FB. Whereas this increase is clearly significant for Cyg X-2 and Sco X-1, the polarization remains consistent at the 90% confidence level for GX 5–1 and GX 349+2, while for XTE J1701–462 and GX 340+0 only upper limits are found in the FB. For most sources, the average polarization angle in the 2–8 keV range remains consistent along the CCD; however, we observe a significant rotation for both Sco X-1 and GX 349+2 (at the 90% confidence level) as they move from the NB to the FB. In addition, we observe a significant increase in the polarization degree with energy in most of the observed Z-sources, with some also exhibiting a rotation of the polarization angle with energy (approximately by 20° −30°).

We present an X-ray spectro-polarimetric study of the weakly magnetized neutron star low-mass X-ray binary GX 9+1, utilizing data from the Imaging X-ray Polarimetry Explorer (IXPE), alongside simultaneous NuSTAR, NICER, and INTEGRAL observations. GX 9+1, located in the Galactic bulge, is a persistently bright atoll source known for its spectral variability along the color–color diagram. Our spectral analysis during the soft state confirms that the emission is dominated by a soft blackbody and thermal Comptonization components, with no evidence of a hard X-ray tail. Moreover, these observations suggest a relatively low-inclination system (23° < i < 46°) with a weak reflection component, consistent with emission from the accretion disk and neutron star boundary layer. Spectro-polarimetric analysis reveals no significant polarization in the 2–8 keV range, with a 3σ level upper limit on the polarization degree of 1.9%. However, marginal evidence of polarization is detected in the 2–3 keV band at the 95.5% confidence level (2σ), suggesting potential contributions from scattering effects in the individual spectral components (disk, reflection, and Comptonization) that may cancel each other out due to the different orientations of their polarization angles. This behavior aligns with other atoll sources observed by IXPE, which typically exhibit lower and less variable polarization degrees compared to Z–class sources.

Abstract While about 20 type II supernova (SN II) progenitors have been identified using optical data from the Hubble Space Telescope (HST), direct detection of type Ib/Ic supernova (SN Ib/Ic) progenitors remains challenging, due to their faint optical brightness and highly obscured environments. This study aims to investigate the detection limits and advantages of near-infrared (near-IR) observations with the James Webb Space Telescope (JWST) and the Nancy Grace Roman Space Telescope (NGRST) for the detection of SN Ib/Ic progenitors. The spectral energy distributions of SN Ib/Ic progenitor models with various masses, chemical compositions, and mass-loss rates are calculated with the non-LTE radiative transfer code CMFGEN. We then assess the detectability of SN Ib/Ic progenitors using near-IR filters from JWST and NGRST, comparing the results to the capabilities of HST. Our analysis indicates that near-IR observations significantly outperform HST in detecting SN Ib/Ic progenitors when considering the effect of extinction. Near-IR magnitudes also provide better constraints on the mass-loss rates of progenitors, because of the free–free emission from the wind matter. Additionally, near-IR magnitudes and color–color diagrams are effective in distinguishing SN Ib/Ic progenitors from possible companion and/or background objects. This study suggests that JWST and NGRST can play a crucial role in advancing our understanding of SN Ib/Ic progenitors, by improving detectability and offering better constraints on progenitor properties. We emphasize that observations with exposure times exceeding 1 hr would be needed to detect typical SNe Ib/Ic progenitors at distances greater than 10 Mpc.

Abstract Compact objects undergoing mass transfer exhibit significant (and double-peaked) H α emission lines. Recently, new methods have been developed to identify black hole X-ray binaries and calculate their systematic parameters using H α line parameters, such as the full width at half-maximum (FWHM), equivalent width (EW), and separation of double peaks. In addition, the FWHM–EW plane from spectroscopy and the H α color–color diagram from photometry can be used for rapid stellar classification. We measure the H α and H β profiles (e.g., FWHM and EW) using the LAMOST DR9 low- and medium-resolution spectra, and calculate the systematic parameters (e.g., velocity semiamplitude of the donor star, mass ratio, inclination angle, and mass of the accretor). A new correlation between FWHM and K 2, K 2 = 0.205(18) FWHM, is obtained for cataclysmic variables (CVs) in our sample. Both the FWHM–EW plane and the H α color–color diagram can distinguish CVs with FWHM ≳ 1000 km s−1 from Be stars and young stellar objects to some extent. To improve classification accuracy and enhance the selection of compact objects, we propose a new set of idealized filters with effective widths of 30, 130, and 400 Å for the narrow H α filter, broad H α filter, and r-band filter, respectively.

Abstract This paper presents a quantitative analysis of the stellar content in the Local Group dwarf irregular galaxy NGC 6822 by comparing stellar evolution models and observations in color–magnitude diagrams (CMDs) and color–color diagrams (CC-Ds). Our analysis is based on optical ground-based g, r, i photometry, and deep archival Hubble Space Telescope photometry of two fields in the galactic disk. We compared young, intermediate-age, and old stellar populations with isochrones from the BaSTI-IAC library and found that NGC 6822 hosts a quite metal-rich ([Fe/H] = −0.7 to −0.4) young component with an age ranging from 20–100 Myr. The intermediate-age population experienced a modest chemical enrichment between 4 and 8 Gyr ago, while stars older than 11 Gyr have a low metal abundance ([Fe/H] ∼ −1.70). We also identified the asymptotic giant branch (AGB) clump population with a luminosity peak at i ∼ 23.35 mag. Our analysis of both the CMD and the optical–near-IR (NIR)–mid-IR (MIR) CC-Ds of AGB oxygen- and carbon-rich stars, using the PARSEC+COLIBRI isochrones with and without circumstellar dust, reveals that this stellar component exhibits a spread in age from 1–2 Gyr and in metallicity between [Fe/H] = −1.30 and −1.70. The stellar models we used reproduce very well the two distinct color sequences defined by AGB O- and C-rich stars in the various optical–NIR–MIR CC-Ds, suggesting that they are reliable diagnostics to identify and characterize intermediate-age stellar populations. However, we also find that evolutionary prescriptions in the optical i-(r − i) CMDs predict, at fixed color, systematically lower luminosities than observed AGB stars.

Two modifications of ZnMoO4 were successfully obtained by mechanochemical treatment with two milling speeds applied at 500 and 850 rpm. The phase formation was monitored by XRD analysis. The metastable monoclinic ß-ZnMoO4 was directly synthesized at room temperature using the higher milling speed of 850 rpm. The thermodynamically stable triclinic α-ZnMoO4 was obtained by combining heat treatment t 600 °C and ball milling at the lower milling speed of 500 rpm. The IR spectra contain typical vibration bands and confirm the formation of both ZnMoO4 polymorphs. UV-Vis absorption and photoluminescence (PL) spectroscopy are used to study the optical properties of the as-prepared samples. The calculated optical band gaps for α- and ß-ZnMoO4 are 4.09 and 3.02 eV. The photoluminescence emission spectrum of both samples shows peaks with different maximum intensity at 615 and 403 nm for α and ß phase, respectively. CIE co-ordinates are located in the orange and blue range of the color diagram.