446494 research outputs found
Sort by
The internal kinematics of local young stellar associations
No full textContext. The local (<200 pc away) young (<50 Myr old) stellar associations (LYSAs) provide fundamental evidence for the study of the star formation process in the local neighbourhood.
Aims. We explore robust statistical correlations in the internal kinematics of LYSAs and of these with age.
Methods. We analysed a public dataset containing the linear velocity field parameters and expansion ages of 18 LYSAs. We identified the most robust correlations using frequentist and Bayesian methods.
Results. Of the 45 correlations studied, we identified only four that satisfied both frequentist and Bayesian criteria, and all four are related to radial motions in the Galactic Z direction. We hypothesise several origins for these four correlations and identify the gravitational potential of the Galactic disk as the most likely driving element. It imprinted the observed motions in the parent molecular clouds, and once the stars were formed, it also damped these motions on a timescale shorter than the LYSAs’ ages.
Conclusions. The internal kinematics of LYSAs contain fundamental information about the star formation process that is not fully addressed by star formation theories, in particular rotation and shear. Although the Galactic potential appears to be the driving force of these correlations, we urge the theoretical community to provide predictions about the internal motions of expansion, rotation, and shear of stellar associations
Modeling the Milky Way wind: Supernova-driven outflows accelerate HI clouds near the Galactic center
No full textMultiwavelength observations, from radio to X-rays, have revealed the presence of multiphase high-velocity gas near the center of the Milky Way likely associated with powerful galactic outflows. This region offers a unique laboratory to study the physics of feedback and the nature of multiphase winds in detail. To this end, we have developed physically motivated semi-analytical models of a multiphase outflow consisting of a hot gas phase (T ≫ 106 K) that embeds colder clouds (T ~ 5000 K). Our models include the gravitational potential of the Milky Way; the drag force exerted by the hot phase onto the cold clouds; and the exchange of mass, momentum, and energy between gas phases. Using Bayesian inference, we compared the predictions of our models with observations of a population of H
Experimental Determination of the Dielectric Constant of Micellar Hydration Layer via Localized Surface Plasmon Resonance of Gold Nanoparticles
No full textThe localized surface plasmon resonance (LSPR) of plasmonic nanoparticles can be used both for measuring the dielectric constant in which they are dispersed and for determining changes in the structure of the medium around them. In this work, we explored the shift in the LSPR of gold nanoparticles (AuNPs), obtaining the out-of-plane dielectric constant of the hydration layer of nanoparticles dispersed in aqueous solutions of sodium dodecyl sulfate for concentrations below and above the critical micelle concentration. A reduction is observed, which is due to a soft confinement between the nanoparticle and the micelles. The confinement favors the in-plane alignment of the water’s molecular dipoles, hindering a rotation out-of-plane and reducing the tendency to align with an external electric field, i.e., diminishing the medium’s polarization
TDCOSMO. XXIV. First spatially resolved kinematics of the lens galaxy obtained using JWST-NIRSpec to improve time-delay cosmography
No full textSpatially resolved stellar kinematics has become a key ingredient in time-delay cosmography to break the mass-sheet degeneracy in the mass profile and in turn provide a precise constraint on the Hubble constant and other cosmological parameters. In this paper, we present the first measurements of 2D resolved stellar kinematics for the lens galaxy in the quadruply lensed quasar system łensname using integral field spectroscopy from JWST's Near-Infrared Spectrograph (NIRSpec), marking the first such measurement conducted with JWST. In extracting robust kinematic measurements from this first-of-its-kind dataset, we have made methodological improvements both in the data reduction and kinematic extraction. In our kinematic extraction procedure, we performed joint modeling of the lens galaxy, the quasar, and its host galaxy's contributions in the spectra to deblend the lens galaxy component and robustly constrain its stellar kinematics. Our improved methodological frameworks are released as software pipelines for future use: squirrel , for extracting stellar kinematics, and , for JWST-NIRSpec data reduction. We incorporated additional artifact cleaning beyond the standard JWST pipeline. We compared our measured stellar kinematics from the JWST NIRSpec with previously obtained ground-based measurements from the Keck Cosmic Web Imager integral field unit and find that the two datasets are statistically consistent at a ∼1.1σ confidence level. Our measured kinematics will be used in a future study to improve the precision of the Hubble constant measurement. RegalJumpe
Ionization equilibrium of nitrogen under kappa electron distributions
No full textNon-Maxwellian electron energy distributions, such as kappa distributions, have been proposed to explain discrepancies in observed astrophysical plasmas. We employed the coronal approximation to study the level populations of ionized nitrogen under kappa distributions across a range of electron temperatures and densities. Both ground and metastable levels were considered. We propose a novel density diagnostic method that combines these level populations with spectroscopic measurements: level-resolved cross sections for key atomic processes -- electron impact ionization, photoionization (PI), radiative recombination, and dielectronic recombination (DR) -- are calculated using the level-to-level distorted wave method in the Flexible Atomic Code, generalized for kappa distributions, and the corresponding rate coefficients are then derived. Using these coefficients, we computed the ionization equilibrium, with a particular focus on the roles of DR and PI. We also investigated the suppression of DR by electron density and its influence on the resulting ionization equilibrium
Physical properties of long-rising type II supernovae. Bayesian analytic modeling and spectrophotometric correlations
No full textThe supernova (SN) 1987A, with its long-rising (≳40 days) light curve, defines a rare subclass of type II SNe known as events. Representing only ∼1–3% of all core-collapse SNe and often found in low-metallicity environments, their large diversity suggests a wide range of progenitor and explosion properties.
Our aim with this study is to improve the understanding of SNe by characterizing their explosion parameters, including kinetic energy, ejected mass, progenitor radius at the explosion, and synthesized mass. Additionally, we seek to identify systematic trends in both the physical properties and the observed spectrophotometric features of these peculiar events.
A new Bayesian parameter estimation method based on our 56 Ni-dependent analytical model for hydrogen-rich SNe is applied to derive explosion parameters from the light curves and expansion velocities of one of the largest and most comprehensive SN samples to date. These data are measured through a consistent analysis of observations available in the literature.
The analysis reveals a heterogeneous population that nevertheless clusters into two main groups: (i) lower-energy explosions with modest yields (∼0.07 M_⊙), similar to SN 1987A, and (ii) more energetic events (up to ∼5 foe) with larger nickel production and, in some cases, unusually extended progenitors. We confirm a robust correlation between mass, peak luminosity, and explosion energy, as well as between ejecta mass and the recombination timescale. An anticorrelation between Ba II line strength and photospheric velocity indicates that stronger Ba II absorptions in SNe arise from more compact, slowly expanding ejecta.
Our findings indicate that 87A-like SNe populate a continuous distribution of explosion energies and progenitor radii. The study underscores the need to extend analytical frameworks to include additional power sources that will enable scalable and accurate modeling of the growing number of peculiar transients that will be discovered by current and upcoming surveys (e.g., ZTF and LSST)
From main-sequence binary to blast: MESA modeling of the double-detonation progenitor PTF1 J2238+7430
No full textHot subdwarf B (sdB) stars in close binaries with white dwarf (WD) companions are potential progenitors of double-detonation thermonuclear supernovae. The recently discovered system PTF1 J2238+7430 is a candidate for this evolutionary channel, as it hosts a low-mass sdB and a comparatively massive white dwarf in a compact orbit.
We aim to reproduce the evolutionary history of PTF1 J2238+7430, in which the sdB forms first through stable mass transfer, followed by the formation of the white dwarf through a subsequent common-envelope (CE) phase. Additionally, we seek to constrain the range of initial binary parameters that can lead to such double-detonation progenitors.
Using the Modules for Experiments in Stellar Astrophysics (MESA), we performed detailed binary evolution simulations from the zero-age main sequence to the present-day configuration. We explored initial stellar masses, orbital periods, and mass-loss fractions, including the effects of angular momentum transfer, tidal synchronization, and gravitational-wave-driven orbital evolution. We derived the post-common envelope binary properties using the standard energy formalism during common envelope evolution.
Our models successfully reproduce the observed properties of PTF1 J2238+7430: a 0.406,M_⊙ sdB and a 0.72 M_⊙ white dwarf in a 76.34-minute orbit. Stable Roche-lobe overflow of an sim2.7 M_⊙ donor produces the sdB, while the white dwarf forms from the initially less massive companion during an episode of common envelope evolution. We find that the common envelope ejection efficiency must be high ̊m CE ≈ 0.87) to match the observed orbit, exceeding the canonical values for similar systems. We further delineate the allowed parameter space for initial binaries that can evolve into sdB+WD systems consistent with double-detonation progenitors. These limits are preliminary; a systematic exploration of all parameters is needed to obtain robust constraints. We highlight the main challenges in our MESA simulations and provide a useful starting point for future work.
Our findings identify promising regions of parameter space for the formation of PTF1 J2238+7430–like systems and provide a foundation for future systematic studies of sdB+WD binaries as potential double-detonation Type Ia supernova progenitors
Polarimetric and spectropolarimetric observations with FoReRo2: Instrument overview and standard star monitoring
No full textIn this paper, we present a description and characterisation of the 2-Channel Focal Reducer Rozhen (FoReRo2), with an emphasis on its polarimetric and spectropolarimetric observation modes. FoReRo2 is a multimode instrument mounted at the Ritchey–Chrétien (RC) focus of the 2-meter Ritchey–Chrétien-Coude (RCC) telescope at the Bulgarian National Astronomical Observatory (BNAO) -- Rozhen. The primary targets of this instrument include novae, Be/X-ray binaries, symbiotic stars, asteroids, and comets. Standard stars with a high degree of polarisation are an essential part of the polarimetric observations. In our sample, HD 204827 shows short-term variability in the position angle (PA), making it unsuitable for calibration. HD 183143 displays intrinsic polarisation variability, but remains stable in terms of the PA. For the first time, we present a statistical study of the K and łmax parameters of Serkowski's law, including the mean value, standard deviation, and distribution. To demonstrate FoReRo2's polarimetric capabilities, we present several examples. The recurrent nova RS Oph shows the variability of Serkowski's K parameter, which is due to dust formation within the first few days after the 2021 outburst. These examples also include the imaging polarimetry of comet C/2019 Y4 (ATLAS) and spectropolarimetric observations of the symbiotic star Z And
Synthesis and characterization of Fe(III)-ion imprinted polymers (Fe-IIPs) as selective sorbents with Alizarin Red-S and 2-vinylpyridine
No full textIron (Fe) is an essential trace element that requires monitoring and removal when it acts as a pollutant. Previous studies have demonstrated limited selectivity in separating Fe(III) from complex sample matrices. To overcome these drawbacks, in this study Fe(III)-Ion Imprinted polymers (Fe-IIPs) were synthesized as selective sorbents with Alizarin Red-S as a ligand and 2- Vinylpyridine as a functional monomer. Bulk polymerization was carried out with Trimethylolpropane trimethacrylate (TMPTMA) as a crosslinker. Fe(III) ions were eluted with an HNO3 solution to create the template. Non-Imprinted Polymers (NIPs) prepared without an imprinted ion, served as controls. The synthesized Fe-IIPs were characterized by FTIR (spectra), SEM (morphology), and EDX (elemental content). The effects of contact time, pH, and initial concentration were studied. Adsorption equilibrium was reached within 30 minutes. The maximum adsorption capacity of Fe-IIPs was 134.224 mg g-1 at pH 5. The adsorption isotherm of Fe-IIPs conformed to the Langmuir model, while the kinetic adsorption data fitted the pseudo-second order model. The selectivity coefficient for Fe(III) ions relative to interfering ions exceeded unity, indicative of the imprinting effect
Optimization of Rosemary (
No full textRosemary essential oil is widely utilized in pharmaceutical, cosmetic, and food industries due to its bioactive components. Solvent-Free Microwave Extraction (SFME) offers a green and energy-efficient alternative to conventional hydrodistillation. Previous studies on rosemary essential oil extraction using SFME or RSM have generally focused on isolated process parameters or limited optimization scopes. The novelty of this work lies in the systematic and simultaneous optimization of microwave power, feed-to-distiller ratio, and extraction time using a Box–Behnken Design, enabling a comprehensive evaluation of their individual and quadratic effects on essential oil yield. This study aims to optimize rosemary essential oil extraction using Response Surface Methodology (RSM) with a Box–Behnken Design (BBD). Three variables were evaluated : feed-to-distiller ratio (0.05–0.15 g/mL), extraction time (30–90 min), and microwave power (150–450 W). A quadratic model was successfully developed and validated through analysis of variance (ANOVA). The optimum conditions were achieved at a feed-to-distiller ratio of 0.10 g/mL, an extraction time of 60 min, and a microwave power of 300 W, resulting in a maximum essential oil yield of 3.1679%. The RSM–BBD model demonstrated strong predictive capability, confirming the significant influence of quadratic terms. The optimized SFME method provides an efficient, solvent-free extraction approach with potential applicability for industrial-scale natural product processing