First author: Ryan D. Boyden
The stellar cluster environment is expected to play a central role in the evolution of circumstellar disks. We use thermochemical modeling to constrain the dust and gas masses, disk sizes, UV and X-ray radiation fields, viewing geometries, and central stellar masses of 20 Class II disks in the Orion Nebula Cluster (ONC). We fit a large grid of disk models to $350$ GHz continuum, CO $J=3-2$, and HCO$^+$ $J=4-3$ ALMA observations of each target, and we introduce a procedure for modeling interferometric observations of gas disks detected in absorption against a bright molecular cloud background.
First author: Prabin Sherpaili
An increase in satellite application has skyrocketed the number of satellites, especially in the low earth orbit (LEO). The major concern today is that these satellites become debris after the end of life, negatively affecting the space environment. As per the International Guidelines of the European Space Agency, it is mandatory to deorbit the satellite within 25 years of its end of life. This paper is aimed to design the solid chemical propellant thruster to deorbit the StudSat II from its original orbit to the lower orbit.
First author: A. D. Supanitsky
Cosmic rays are relativistic particles that come to the Earth from outer space. Despite a great effort made in both experimental and theoretical research, their origin is still unknown. One of the main keys to understand their nature is the determination of its chemical composition as a function of primary energy. In this paper, we review the measurements of the mass composition above $10^{15}$ eV.
First author: D. Navarro-Almaida
HCN, HNC, and their isotopologues are ubiquitous molecules that can serve as chemical thermometers and evolutionary tracers to characterize star-forming regions. Despite their importance in carrying information that is vital to studies of the chemistry and evolution of star-forming regions, the collision rates of some of these molecules have not been available for rigorous studies in the past. We perform an up-to-date gas and dust chemical characterization of two different star-forming regions, TMC 1-C and NGC 1333-C7, using new collisional rates of HCN, HNC, and their isotopologues.
First author: I. A. Zinchenko
We constructed an oxygen abundance map and N/O ratio map of the unusually low excitation dwarf irregular galaxy NGC 4163 based on publicly available spectroscopy obtained by the MaNGA survey. We detected auroral emission line [OII]$\lambda\lambda$7320,7330 which allows us to measure chemical abundance by direct T$_e$ method. We found that the scatter of the oxygen abundance derived by the strong line method is large. The oxygen abundances 12 + log(O/H) derived by strong line method vary from ~7.
First author: Lia C. Corazza
We propose a semi-analytic model that is developed to understand the cosmological evolution of the mean metallicity in the Universe. In particular, we study the contributions of Population III (Pop III) and Population II (Pop II) stars to the production of $\mathrm{Fe,~Si,~Zn, ~Ni,~P, ~Mg, ~Al, ~S, ~C, ~N}$, and $\mathrm{~O}$. We aim to quantify the roles of two different models in the chemical enrichment of the Universe.
First author: F. D. Priestley
Models of prestellar cores often assume that the cores are isolated from their environment - material outside the core boundary plays no role in the subsequent evolution. This is unlikely to be the case in reality, where cores are located within hierarchically substructured molecular clouds. We investigate the dynamical and chemical evolution of prestellar cores, modelled as Bonnor-Ebert spheres, and show that the density of the ambient medium has a large impact on the resulting chemical properties of the cores.
First author: Takuji Tsujimoto
Massive ($\geq$8 $M_\odot$) stars perish via one of two fates: core-collapse supernovae (CCSNe), which release synthesized heavy elements, or failed supernovae, thereby forming black holes. In the conventional Galactic chemical evolution (GCE) scheme, a substantial portion of massive stars, e.g., all stars in the mass range of 8-100 $M_{\odot},$ are assumed to enrich the Galaxy with their nucleosynthetic products. However, this hypothesis conflicts with the observations, namely, few CCSNe whose progenitor stars are more massive than $\sim$18 $M_{\odot}.
First author: M. P. Roriz
We present detailed chemical compositions of four stars on the first-ascent red giant branch that are classified as chemically peculiar, but lack comprehensive analyses at high spectral resolution. For BD+03{\deg}2688, HE 0457-1805, HE 1255-2324, and HE 2207-1746, we derived metallicities [Fe/H] $=-1.21$, $-0.19$, $-0.31$, and $-0.55$, respectively, indicating a range in Galactic population membership. In addition to atmospheric parameters, we extracted elemental abundances for 28 elements, including the evolutionary-sensitive CNO group and $^{12}$C/$^{13}$C ratios.
First author: P. B. Changala
We report the detection of magnesium dicarbide, MgC$_2$, in the laboratory at centimeter wavelengths and assign $^{24}$MgC$_2$, $^{25}$MgC$_2$, and $^{26}$MgC$_2$ to 14 unidentified lines in the radio spectrum of the circumstellar envelope of the evolved carbon star IRC+10216. The structure of MgC$_2$ is found to be T-shaped with a highly ionic bond between the metal atom and the C$_2$ unit, analogous to other dicarbides containing electropositive elements.
