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The super star cluster NGC1569-B has recently been observed to have an extremely high [Ba/Fe]. We consider that the observed high [Ba/Fe] ($\sim$ 1.3) is due to the chemical enrichment of giant molecular clouds by either collapsars, neutron star mergers, or magneto-rotational supernovae, and thereby investigate which of the three polluters can best reproduce the observed [Ba/Fe]. Since it is found that collapsars can best reproduce such an extremely high Ba abundance, we numerically investigate the star cluster formation in NGC1569 using chemodynamical simulations of merging dwarf galaxies with chemical enrichment by collapsars. The principal results are as follows. First, a cluster of the same scale as NGC1569-B was found to match both the observed [Ba/Fe] and [Fe/H] values, the best cluster having [Ba/Fe]= 1.3 $\pm$ 0.2 and [Fe/H] = $-$0.7 $\pm$ 0.2. This simulation used a core-collapse supernova per collapsar rate of 70, a standard initial mass function and an initial metallicity of [Fe/H]=-1.5. Second, a prediction of the Eu abundance of NGC1569-B is made: [Eu/Fe]= 1.9 $\pm$ 0.2. These results are shown to be invariant under a change in the orbit parameters used for the merger. The need for a merger to promote the star formation that leads to the synthesis of the Ba and the star cluster formation is confirmed. Collapsars can not only better explain [Ba/Fe] but also be consistent with the observed star formation rate and stellar mass of the dwarf galaxy., Comment: 14 pages, 6 figures, 1 table. Submitted to Monthly Notices of the Royal Astronomical Society (MNRAS)

A unified algebraic interpretation of both finite families of orthogonal polynomials and biorthogonal rational functions of $q$-Hahn type is provided. The approach relies on the meta $q$-Hahn algebra and its finite-dimensional bidiagonal representations. The functions of $q$-Hahn type are identified as overlaps (up to global factors) between bases solving ordinary or generalized eigenvalue problems in the representation of the meta $q$-Hahn algebra. Moreover, (bi)orthogonality relations, recurrence relations, difference equations and some contiguity relations satisfied by these functions are recovered algebraically using the actions of the generators of the meta $q$-Hahn algebra on various bases., Comment: 27 pages

In this paper, we propose a novel method for interfering frequency-multiplexed photonic quantum states without the use of optical nonlinear effects, and experimentally demonstrate this technique via frequency-domain Hong-Ou-Mandel (HOM) interference. By cascading the generation of quantum states onto arbitrary orthogonal modes, we can induce interference across any desired frequency mode. Following the generation of quantum states onto the frequency modes, performing measurements in independent frequency bands enables the realisation of a frequency-domain linear optical circuit analogous to linear interference in the spatial domain. We successfully demonstrated programmable quantum interference by controlling the spectral mode functions and measurement bases. Our method offers a new approach to harness the full potential of light's temporal-frequency degrees of freedom, providing a path towards scalable and programmable photonic quantum computing architectures without the need for optical nonlinearities or spatial-mode beam splitters., Comment: 11 pages, 10 figures

We report the discovery of a characteristic trend in the intensity ratios of SiO emissions across the Central Molecular Zone (CMZ) of our Galaxy. Using the Nobeyama Radio Observatory 45-m telescope, we conducted large-scale, high-sensitivity imaging observations in molecular lines including SiO $J$=2$-$1 and CS $J$=2$-$1. By identifying SiO-emitting clouds and examining their intensity ratios relative to the other molecular lines, we unveiled a parabolic-like trend showing lower ratios near the Galactic nucleus, Sgr A$^*$, with gradual increases toward the edges of the CMZ. This pattern suggests a possible outburst of the nucleus within the last $\sim 10^5$ yr, which may have propagated through the entire CMZ with strong shocks. Alternatively, the observed trend may also be attributed to the destruction of small dust grains by high-energy photons. Our results can potentially lead to a new perspective on the history of nuclear activity and its impact on the surrounding molecular environment., Comment: 9 pages, 4 figures, accepted for publication in the Astrophysical Journal Letters

We included the intrinsic line profiles of the strongest fluorescent lines in the X-ray radiative transfer code SKIRT to model the cold-gas structure and kinematics based on high-resolution line observations from XRISM/Resolve and Athena/X-IFU. The intrinsic line profiles of the Ka and Kb lines of Cr, Mn, Fe, Co, Ni, and Cu were implemented based on a multi-Lorentzian parameterisation and line energies are sampled from these Lorentzian components during the radiative transfer routine. In the optically thin regime, the SKIRT results match the intrinsic line profiles as measured in the laboratory. With a more complex 3D model that also includes kinematics, we find that the intrinsic line profiles are broadened and shifted to an extent that will be detectable with XRISM/Resolve; this model also demonstrates the importance of the intrinsic line shapes for constraining kinematics. We find that observed line profiles directly trace the cold-gas kinematics, without any additional radiative transfer effects. With the advent of the first XRISM/Resolve data, this update to the X-ray radiative transfer framework of SKIRT is timely and provides a unique tool for constraining the velocity structure of cold gas from X-ray microcalorimeter spectra., Comment: 6 pages, 3 figures, accepted for publication in Astronomy & Astrophysics

Explaining temporal changes between satellite images taken at different times is important for urban planning and environmental monitoring. However, manual dataset construction for the task is costly, so human-AI collaboration is promissing. Toward the direction, in this paper, we investigate the ability of Large-scale Vision-Language Models (LVLMs) to explain temporal changes between satellite images. While LVLMs are known to generate good image captions, they receive only a single image as input. To deal with a par of satellite images as input, we propose three prompting methods. Through human evaluation, we found the effectiveness of our step-by-step reasoning based prompting., Comment: 11 pages, 6 figures

Flux spectrum, event rate, and experimental sensitivity are investigated for the diffuse supernova neutrino background (DSNB), which originates from past stellar collapses and is also known as a supernova relic neutrino background. For this purpose, the contribution of collapses that lead to successful supernova (SN) explosion and black hole (BH) formation simultaneously, which are suggested to be a non-negligible population from the perspective of Galactic chemical evolution, is taken into account. If the BH-forming SNe involve the matter fallback onto the protoneutron star for the long term, their total emitted neutrino energy becomes much larger than that of ordinary SNe and failed SNe (BH formation without explosion). Then, in the case of the normal mass hierarchy in neutrino oscillations and with half of all core-collapse SNe being BH-forming SNe, the expected event rate according to the current DSNB model is enhanced by up to a factor of two due to the BH-forming SNe. While substantial uncertainties exist regarding the duration of the matter fallback, which determines the total amount of emitted neutrinos, and the fraction of BH-forming SNe, the operation time required to detect the DSNB at Hyper-Kamiokande would be reduced by such contribution in any case., Comment: 13 pages, 5 figures, published in ApJ

Monitor of All-sky X-ray Image (MAXI) detected a superflare, releasing $5\times 10^{37}$ erg in 2$-$10 keV, of the RS CVn-type star IM Peg at 10:41 UT on 2023 July 23 with its Gas Slit Camera (GSC; 2$-$30 keV). We conducted X-ray follow-up observations of the superflare with Neutron Star Interior Composition ExploreR (NICER; 0.2$-$12 keV) starting at 16:52 UT on July 23 until 06:00 UT on August 2. NICER X-ray spectra clearly showed emission lines of the Fe XXV He$\alpha$ and Fe XXVI Ly$\alpha$ for $\sim 1.5$ days since the MAXI detection. The Fe XXV He$\alpha$ line was blue-shifted with its maximum Doppler velocity reaching $-2200 \pm 600$ $\mathrm{km \: s^{-1}}$, suggesting an upward-moving plasma during the flare, such as a coronal mass ejection (CME) and/or chromospheric evaporation. This is the first case that the Fe XXV He$\alpha$ line is blue-shifted during a stellar flare and its velocity overwhelmingly exceeds the escape velocity of the star ($-230$ $\mathrm{km \: s^{-1}}$). One hour before the most pronounced blueshift detection, a signature of reheating the flare plasma was observed. We discuss the origin of the blueshift, a CME or high-velocity chromospheric evaporation., Comment: 14 pages, 9 figures. Accepted for publication in The Astrophysical Journal Letters

Recent observations have shown that [P/Fe] in the Galactic stars decreases with increasing [Fe/H] for [Fe/H] > -1 whereas it is almost subsolar for [Fe/H]< -2. These [P/Fe] trends with [Fe/H] have not been well reproduced by previous theoretical models incorporating phosphorus (P) enrichment only by core collapse supernoave. We here show, for the first time, that the trends can be naturally explained by our new models incorporating P enrichment by oxygen-neon (ONe) novae which occur at the surface of massive white dwarfs whose masses are larger than 1.25 M_sun with a metallicity-dependence rate. We also show that the observations can be better reproduced by the models by assuming that (i) the total mass of gaseous ejecta per ONe nov (M_ej) is as high as 4 * 10^{-5} M_sun and (ii) the number of such novae per unit mass (N_ONe) is as large as 0.01 at [Fe/H]~-3. The assumed M_ej is consistent with observations, and the high N_ONe is expected from recent theoretical models for ONe nova fractions. We predict that (i) [P/Fe] increases with increasing [Fe/H] for -2 < [Fe/H] < -1 and (ii) [P/Fe] and [Cl/Fe] trends with [Fe/H] are very similar with each other due to very large yields of P and Cl from ONe nova. It is thus worthwhile for future observations to assess the validity of the proposed P enrichment by ONe novae by confirming or ruling out these two predictions., Comment: 5 pages, 5 figures, published in ApJL

The finite families of biorthogonal rational functions and orthogonal polynomials of Hahn type are interpreted algebraically in a unified way by considering the three-generated meta Hahn algebra and its finite-dimensional representations. The functions of interest arise as overlaps between eigensolutions of generalized and ordinary eigenvalue problems on the representation space. The orthogonality relations and bispectral properties naturally follow from the framework.

The enrichment history of $r$-process elements has been imprinted on the stellar abundances that change in accordance with increasing metallicity in galaxies. Close examination of the [Eu/Fe] feature caused by stars in nearby galaxies, including the Large Magellanic Cloud (LMC), shows its perplexity. The decreasing trend of the [Eu/Fe] feature is followed by a nearly constant value; this trend is generally attributed to an onset of the delayed Fe release from type Ia supernovae (SNe Ia), which is the same interpretation of the [$\alpha$/Fe] feature. However, this feature appears in the LMC at [Fe/H] of approximately -0.7, which is significantly higher than that for the [alpha/Fe] case ($\approx$ -2). This result potentially indicates the presence of an overlooked property of the $r$-process site that remains unseen in the study of the Milky Way. Here, we propose that this [Eu/Fe]-knee feature is created by a fade-out of core-collapse SNe producing $r$-process elements; these elements along with neutron star mergers (NSMs) promote the $r$-process enrichment under the condition for this specific SNe such that their occurrence is limited to a low-metallicity environment. This metallicity threshold for the occurrence rate of $r$-process SNe at a subsolar is nearly identical to that for long gamma-ray bursts whose origin may be connected to fast-rotating massive stars. Moreover, we reason that the contribution of Eu from NSMs is crucial to maintain a high [Eu/Fe] at an early stage in dwarf galaxies by a balance with Fe from SNe Ia; both enrichments via NSMs and SNe Ia proceed with similar delay time distributions., Comment: 7 pages including 4 figures, accepted for publication in ApJ

We report the results of the CO $\textit J$=1-0 and SiO $\textit J$=2-1 mapping observations towards the broad-velocity-width molecular feature CO 16.134-0.553 with the Nobeyama Radio Observatory 45 m telescope. The high quality CO map shows that the 5-pc size broad-velocity-width feature bridges two separate velocity components at $\textit V_{\rm{LSR}}$$\quad$$\simeq$ 40 km s$^{-1}$ and 65 km s$^{-1}$ in the position-velocity space. The kinetic power of CO 16.134-0.553 amounts to $7.8\times10^2$ $\textit L$$_\odot$ whereas no apparent driving sources were identified. Prominent SiO emission was detected from the broad-velocity-width feature and its root in the $\textit V_{\rm{LSR}}$$\quad$$\simeq$ 40 km s$^{-1}$ component. In the CO Galactic plane survey data, CO 16.134-0.553 appears to correspond to the Galactic eastern rim of a 15-pc diameter expanding CO shell. An $1\deg$-diameter H I emission void and $4\deg$-long vertical H I filament were also found above and below the CO shell, respectively. We propose that the high-velocity plunge of a dark matter subhalo with a clump of baryonic matter was responsible for the formation of the H I void, CO 16.134-0.553/CO shell, and the H I filament., Comment: 7 pages, 6 figures, 2 table, accepted for publication in ApJ

We show that there can exist two liquid states in distinguishable helium-4 ($^4$He) obeying Boltzmann statistics by path integral centroid molecular dynamics (CMD) simulations. This is an indication of quantum liquid polyamorphism induced by nuclear quantum effect. For 0.08-3.3 K and 1-500 bar, we extensively conducted the isothermal-isobaric CMD simulations to explore not only possible states and state diagram but the state characteristics. The distinguishable $^4$He below 25 bar does not freeze down to 0.1 K even though it includes no Bosonic exchange effect and therefore no Bose condensation. One liquid state, low quantum-dispersion liquid (LQDL), is nearly identical to normal liquid He-I of real $^4$He. The other is high quantum-dispersion liquid (HQDL) consisting of atoms with longer quantum wavelength. This is another non-superfluid existing below 0.5 K or the temperatures of LQDL. The HQDL is also a low-entropy and fragile liquid to exhibit, unlike conventional liquids, rather gas-like relaxation of velocity autocorrelation function, while there the atoms diffuse without noticeable contribution from quantum tunneling. The LQDL-HQDL transition is not a thermodynamic phase transition but a continuous crossover accompanied by the change of the expansion factor of quantum wavelength. Freezing of HQDL into the low quantum-dispersion amorphous solid occurs by heating from 0.2 to 0.3 K at 40-50 bar, while this $P$-$T$ condition coincides with the Kim-Chan normal-supersolid phase boundary of real $^4$He. The obtained state diagram was compared with that of the confined subnano-scale $^4$He systems where Bosonic correlation is considerably suppressed., Comment: 19 pages, 15 figures (Supplementary material: 27 pages)

We detected a giant X-ray flare from the RS-CVn type binary star UX Ari using MAXI on 2020 August 17 and started a series of NICER observations 89 minutes later. For a week, the entire duration of the flare was covered with 32 snapshot observations including the rising phase. The X-ray luminosity reached 2$\times$10$^{33}$ erg s$^{-1}$ and the entire energy release was $\sim 10^{38}$ erg in the 0.5--8.0~keV band. X-ray spectra characterized by continuum emission with lines of Fe XXV He$\alpha$ and Fe XXVI Ly$\alpha$ were obtained. We found that the temperature peaks before that of the flux, which suggests that the period of plasma formation in the magnetic flare loop was captured. Using the continuum information (temperature, flux, and their delay time), we estimated the flare loop size to be $\sim 3 \times 10^{11}$ cm and the peak electron density to be $\sim 4\times10^{10}$ cm$^{-3}$. Furthermore, using the line ratio of Fe XXV and Fe XXVI, we investigated any potential indications of deviation from collisional ionization equilibrium (CIE). The X-ray spectra were consistent with CIE plasma throughout the flare, but the possibility of an ionizing plasma away from CIE was not rejected in the flux rising phase., Comment: 9 pages, 6 figures. Accepted by ApJ

Two strings of the same length are said to Cartesian-tree match (CT-match) if their Cartesian-trees are isomorphic [Park et al., TCS 2020]. Cartesian-tree matching is a natural model that allows for capturing similarities of numerical sequences. Oizumi et al. [CPM 2022] showed that subsequence pattern matching under CT-matching model can be solved in polynomial time. This current article follows and extends this line of research: We present the first polynomial-time algorithm that finds the longest common subsequence under CT-matching of two given strings $S$ and $T$ of length $n$, in $O(n^6)$ time and $O(n^4)$ space for general ordered alphabets. We then show that the problem has a faster solution in the binary case, by presenting an $O(n^2 / \log n)$-time and space algorithm.

The spectroscopic performance of x-ray instruments can be affected at high count rates. The effects and mitigation in the optical chain, such as x-ray attenuation filters or de-focusing mirrors, are widely discussed, but those in the signal chain are not. Using the Resolve x-ray microcalorimeter onboard the XRISM satellite, we discuss the effects observed during high count rate measurements and how these can be modeled. We focus on three instrumental effects that impact performance at high count rate: CPU limit, pile up, and electrical cross talk. High count rate data were obtained during ground testing using the flight model instrument and a calibration x-ray source. A simulated observation of GX 13+1 is presented to illustrate how to estimate these effects based on these models for observation planning. The impact of these effects on high count rate observations is discussed., Comment: 16 pages, 20 figures, Proc. SPIE

Communication using terahertz (~10^12 Hz) electromagnetic waves is critical for developing 6th-generation wireless network infrastructures. Conflictions between stable radiation and the modulation frequency of terahertz sources impede the superposing of transmitting signals on carrier waves. The Josephson junctions included in a cuprate superconductor radiate terahertz waves with frequencies proportional to the bias voltages. Thus, the modulation of the bias voltage leads to the modulation of the Josephson plasma emission (JPE) frequency. This study aims to demonstrate the generation of frequency-modulated (FM) terahertz continuous waves from Josephson junctions. The results verify that the instantaneous JPE frequency follows the gigahertz-modulated bias voltage. The wide-band FM terahertz generation by a monolithic device shows a sharp contrast to the mode-lock frequency comb constructed by highly sophisticated optics on a bench. A further increase of the modulation amplitude facilitates up- or down-frequency conversion over more than one octave. The obtained FM bandwidth exhibited an improvement of two orders of magnitude in the demodulation signal-to-noise ratio compared to the amplitude-modulated signal. The demonstrated FM-JPE stimulates further research on terahertz communication technology and metrology using superconducting devices., Comment: 17 pages, 6 figures, 7 pages Supplemental information

Japan Astrometry Satellite Mission for INfrared Exploration (JASMINE) is a planned M-class science space mission by the Institute of Space and Astronautical Science, the Japan Aerospace Exploration Agency. JASMINE has two main science goals. One is the Galactic archaeology with Galactic Center Survey, which aims to reveal the Milky Way's central core structure and formation history from Gaia-level (~25 $\mu$as) astrometry in the Near-Infrared (NIR) Hw-band (1.0-1.6 $\mu$m). The other is the Exoplanet Survey, which aims to discover transiting Earth-like exoplanets in the habitable zone from NIR time-series photometry of M dwarfs when the Galactic center is not accessible. We introduce the mission, review many science objectives, and present the instrument concept. JASMINE will be the first dedicated NIR astrometry space mission and provide precise astrometric information of the stars in the Galactic center, taking advantage of the significantly lower extinction in the NIR. The precise astrometry is obtained by taking many short-exposure images. Hence, the JASMINE Galactic center survey data will be valuable for studies of exoplanet transits, asteroseismology, variable stars and microlensing studies, including discovery of (intermediate mass) black holes. We highlight a swath of such potential science, and also describe synergies with other missions., Comment: 50 pages, 22 figures, accepted for publication in PASJ

Super Soft X-ray Sources (SSS) are white dwarf (WD) binaries that radiate almost entirely below $\sim$1~keV. Their X-ray spectra are often complex when viewed with the X-ray grating spectrometers, where numerous emission and absorption features are intermingled and hard to separate. The absorption features are mostly from the WD atmosphere, for which radiative transfer models have been constructed. The emission features are from the corona surrounding the WD atmosphere, in which incident emission from the WD surface is reprocessed. Modeling the corona requires different solvers and assumptions for the radiative transfer, which is yet to be achieved. We chose CAL87, a SSS in the Large Magellanic Cloud, which exhibits emission-dominated spectra from the corona as the WD atmosphere emission is assumed to be completely blocked by the accretion disk. We constructed a radiative transfer model for the corona using the two radiative transfer codes; xstar for a one-dimensional two-stream solver and MONACO for a three-dimensional Monte Carlo solver. We identified their differences and limitations in comparison to the spectra taken with the Reflection Grating Spectrometer onboard the XMM-Newton satellite. We finally obtained a sufficiently good spectral model of CAL87 based on the radiative transfer of the corona plus an additional collisionally ionized plasma. In the coming X-ray microcalorimeter era, it will be required to interpret spectra based on radiative transfer in a wider range of sources than what is presented here., Comment: 15 pages, 15 figures, ApJ in press

We explore the influence of the Milky Way galaxy's chemical evolution on the formation, structure, and habitability of the Solar system. Using a multi-zone Galactic Chemical Evolution (GCE) model, we successfully reproduce key observational constraints, including the age-metallicity ([Fe/H]) relation, metallicity distribution functions, abundance gradients, and [X/Fe] ratio trends for critical elements involved in planetary mineralogy, including C, O, Mg, and Si. Our GCE model suggests that the Sun formed in the inner Galactic disc, $R_{\rm birth,\odot}\approx 5$ kpc. We also combined a stoichiometric model with the GCE model to examine the temporal evolution and spatial distribution of planet building blocks (PBBs) within the Milky Way galaxy, revealing trends in the condensed mass fraction ($f_{\rm cond}$), iron-to-silicon mass fraction ($f_{\rm iron}$), and water mass fraction ($f_{\rm water}$) over time and towards the inner Galactic disc regions. Specifically, our model predicts a higher $f_{\rm cond}$ in the protoplanetary disc within the inner regions of the Milky Way galaxy, as well as an increased $f_{\rm iron}$ and a decreased $f_{\rm water}$ in the inner regions. Based on these findings, we discuss the potential impact of the Sun's birth location on the overall structure and habitability of the Solar System., Comment: 15 pages, 10 figures. Accepted for publication in MNRAS

Circinus X-1 (Cir X-1) is a neutron star binary with an elliptical orbit of 16.6~days. The source is unique for its extreme youth, providing a key to understanding early binary evolution. However, its X-ray variability is too complex to reach a clear interpretation. We conducted the first high cadence (every 4 hours on average) observations covering one entire orbit using the NICER X-ray telescope. The X-ray flux behavior can be divided into stable, dip, and flaring phases. The X-ray spectra in all phases can be described by a common model consisting of a partially covered disk black body emission and the line features from a highly-ionized photo-ionized plasma. The spectral change over the orbit is attributable to rapid changes of the partial covering medium in the line-of-sight and gradual changes of the disk black body emission. Emission lines of the H-like and He-like Mg, Si, S, and Fe are detected, most prominently in the dip phase. The Fe emission lines change to absorption in the course of the transition from the dip phase to the flaring phase. The estimated ionization degree indicates no significant changes, suggesting that the photo-ionized plasma is stable over the orbit. We propose a simple model in which the disk black body emission is partially blocked by such a local medium in the line-of-sight that has spatial structures depending on the azimuth of the accretion disk. Emission lines upon the continuum emission are from the photo-ionized plasma located outside of the blocking material., Comment: Accepted for publication in ApJ, 16 pages, 7 figures

Metallicity gradients refer to the sloped radial profile of metallicities of gas and stars and are commonly seen in disk galaxies. A well-defined metallicity gradient of the Galactic disk is observed particularly well with classical Cepheids, which are good stellar tracers thanks to their period-luminosity relation allowing precise distance estimation and other advantages. However, the measurement of the inner-disk gradient has been impeded by the incompleteness of previous samples of Cepheids and limitations of optical spectroscopy in observing highly reddened objects. Here we report the metallicities of 16 Cepheids measured with high-resolution spectra in the near-infrared YJ bands. These Cepheids are located at 3-5.6 kpc in the Galactocentric distance, R(GC), and reveal the metallicity gradient in this range for the first time. Their metallicities are mostly between 0.1 and 0.3 dex in [Fe/H] and more or less follow the extrapolation of the metallicity gradient found in the outer part, R(GC) larger than 6.5 kpc. The gradient in the inner disk may be shallower or even flat, but the small sample does not allow to determine the slope precisely. More extensive spectroscopic observations would also be necessary for studying minor populations, if any, with higher or lower metallicities that were reported in previous literature. In addition, three-dimensional velocities of our inner-disk Cepheids show the kinematic pattern that indicates non-circular orbits caused by the Galactic bar, which is consistent with the patterns reported in recent studies on high-mass star-forming regions and red giant branch stars., Comment: Accepted for publication in ApJ. 10 pages, 2 figures, and 2 tables

Classical Cepheids (CCs) are solid distance indicators and tracers of young stellar populations. Our aim is to provide iron, oxygen, and sulfur abundances for the largest and most homogeneous sample of Galactic CCs ever analyzed. The current sample covers a wide range in Galactocentric distances (RG), pulsation modes and periods. High-resolution and high S/N spectra collected with different spectrographs were adopted to estimate the atmospheric parameters. Individual distances are based on Gaia trigonometric parallaxes or on near-infrared Period-Luminosity relations. We found that Fe and alpha-element radial gradients based on CCs display a well-defined change in the slope for RG larger than 12 kpc. Radial gradients based on open clusters, covering a wide range in age, display similar trends, meaning that the flattening in the outer disk is an intrinsic feature of the radial gradients since it is independent of age. Empirical evidence indicates that the radial gradient for S is steeper than for Fe. The difference in the slope is a factor of two in the linear fit. We also found that S is, on average, under-abundant compared with O. We performed a detailed comparison with Galactic chemical evolution models and we found that a constant Star Formation Efficiency for RG larger than 12 kpc takes account for the flattening in both Fe and alpha-elements. To further constrain the impact that predicted S yields for massive stars have on radial gradients, we adopted a "toy model" and we found that the flattening in the outermost regions requires a decrease of a factor of four in the current S predictions. Sulfur photospheric abundances, compared with other alpha-elements, have the key advantage of being a volatile element. Therefore, stellar S abundances can be directly compared with nebular S abundances in external galaxies., Comment: 21 pages, 13 figures, 3 tables; to be published in the A&A journal

Recent JWST observations of the z=10.6 galaxy GN-z11 have revealed a very high gas-phase nitrogen abundance (higher than four times the solar value), a very small half-light radius(~ 60 pc), and a large stellar mass (M_s ~ 10^9 M_sun) for its size. We consider that this object is a forming galactic nucleus or ultra-compact dwarf galaxy rather than a proto globular cluster, and thereby investigate the chemical abundance pattern using one-zone chemical evolution models.The principal results of the models are as follows. The observed log (N/O) > -0.24, log (C/O)>-0.78, and 12+log (O/H) ~ 7.8 can be self-consistently reproduced by the models both with very short star formation timescales (< 10^7 yr) and with top-heavy stellar initial mass functions (IMFs). The adopted assumption of no chemical enrichment by massive (m>25 M_sun) core collapse supernovae (CCSNe) is also important for the reproduction of high gas-phase log (N/O), because such CCSNe can decrease high log (N/O) of gas polluted by OB and Wolf-Rayet stars. GN-z11 can have a significant fraction (>0.5) of nitrogen-rich ([N/Fe]>0.5) stars, which implies a possible link between nitrogen-rich stellar populations of the inner Galaxy and giant elliptical galaxies and high-z objects with high gas-phase log (N/O) like GN-z11., Comment: 5 pages, 3 figures, accepted for publication in MNRAS (Letters)

Newly-developed spectrographs with increased resolving powers, particularly those covering the near-IR range, allow the characterization of more and more absorption lines in stellar spectra. This includes the identification and confirmation of absorption lines and the calibration of oscillator strengths. In this study, we provide empirical values of loggf based on abundances of classical Cepheids obtained with optical spectra in Luck (2018), in order to establish the consistency between optical and infrared abundance results. Using time-series spectra of classical Cepheids obtained with WINERED spectrograph (0.97-1.35 $\mu$ m, R ~28000, we demonstrate that we can determine the stellar parameters of the observed Cepheids, including effective temperature (Teff), surface gravity (logg), microturbulence, and metallicity. With the newly calibrated relations of line-depth ratios (LDRs), we can achieve accuracy and precision comparable to optical studies (Luck 2018), with uncertainties of 90K and 0.108 dex for Teff, and log g, respectively. Finally, we created a new atlas of absorption lines, featuring precise abundance measurements of various elements found in the atmosphere of Cepheids (including neutron-capture elements), with loggf values that have been astrophysically calibrated., Comment: 25 pages, 10 figures, supplementary material (figures_

Tantalum thin films sputtered on unheated silicon substrates are characterized with microwaves at around 10 GHz in a 10 mK environment. We show that the phase of tantalum with a body-centered cubic lattice ($\alpha$-Ta) can be grown selectively by depositing a niobium buffer layer prior to a tantalum film. The physical properties of the films, such as superconducting transition temperature and crystallinity, change markedly with the addition of the buffer layer. Coplanar waveguide resonators based on the composite film exhibit significantly enhanced internal quality factors compared with a film without the buffer layer. The internal quality factor approaches $2\times 10^7$ at a large-photon-number limit. While the quality factor decreases at the single-photon level owing to two-level system (TLS) loss, we have identified the primary cause of TLS loss to be the amorphous silicon layer at the film-substrate interface, which originates from the substrate cleaning before the film deposition rather than the film itself. The temperature dependence of the internal quality factors shows a marked rise below 200 mK, suggesting the presence of TLS-TLS interactions. The present low-loss tantalum films can be deposited without substrate heating and thus have various potential applications in superconducting quantum electronics., Comment: 7 pages, 4 figures + Supplementary Material (8 pages, 5 figures)