Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Pulsating stars in eclipsing binaries are very important for understanding the structure of stellar interiors through asteroseismology because their absolute parameters such as their masses and radii can be determined with high precision based on photometric and spectroscopic data. The high-precision and continuous time-series photometric data of the Transiting Exoplanet Survey Satellite (TESS) provides an unprecedented opportunity to search for and study these kinds of variable stars in the whole sky. About 1626 Algol-type (EA-type) eclipsing-binary systems were observed by TESS in the 1–45 sectors with 2 minutes short cadence. By analyzing these TESS data, we found 57 new pulsating stars in EA-type binary stars. The preliminary results show that these binary systems have orbital periods in the range from 0.4 to 27 days, while the periods of pulsating components are in the range from 0.02 to 5 days. It is detected that 43 targets follow the correlation between the pulsation and orbital periods of Algol-type oscillating eclipsing binaries (oEA stars), which may indicate that they are typical oEA stars. The other 14 targets may be other types of variable stars in eclipsing-binary systems. These objects are a very interesting source to investigate binary structures and evolution as well as to understand the influences of tidal forces and mass transfer on stellar pulsations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a value-added catalog containing stellar parameters estimated from 7.10 million low-resolution spectra for 5.16 million unique stars with spectral signal-to-noise ratios (S/N) higher than 10 obtained by the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) Galactic spectroscopic surveys. The catalog presents values of stellar atmospheric parameters (effective temperature <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub>, surface gravity log <jats:italic>g</jats:italic>, metallicity [Fe/H]/[M/H]), <jats:italic>α</jats:italic>-element to metal abundance ratio [<jats:italic>α</jats:italic>/M], carbon and nitrogen to iron abundance ratios [C/Fe] and [N/Fe], and 14 bands’ absolute magnitudes deduced from LAMOST spectra using the neural network method. The spectrophotometric distances of those stars are also provided based on the distance modulus. For stars with a spectral S/N larger than 50, precisions of <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub>, log <jats:italic>g</jats:italic>, [Fe/H], [M/H], [C/Fe], [N/Fe], and [<jats:italic>α</jats:italic>/M] are 85 K, 0.098 dex, 0.05 dex, 0.05 dex, 0.052 dex, 0.082 dex, and 0.027 dex, respectively. The errors of 14 band’s absolute magnitudes are 0.16–0.22 mag for stars with a spectral S/N larger than 50. The spectrophotometric distance is accurate to 8.5% for stars with a spectral S/N larger than 50 and is more accurate than the geometrical distance for stars with a distance larger than 2.0 kpc. Our estimates of [Fe/H] are reliable down to [Fe/H] ∼−3.5 dex, significantly better than previous results. The catalog provides 26,868 unique very metal-poor star candidates ([Fe/H] ≤−2.0). The catalog would be a valuable dataset to study the structure and evolution of the galaxy, especially the solar neighborhood and the outer disk.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This work reports large-scale calculations of electron excitation effective collision strengths and transition rates for a wide range of Sc <jats:sc>ii</jats:sc> spectral lines for astrophysical analysis and modeling. The present results are important for reliable abundance determinations in various astrophysical objects, including metal-poor stars, H <jats:sc>ii</jats:sc> regions, and gaseous nebulae. Accurate descriptions of the target wave functions and adequate accounts of the various interactions between the target levels are of primary importance for calculations of collision and radiative parameters. The target wave functions have been determined by a combination of the multiconfiguration Hartree–Fock and B-spline box-based close-coupling methods, together with the nonorthogonal orbitals technique. The calculations of the collision strengths have been performed using the B-spline Breit–Pauli R-matrix method. The close-coupling expansion includes 145 fine-structure levels of Sc <jats:sc>ii</jats:sc> belonging to the terms of the 3<jats:italic>p</jats:italic> <jats:sup>6</jats:sup>3<jats:italic>d</jats:italic> <jats:sup>2</jats:sup>, 3<jats:italic>p</jats:italic> <jats:sup>6</jats:sup>3<jats:italic>d</jats:italic>4<jats:italic>l</jats:italic> (<jats:italic>l</jats:italic> = 0–3), 3<jats:italic>p</jats:italic> <jats:sup>6</jats:sup>3<jats:italic>d</jats:italic>5<jats:italic>l</jats:italic> (<jats:italic>l</jats:italic> = 0–3), 3<jats:italic>p</jats:italic> <jats:sup>6</jats:sup>3<jats:italic>d</jats:italic>6<jats:italic>s</jats:italic>, 3<jats:italic>p</jats:italic> <jats:sup>6</jats:sup>4<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>, 3<jats:italic>p</jats:italic> <jats:sup>6</jats:sup>4<jats:italic>s</jats:italic>4<jats:italic>l</jats:italic> (<jats:italic>l</jats:italic> = 0–3), 3<jats:italic>p</jats:italic> <jats:sup>6</jats:sup>4<jats:italic>s</jats:italic>5<jats:italic>l</jats:italic> (<jats:italic>l</jats:italic> = 0–1), and 3<jats:italic>p</jats:italic> <jats:sup>6</jats:sup>4<jats:italic>p</jats:italic> <jats:sup>2</jats:sup> configurations. The effective collision strengths are reported as a function of electron temperature in the range from 10<jats:sup>3</jats:sup> to 10<jats:sup>5</jats:sup> K. The collision and radiative rates are reported for all of the possible transitions between the 145 fine-structure levels. Striking discrepancies exist with the previous R-matrix calculations of the effective collision strengths for the majority of the transitions, indicating possible systematic errors in these calculations. Thus, there is a need for accurate calculations to reduce the uncertainties in the atomic data. The likely uncertainties in our effective collision strengths and radiative parameters have been assessed by means of comparisons with other collision calculations and available experimental radiative parameters.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The CNIa0.02 project aims to collect a complete, nearby sample of Type Ia supernovae (SNe Ia) light curves, and the SNe are volume-limited with host-galaxy redshifts <jats:italic>z</jats:italic> <jats:sub>host</jats:sub> &lt; 0.02. The main scientific goal is to infer the distributions of key properties (e.g., the luminosity function) of local SNe Ia in a complete and unbiased fashion in order to study SN explosion physics. We spectroscopically classify any SN candidate detected by the All-Sky Automated Survey for Supernovae (ASAS-SN) that reaches a peak brightness &lt;16.5 mag. Since ASAS-SN scans the full sky and does not target specific galaxies, our target selection is effectively unbiased by host-galaxy properties. We perform multiband photometric observations starting from the time of discovery. In the first data release (DR1), we present the optical light curves obtained for 247 SNe from our project (including 148 SNe in the complete sample), and we derive parameters such as the peak fluxes, Δ<jats:italic>m</jats:italic> <jats:sub>15</jats:sub>, and <jats:italic>s</jats:italic> <jats:italic> <jats:sub>BV</jats:sub> </jats:italic>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>There is a complex inclination structure present in the trans-Neptunian object (TNO) orbital distribution in the main classical-belt region (between orbital semimajor axes of 39 and 48 au). The long-term gravitational effects of the giant planets make TNO orbits precess, but nonresonant objects maintain a nearly constant “free” inclination (<jats:italic>I</jats:italic> <jats:sub>free</jats:sub>) with respect to a local forced precession pole. Because of the likely cosmogonic importance of the distribution of this quantity, we tabulate free inclinations for all main-belt TNOs, each individually computed using barycentric orbital elements with respect to each object’s local forcing pole. We show that the simplest method, based on the Laplace–Lagrange secular theory, is unable to give correct forcing poles for objects near the <jats:italic>ν</jats:italic> <jats:sub>18</jats:sub> secular resonance, resulting in poorly conserved <jats:italic>I</jats:italic> <jats:sub>free</jats:sub> values in much of the main belt. We thus instead implemented an averaged Hamiltonian to obtain the expected nodal precession for each TNO, yielding significantly more accurate free inclinations for nonresonant objects. For the vast majority (96%) of classical-belt TNOs, these <jats:italic>I</jats:italic> <jats:sub>free</jats:sub> values are conserved to &lt; 1° over 4 Gyr numerical simulations, demonstrating the advantage of using this well-conserved quantity in studies of the TNO population and its primordial inclination profile; our computed distributions only reinforce the idea of a very coplanar surviving “cold” primordial population, overlain by a large <jats:italic>I</jats:italic>-width implanted “hot” population.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Measuring the redshift of active galactic nuclei (AGNs) requires the use of time-consuming and expensive spectroscopic analysis. However, obtaining redshift measurements of AGNs is crucial as it can enable AGN population studies, provide insight into the star formation rate, the luminosity function, and the density rate evolution. Hence, there is a requirement for alternative redshift measurement techniques. In this project, we aim to use the Fermi Gamma-ray Space Telescope’s 4LAC Data Release 2 catalog to train a machine-learning (ML) model capable of predicting the redshift reliably. In addition, this project aims at improving and extending with the new 4LAC Catalog the predictive capabilities of the ML methodology published in Dainotti et al. Furthermore, we implement feature engineering to expand the parameter space and a bias correction technique to our final results. This study uses additional ML techniques inside the ensemble method, the SuperLearner, previously used in Dainotti et al. Additionally, we also test a novel ML model called Sorted L-One Penalized Estimation. Using these methods, we provide a catalog of estimated redshift values for those AGNs that do not have a spectroscopic redshift measurement. These estimates can serve as a redshift reference for the community to verify as updated Fermi catalogs are released with more redshift measurements.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present observations of the carbon-rich protoplanetary nebula CRL 2688 made with the Institut de Radioastronomie Millimétrique 30 m telescope in the 3 and 2 mm bands. In total, 196 transition lines belonging to 38 molecular species and isotopologues are detected, among which, to the best of our knowledge, 153 transition lines and 13 species are the first reported for this object. Additionally, in order to contribute to future research, we have collected observational data on the molecular lines of CRL 2688 from the literature and compiled them into a single unified catalog. We find that the molecular abundance of CRL 2688 cannot be explained by the standard model of a circumstellar envelope. The implications of metal-bearing molecules on circumstellar chemistry are discussed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We propose a novel algorithm for the temporal integration of the resistive magnetohydrodynamics (MHD) equations. The approach is based on exponential Rosenbrock schemes in combination with Leja interpolation. It naturally preserves Gauss’s law for magnetism and is unencumbered by the stability constraints observed for explicit methods. Remarkable progress has been achieved in designing exponential integrators and computing the required matrix functions efficiently. However, employing them in MHD simulations of realistic physical scenarios requires a matrix-free implementation. We show how an efficient algorithm based on Leja interpolation that only uses the right-hand side of the differential equation (i.e., matrix free) can be constructed. We further demonstrate that it outperforms Krylov-based exponential integrators as well as explicit and implicit methods using test models of magnetic reconnection and the Kelvin–Helmholtz instability. Furthermore, an adaptive step-size strategy that gives excellent and predictable performance, particularly in the lenient- to intermediate-tolerance regime that is often of importance in practical applications, is employed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The generation-defining Vera C. Rubin Observatory will make state-of-the-art measurements of both the static and transient universe through its Legacy Survey for Space and Time (LSST). With such capabilities, it is immensely challenging to optimize the LSST observing strategy across the survey’s wide range of science drivers. Many aspects of the LSST observing strategy relevant to the LSST Dark Energy Science Collaboration, such as survey footprint definition, single-visit exposure time, and the cadence of repeat visits in different filters, are yet to be finalized. Here, we present metrics used to assess the impact of observing strategy on the cosmological probes considered most sensitive to survey design; these are large-scale structure, weak lensing, type Ia supernovae, kilonovae, and strong lens systems (as well as photometric redshifts, which enable many of these probes). We evaluate these metrics for over 100 different simulated potential survey designs. Our results show that multiple observing strategy decisions can profoundly impact cosmological constraints with LSST; these include adjusting the survey footprint, ensuring repeat nightly visits are taken in different filters, and enforcing regular cadence. We provide public code for our metrics, which makes them readily available for evaluating further modifications to the survey design. We conclude with a set of recommendations and highlight observing strategy factors that require further research.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We propose a new, efficient multiscale method to decompose a map (or signal in general) into component maps that contain structures of different sizes. In the widely used wave transform, artifacts containing negative values arise around regions with sharp transitions due to the application of band-limited filters. In our approach, the decomposition is achieved by solving a modified, nonlinear version of the diffusion equation. This is inspired by the anisotropic diffusion methods, which establish the link between image filtering and partial differential equations. In our case, the artifact issue is addressed where the positivity of the decomposed images is guaranteed. Our new method is particularly suitable for signals which contain localized, nonlinear features, as typical of astronomical observations. It can be used to study the multiscale structures of astronomical maps quantitatively and should be useful in observation-related tasks such as background removal. We thus propose a new measure called the “scale spectrum,” which describes how the image values distribute among different components in the scale space, to describe maps. The method allows for input arrays of an arbitrary number of dimensions, and a <jats:monospace>python3</jats:monospace> implementation of the algorithms is included in the Appendix and available at <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://github.com/gxli/constrained_diffusion_decomposition" xlink:type="simple">https://github.com/gxli/constrained_diffusion_decomposition</jats:ext-link>.</jats:p>