Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The estimate of the solar wind magnetic fields’ parallel correlation length, <jats:italic>λ</jats:italic>, be it from the measured fields’ correlation functions or their spectral power at “zero” frequency, have long pointed toward short values on the order of 0.01 au. Evaluation of the mean cross-field displacements (CFDs), however, fails to show the decorrelation and resulting diffusion at the expected scales, pointing instead toward <jats:italic>λ</jats:italic> values on the order of 0.1 au or more. In an effort to understand this “order-of-magnitude” discrepancy and reconcile the approaches using correlation functions and the CFD diffusivity test, both approaches are applied here, with renewed attention to the “details” as well as the broader sense of the calculations, to a large, 20 yr long set of magnetic field and flow data from the ACE spacecraft. It is found that solar wind intervals too short relative to <jats:italic>λ</jats:italic> are a likely reason for some underestimate through the correlation-function approach, causing a premature drop of the correlation functions. Once converged to their long-time limit, however, the correlation functions produce magnetic field correlation lengths very much consistent with the magnetic-field-line (MFL) correlation lengths of the diffusivity test, with nearly matching distributions of the correlation lengths corrected by the proper ratio of their theoretical estimates. The fields’ correlation lengths mostly range from 0.03 to 0.08 au, and the MFL correlation lengths from 0.04 to 0.3 au, with peaks at 0.075 and 0.15 au, likely due to nonlinear and quasilinear regimes of MFL wandering. As for the power-at-zero-frequency approach, it is doomed by the solar rotation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>V410 Aur is a known deep and low-mass-ratio contact binary with a spectroscopically tertiary component and a visual companion. However, the physical and orbital properties of the tertiary are unknown. We constructed (<jats:italic>O</jats:italic> − <jats:italic>C</jats:italic>) curve with 117 new eclipse times and those collected from the literature, which shows a cyclical variation with a period of 25.44 (±1.17) yr and a projected semimajor axis of 0.0348 (±0.0021) days while it undergoes a long-term period decrease at a rate of <jats:italic>dP</jats:italic>/<jats:italic>dt</jats:italic> = −1.58 × 10<jats:sup>−7</jats:sup>daysyr<jats:sup>−1</jats:sup>. The cyclical variation is analyzed for the light-travel time effect. The minimum mass of the third body is determined as 1.39 (±0.13) <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> that is much larger than the inferred value (0.97 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) of spectroscopic investigation, which indicates that the spectroscopically tertiary is a single-lined spectroscopic binary with an unseen component. The maximum orbital semimajor axis 6.19 (±0.67) au of the third body is determined. Gaia detected a visual companion to V410 Aur at practically the same distance from the Sun nicely confirming the physical bond. These results reveal that V410 Aur contains a single-lined spectroscopic binary with a visual companion in a quintuple stellar system. TESS photometric solutions confirmed that V410 Aur is a deep overcontact binary with a fill-out factor of 73.83(88)% where the additional light contribution is about 24.80(18)%. The continuous variations of light curves are explained by the evolution of a dark spot on the more massive component. The parabolic variation in the (<jats:italic>O</jats:italic> − <jats:italic>C</jats:italic>) curve may be caused by the mass transfer from the massive component to the less massive one in the deep overcontact binary.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Water clouds are expected to form on Y dwarfs and giant planets with equilibrium temperatures near or below that of Earth, drastically altering their atmospheric compositions and their albedos and thermal emission spectra. Here we use the 1D Community Aerosol and Radiation Model for Atmospheres (CARMA) to investigate the microphysics of water clouds on cool substellar worlds to constrain their typical particle sizes and vertical extent, taking into consideration nucleation and condensation, which have not been considered in detail for water clouds in H/He atmospheres. We compute a small grid of Y-dwarf and temperate giant-exoplanet atmosphere models with water clouds forming through homogeneous nucleation and heterogeneous nucleation on cloud condensation nuclei composed of meteoritic dust, organic photochemical hazes, and upwelled potassium chloride cloud particles. We present comparisons with the Ackerman &amp; Marley parameterization of cloud physics to extract the optimal sedimentation efficiency parameter (<jats:italic>f</jats:italic> <jats:sub>sed</jats:sub>) using <jats:monospace>Virga</jats:monospace>. We find that no <jats:monospace>Virga</jats:monospace> model replicates the CARMA water clouds exactly and that a transition in <jats:italic>f</jats:italic> <jats:sub>sed</jats:sub> occurs from the base of the cloud to the cloud top. Furthermore, we generate simulated thermal emission and geometric albedo spectra and find large, wavelength-dependent differences between the CARMA and <jats:monospace>Virga</jats:monospace> models, with different gas absorption bands reacting differently to the different cloud distributions and particularly large differences in the <jats:italic>M</jats:italic> band. Therefore, constraining the vertically dependent properties of water clouds will be essential to estimate the gas abundances in these atmospheres.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have carried out a high-sensitivity and high-resolution radio continuum study toward a sample of 47 massive dense cores (MDCs) in the Cygnus X star-forming complex using the Karl G. Jansky Very Large Array, aiming to detect and characterize the radio emission associated with star-forming activities down to ∼0.01 pc scales. We have detected 64 radio sources within or closely around the FWHMs of the MDCs, of which 37 are reported for the first time. The majority of the detected radio sources are associated with dust condensations embedded within the MDCs, and they are mostly weak and compact. We are able to build spectral energy distributions for eight sources. Two of them indicate nonthermal emission and the other six indicate thermal free–free emission. We have determined that most of the radio sources are ionized jets or winds originating from massive young stellar objects, whereas only a few sources are likely to be ultracompact H <jats:sc>ii</jats:sc> regions. Further quantitative analyses indicate that the radio luminosity of the detected radio sources increases along the evolution path of the MDCs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Abundance Matching Box for the Epoch of Reionization (AMBER) is a semi-numerical code for modeling the cosmic dawn. The new algorithm is not based on the excursion set formalism for reionization, but takes the novel approach of calculating the reionization-redshift field <jats:inline-formula> <jats:tex-math> <?CDATA ${z}_{\mathrm{re}}({\boldsymbol{x}})$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>re</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:mi mathvariant="bold-italic">x</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5116ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> assuming that hydrogen gas encountering higher radiation intensity are photoionized earlier. Redshift values are assigned while matching the abundance of ionized mass according to a given mass-weighted ionization fraction <jats:inline-formula> <jats:tex-math> <?CDATA ${\bar{x}}_{{\rm{i}}}(z)$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>x</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">i</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:mi>z</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5116ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>. The code has the unique advantage of allowing users to directly specify the reionization history through the redshift midpoint <jats:italic>z</jats:italic> <jats:sub>mid</jats:sub>, duration Δ<jats:sub>z</jats:sub>, and asymmetry <jats:italic>A</jats:italic> <jats:sub>z</jats:sub> input parameters. The reionization process is further controlled through the minimum halo mass <jats:italic>M</jats:italic> <jats:sub>min</jats:sub> for galaxy formation and the radiation mean free path <jats:italic>l</jats:italic> <jats:sub>mfp</jats:sub> for radiative transfer. We implement improved methods for constructing density, velocity, halo, and radiation fields, which are essential components for modeling reionization observables. We compare AMBER with two other semi-numerical methods and find that our code more accurately reproduces the results from radiation-hydrodynamic simulations. The parallelized code is over four orders of magnitude faster than radiative transfer simulations and will efficiently enable large-volume models, full-sky mock observations, and parameter-space studies. AMBER will be made publicly available to facilitate and transform studies of the Epoch of Reionization.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Over the last decades, international attempts have been made to develop realistic space weather prediction tools aiming to forecast the conditions on the Sun and in the interplanetary environment. These efforts have led to the development of appropriate metrics to assess the performance of those tools. Metrics are necessary to validate models, to compare different models, and to monitor the improvements to a certain model over time. In this work, we introduce dynamic time warping (DTW) as an alternative way of evaluating the performance of models and, in particular, of quantifying the differences between observed and modeled solar wind time series. We present the advantages and drawbacks of this method, as well as its application to Wind observations and EUHFORIA predictions at Earth. We show that DTW can warp sequences in time, aiming to align them with the minimum cost by using dynamic programming. It can be applied for the evaluation of modeled solar wind time series in two ways. The first calculates the <jats:italic>sequence similarity factor</jats:italic>, a number that provides a quantification of how good the forecast is compared to an ideal and a nonideal prediction scenario. The second way quantifies the time and amplitude differences between the points that are best matched between the two sequences. As a result, DTW can serve as a hybrid metric between continuous measurements (e.g., the correlation coefficient) and point-by-point comparisons. It is a promising technique for the assessment of solar wind profiles, providing at once the most complete evaluation portrait of a model.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Fine-grained rims (FGRs) are frequently found around chondrules in primitive chondrites. The remarkable feature of FGRs is their submicron-sized and nonporous nature. The typical thickness of FGRs around chondrules is 10–100 <jats:italic>μ</jats:italic>m. Recently, a novel idea was proposed for the origin of FGRs: high-speed collisions between chondrules and fine dust grains called the kinetic dust aggregation process. Experimental studies revealed that (sub)micron-sized ceramic particles can stick to a ceramic substrate in a vacuum when the impact velocity is approximately in the range of 0.1–1 km s<jats:sup>−1</jats:sup>. In this study, we examine the possibility of FGR formation via kinetic dust aggregation in chondrule-forming shock waves. When shock waves are created by undifferentiated icy planetesimals, fine dust grains would be released from the planetary surface due to the evaporation of icy planetesimals. We consider the dynamics of chondrules behind the shock front and calculate the growth of FGRs via kinetic dust aggregation based on simple one-dimensional calculations. We found that nonporous FGRs with a thickness of 10–100 <jats:italic>μ</jats:italic>m would be formed in shock waves around evaporating icy planetesimals.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Black hole feedback has been widely implemented as the key recipe to quench star formation in massive galaxies in modern semianalytic models and hydrodynamical simulations. As the theoretical details surrounding the accretion and feedback of black holes continue to be refined, various feedback models have been implemented across simulations, with notable differences in their outcomes. Yet, most of these simulations have successfully reproduced some observations, such as the stellar mass function and star formation rate density in the local universe. We use the recent observation of the change in the neutral hydrogen gas mass (including both H<jats:sub>2</jats:sub> and H I) with the star formation rate of massive central disk galaxies as a critical constraint of black hole feedback models across several simulations. We find that the predictions of IllustrisTNG agree with the observations much better than the other models tested in this work. This favors IllustrisTNG’s treatment of active galactic nuclei (AGN)—where kinetic winds are driven by black holes at low accretion rates—as more plausible among those we test. In turn, this also indirectly supports the idea that the massive central disk galaxy population in the local universe was likely quenched by AGN feedback.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the results of Monitor of All-sky X-ray Image (MAXI) monitoring and two Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the recently discovered faint X-ray transient MAXI J1848015. Analysis of the MAXI light curve shows that the source underwent a rapid flux increase beginning on 2020 December 20, followed by a rapid decrease in flux after only ∼5 days. NuSTAR observations reveal that the source transitioned from a bright soft state with unabsorbed, bolometric (0.1–100 keV) flux <jats:italic>F</jats:italic> = 6.9 ± 0.1 × 10<jats:sup>−10</jats:sup> erg cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup>, to a low hard state with flux <jats:italic>F</jats:italic> = 2.85 ± 0.04 × 10<jats:sup>−10</jats:sup> erg cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup>. Given a distance of 3.3 kpc, inferred via association of the source with the GLIMPSE-C01 cluster, these fluxes correspond to an Eddington fraction of the order of 10<jats:sup>−3</jats:sup> for an accreting neutron star (NS) of mass <jats:italic>M</jats:italic> = 1.4<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, or even lower for a more massive accretor. However, the source spectra exhibit strong relativistic reflection features, indicating the presence of an accretion disk that extends close to the accretor, for which we measure a high spin, <jats:italic>a</jats:italic> = 0.967 ± 0.013. In addition to a change in flux and spectral shape, we find evidence for other changes between the soft and hard states, including moderate disk truncation with the inner disk radius increasing from <jats:italic>R</jats:italic> <jats:sub>in</jats:sub> ≈ 3 <jats:italic>R</jats:italic> <jats:sub>g</jats:sub> to <jats:italic>R</jats:italic> <jats:sub>in</jats:sub> ≈ 8 <jats:italic>R</jats:italic> <jats:sub>g</jats:sub>, narrow Fe emission whose centroid decreases from 6.8 ± 0.1 keV to 6.3 ± 0.1 keV, and an increase in low-frequency (10<jats:sup>−3</jats:sup>–10<jats:sup>−1</jats:sup> Hz) variability. Due to the high spin, we conclude that the source is likely to be a black hole rather than an NS, and we discuss physical interpretations of the low apparent luminosity as well as the narrow Fe emission.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Identifying multiply imaged quasars is challenging owing to their low density in the sky and the limited angular resolution of wide-field surveys. We show that multiply imaged quasars can be identified using unresolved light curves, without assuming a light-curve template or any prior information. After describing our method, we show, using simulations, that it can attain high precision and recall when we consider high-quality data with negligible noise well below the variability of the light curves. As the noise level increases to that of the Zwicky Transient Facility telescope, we find that precision can remain close to 100% while recall drops to ∼60%. We also consider some examples from Time Delay Challenge 1 and demonstrate that the time delays can be accurately recovered from the joint light-curve data in realistic observational scenarios. We further demonstrate our method by applying it to publicly available COSMOGRAIL data of the observed lensed quasar SDSS J1226−0006. We identify the system as a lensed quasar based on the unresolved light curve and estimate a time delay in good agreement with the one measured by COSMOGRAIL using the individual image light curves. The technique shows great potential to identify lensed quasars in wide-field imaging surveys, especially the soon-to-be-commissioned Vera Rubin Observatory.</jats:p>