Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We present deep Hubble Space Telescope (HST) near-infrared (NIR) observations of the magnetar SGR 1935+2154 from 2021 June, approximately 6 yr after the first HST observations, a year after the discovery of fast-radio-burst-like emission from the source, and in a period of exceptional high-frequency activity. Although not directly taken during a bursting period the counterpart is a factor of ∼1.5–2.5 brighter than seen at previous epochs with F140W(AB) = 24.65 ± 0.02 mag. We do not detect significant variations of the NIR counterpart within the course of any one orbit (i.e., on minutes to hour timescales), and contemporaneous X-ray observations show SGR 1935+2154 to be at the quiescent level. With a time baseline of 6 yr from the first identification of the counterpart we place stringent limits on the proper motion (PM) of the source, with a measured PM of <jats:italic>μ</jats:italic> = 3.1 ± 1.5 mas yr<jats:sup>−1</jats:sup>. The direction of PM indicates an origin of SGR 1935+2154 very close to the geometric center of SNR G57.2+08, further strengthening their association. At an adopted distance of 6.6 ± 0.7 kpc, the corresponding tangential space velocity is <jats:italic>ν</jats:italic> <jats:sub> <jats:italic>T</jats:italic> </jats:sub> = 97 ± 48 km s<jats:sup>−1</jats:sup> (corrected for differential Galactic rotation and peculiar solar motion), although its formal statistical determination may be compromised owing to few epochs of observation. The current velocity estimate places it at the low end of the kick distribution for pulsars, and makes it among the lowest known magnetar kicks. When collating the few-magnetar kick constraints available, we find full consistency between the magnetar kick distribution and the much larger pulsar kick sample.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Broad-line regions (BLRs) in high-redshift quasars provide crucial information on chemical enrichment in the early universe. Here we present a study of BLR metallicities in 33 quasars at redshift 5.7 &lt; <jats:italic>z</jats:italic> &lt; 6.4. Using the near-IR spectra of the quasars obtained from the Gemini telescope, we measure their rest-frame UV emission-line flux and calculate flux ratios. We then estimate BLR metallicities with empirical calibrations based on photoionization models. The inferred median metallicity of our sample is a few times the solar value, indicating that the BLR gas had been highly metal enriched at <jats:italic>z</jats:italic> ∼ 6. We compare our sample with a low-redshift quasar sample with similar luminosities and find no evidence of redshift evolution in quasar BLR metallicities. This is consistent with previous studies. The Fe <jats:sc>ii</jats:sc>/Mg <jats:sc>ii</jats:sc> flux ratio, a proxy for the Fe/<jats:italic>α</jats:italic> element abundance ratio, shows no redshift evolution as well, further supporting rapid nuclear star formation at <jats:italic>z</jats:italic> ∼ 6. We also find that the black hole mass–BLR metallicity relation at <jats:italic>z</jats:italic> ∼ 6 is consistent with the relation measured at 2 &lt; <jats:italic>z</jats:italic> &lt; 5, suggesting that our results are not biased by a selection effect due to this relation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the empirical dust attenuation (EDA) framework—a flexible prescription for assigning realistic dust attenuation to simulated galaxies based on their physical properties. We use the EDA to forward model synthetic observations for three state-of-the-art large-scale cosmological hydrodynamical simulations: SIMBA, IllustrisTNG, and EAGLE. We then compare the optical and UV color–magnitude relations, (<jats:italic>g</jats:italic> − <jats:italic>r</jats:italic>) − <jats:italic>M</jats:italic> <jats:sub> <jats:italic>r</jats:italic> </jats:sub> and (far-UV −near-UV) − <jats:italic>M</jats:italic> <jats:sub> <jats:italic>r</jats:italic> </jats:sub>, of the simulations to a <jats:italic>M</jats:italic> <jats:sub> <jats:italic>r</jats:italic> </jats:sub> &lt; − 20 and UV complete Sloan Digital Sky Survey galaxy sample using likelihood-free inference. Without dust, none of the simulations match observations, as expected. With the EDA, however, we can reproduce the observed color–magnitude with all three simulations. Furthermore, the attenuation curves predicted by our dust prescription are in good agreement with the observed attenuation–slope relations and attenuation curves of star-forming galaxies. However, the EDA does not predict star-forming galaxies with low <jats:italic>A</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> since simulated star-forming galaxies are intrinsically much brighter than observations. Additionally, the EDA provides, for the first time, predictions on the attenuation curves of quiescent galaxies, which are challenging to measure observationally. Simulated quiescent galaxies require shallower attenuation curves with lower amplitude than star-forming galaxies. The EDA, combined with forward modeling, provides an effective approach for shedding light on dust in galaxies and probing hydrodynamical simulations. This work also illustrates a major limitation in comparing galaxy formation models: by adjusting dust attenuation, simulations that predict significantly different galaxy populations can reproduce the same UV and optical observations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Imaging algorithms form powerful analysis tools for very long baseline interferometry (VLBI) data analysis. However, these tools cannot measure certain image features (e.g., ring diameter) by their nonparametric nature. This is unfortunate since these image features are often related to astrophysically relevant quantities such as black hole mass. This paper details a new general image feature-extraction technique that applies to a wide variety of VLBI image reconstructions called <jats:italic>variational image domain analysis</jats:italic>. Unlike previous tools, variational image domain analysis can be applied to any image reconstruction regardless of its structure. To demonstrate its flexibility, we analyze thousands of reconstructions from previous Event Horizon Telescope synthetic data sets and recover image features such as diameter, orientation, and ellipticity. By measuring these features, our technique can help extract astrophysically relevant quantities such as the mass and orientation of the central black hole in M87.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study near-infrared (<jats:italic>JHK</jats:italic>) and X-ray light curves of Cyg X-3 obtained with the 2.5 m telescope of the Caucasian Mountain Observatory of MSU SAI and collected from the RXTE ASM and MAXI archives. The light curves in the X-ray and IR domains are strongly affected by irregular variations. However, the mean curves are remarkably stable and qualitatively similar in both domains. This means that the IR flux of the system originates not only from the free–free radiation of the Wolf–Rayet (WR) wind but also from a compact IR source located near the relativistic companion. The shape of the mean X-ray and IR light curves suggest the existence of two additional structures in the WR wind—a bow shock near the relativistic companion and a so-called “clumpy trail.” Modeling of the mean X-ray and IR light curves allowed us to obtain important system parameters: the orbital phase of the superior conjunction of the relativistic companion <jats:italic>ϕ</jats:italic> <jats:sub>0</jats:sub> = −0.066 ± 0.006, the orbital inclination angle <jats:italic>i</jats:italic> = 29.°5 ± 1.°2, and the WR mass-loss rate <jats:inline-formula> <jats:tex-math> <?CDATA $\dot{M}=(0.96\pm 0.14)\times {10}^{-5}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> <mml:mo>=</mml:mo> <mml:mo stretchy="false">(</mml:mo> <mml:mn>0.96</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.14</mml:mn> <mml:mo stretchy="false">)</mml:mo> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>5</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mspace width="0.25em" /> <mml:msup> <mml:mrow> <mml:mi>yr</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4047ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. By using relations between <jats:inline-formula> <jats:tex-math> <?CDATA $\dot{M}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4047ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and the rate of the period change and between <jats:inline-formula> <jats:tex-math> <?CDATA $\dot{M}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4047ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> and the WR mass, we estimated the probable mass of the relativistic companion <jats:italic>M</jats:italic> <jats:sub>C</jats:sub> ≃ 7.2 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, which points toward the black hole hypothesis. However, this estimate is based on the assumption of a smooth WR wind. Considering the uncertainty associated with clumping, the mass-loss rate can be lower, which leaves room for the neutron star hypothesis.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Benzene ice contributes to an emission feature detected by the Cassini Composite InfraRed Spectrometer (CIRS) near 682 cm<jats:sup>−1</jats:sup> in Titan’s late southern fall polar stratosphere. It is also one of the dominant components of the CIRS-observed High-Altitude South Polar ice cloud observed in Titan’s mid stratosphere during late southern fall. Titan’s stratosphere exhibits significant seasonal changes with temperatures that spatially vary with seasons. A quantitative analysis of the chemical composition of infrared emission spectra of Titan’s stratospheric ice clouds relies on consistent and detailed laboratory transmittance spectra obtained at numerous temperatures. However, there is a substantial lack of experimental data on the spectroscopic and optical properties of benzene ice and its temperature dependence, especially at Titan-relevant stratospheric conditions. We have therefore analyzed in laboratory the spectral characteristics and evolution of benzene ice’s vibrational modes at deposition temperatures ranging from 15 to 130 K, from the far- to mid-IR spectral region (50–8000 cm<jats:sup>−1</jats:sup>). We have determined the amorphous-to-crystalline phase transition of benzene ice and identified that a complete crystallization is achieved for deposition temperatures between 120 and 130 K. We have also measured the real and imaginary parts of the ice complex refractive index of benzene ice from 15 to 130 K. Our experimental results significantly extend the current state of knowledge on the deposition temperature dependence of benzene ice over a broad infrared spectral range, and provide useful new data for the analysis and interpretation of Titan-observed spectra.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The supernova remnant (SNR) G106.3+2.7 was recently found to be one of the few potential Galactic hadronic PeVatrons. Aiming to test the solidity of the SNR’s association with the molecular clouds (MCs) that are thought to be responsible for hadronic interaction, we performed a new CO observation with the IRAM 30 m telescope toward its “belly” region, which is coincident with the centroid of the <jats:italic>γ</jats:italic>-ray emission. There is a filament structure in the local standard of rest velocity interval −8 to −5 km s<jats:sup>−1</jats:sup> that nicely follows the northern radio boundary of the SNR. We have seen asymmetric broad profiles of <jats:sup>12</jats:sup>CO lines, with widths of a few km s<jats:sup>−1</jats:sup>, along the northern boundary and in the “belly” region of G106.3+2.7, but similar <jats:sup>12</jats:sup>CO-line profiles are also found outside the SNR boundary. Further, the low <jats:sup>12</jats:sup>CO <jats:italic>J</jats:italic> = 2–1/<jats:italic>J</jats:italic> = 1–0 line ratios suggest the MCs are cool. Therefore, it is still uncertain whether the MCs are directly disturbed by the SNR shocks, but we do find some clues that the MCs are nearby and thus can still be illuminated by the protons that escaped from the SNR. Notably, we find an expanding molecular structure with a velocity of ∼3.5 km s<jats:sup>−1</jats:sup> and a velocity gradient of the MCs across the SNR from ∼−3 to −7 km s<jats:sup>−1</jats:sup>, which could be explained as the effect of the wind blown by the SNR’s progenitor star.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Tidal interactions play an important role in many astrophysical systems, but uncertainties regarding the tides of rapidly rotating, centrifugally distorted stars and gaseous planets remain. We have developed a precise method for computing the dynamical, nondissipative tidal response of rotating planets and stars, based on summation over contributions from normal modes driven by the tidal potential. We calculate the normal modes of isentropic polytropes rotating at up to ≃90% of their critical breakup rotation rates, and tabulate fits to mode frequencies and tidal overlap coefficients that can be used to compute the frequency-dependent, nondissipative tidal response (via potential Love numbers <jats:italic>k</jats:italic> <jats:sub> <jats:italic>ℓm</jats:italic> </jats:sub>). Although fundamental modes (f-modes) possess dominant tidal overlap coefficients at (nearly) all rotation rates, we find that the strong coupling of retrograde inertial modes (i-modes) to tesseral (<jats:italic>ℓ</jats:italic> &gt; ∣<jats:italic>m</jats:italic>∣) components of the tidal potential produces resonances that may be relevant to gas giants like Jupiter and Saturn. The coupling of f-modes in rapid rotators to multiple components of both the driving tidal potential and the induced gravitational field also affect the tesseral response, leading to significant deviations from treatments of rotation that neglect centrifugal distortion and high-order corrections. For very rapid rotation rates (≳70% of breakup), mixing between prograde f-modes and i-modes significantly enhances the sectoral (<jats:italic>ℓ</jats:italic> = ∣<jats:italic>m</jats:italic>∣) tidal overlap of the latter. The tidal response of very rapidly rotating, centrifugally distorted planets or stars can also be modified by resonant sectoral f-modes that are secularly unstable via the Chandrasekhar–Friedman–Schutz mechanism.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Rapidly evolving transients, or objects that rise and fade in brightness on timescales two to three times shorter than those of typical Type Ia or Type II supernovae (SNe), have uncertain progenitor systems and powering mechanisms. Recent studies have noted similarities between rapidly evolving transients and Type Ibn SNe, which are powered by ejecta interacting with He-rich circumstellar material (CSM). In this work we present multiband photometric and spectroscopic observations from Las Cumbres Observatory and Swift of four fast-evolving Type Ibn SNe. We compare these observations with those of rapidly evolving transients identified in the literature. We discuss several common characteristics between these two samples, including their light curve and color evolution as well as their spectral features. To investigate a common powering mechanism we construct a grid of analytical model light curves with luminosity inputs from CSM interaction as well as <jats:sup>56</jats:sup>Ni radioactive decay. We find that models with ejecta masses of ≈1–3 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, CSM masses of ≈0.2–1 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, and CSM radii of ≈20–65 au can explain the diversity of peak luminosities, rise times, and decline rates observed in Type Ibn SNe and rapidly evolving transients. This suggests that a common progenitor system—the core collapse of a high-mass star within a dense CSM shell—can reproduce the light curves of even the most luminous and fast-evolving objects, such as AT 2018cow. This work is one of the first to reproduce the light curves of both SNe Ibn and other rapidly evolving transients with a single model.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Main-sequence radio pulse emitters (MRPs) are magnetic early-type stars from which periodic radio pulses, produced via electron cyclotron maser emission (ECME), are observed. Despite the fact that these stars can naturally offer suitable conditions for triggering ECME, only seven such stars have been reported so far within a span of more than two decades. In this paper, we report the discovery of eight more MRPs, thus more than doubling the sample size of such objects. These discoveries are the result of our sub-GHz observation program using the Giant Metrewave Radio Telescope over the years 2015–2021. Adding these stars to the previously known MRPs, we infer that at least 32% of the magnetic hot stars exhibit this phenomenon, thus suggesting that observation of ECME is not a rare phenomenon. The significantly larger sample of MRPs allows us for the first time to perform a statistical analysis comparing their physical properties. We present an empirical relation that can be used to predict whether a magnetic hot star is likely to produce ECME. Our preliminary analysis suggests that the physical parameters that play the primary role in the efficiency of the phenomenon are the maximum surface magnetic field strength and the surface temperature. In addition, we present strong evidence of the influence of the plasma density distribution on ECME pulse profiles. Results of this kind further motivate the search for MRPs, as a robust characterization of the relation between observed ECME properties and stellar physical parameters can only be achieved with a large sample.</jats:p>