Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>In the context of cosmic microwave background data analysis, we study the solution to the equation that transforms scanning data into a map. As originally suggested in “messenger” methods for solving linear systems, we split the noise covariance into uniform and nonuniform parts and adjust their relative weights during the iterative solution. With simulations, we study mock instrumental data with different noise properties, and find that this “cooling” or perturbative approach is particularly effective when there is significant low-frequency noise in the timestream. In such cases, a conjugate gradient algorithm applied to this modified system converges faster and to a higher fidelity solution than the standard conjugate gradient approach. We give an analytic estimate for the parameter that controls how gradually the linear system should change during the course of the solution.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We perform a hierarchical Bayesian inference to investigate the population properties of the coalescing compact binaries involving at least one neutron star (NS). With the current gravitational-wave (GW) observation data, we can rule out none of the double Gaussian, single Gaussian, and uniform NS mass distribution models, though a specific double Gaussian model inferred from the Galactic NSs is found to be slightly more preferred. The mass distribution of black holes (BHs) in the neutron star–black hole (NSBH) population is found to be similar to that in the Galactic X-ray binaries. Additionally, the ratio of the merger rate densities between NSBHs and BNSs is estimated to be ∼3:7. The spin properties of the binaries, though constrained relatively poorly, play a nontrivial role in reconstructing the mass distribution of NSs and BHs. We find that a perfectly aligned spin distribution can be ruled out, while a purely isotropic distribution of spin orientation is still allowed. To evaluate the feasibility of reliably determining the population properties of NSs in the coalescing compact binaries with upcoming GW observations, we perform simulations with a mock population. We find that with 100 detections (including BNSs and NSBHs) the mass distribution of NSs can be well determined, and the fraction of BNSs can also be accurately estimated.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this work, we propose an accreting stellar binary model for understanding the active periodic fast radio bursts (FRBs). The system consists of a stellar compact object (CO) and a donor star (DS) companion in an eccentric orbit, where the DS fills its own Roche lobe near the periastron. The CO accretes the material from the DS and then drives relativistic magnetic blobs. The interaction between the magnetic blobs and the stellar wind of the DS produces a pair of shocks. We find that both the reverse shock and the forward shock are likely to produce FRBs via the synchrotron maser mechanism. We show that this system can in principle sufficiently produce highly active FRBs with a long lifetime, and also can naturally explain the periodicity and the duty cycle of the activity that appeared in FRBs 180916 and 121102. The radio nebula excited by the long-term injection of magnetic blobs into the surrounding environment may account for the associated persistent radio source. In addiction, we discuss the possible multiwavelength counterparts of FRB 180916 in the context of this model. Finally, we encourage the search for FRBs in ultraluminous X-ray sources.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The absorption feature in the global spectrum is likely the first 21 cm observable from the cosmic dawn, which provides valuable insights into the earliest history of structure formation. We run a set of high-resolution hydrodynamic simulations of early structure formation to assess the effect of nonlinear structure formation on the maximum absorption level (i.e., assuming the spin temperature coupling is saturated) of the global 21 cm spectrum in the standard cosmological framework. We ignore the star formation and feedbacks, which also tend to reduce the absorption signal, but take into account the inevitable nonlinear density fluctuations in the intergalactic medium (IGM), shock-heating, and Compton-heating, which can reduce the absorption level. We found that the combination of these reduced the maximum absorption signal by ∼15% at redshift 17, as compared with the homogeneous or linearly-fluctuating IGM. These effects have to be carefully accounted for when interpreting the observational results, especially when considering the necessity of introducing new physics.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>During galaxy merger events, the supermassive black holes in the center of the galaxies may form a pair of active galactic nuclei (AGN) with kiloparsec-scale or even parsec-scale separation. Recently, optical observations revealed a promising dual-AGN candidate at the center of the galaxy SDSS J101022.95+141300.9 (hereafter J1010+1413). The presence of two distinct [O <jats:sc>iii</jats:sc>]-emitting point sources with a projected separation of ∼430 pc indicates a dual-AGN system. To search for AGN-dominated radio emission originating from the Hubble Space Telescope (HST) point sources, we carried out very long baseline interferometry observations. We resolved the radio structure of J1010+1413 and detected a single feature offset from the HST point sources and also from the Gaia optical position of the object. Our multiwavelength analysis of J1010+1413 inferred two possible interpretations of the observed properties challenging its proposed dual-AGN classification.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Electromagnetic waves due to electron–positron clouds (bunches), created by cascading processes in pulsar magnetospheres, have been proposed to explain the pulsar radio emission. In order to verify this hypothesis, we utilized for the first time Particle-in-Cell (PIC) code simulations to study the nonlinear evolution of electron–positron bunches dependant on the initial relative drift speeds of electrons and positrons, plasma temperature, and distance between the bunches. For this sake, we utilized the PIC code ACRONYM with a high-order field solver and particle weighting factor, appropriate to describe relativistic pair plasmas. We found that the bunch expansion is mainly determined by the relative electron–positron drift speed. Finite drift speeds were found to cause the generation of strong electrostatic superluminal waves at the bunch density gradients that reach up to <jats:italic>E</jats:italic> ∼ 7.5 × 10<jats:sup>5</jats:sup> V cm<jats:sup>−1</jats:sup> (<jats:italic>E</jats:italic>/(<jats:italic>m</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> <jats:italic>c</jats:italic> <jats:italic>ω</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub> <jats:italic>e</jats:italic> <jats:sup>−1</jats:sup>) ∼ 4.4) and strong plasma heating. As a result, up to 15% of the initial kinetic energy is transformed into the electric field energy. Assuming the same electron and positron distributions, we found that the fastest (in the bunch reference frame) particles of consecutively emitted bunches eventually overlap in momentum (velocity) space. This overlap causes two-stream instabilities that generate electrostatic subluminal waves with electric field amplitudes reaching up to <jats:italic>E</jats:italic> ∼ 1.9 × 10<jats:sup>4</jats:sup> V cm<jats:sup>−1</jats:sup> (<jats:italic>E</jats:italic>/(<jats:italic>m</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> <jats:italic>c</jats:italic> <jats:italic>ω</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub> <jats:italic>e</jats:italic> <jats:sup>−1</jats:sup>) ∼ 0.11). We found that in all simulations the evolution of electron–positron bunches may lead to the generation of electrostatic superluminal or subluminal waves, which, in principle, can be behind the observed electromagnetic emissions of pulsars in the radio wave range.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We explore the observational appearance of the merger of a low-mass star with a white dwarf (WD) binary companion. We are motivated by recent work finding that multiple tensions between the observed properties of cataclysmic variables (CVs) and standard evolution models are resolved if a large fraction of CV binaries merge as a result of unstable mass transfer. Tidal disruption of the secondary forms a geometrically thick disk around the WD, which subsequently accretes at highly super-Eddington rates. Analytic estimates and numerical hydrodynamical simulations reveal that outflows from the accretion flow unbind a large fraction ≳90% of the secondary at velocities ∼500–1000 km s<jats:sup>−1</jats:sup> within days of the merger. Hydrogen recombination in the expanding ejecta powers optical transient emission lasting about a month with a luminosity ≳10<jats:sup>38</jats:sup> erg s<jats:sup>−1</jats:sup>, similar to slow classical novae and luminous red novae from ordinary stellar mergers. Over longer timescales the mass accreted by the WD undergoes hydrogen shell burning, inflating the remnant into a giant of luminosity ∼300–5000 <jats:italic>L</jats:italic> <jats:sub>⊙</jats:sub>, effective temperature <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> ≈ 3000 K, and lifetime ∼10<jats:sup>4</jats:sup>–10<jats:sup>5</jats:sup> yr. We predict that ∼10<jats:sup>3</jats:sup>–10<jats:sup>4</jats:sup> Milky Way giants are CV merger products, potentially distinguishable by atypical surface abundances. We explore whether any Galactic historical slow classical novae are masquerading CV mergers by identifying four such post-nova systems with potential giant counterparts for which a CV merger origin cannot be ruled out. We address whether the historical transient CK Vul and its gaseous/dusty nebula resulted from a CV merger.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have theoretically determined the absorption oscillator strengths and wavenumbers for rotationally resolved transitions of the c<jats:sub>4</jats:sub>′<jats:sup>1</jats:sup>Σ<jats:sub>u</jats:sub> <jats:sup>+</jats:sup> (6)-X<jats:sup>1</jats:sup>Σ<jats:sub>g</jats:sub> <jats:sup>+</jats:sup>(0–9) bands of N<jats:sub>2</jats:sub>, which are relevant to analyze the spectra of planetary atmospheres. The Molecular Quantum Defect Orbital method has been used in our calculations. The interaction between the c<jats:sub>4</jats:sub>′<jats:sup>1</jats:sup>Σ<jats:sub>u</jats:sub> <jats:sup>+</jats:sup> (6) Rydberg state and the b′<jats:sup>1</jats:sup>Σ<jats:sub>u</jats:sub> <jats:sup>+</jats:sup> valence states has been considered using an adequate rovibronic energy matrix. In addition, we have calculated the lifetimes of the rotational levels of the c<jats:sub>4</jats:sub>′<jats:sup>1</jats:sup>Σ<jats:sub>u</jats:sub> <jats:sup>+</jats:sup> (6) state. We hope that the reported data, most of them for the first time, can be useful in the interpretation of planetary atmospheres where N<jats:sub>2</jats:sub> is present.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present an improved weak-lensing (WL) study of the high-<jats:italic>z</jats:italic> (<jats:italic>z</jats:italic> = 0.87) merging galaxy cluster ACT-CL J0102–4915 (“El Gordo”) based on new wide-field Hubble Space Telescope imaging data. The new imaging data cover the ∼3.5 × ∼3.5 Mpc region centered on the cluster and enable us to detect WL signals beyond the virial radius, which was not possible in previous studies. We confirm the binary mass structure consisting of the northwestern (NW) and southeastern (SE) subclusters and the ∼2<jats:italic>σ</jats:italic> dissociation between the SE mass peak and the X-ray cool core. We obtain the mass estimates of the subclusters by simultaneously fitting two Navarro–Frenk–White (NFW) halos without employing mass–concentration relations. The masses are <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{200c}^{\mathrm{NW}}={9.9}_{-2.2}^{+2.1}\,\times $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>200</mml:mn> <mml:mi>c</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>NW</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>9.9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2.2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2.1</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em" /> <mml:mo>×</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac294fieqn1.gif" xlink:type="simple" /> </jats:inline-formula> 10<jats:sup>14</jats:sup> and <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{200c}^{\mathrm{SE}}={6.5}_{-1.4}^{+1.9}\,\times $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>200</mml:mn> <mml:mi>c</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>SE</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>6.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.9</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em" /> <mml:mo>×</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac294fieqn2.gif" xlink:type="simple" /> </jats:inline-formula> 10<jats:sup>14</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> for the NW and SE subclusters, respectively. The mass ratio is consistent with our previous WL study but significantly different from the previous strong-lensing results. This discrepancy is attributed to the use of extrapolation in strong-lensing studies because the SE component possesses a higher concentration. By superposing the two best-fit NFW halos, we determine the total mass of El Gordo to be <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{200c}={2.13}_{-0.23}^{+0.25}\,\times $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>200</mml:mn> <mml:mi>c</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>2.13</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.23</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.25</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em" /> <mml:mo>×</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac294fieqn3.gif" xlink:type="simple" /> </jats:inline-formula> 10<jats:sup>15</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, which is ∼23% lower than our previous WL result [<jats:italic>M</jats:italic> <jats:sub>200<jats:italic>c</jats:italic> </jats:sub> = (2.76 ± 0.51) × 10<jats:sup>15</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>]. Our updated mass is a more direct measurement, since we are not extrapolating to <jats:italic>R</jats:italic> <jats:sub>200<jats:italic>c</jats:italic> </jats:sub> as in all previous studies. The new mass is compatible with the current ΛCDM cosmology.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Supervised machine-learning models are trained with various molecular descriptors to predict infrared (IR) emission spectra of interstellar polycyclic aromatic hydrocarbons. We demonstrate that a feature importance analysis based on the random forest algorithm can be utilized to explore the physical correlation between emission features. Astronomical correlations between IR bands are analyzed as examples of demonstration by finding the common molecular fragments responsible for different bands, which improves the current understanding of the long-observed correlations. We propose a way to quantify the band correlation by measuring the similarity of the feature importance arrays of different bands, by which a correlation map is obtained for emissions in the out-of-plane bending region. Moreover, a comparison between the predictions using different combinations of descriptors underscores the strong prediction power of the extended-connectivity molecular fingerprint, and shows that the combinations of multiple descriptors of other types in general lead to improved predictivity.</jats:p>