Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Using a suite of self-similar cosmological simulations, we measure the probability distribution functions (PDFs) of real-space density, redshift-space density, and their geometric mean. We find that the real-space density PDF is well-described by a function of two parameters: <jats:italic>n</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub>, the spectral slope, and <jats:italic>σ</jats:italic> <jats:sub> <jats:italic>L</jats:italic> </jats:sub>, the linear rms density fluctuation. For redshift-space density and the geometric mean of real- and redshift-space densities, we introduce a third parameter, <jats:inline-formula> <jats:tex-math> <?CDATA ${s}_{L}=\sqrt{\langle {\left({{dv}}_{\mathrm{pec}}^{L}/{dr}\right)}^{2}\rangle }/H$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msqrt> <mml:mrow> <mml:mo stretchy="false">〈</mml:mo> <mml:msup> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="italic">dv</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>pec</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> </mml:msubsup> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="italic">dr</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">〉</mml:mo> </mml:mrow> </mml:msqrt> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi>H</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5e9fieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. We find that density PDFs for the LCDM cosmology is also well-parameterized by these three parameters. As a result, we are able to use a suite of self-similar cosmological simulations to approximate density PDFs for a range of cosmologies. We make the density PDFs publicly available and provide an analytical fitting formula for them.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present an analysis of 991 heartbeat stars (HBSs) from the OGLE Collection of Variable Stars. The sample consists of 512 objects located toward the Galactic bulge, 439 in the Large Magellanic Cloud, and 40 in the Small Magellanic Cloud. We model the <jats:italic>I</jats:italic>-band OGLE light curves using an analytical model of flux variations reflecting tidal deformations between stars. We present distributions of the model parameters that include the eccentricity, orbital inclination, and argument of the periastron but also the period–amplitude diagrams. On the Hertzsprung–Russell diagram, our HBS sample forms two separate groups of different evolutionary status. The first group, including about 90 systems with short orbital periods (<jats:italic>P</jats:italic> ≲ 50 days), consists of an early-type primary star lying on (or close to) the main sequence. The second group, including about 900 systems with long orbital periods (<jats:italic>P</jats:italic> ≳ 100 days), contains a red giant (RG). The position of the RG HBSs on the period–luminosity diagram strongly indicates their binary nature. They appear to be a natural extension of confirmed binary systems that include the OGLE ellipsoidal and long secondary period variables. We also present a time-series analysis leading to detection of tidally excited oscillations (TEOs). We identify such pulsations in about 5% of stars in the sample with a total of 78 different modes. This first relatively large homogeneous sample of TEOs allowed us to construct a diagram revealing the correlation between the TEO’s orbital harmonic number and the eccentricity of the host binary system.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a new reconstruction of the distribution of atomic hydrogen in the inner Galaxy that is based on explicit radiation transport modeling of line and continuum emission and a gas-flow model in the barred Galaxy that provides distance resolution for lines of sight toward the Galactic center. The main benefits of the new gas model are (a) the ability to reproduce the negative line signals seen with the HI4PI survey and (b) the accounting for gas that primarily manifests itself through absorption. We apply the new model of Galactic atomic hydrogen to an analysis of the diffuse gamma-ray emission from the inner Galaxy, for which an excess at a few GeV was reported that may be related to dark matter. We find with high significance an improved fit to the diffuse gamma-ray emission observed with the Fermi-LAT, if our new H <jats:sc>i</jats:sc> model is used to estimate the cosmic-ray induced diffuse gamma-ray emission. The fit still requires a nuclear bulge at high significance. Once this is included there is no evidence of a dark-matter signal, be it cuspy or cored. But an additional so-called boxy bulge is still favored by the data. This finding is robust under the variation of various parameters, for example, the excitation temperature of atomic hydrogen, and a number of tests for systematic issues.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Identifying the material source of coronal mass ejections (CMEs) is crucial for understanding the generation mechanisms of CMEs. The composition parameters of interplanetary coronal mass ejections (ICMEs) associated with different activities on the Sun may be diverse, as the materials come from distinct regions or are generated by different processes. We classified ICMEs into three types by associated activities on the Sun, with (T1) and without (T3) flares and hot channels, and only associated with flares (T2). The composition parameters of each type of ICMEs were analyzed. We found that all CMEs with hot channels are accompanied by flares, and strong flares are all associated with hot channels in our database. The average length of the filaments in T1 cases are much shorter than those in T3 cases. The average charge states of iron (<jats:italic>Q</jats:italic> <jats:sub>Fe</jats:sub>) and helium abundance (<jats:italic>A</jats:italic> <jats:sub>He</jats:sub>) for T3 ICMEs are less than 12% and 7%, respectively. The <jats:italic>Q</jats:italic> <jats:sub>Fe</jats:sub> and <jats:italic>A</jats:italic> <jats:sub>He</jats:sub> for T1 ICMEs present clear bimodal distributions with the minimum between two peaks at 12% and 7%, respectively. Nearly two-thirds of the hot plasma (with higher <jats:italic>Q</jats:italic> <jats:sub>Fe</jats:sub>) inside ICMEs is associated with higher <jats:italic>A</jats:italic> <jats:sub>He</jats:sub>. The <jats:italic>Q</jats:italic> <jats:sub>Fe</jats:sub> and <jats:italic>A</jats:italic> <jats:sub>He</jats:sub> are both positively correlated with the flare intensities. The <jats:italic>A</jats:italic> <jats:sub>He</jats:sub> and filament scales are not explicitly linked to each other. The statistical results demonstrate that the material contribution of the filaments to ICMEs is low and more than half of the hot materials inside ICMEs originate from the chromosphere in our database. We suggest that they are heated by the chromospheric evaporation process at the hot channel (flux rope) footpoint regions before and/or during the flaring process.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The X-ray binary pulsar XTE J1829-098 has been observed at extremely low luminosities for its spin period of 7.8448 s. Although its distance is uncertain by a factor of 4, the lowest observed X-ray fluxes may not correspond to its minimal-accretion propeller state or to nonaccreting states occurring at even lower X-ray luminosities, in which case the source has been caught at the bottom of the Corbet gap. We analyze all proposed distances <jats:italic>D</jats:italic> to the binary and the lowest X-ray fluxes, and we find only two physically acceptable solutions: (a) For <jats:italic>D</jats:italic> = 4.5 kpc (if the companion is a main-sequence B0 star), the neutron star is canonical with mass 1.41 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, radius 10.1 km, and a purely dipolar magnetic field as indicated by a cyclotron absorption line detected at 15 keV. In this case, the source has been observed at the bottom of the Corbet gap, the third high-mass X-ray binary pulsar to be caught in this state after the “twins” 4U 0115+63 and V 0332+53 found by Tsygankov et al. (b) For <jats:italic>D</jats:italic> = 18 kpc (if the companion is a B0.5Ib supergiant), the neutron star is ultramassive with mass 2.62 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, radius 18.7 km, and a dominant nondipolar magnetic field <jats:italic>B</jats:italic> <jats:sub>mul</jats:sub> = 1.26 TG (versus a dipolar component of only <jats:italic>B</jats:italic> <jats:sub>dip</jats:sub> = 0.43 TG). In this case, the source has been observed in its propeller state.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present fully relativistic predictions for the electromagnetic emission produced by accretion disks surrounding spinning and nonspinning supermassive binary black holes on the verge of merging. We use the code <jats:monospace>Bothros</jats:monospace> to post-process data from 3D general relativistic magnetohydrodynamic simulations via ray-tracing calculations. These simulations model the dynamics of a circumbinary disk and the mini-disks that form around two equal-mass black holes orbiting each other at an initial separation of 20 gravitational radii, and evolve the system for more than 10 orbits in the inspiral regime. We model the emission as the sum of thermal blackbody radiation emitted by an optically thick accretion disk and a power-law spectrum extending to hard X-rays emitted by a hot optically thin corona. We generate time-dependent spectra, images, and light curves at various frequencies to investigate intrinsic periodic signals in the emission, as well as the effects of the black hole spin. We find that prograde black hole spin makes mini-disks brighter since the smaller innermost stable circular orbit angular momentum demands more dissipation before matter plunges to the horizon. However, compared to mini-disks in larger separation binaries with spinning black holes, our mini-disks are less luminous: unlike those systems, their mass accretion rate is lower than in the circumbinary disk, and they radiate with lower efficiency because their inflow times are shorter. Compared to a single black hole system matched in mass and accretion rate, these binaries have spectra noticeably weaker and softer in the UV. Finally, we discuss the implications of our findings for the potential observability of these systems.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on the discovery of an absorption line at <jats:inline-formula> <jats:tex-math> <?CDATA $E={8.56}_{-0.11}^{+0.05}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>E</mml:mi> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>8.56</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.11</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.05</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5e37ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> keV detected with a significance of &gt;3.3<jats:italic>σ</jats:italic> in the NuSTAR and XMM-Newton spectra of a newly discovered hyperluminous X-ray source (<jats:italic>L</jats:italic> <jats:sub>X</jats:sub> &gt; 10<jats:sup>41</jats:sup> erg s<jats:sup>−1</jats:sup>) in the galaxy NGC 4045 at a distance of 32 Mpc. The source was first discovered serendipitously in a Swift/XRT observation of the galaxy, and Swift monitoring reveals a highly variable source changing by over an order of magnitude from maximum to minimum. The origin of the absorption line appears likely to be from highly ionized iron with a blueshift of 0.19<jats:italic>c</jats:italic>, indicating an ultrafast outflow. However, the large equivalent width of the line (<jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{EW}=-{0.22}_{-0.09}^{+0.08}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>EW</mml:mi> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0.22</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.09</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.08</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5e37ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> keV) paired with the lack of other absorption lines detected is difficult to reconcile with models. An alternative explanation is that the line is due to a cyclotron resonance scattering feature produced by the interaction of X-ray photons with the powerful magnetic field of a neutron star.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In recent years, many Type IIn supernovae have been found to share striking similarities with the peculiar SN 2009ip, whose true nature is still under debate. Here, we present 10 yr of observations of SN 2011fh, an interacting transient with spectroscopic and photometric similarities to SN 2009ip. SN 2011fh had an <jats:italic>M</jats:italic> <jats:sub> <jats:italic>r</jats:italic> </jats:sub> ∼ −16 mag brightening event, followed by a brighter <jats:italic>M</jats:italic> <jats:sub> <jats:italic>r</jats:italic> </jats:sub> ∼ −18 mag luminous outburst in 2011 August. The spectra of SN 2011fh are dominated by narrow to intermediate Balmer emission lines throughout its evolution, with P Cygni profiles indicating fast-moving material at ∼6400 km s<jats:sup>−1</jats:sup>. HST/WFC3 observations from 2016 October revealed a bright source with <jats:italic>M</jats:italic> <jats:sub>F814W</jats:sub> ≈ −13.3 mag, indicating that we are seeing the ongoing interaction of the ejecta with the circumstellar material or that the star might be going through an eruptive phase five years after the luminous outburst of 2011. Using HST photometry of the stellar cluster around SN 2011fh, we estimated an age of ∼4.5 Myr for the progenitor, which implies a stellar mass of ∼60 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, using single-star evolution models, or a mass range of 35–80 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, considering a binary system. We also show that the progenitor of SN 2011fh exceeded the classical Eddington limit by a large factor in the months preceding the luminous outburst of 2011, suggesting strong super-Eddington winds as a possible mechanism for the observed mass loss. These findings favor an energetic outburst in a young and massive star, possibly a luminous blue variable.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The physical origin of fast radio bursts (FRBs) remains unclear. Finding multiwavelength counterparts of FRBs can provide a breakthrough for understanding their nature. In this work, we perform a systematic search for astronomical transients whose positions are consistent with FRBs. We find an unclassified optical transient AT2020hur (<jats:italic>α</jats:italic> = 01<jats:sup>h</jats:sup>58<jats:sup>m</jats:sup>00.ˢ750 ± 1″, <jats:inline-formula> <jats:tex-math> <?CDATA $\delta =65^\circ {43}^{{\prime} }00\buildrel{\prime\prime}\over{.} 30\pm 1^{\prime\prime} $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>δ</mml:mi> <mml:mo>=</mml:mo> <mml:mn>65</mml:mn> <mml:mo>°</mml:mo> <mml:msup> <mml:mrow> <mml:mn>43</mml:mn> </mml:mrow> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> </mml:msup> <mml:mn>00</mml:mn> <mml:mo>.″</mml:mo> <mml:mn>30</mml:mn> <mml:mo>±</mml:mo> <mml:mn>1</mml:mn> <mml:mo accent="false">″</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5d5aieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) that is spatially coincident with the repeating FRB 180916B (<jats:italic>α</jats:italic> = 01<jats:sup>h</jats:sup>58<jats:sup>m</jats:sup>00.ˢ7502 ± 2.3 mas, <jats:inline-formula> <jats:tex-math> <?CDATA $\delta =65^\circ {43}^{{\prime} }00\buildrel{\prime\prime}\over{.} 3152\pm 2.3$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>δ</mml:mi> <mml:mo>=</mml:mo> <mml:mn>65</mml:mn> <mml:mo>°</mml:mo> <mml:msup> <mml:mrow> <mml:mn>43</mml:mn> </mml:mrow> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> </mml:msup> <mml:mn>00</mml:mn> <mml:mo>.″</mml:mo> <mml:mn>3152</mml:mn> <mml:mo>±</mml:mo> <mml:mn>2.3</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5d5aieqn2.gif" xlink:type="simple" /> </jats:inline-formula> mas; Marcote et al. 2020). The chance possibility of the AT2020hur–FRB 180916B association is about 0.04%, which corresponds to a significance of 3.5<jats:italic>σ</jats:italic>. We develop a giant flare (GF) afterglow model to fit AT2020hur. Although the GF afterglow model can interpret the observations of AT2020hur, the derived kinetic energy of such a GF is at least three orders of magnitude larger than that of a typical GF, and a lot of fine-tuning and coincidences are required for this model. Another possible explanation is that AT2020hur might consist of two or more optical flares originating from the FRB source, e.g., fast optical bursts produced by the inverse Compton scattering of FRB emission. Besides, AT2020hur is located in one of the activity windows of FRB 180916B, which provides independent support for the association. This coincidence may be due to the optical counterparts being subject to the same periodic modulation as FRB 180916B, as implied by the prompt FRB counterparts. Future simultaneous observations of FRBs and their optical counterparts may help to reveal their physical origin.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Cepheid variables in the Small Magellanic Cloud (SMC), the Large Magellanic Cloud (LMC), the Milky Way, M33, and M31 are used to examine the dependence of pulsation mode on metallicity, which was previously found in red supergiants. The initial samples of Cepheids are collected from the Cepheid catalogs identified from the Optical Gravitational Lensing Experiment, PS1, DIRECT, Wide-field Infrared Survey Explorer, and Zwicky Transient Facility surveys. The contaminants are removed with the help of the Gaia/EDR3 astrometric information for extra galaxies or by comparing the geometric distance and the distance from the <jats:italic>P</jats:italic>–<jats:italic>L</jats:italic> relation for the Milky Way. The division of fundamental (FU) and first-overtone (1O) modes is refined according to the gap between the two modes in the <jats:italic>P</jats:italic>–<jats:italic>L</jats:italic> diagram of the objects in each galaxy. The ratio of FU/(FU+1O) is found to be 0.59, 0.60, 0.69, 0.83, and 0.85 for the SMC, the LMC, the Milky Way, M33, and M31, respectively, in order of metallicity, which confirms that the pulsation mode depends on metallicity in the way that the ratio of FU/(FU+1O) increases with metallicity. This dependence is not changed if the incompleteness of the samples is taken into account.</jats:p>