Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Star-forming galaxies are the sources likely to have reionized the universe. As we cannot observe them directly due to the opacity of the intergalactic medium at <jats:italic>z</jats:italic> ≳ 5, we study <jats:italic>z</jats:italic> ∼ 3–5 galaxies as proxies to place observational constraints on cosmic reionization. Using new deep Hubble Space Telescope rest-frame UV F336W and F435W imaging (30 orbits, ∼40 arcmin<jats:sup>2</jats:sup>, ∼29–30 mag depth at 5<jats:italic>σ</jats:italic>), we attempt to identify a sample of Lyman continuum galaxies (LCGs). These are individual sources that emit ionizing flux below the Lyman break (&lt;912 Å). This population would allow us to constrain cosmic reionization parameters such as the number density and escape fraction (<jats:italic>f</jats:italic> <jats:sub>esc</jats:sub>) of ionizing sources. We compile a comprehensive parent sample that does not rely on the Lyman-break technique for redshifts. We present three new spectroscopic candidates at <jats:italic>z</jats:italic> ∼ 3.7–4.4 and 32 new photometric candidates. The high-resolution multiband HST imaging and new Keck/Low Resolution Imaging Spectrometer (LRIS) redshifts make these promising spectroscopic LCG candidates. Using both a traditional and a probabilistic approach, we find that the most likely <jats:italic>f</jats:italic> <jats:sub>esc</jats:sub> values for the three spectroscopic LCG candidates are &gt;100% and therefore not physical. We are unable to confirm the true nature of these sources with the best available imaging and direct blue Keck/LRIS spectroscopy. More spectra, especially from the new class of 30 m telescopes, will be required to build a statistical sample of LCGs to place firm observational constraints on cosmic reionization.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Gamma-ray burst (GRB) afterglow emission can be observed from sub-TeV to radio wavelengths, though only 6.6% of observed GRBs present radio afterglows. We examine GRB radio light curves (LCs) to look for the presence of radio plateaus resembling the plateaus observed at X-ray and optical wavelengths. We analyze 404 GRBs from the literature with observed radio afterglow and fit 82 GRBs with at least five data points with a broken power-law model, requiring four parameters. From these, we find 18 GRBs that present a break feature resembling a plateau. We conduct the first multiwavelength study of the Dainotti correlation between the luminosity <jats:italic>L</jats:italic> <jats:sub> <jats:italic>a</jats:italic> </jats:sub> and the rest-frame time of break <jats:italic>T</jats:italic> <jats:sub> <jats:italic>a</jats:italic> </jats:sub>* for those 18 GRBs, concluding that the correlation exists and resembles the corresponding correlation at X-ray and optical wavelengths after correction for evolutionary effects. We compare <jats:italic>T</jats:italic> <jats:sub> <jats:italic>a</jats:italic> </jats:sub>* for the radio sample with <jats:italic>T</jats:italic> <jats:sub> <jats:italic>a</jats:italic> </jats:sub>* values in X-ray and optical data, finding significantly later break times in the radio. We propose that this late break time and the compatibility in slope suggest either a long-lasting plateau or the passage of a spectral break in the radio band. We also correct the distribution of the isotropic energy <jats:italic>E</jats:italic> <jats:sub>iso</jats:sub> versus the rest-frame burst duration <jats:italic>T</jats:italic> <jats:sup>*</jats:sup> <jats:sub>90</jats:sub> for evolutionary effects and conclude that there is no significant difference between the <jats:italic>T</jats:italic>*<jats:sub>90</jats:sub> distributions for the radio LCs with a break and for those without.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present panchromatic observations and modeling of supernova (SN) 2020tlf, the first normal Type II-P/L SN with confirmed precursor emission, as detected by the Young Supernova Experiment transient survey. Pre-SN activity was detected in <jats:italic>riz</jats:italic>-bands at −130 days and persisted at relatively constant flux until first light. Soon after discovery, “flash” spectroscopy of SN 2020tlf revealed narrow, symmetric emission lines that resulted from the photoionization of circumstellar material (CSM) shed in progenitor mass-loss episodes before explosion. Surprisingly, this novel display of pre-SN emission and associated mass loss occurred in a red supergiant (RSG) progenitor with zero-age main-sequence mass of only 10–12 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, as inferred from nebular spectra. Modeling of the light curve and multi-epoch spectra with the non-LTE radiative-transfer code CMFGEN and radiation-hydrodynamical code HERACLES suggests a dense CSM limited to <jats:italic>r</jats:italic> ≈ 10<jats:sup>15</jats:sup> cm, and mass-loss rate of 10<jats:sup>−2</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>. The luminous light-curve plateau and persistent blue excess indicates an extended progenitor, compatible with an RSG model with <jats:italic>R</jats:italic> <jats:sub>⋆</jats:sub> = 1100 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub>. Limits on the shock-powered X-ray and radio luminosity are consistent with model conclusions and suggest a CSM density of <jats:italic>ρ</jats:italic> &lt; 2 × 10<jats:sup>−16</jats:sup> g cm<jats:sup>−3</jats:sup> for distances from the progenitor star of <jats:italic>r</jats:italic> ≈ 5 × 10<jats:sup>15</jats:sup> cm, as well as a mass-loss rate of <jats:inline-formula> <jats:tex-math> <?CDATA $\dot{M}\lt 1.3\times {10}^{-5}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$?> </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>&lt;</mml:mo> <mml:mn>1.3</mml:mn> <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="apjac3f3aieqn1.gif" xlink:type="simple" /> </jats:inline-formula> at larger distances. A promising power source for the observed precursor emission is the ejection of stellar material following energy disposition into the stellar envelope as a result of gravity waves emitted during either neon/oxygen burning or a nuclear flash from silicon combustion.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The effects of the <jats:italic>ϕ</jats:italic> meson on the properties of hyperon stars are studied systematically in the framework of the density-dependent relativistic mean field (DDRMF) model. The <jats:italic>ϕ</jats:italic> meson shifts the hyperon threshold to a higher density and reduces the hyperon fractions in neutron star cores. It also strongly stiffens the equation of state calculated with various DDRMF effective interactions and increases the maximum mass of hyperon stars, but only a few effective interactions survive under the constraints from recent astrophysical observations. In the DDRMF model, the conformal limit of the sound velocity is still in strong tension with the fact that the maximum mass of neutron stars obtained in theoretical calculations reaches about 2 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. Based on different interior composition assumptions, we discuss the possibility of the secondary object of GW190814 as a neutron star. When the <jats:italic>ϕ</jats:italic> meson is considered, DD-ME2 and DD-MEX support the possibility that the secondary object of GW190814 is a hyperon star rapidly rotating with Kepler frequency.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present new radio and optical data, including very-long-baseline interferometry, as well as archival data analysis, for the luminous, decades-long radio transient FIRST J141918.9+394036. The radio data reveal a synchrotron self-absorption peak around 0.3 GHz and a radius of around 1.3 mas (0.5 pc) 26 yr post-discovery, indicating a blastwave energy ∼5 × 10<jats:sup>50</jats:sup> erg. The optical spectrum shows a broad [O <jats:sc>iii</jats:sc>]<jats:italic>λ</jats:italic>4959,5007 emission line that may indicate collisional excitation in the host galaxy, but its association with the transient cannot be ruled out. The properties of the host galaxy are suggestive of a massive stellar progenitor that formed at low metallicity. Based on the radio light curve, blastwave velocity, energetics, nature of the host galaxy and transient rates, we find that the properties of J1419+3940 are most consistent with long gamma-ray burst (LGRB) afterglows. Other classes of (optically discovered) stellar explosions as well as neutron star mergers are disfavored, and invoking any exotic scenario may not be necessary. It is therefore likely that J1419+3940 is an off-axis LGRB afterglow (as suggested by Law et al. and Marcote et al.), and under this premise the inverse beaming fraction is found to be <jats:inline-formula> <jats:tex-math> <?CDATA ${f}_{b}^{-1}\simeq {280}_{-200}^{+700}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>f</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>b</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>≃</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>280</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>200</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>700</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3330ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, corresponding to an average jet half-opening angle <jats:inline-formula> <jats:tex-math> <?CDATA $\lt {\theta }_{j}\gt \simeq {5}_{-2}^{+4}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>&lt;</mml:mo> <mml:msub> <mml:mrow> <mml:mi>θ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>j</mml:mi> </mml:mrow> </mml:msub> <mml:mo>&gt;</mml:mo> <mml:mo>≃</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3330ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> degrees (68% confidence), consistent with previous estimates. From the volumetric rate we predict that surveys with the Very Large Array, Australian Square Kilometre Array Pathfinder, and MeerKAT will find a handful of J1419+3940-like events over the coming years.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This paper investigates the evolution of turbulence within the magnetotail reconnection exhaust observed by the Magnetospheric Multiscale spacecraft. The reconnection was in an unsteady state that caused significant temporal variations in the outflow speed. By dividing the exhaust into nine fast flows, we analyzed and compared the characteristics of turbulence in these nine flows. We find that the strength of the intermittency has a good relationship with the peak speed of the fast flows. The higher-order analysis of magnetic field fluctuations reveals that the turbulence is multifractal in the inertial range for these flows except one with the highest peak speed. Moreover, the turbulence is monofractal on kinetic scales in all of these fast flows. The magnetic energy was intermittently dissipated in these turbulent flows, predominantly occurred in the coherent structures. Since the coherent structures with the largest energy dissipation in these flows are different, we suggest that the mechanism of energy dissipation may be different among these flows.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Magnetic flux ropes are bundles of twisted magnetic field enveloping a central axis. They harbor free magnetic energy and can be progenitors of coronal mass ejections (CMEs). However, identifying flux ropes on the Sun can be challenging. One of the key coronal observables that has been shown to indicate the presence of a flux rope is a peculiar bright coronal structure called a sigmoid. In this work, we show Hinode EUV Imaging Spectrometer observations of sigmoidal active region (AR) 10977. We analyze the coronal plasma composition in the AR and its evolution as a sigmoid (flux rope) forms and erupts as a CME. Plasma with photospheric composition was observed in coronal loops close to the main polarity inversion line during episodes of significant flux cancellation, suggestive of the injection of photospheric plasma into these loops driven by photospheric flux cancellation. Concurrently, the increasingly sheared core field contained plasma with coronal composition. As flux cancellation decreased and a sigmoid/flux rope formed, the plasma evolved to an intermediate composition in between photospheric and typical AR coronal compositions. Finally, the flux rope contained predominantly photospheric plasma during and after a failed eruption preceding the CME. Hence, plasma composition observations of AR 10977 strongly support models of flux rope formation by photospheric flux cancellation forcing magnetic reconnection first at the photospheric level then at the coronal level.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>M51 ULX7 is among a small group of known ultraluminous X-ray pulsars (ULXPs). The neutron star powering the source has a spin period of 2.8 s, orbits its companion star with a period of 2 days, and a superorbital period of 38 days is evident in its X-ray lightcurve. Here we present NuSTAR and XMM-Newton data on the source from 2019 obtained when the source was near its peak brightness. We detect the pulsations, having spun up at a rate of 3 ± 0.5 × 10<jats:sup>−10</jats:sup> s s<jats:sup>−1</jats:sup> since they were previously detected in 2018. The data also provide the first high-quality broadband spectrum of the source. We find it to be very similar to that of other ULXPs, with two disk-like components, and a high-energy tail. When combined with XMM-Newton data obtained in 2018, we explore the evolution of the spectral components with superorbital phase, finding that the luminosity of the hotter component drives the superorbital flux modulation. The inclination the disk components appear to change with phase, which may support the idea that these superorbital periods are caused by disk precession. We also reexamine the superorbital period with 3 yr of Swift/XRT monitoring, finding that the period is variable, increasing from 38.2 ± 0.5 days in 2018–2019 to 44.2 ± 0.9 days in 2020–2021, which rules out alternative explanations for the superorbital period.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report a discovery of a double radio relic in the cluster merger ZwCl1447.2+2619 (<jats:italic>z</jats:italic> = 0.376) with uGMRT observations at 420 MHz and 700 MHz. The linear sizes of the northern and southern relics are ∼0.3 Mpc and ∼1.2 Mpc, respectively, which is consistent with the theoretical expectation that a larger relic is produced in the less massive subcluster side. However, ZwCl1447.2+2619 is unlike other known double radio relic systems, where the larger relics are much more luminous by several factors. In this merger, the higher surface brightness of the smaller northern relic makes its total radio luminosity comparable to that of the much larger southern relic. The surface brightness ratio ∼0.1 between the two radio relics differs significantly from the relation observed in other double radio relic systems. From our radio spectral analysis, we find that both relics signify similar weak shocks with Mach numbers of 2.9 ± 0.8 and 2.0 ± 0.7 for the northern and southern relics, respectively. Moreover, the northern relic is connected to a discrete radio source with an optical counterpart, which indicates the possible presence of cosmic-ray injection and reacceleration. Therefore, we propose that this atypical surface brightness ratio can be explained with the particle acceleration efficiency precipitously dropping in the weak shock regime and/or with reacceleration of fossil cosmic rays. Our multi-wavelength analysis and numerical simulation suggest that ZwCl1447.2+2619 is a postmerger, which has experienced a near head-on collision ∼0.7 Gyr ago.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We analyze low-resolution Spitzer infrared (IR) 5−14 <jats:italic>μ</jats:italic>m spectra of the diffuse emission toward a carefully selected sample of stars. The sample is composed of sight lines toward stars that have well-determined ultraviolet (UV) extinction curves and that are shown to lie beyond effectively all of the extinguishing and emitting dust along their lines of sight. Our sample includes sight lines whose UV curve extinction curves exhibit a wide range of curve morphology and that sample a variety of interstellar environments. As a result, this unique sample enabled us to study the connection between the extinction and emission properties of the same grains, and to examine their response to different physical environments. We quantify the emission features in terms of the polycyclic aromatic hydrocarbon (PAH) model given by Draine &amp; Li and a set on additional features not known to be related to PAH emission. We compare the intensities of the different features in the Spitzer mid-infrared spectra with the Fitzpatrick &amp; Massa parameters that describe the shapes of UV to near-infrared extinction curves. Our primary result is that there is a strong correlation between the area of the 2175 Å UV bump in the extinction curves of the program stars and the strengths of the major PAH emission features in the mid-infrared spectra for the same lines of sight.</jats:p>