Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>iPTF14hls is a luminous Type II supernova (SN) with a bumpy light curve whose origin remains under debate. It maintains a roughly constant effective temperature and luminosity for about 600 days after discovery, followed by a slow decay. About ∼1000 days after discovery, the light curve transitions to a very steep decline. A spectrum taken during this steep-decline phase shows clear signatures of a shock interaction with a dense circumstellar medium (CSM). Here, we explore the possibility of iPTF14hls as an interaction-powered SN. The light curve of iPTF14hls can be fitted with wind-like CSMs. Analytic modeling indicates that iPTF14hls may have undertaken six episodes of mass loss during the last ∼200 yr. Assuming that the 1954 eruption triggered the last mass-loss episode, the stellar wind velocity is determined to be 40−70 km s<jats:sup>−1</jats:sup>, depending on different models. Mass-loss rates are in the range 0.4–3.3<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>. The inferred total mass of the ejecta and CSMs (<jats:italic>M</jats:italic> <jats:sub>ej</jats:sub> + <jats:italic>M</jats:italic> <jats:sub>CSMs</jats:sub> ≃ 245<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) supports the idea that iPTF14hls may be a candidate for a (pulsational) pair-instability SN. Discoveries and observations of similar stellar explosions will help us to understand these peculiar SNe.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Jet precessions are widely involved in astrophysical phenomena from galaxies to X-ray binaries and gamma-ray bursts (GRBs). Polarization presents a unique probe of the magnetic fields in GRB jets. The precession of GRB relativistic jets will change the geometry within the observable emitting region of the jet, which can potentially affect the polarization of the afterglow. In this paper, we take into account jet precession to study the polarization evolution and corresponding light curves in GRB early optical afterglows with ordered and random magnetic field geometries. We find that the jet precession in long-lived engines can significantly reduce the polarization degree (PD) regardless of the magnetic field structure. The strongest PD attenuation is found when the line of sight is aligned with the precession axis. Our results show that jet precession can provide new insight into the low PD measured in the early optical afterglows of GRBs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We evaluate the cosmological coalescence and detection rates for massive black hole (MBH) binaries targeted by the gravitational wave observatory Laser Interferometer Space Antenna (LISA). Our calculation starts with a population of gravitationally unbound MBH pairs, drawn from the TNG50-3 cosmological simulation, and follows their orbital evolution from kiloparsec scales all the way to coalescence using a semi-analytic model developed in our previous work. We find that for the majority of MBH pairs that coalesce within a Hubble time dynamical friction is the most important mechanism that determines their coalescence rate. Our model predicts an MBH coalescence rate ≲0.45 yr<jats:sup>−1</jats:sup> and a LISA detection rate ≲0.34 yr<jats:sup>−1</jats:sup>. Most LISA detections should originate from 10<jats:sup>6</jats:sup> to 10<jats:sup>6.8</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> MBHs in gas-rich galaxies at redshifts 1.6 ≤ <jats:italic>z</jats:italic> ≤ 2.4 and have a characteristic signal-to-noise ratio S/N ∼100. We however find a dramatic reduction in the coalescence and detection rates, as well as the average S/N, if the effects of radiative feedback from accreting MBHs are taken into account. In this case, the MBH coalescence rate is reduced by 78% (to ≲0.1 yr<jats:sup>−1</jats:sup>), and the LISA detection rate is reduced by 94% (to 0.02 yr<jats:sup>−1</jats:sup>), whereas the average S/N is ∼10. We emphasize that our model provides a conservative estimate of the LISA detection rates, due to the limited MBH mass range in TNG50-3, consistent with other works in the literature that draw their MBH pairs from cosmological simulations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Plasma jets and jet fronts are common phenomena in planetary magnetospheres. They are usually associated with many plasma waves and can play a key role in the energy conversion, the excitation of wave emissions, particle acceleration, and the evolution of many astrophysical phenomena, which are major issues in the study of helio-terrestrial space physics. In this paper, we carefully investigated the properties of the whistler-mode wave and large-amplitude electrostatic wave in a plasma jet (bursty bulk flow (BBF)) using the Magnetospheric Multiscale mission data on the Earth's magnetosphere. At the leading part of the BBF, intense whistler-mode waves were observed inside the ion mirror-mode structures, which should be excited by the perpendicular temperature anisotropy of trapping electrons. A small-scale dipolarization front (DF) was then observed at the center of this BBF as a boundary between the leading and trailing parts of the BBF. Behind the DF, both an ion mirror-mode structure and whistler-mode waves disappear, while a large-amplitude electrostatic wave was detected and was associated with the cold ions at the trailing part of the BBF. The electrostatic wave is supposed to be generated by ion beam instability. These results will significantly improve the understanding of the kinetic process associated with the important boundary layer DF within plasma jets. The corresponding wave–particle interaction in space and the plasma environment can be further understood.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In coronal loop modeling, it is commonly assumed that the loops are semicircular with a uniform cross-sectional area. However, observed loops are rarely semicircular, and extrapolations of the magnetic field show that the field strength decreases with height, implying that the cross-sectional area expands with height. We examine these two assumptions directly, to understand how they affect the hydrodynamic and radiative response of short, hot loops to strong, impulsive electron beam heating events. Both the magnitude and rate of area expansion impact the dynamics directly, and an expanding cross section significantly lengthens the time for a loop to cool and drain, increases upflow durations, and suppresses sound waves. The standard <jats:italic>T</jats:italic> ∼ <jats:italic>n</jats:italic> <jats:sup>2</jats:sup> relation for radiative cooling does not hold with expanding loops, which cool with relatively little draining. An increase in the eccentricity of loops, on the other hand, only increases the draining timescale, and is a minor effect in general. Spectral line intensities are also strongly impacted by the variation in the cross-sectional area because they depend on both the volume of the emitting region as well as the density and ionization state. With a larger expansion, the density is reduced, so the lines at all heights are relatively reduced in intensity, and because of the increase of cooling times, the hottest lines remain bright for significantly longer. Area expansion is critical to accurate modeling of the hydrodynamics and radiation, and observations are needed to constrain the magnitude, rate, and location of the expansion—or lack thereof.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The astronomical detection of formamide (NH<jats:sub>2</jats:sub>CHO) toward various star-forming regions and in cometary material implies that the simplest amide might have an early origin in dark molecular clouds at low temperatures. Laboratory studies have proven the efficient NH<jats:sub>2</jats:sub>CHO formation in interstellar CO:NH<jats:sub>3</jats:sub> ice analogs upon energetic processing. However, it is still under debate, whether the proposed radical–radical recombination reactions forming complex organic molecules remain valid in an abundant H<jats:sub>2</jats:sub>O environment. The aim of this work was to investigate the formation of NH<jats:sub>2</jats:sub>CHO in H<jats:sub>2</jats:sub>O- and CO-rich ices under conditions prevailing in molecular clouds. Therefore, different ice mixtures composed of H<jats:sub>2</jats:sub>O:CO:NH<jats:sub>3</jats:sub> (10:5:1), CO:NH<jats:sub>3</jats:sub> (4:1), and CO:NH<jats:sub>3</jats:sub> (0.6:1) were exposed to vacuum ultraviolet photons in an ultra-high vacuum chamber at 10 K. Fourier-transform infrared spectroscopy was utilized to monitor in situ the initial and newly formed species as a function of photon fluence. The infrared spectral identifications are complementarily secured by a temperature-programmed desorption experiment combined with a quadrupole mass spectrometer. The energetic processing of CO:NH<jats:sub>3</jats:sub> ice mixtures mainly leads to the formation of NH<jats:sub>2</jats:sub>CHO, along with its chemical derivatives such as isocyanic acid (HNCO) and cyanate ion (OCN<jats:sup>−</jats:sup>). The formation kinetics of NH<jats:sub>2</jats:sub>CHO shows an explicit dependency on ice ratios and compositions; the highest yield is found in H<jats:sub>2</jats:sub>O-rich ice. The astronomical relevance of the resulting reaction network is discussed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Recent observations provided evidence that the solar chromosphere of sunspot regions is pervaded by Alfvénic waves—transverse magnetohydrodynamic (MHD) waves (Alfvén waves or kink waves). In order to systematically investigate the physical characteristics of Alfvénic waves over a wide range of periods, we analyzed the time series of line-of-sight velocity maps constructed from the H<jats:italic>α</jats:italic> spectral data of a small sunspot region taken by the Fast Imaging Solar Spectrograph of the Goode Solar Telescope at Big Bear. We identified each Alfvénic wave packet by examining the cross-correlation of band-filtered velocity between two points that are located a little apart presumably on the same magnetic field line. As result, we detected a total of 279 wave packets in the superpenumbral region around the sunspot and obtained their statistics of period, velocity amplitude, and propagation speed. An important finding of ours is that the detected Alfvénic waves are clearly separated into two groups: 3-minute period (&lt;7 minutes) waves and 10-minute period (&gt;7 minutes) waves. We propose two tales on the origin of Alfvénic waves in the chromosphere; the 3-minute Alfvénic waves are excited by the upward-propagating slow waves in the chromosphere through the slow-to-Alfvénic mode conversion, and the 10-minute Alfvénic waves represent the chromospheric manifestation of the kink waves driven by convective motions in the photosphere.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A set of 464 minutes of high-resolution high-cadence observations were acquired for a region near the Sun’s disk center using the Interferometric BI-dimensional Spectrometer installed at the Dunn Solar Telescope. Ten sets of Dopplergrams are derived from the bisector of the spectral line corresponding approximately to different atmospheric heights, and two sets of Dopplergrams are derived using an MDI-like algorithm and center-of-gravity method. These data are then filtered to keep only acoustic modes, and phase shifts are calculated between Doppler velocities of different atmospheric heights as a function of acoustic frequency. The analysis of the frequency- and height-dependent phase shifts shows that, for evanescent acoustic waves, oscillations in the higher atmosphere lead those in the lower atmosphere by an order of 1 s when their frequencies are below about 3.0 mHz, and lags behind by about 1 s when their frequencies are above 3.0 mHz. Nonnegligible phase shifts are also found in areas with systematic upward or downward flows. All these frequency-dependent phase shifts cannot be explained by vertical flows or convective blueshifts, but are likely due to complicated hydrodynamics and radiative transfer in the nonadiabatic atmosphere in and above the photosphere. These phase shifts in the evanescent waves pose great challenges to the interpretation of some local helioseismic measurements that involve data acquired at different atmospheric heights or in regions with systematic vertical flows. More quantitative characterization of these phase shifts is needed so that they can either be removed during measuring processes or be accounted for in helioseismic inversions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Seyfert 1 galaxy NGC 7469 possesses a prominent nuclear starburst ring and a luminous active galactic nucleus (AGN). Evidence of an outflow in the innermost nuclear region has been found in previous works. We detect the ionized gas outflow on a larger scale in the galaxy using the archival Very Large Telescope/MUSE and Chandra observations. The optical emission lines are modeled using two Gaussian components, and a nonparametric approach is applied to measure the kinematics of [O <jats:sc>iii</jats:sc>] and H<jats:italic>α</jats:italic> emitting gas. Line ratio diagnostics and spatially resolved maps are derived to examine the origin of the outflow. The kiloparsec-scale kinematics of [O <jats:sc>iii</jats:sc>] are dominated by a blueshifted component whereas the velocity map of H<jats:italic>α</jats:italic> shows a rotational disk with a complex nonrotational substructure. The starburst wind around the circumnuclear ring is confirmed, and we find evidence of an AGN-driven outflow extending to a radial distance of ∼ 2 kpc from the nucleus, with a morphology consistent with a nearly face-on ionization cone. The previously reported circumnuclear outflow resembles part of the bright base. We derive mass and energy outflow rates for both the starburst wind and the AGN-driven outflow. The estimated kinetic coupling efficiency of the kiloparsec-scale AGN outflow is <jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{E}}_{\mathrm{out}}/{L}_{\mathrm{bol}}\sim 0.1 \% $?> </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>E</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>out</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>bol</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∼</mml:mo> <mml:mn>0.1</mml:mn> <mml:mo>%</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac7222ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, lower than the threshold predicted by the “two-stage” theoretical model for effective feedback. Our results reinforce the importance of spatially resolved study to disentangle feedback where AGNs and starbursts coexist, which may be common during the cosmic noon of black hole and galaxy growth.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We perform a full nuclear-network numerical calculation of the <jats:italic>r</jats:italic>-process nuclei in binary neutron-star mergers (NSMs), with the aim of estimating gamma-ray emissions from the remnants of Galactic NSMs up to 10<jats:sup>6</jats:sup> yr old. The nucleosynthesis calculation of 4070 nuclei is adopted to provide the elemental composition ratios of nuclei with an electron fraction <jats:italic>Y</jats:italic> <jats:sub>e</jats:sub> between 0.10 and 0.45. The decay processes of 3237 unstable nuclei are simulated to extract the gamma-ray spectra. As a result, the NSMs have different spectral colors in the gamma-ray band from various other astronomical objects at less than 10<jats:sup>5</jats:sup> yr old. In addition, we propose a new line diagnostic method for <jats:italic>Y</jats:italic> <jats:sub>e</jats:sub> that uses the line ratios of either <jats:sup>137m</jats:sup>Ba/<jats:sup>85</jats:sup>K or <jats:sup>243</jats:sup>Am/<jats:sup>60m</jats:sup>Co, which become larger than unity for young and old <jats:italic>r</jats:italic>-process sites, respectively, with a low<jats:italic>-Y</jats:italic> <jats:sub>e</jats:sub> environment. From an estimation of the distance limit for gamma-ray observations as a function of age, the high sensitivity in the sub-megaelectronvolt band, at approximately 10<jats:sup>−9</jats:sup> photons s<jats:sup>−1</jats:sup> cm<jats:sup>−2</jats:sup> or 10<jats:sup>−15</jats:sup> erg s<jats:sup>−1</jats:sup> cm<jats:sup>−2</jats:sup>, is required to cover all the NSM remnants in our Galaxy, if we assume that the population of NSMs by Wu et al. A gamma-ray survey with sensitivities of 10<jats:sup>−8</jats:sup>–10<jats:sup>−7</jats:sup> photons s<jats:sup>−1</jats:sup> cm<jats:sup>−2</jats:sup> or 10<jats:sup>−14</jats:sup>–10<jats:sup>−13</jats:sup> erg s<jats:sup>−1</jats:sup> cm<jats:sup>−2</jats:sup> in the 70–4000 keV band is expected to find emissions from at least one NSM remnant under the assumption of an NSM rate of 30 Myr<jats:sup>−1</jats:sup>. The feasibility of gamma-ray missions observing Galactic NSMs is also studied.</jats:p>