Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>This paper compares the population of binary black hole (BBH) mergers detected by LIGO/Virgo with selected long gamma-ray burst (GRB) world models convolved with a delay function (LGRBs are used as a tracer of stellar-mass BH formation). The comparison involves the redshift distribution and the fraction of LGRBs required to produce the local rate of BBH mergers. We find that BBH mergers and LGRBs cannot have the same formation history, unless BBH mergers have a long coalescence time of several Gyr. This would imply that BHs born during the peak of long GRB formation at redshift <jats:italic>z</jats:italic> ≈ 2−3 merge within the horizon of current GW interferometers. We also show that LGRBs are more numerous than BBH mergers, meaning that most of them do not end their lives in BBH mergers. We interpret these results as an indication that BBH mergers and LGRBs constitute two distinct populations of stellar-mass BHs, with LGRBs being more frequent than BBH mergers. We speculate that the descendants of LGRBs may resemble galactic high-mass X-ray binaries more than BBH mergers. Finally, we discuss the possible existence of a subpopulation of fast-spinning LGRB descendants among BBH mergers, showing that this population, if it exists, is expected to become dominant beyond redshift <jats:italic>z</jats:italic> ≈ 1, leading to a change in the observed properties of BBH mergers.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have presented the first joint XMM-Newton and NuSTAR analysis of the millisecond pulsar (MSP) binary PSR J1653−0158. The 75 minute orbital period inferred from optical and gamma-ray observations together with the 1.97 ms pulsation in the gamma-rays indicate that this system is the most compact Black Widow MSP system known to date. The orbital period was not detected in the XMM-Newton and NuSTAR data, probably due to insufficient photon counts obtained in the observations. Fitting the joint X-ray spectrum of PSR J1653−0158 with a power law gives a photon index Γ = 1.71 ± 0.09. The X-ray luminosity of the source in the (0.2–40) keV band is deduced to be 1.18 × 10<jats:sup>31</jats:sup> erg s<jats:sup>−1</jats:sup>, for an adopted distance of 0.84 kpc. We have shown that the broadband X-ray spectrum can be explained by synchrotron radiation from electrons accelerated in the intrabinary shock, and the gamma-rays detected in the Fermi data are curvature radiations from electrons and positrons in the pulsar magnetosphere. Our kinematic analysis of the Tidarren systems PSR J1653–0158 and PSR J1311–3430 indicates that the two Tidarren systems are likely to have originated in the Galactic disk.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The typical spectrum of the prompt emission of gamma-ray bursts (GRBs) indicates that the electron cooling is suppressed in spite of the strong magnetic field in the standard synchrotron model. Recent particle-in-cell simulations show that the particle acceleration by magnetic reconnection in a magnetically dominated plasma can lead to small pitch angles especially in a low-energy region. Such a small pitch angle prevents electrons from cooling via synchrotron radiation. In this paper, taking into account the effects of the synchrotron cooling and the adiabatic cooling, we numerically calculate the synchrotron spectra with anisotropic electron distributions. If we require a Poynting flux larger than 10<jats:sup>50</jats:sup> erg s<jats:sup>−1</jats:sup> as the model is motivated by magnetic reconnection, the bulk Lorentz factor of ∼1000 and the electron minimum Lorentz factor of <jats:italic>γ</jats:italic> <jats:sub>min</jats:sub> ∼ 10<jats:sup>4</jats:sup> are required to reproduce the typical GRB spectrum.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Born-again planetary nebulae (PNs) allow investigating stellar evolution, dust production, and nebular shocks in human timescales. Here we present an analysis of multiepoch optical spectroscopic observations of the born-again PN A 58 around V605 Aql, which experienced a very late thermal pulse about a century ago. The H-deficient ejecta has experienced a considerable brightening in the time period considered, from 1996 to 2021, with notable changes also in many emission line ratios. Neither the reduction of the extinction caused by the dilution of the ejecta nor the increase of the ionizing photon flux from the central star seem capable to produce these spectral changes, which are instead attributed to shocks in the bipolar H-poor outflow, dissociating molecular material, and propagating through the outer nebula.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Weak gravitational lensing is a powerful statistical tool for probing the growth of cosmic structure and measuring cosmological parameters. However, as shown by studies such as by Ménard et al., dust in the circumgalactic region of halos dims and reddens background sources. In a weak lensing analysis, this selects against sources behind overdense regions; since there is more structure in overdense regions, we will underestimate the amplitude of density perturbations <jats:italic>σ</jats:italic> <jats:sub>8</jats:sub> if we do not correct for the effects of circumgalactic dust. To model the dust distribution we employ the <jats:italic>halo model</jats:italic>. Assuming a fiducial dust mass profile based on measurements from Ménard et al., we compute the ratio <jats:italic>Z</jats:italic> of the systematic error to the statistical error for a survey similar to the Nancy Grace Roman Space Telescope reference survey (2000 deg<jats:sup>2</jats:sup> area, single-filter effective source density 30 galaxies arcmin<jats:sup>−2</jats:sup>). For a wave band centered at 1580 nm (<jats:italic>H</jats:italic> band), we find that <jats:italic>Z</jats:italic> <jats:sub> <jats:italic>H</jats:italic> </jats:sub> = 0.37. For a similar survey with wave band centered at 620 nm (<jats:italic>r </jats:italic>band), we also computed <jats:italic>Z</jats:italic> <jats:sub> <jats:italic>r</jats:italic> </jats:sub> = 2.8. Within our fiducial dust model, since <jats:italic>Z</jats:italic> <jats:sub> <jats:italic>r</jats:italic> </jats:sub> &gt; 1, the systematic effect of dust will be significant on weak lensing image surveys. We also computed the dust bias on the amplitude of the power spectrum, <jats:italic>σ</jats:italic> <jats:sub>8</jats:sub>, and found it to be for each wave band Δ<jats:italic>σ</jats:italic> <jats:sub>8</jats:sub>/<jats:italic>σ</jats:italic> <jats:sub>8</jats:sub> = −3.1 × 10<jats:sup>−4</jats:sup> (<jats:italic>H</jats:italic> band) or −2.2 × 10<jats:sup>−3</jats:sup> (<jats:italic>r</jats:italic> band) if all other parameters are held fixed (the forecast Roman statistical-only error <jats:italic>σ</jats:italic>(<jats:italic>σ</jats:italic> <jats:sub>8</jats:sub>)/<jats:italic>σ</jats:italic> <jats:sub>8</jats:sub> is 9 × 10<jats:sup>−4</jats:sup>).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Sagittarius B2 (Sgr B2) molecular cloud complex is an X-ray reflection nebula whose nonthermal X-ray emissions have continued to decrease since 2001 as it reprocesses one or more past energetic outbursts from the supermassive black hole Sagittarius A* at the Galactic Center. The X-ray reflection model explains the observed time variability of Sgr B2 and provides a window into the luminous evolutionary history of our nearest supermassive black hole. In light of evidence of elevated cosmic particle populations in the Galactic Center, X-rays from Sgr B2 are also of interest as a probe of low-energy (sub-GeV) cosmic rays, which may be responsible for an increasing relative fraction of the nonthermal emission as the contribution from X-ray reflection decreases. Here, we present the most recent NuSTAR and XMM-Newton observations of Sgr B2, from 2018, and we emphasize the K<jats:italic>α</jats:italic> fluorescence line of neutral Fe. These 2018 observations reveal small-scale variations within lower-density portions of the complex, including brightening features, yet still enable upper limits on X-rays from low-energy cosmic-ray interactions in Sgr B2. We present Fe K<jats:italic>α</jats:italic> line fluxes from cloud regions of different densities, facilitating comparison with models of ambient low-energy cosmic-ray interactions throughout the cloud.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Massive dense clumps in the Large Magellanic Cloud can be an important laboratory to explore the formation of populous clusters. We report multiscale ALMA observations of the N159W-North clump, which is the most CO-intense region in the galaxy. High-resolution CO isotope and 1.3 mm continuum observations with an angular resolution of ∼0.″25 (∼0.07 pc) revealed more than five protostellar sources with CO outflows within the main ridge clump. One of the thermal continuum sources, MMS-2, shows an especially massive/dense nature whose total H<jats:sub>2</jats:sub> mass and peak column density are ∼10<jats:sup>4</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and ∼10<jats:sup>24</jats:sup> cm<jats:sup>−2</jats:sup>, respectively, and harbors massive (∼100 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) starless core candidates identified as its internal substructures. The main ridge containing this source can be categorized as one of the most massive protocluster systems in the Local Group. The CO high-resolution observations found several distinct filamentary clouds extending southward from the star-forming spots. The CO (1–0) data set with a larger field of view reveals a conical, ∼30 pc long complex extending toward the northern direction. These features indicate that a large-scale gas compression event may have produced the massive star-forming complex. Based on the striking similarity between the N159W-North complex and the other two previously reported high-mass star-forming clouds in the nearby regions, we propose a “teardrops inflow model” that explains the synchronized, extreme star formation across &gt;50 pc, including one of the most massive protocluster clumps in the Local Group.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a detailed X-ray analysis and imaging of stellar coronae of five coronally connected eclipsing binaries, namely, 44 Boo, DV Psc, ER Vul, XY UMa, and TX Cnc. Both components of these binaries are found to be active. The X-ray light curves of detached and semidetached type systems show eclipsed-like features, whereas no evidence for coronal eclipsing is shown by the contact type systems. The X-ray light curve of DV Psc shows the O’Connell-like effect where the first maximum is found to be brighter than that of the second. Results of the coronal imaging using three-dimensional deconvolution of X-ray light curves show the coronae of all these binaries are either in the contact or over-contact configuration, with the primary being 1.7–4 times X-ray brighter than its companion. In the current sample, a minimum of 30%–50% of total UV emission is found to originate from the photosphere and positively correlated with the X-ray emission. X-ray spectra of these systems are well explained by two-temperature plasma models. The temperature corresponding to cool and hot components of plasma are found to be in the ranges of 0.25–0.64 and 0.9–1.1 keV, respectively. For the majority of binaries in the sample, the phase-resolved X-ray spectral analysis shows the orbital modulation in X-ray luminosity and emission measure corresponding to the hot component. A total of seven flaring events are also detected in the four systems with the flare energy in the range of (1.95–27.0) × 10<jats:sup>33</jats:sup> erg and loop length of the order of 10<jats:sup>9–11</jats:sup> cm.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Coronal plumes are long, ray-like, open structures that have been considered as possible sources of the solar wind. Their origin in the largely unipolar coronal holes has long been a mystery. Earlier spectroscopic and imaging observations revealed blueshifted plasma and propagating disturbances (PDs) in plumes that are widely interpreted in terms of flows and/or propagating slow-mode waves, but these interpretations (flows versus waves) remain under debate. Recently we discovered an important clue about plume internal structure: dynamic filamentary features called <jats:italic>plumelets</jats:italic>, which account for most of the plume emission. Here we present high-resolution observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly and the Interface Region Imaging Spectrograph that revealed numerous, quasi-periodic, tiny jets (so-called <jats:italic>jetlets</jats:italic>) associated with transient brightening, flows, and plasma heating at the chromospheric footpoints of the plumelets. By analogy to larger coronal jets, these jetlets are most likely produced within the plume base by magnetic reconnection between closed and open flux at stressed 3D null points. The jetlet-associated brightenings are in phase with plumelet-associated PDs, and vary with a period of ∼3–5 minutes, which is remarkably consistent with the photospheric/chromospheric p-mode oscillation. This reconnection at the open-closed boundary in the chromosphere/transition region is likely modulated or driven by local manifestations of the global p-mode waves. The jetlets extend upward to become plumelets, contribute mass to the solar wind, and may be sources of the switchbacks recently detected by the Parker Solar Probe.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the possibility that the Milky Ways’ cool stellar disk includes mergers with ancient stars. Galaxies are understood to form in a hierarchical manner, where smaller (proto-)galaxies merge into larger ones. Stars in galaxies, like the Milky Way, contain in their motions and elemental abundance tracers of past events and can be used to disentangle merger remnants from stars that formed in the main galaxy. The merger history of the Milky Way is generally understood to be particularly easy to study in the stellar halo. The advent of the ESA astrometric satellite Gaia has enabled the detection of completely new structures in the halo such as the Gaia-Enceladus-Sausage. However, simulations also show that mergers may be important for the build-up of the cool stellar disks. Combining elemental abundances for ∼100 giant branch stars from APOGEE DR17 and astrometric data from Gaia we use elemental abundance ratios to find a hitherto unknown, old stellar component in the cool stellar disk in the Milky Way. We further identify a small sample of RR Lyrae variables with disk kinematics that also show the same chemical signature as the accreted red giant stars in the disk. These stars allow us to date the stars in the accreted component. We find that they are exclusively old.</jats:p>