Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Parker Solar Probe's (PSP's) unique orbital path allows us to observe the solar wind closer to the Sun than ever before. Essential to advancing our knowledge of solar wind and energetic particle formation is identifying the sources of PSP observations. We report on results for the first two PSP solar encounters derived using the Wang–Sheeley–Arge (WSA) model driven by Air Force Data Assimilative Photospheric Flux Transport (ADAPT) model maps. We derive the coronal magnetic field and the 1 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub> source regions of the PSP-observed solar wind. We validate our results with the solar wind speed and magnetic polarity observed at PSP. When modeling results are very reliable, we derive time series of model-derived spacecraft separation from the heliospheric current sheet, magnetic expansion factor, coronal hole boundary distance, and photospheric field strength along the field lines estimated to be connected to the spacecraft. We present new results for Encounter 1, which show time evolution of the far-side mid-latitude coronal hole that PSP corotates with. We discuss how this evolution coincides with solar wind speed, density, and temperature observed at the spacecraft. During Encounter 2, a new active region emerges on the solar far side, making it difficult to model. We show that ADAPT-WSA output agrees well with PSP observations once this active region rotates onto the near side, allowing us to reliably estimate the solar wind sources retrospectively for most of the encounter. We close with ways in which coronal modeling enables scientific interpretation of these encounters that would otherwise not have been possible.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>On 2017 September 2 MAXI J1535–571 went into outburst and peaked at ∼5 Crab in the 2–20 keV energy range. Early in the flare, the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) performed target of opportunity pointings and monitored the source as it transitioned from the hard state to the soft state. Using quasi-simultaneous observations from MAXI/GSC and INTEGRAL/SPI, we studied the temporal and spectral evolution of MAXI J1535–571 in the 2–500 keV range. Early spectra show a Comptonized spectrum and a high-energy component dominant above ∼150 keV. <jats:monospace>CompTT</jats:monospace> fits to the SPectrometer on INTEGRAL (SPI) data found electron temperatures (<jats:italic>kT</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> ) evolve from ∼31 keV to 18 keV with a tied optical depth (<jats:italic>τ</jats:italic> ∼ 0.85) or <jats:italic>τ</jats:italic> evolving from ∼1.2–0.65 with a tied <jats:italic>kT</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> (∼24 keV). To investigate the nature of the high-energy component, we performed a spectral decomposition of the 100–400 keV energy band. The <jats:monospace>CompTT</jats:monospace> flux varies significantly during the hard state while the high-energy component flux is consistent with a constant flux. This result suggests that the two components originate from different locations, which favors a jet origin interpretation for the high-energy component over a hybrid corona interpretation. Lastly, two short rebrightenings during the hard-to-soft transition are compared to similar events reported in MAXI J1820+070.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>By performing two-dimensional axisymmetric general relativistic radiation magnetohydrodynamics simulations with spin parameter <jats:italic>a</jats:italic>* varying from −0.9 to 0.9, we investigate the dependence on the black hole spin of the energy flow from a supercritical accretion disk around a stellar mass black hole. It is found that optically and geometrically thick disks form near the equatorial plane, and a part of the disk matter is launched from the disk surface in all models. The gas ejection is mainly driven by the radiative force, but magnetic force cannot be neglected when ∣<jats:italic>a</jats:italic>*∣ is large. The energy outflow efficiency (total luminosity normalized by <jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{M}}_{\mathrm{in}}{c}^{2};$?> </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>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>in</mml:mi> </mml:mrow> </mml:msub> <mml:msup> <mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo>;</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac7eb8ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> <jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{M}}_{\mathrm{in}}$?> </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>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>in</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac7eb8ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:italic>c</jats:italic> are the mass-accretion rate at the event horizon and the light speed) is higher for rotating black holes than for nonrotating black holes. This is 0.7% for <jats:italic>a</jats:italic>* = −0.7, 0.3% for <jats:italic>a</jats:italic>* = 0, and 5% for <jats:italic>a</jats:italic>* = 0.7 for <jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{M}}_{\mathrm{in}}\sim 100{L}_{\mathrm{Edd}}/{c}^{2}$?> </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>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>in</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∼</mml:mo> <mml:mn>100</mml:mn> <mml:msub> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>Edd</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msup> <mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac7eb8ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> (<jats:italic>L</jats:italic> <jats:sub>Edd</jats:sub> is the Eddington luminosity). Furthermore, although the energy is mainly released by radiation when <jats:italic>a</jats:italic>* ∼ 0, the Poynting power increases with ∣<jats:italic>a</jats:italic>*∣ and exceeds the radiative luminosity for models with <jats:italic>a</jats:italic>* ≥ 0.5 and <jats:italic>a</jats:italic>* ≤ −0.7. The faster the black hole rotates, the higher the power ratio of the kinetic luminosity to the isotropic luminosity tends to be. This implies that objects with a high (low) power ratio may have rapidly (slowly) rotating black holes. Among ultraluminous X-ray sources, IC342 X-1, is a candidate with a rapidly rotating black hole.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A promising astrophysical site to produce the lighter heavy elements of the first <jats:italic>r</jats:italic>-process peak (<jats:italic>Z</jats:italic> = 38 − 47) is the moderately neutron-rich (0.4 &lt; <jats:italic>Y</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> &lt; 0.5) neutrino-driven ejecta of explosive environments, such as core-collapse supernovae and neutron star mergers, where the weak <jats:italic>r</jats:italic>-process operates. This nucleosynthesis exhibits uncertainties from the absence of experimental data from (<jats:italic>α</jats:italic>, <jats:italic>xn</jats:italic>) reactions on neutron-rich nuclei, which are currently based on statistical model estimates. In this work, we report on a new study of the nuclear reaction impact using a Monte Carlo approach and improved (<jats:italic>α</jats:italic>, <jats:italic>xn</jats:italic>) rates based on the Atomki-V2 <jats:italic>α</jats:italic> optical model potential. We compare our results with observations from an up-to-date list of metal-poor stars with [Fe/H] &lt; −1.5 to find conditions of the neutrino-driven wind where the lighter heavy elements can be synthesized. We identified a list of (<jats:italic>α</jats:italic>, <jats:italic>xn</jats:italic>) reaction rates that affect key elemental ratios in different astrophysical conditions. Our study aims to motivate more nuclear physics experiments on (<jats:italic>α</jats:italic>, <jats:italic>xn</jats:italic>) reactions using the current and new generation of radioactive beam facilities and also more observational studies of metal-poor stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Galactic disk exhibits complex chemical and dynamical substructure thought to be induced by the bar, spiral arms, and satellites. Here, we explore the chemical signatures of bar resonances in action and velocity space, and characterize the differences between the signatures of corotation (CR) and higher-order resonances using test particle simulations. Thanks to recent surveys, we now have large data sets containing metallicities and kinematics of stars outside the solar neighborhood. We compare the simulations to the observational data from Gaia EDR3 and LAMOST DR5 and find weak evidence for a slow bar with the “hat” moving group (250 km s<jats:sup>−1</jats:sup> ≲ <jats:italic>v</jats:italic> <jats:sub> <jats:italic>ϕ</jats:italic> </jats:sub> ≲ 270 km s<jats:sup>−1</jats:sup>) associated with its outer Lindblad resonance and “Hercules” (170 km s<jats:sup>−1</jats:sup> ≲ <jats:italic>v</jats:italic> <jats:sub> <jats:italic>ϕ</jats:italic> </jats:sub> ≲ 195 km s<jats:sup>−1</jats:sup>) with CR. While constraints from current data are limited by their spatial footprint, stars closer in azimuth than the Sun to the bar’s minor axis show much stronger signatures of the bar’s outer Lindblad and CR resonances in test particle simulations. Future data sets with greater azimuthal coverage, including the final Gaia data release, will allow reliable chemodynamical identification of bar resonances.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present an analysis of 10 ks snapshot Chandra observations of 12 shocked post-starburst galaxies, which provide a window into the unresolved question of active galactic nuclei (AGN) activity in post-starburst galaxies and its role in the transition of galaxies from active star formation to quiescence. While seven of the 12 galaxies have statistically significant detections (with two more marginal detections), the brightest only obtained 10 photons. Given the wide variety of hardness ratios in this sample, we chose to pursue a forward-modeling approach to constrain the intrinsic luminosity and obscuration of these galaxies, rather than stacking. We constrain the intrinsic luminosity of obscured power laws based on the total number of counts and spectral shape, itself mostly set by the obscuration, with hardness ratios consistent with the data. We also tested thermal models. While all the galaxies have power-law models consistent with their observations, a third of the galaxies are better fit as an obscured power law and another third are better fit as thermal emission. If these post-starburst galaxies, early in their transition, contain AGNs, then these are mostly confined to lower obscuration (<jats:italic>N</jats:italic> <jats:sub> <jats:italic>H</jats:italic> </jats:sub> ≤ 10<jats:sup>23</jats:sup> cm<jats:sup>−2</jats:sup>) and lower luminosity (<jats:italic>L</jats:italic> <jats:sub>2−10 keV</jats:sub> ≤ 10<jats:sup>42</jats:sup> erg s<jats:sup>−1</jats:sup>). Two galaxies, however, are clearly best fit as significantly obscured AGNs. At least half of this sample shows evidence of at least low-luminosity AGN activity, though none could radiatively drive out the remaining molecular gas reservoirs. Therefore, these AGNs are more likely along for the ride, having been fed gas by the same processes driving the transition.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Understanding the halo–galaxy connection is fundamental in order to improve our knowledge on the nature and properties of dark matter. In this work, we build a model that infers the mass of a halo given the positions, velocities, stellar masses, and radii of the galaxies it hosts. In order to capture information from correlations among galaxy properties and their phase space, we use Graph Neural Networks (GNNs), which are designed to work with irregular and sparse data. We train our models on galaxies from more than 2000 state-of-the-art simulations from the Cosmology and Astrophysics with MachinE Learning Simulations project. Our model, which accounts for cosmological and astrophysical uncertainties, is able to constrain the masses of the halos with a ∼0.2 dex accuracy. Furthermore, a GNN trained on a suite of simulations is able to preserve part of its accuracy when tested on simulations run with a different code that utilizes a distinct subgrid physics model, showing the robustness of our method. The PyTorch Geometric implementation of the GNN is publicly available on GitHub (<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://github.com/PabloVD/HaloGraphNet" xlink:type="simple">https://github.com/PabloVD/HaloGraphNet</jats:ext-link>).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present high-cadence optical, ultraviolet (UV), and near-infrared data of the nearby (<jats:italic>D</jats:italic> ≈ 23 Mpc) Type II supernova (SN) 2021yja. Many Type II SNe show signs of interaction with circumstellar material (CSM) during the first few days after explosion, implying that their red supergiant (RSG) progenitors experience episodic or eruptive mass loss. However, because it is difficult to discover SNe early, the diversity of CSM configurations in RSGs has not been fully mapped. SN 2021yja, first detected within ≈ 5.4 hours of explosion, shows some signatures of CSM interaction (high UV luminosity and radio and x-ray emission) but without the narrow emission lines or early light-curve peak that can accompany CSM. Here we analyze the densely sampled early light curve and spectral series of this nearby SN to infer the properties of its progenitor and CSM. We find that the most likely progenitor was an RSG with an extended envelope, encompassed by low-density CSM. We also present archival Hubble Space Telescope imaging of the host galaxy of SN 2021yja, which allows us to place a stringent upper limit of ≲ 9 <jats:italic>M</jats:italic> <jats:sub>☉</jats:sub> on the progenitor mass. However, this is in tension with some aspects of the SN evolution, which point to a more massive progenitor. Our analysis highlights the need to consider progenitor structure when making inferences about CSM properties, and that a comprehensive view of CSM tracers should be made to give a fuller view of the last years of RSG evolution.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We examine variations in energetic storm particle (ESP) heavy ion peak intensities and energy spectra at CME-driven interplanetary shocks. We focus on their dependence with heliolongitude relative to the source region of their associated CMEs, and with CME speed, for events observed in Solar Cycle 24 at the STEREO-A, STEREO-B, and/or ACE spacecraft. We find that observations of ESP events at 1 au are organized by longitude relative to their CME solar source. The ESP event longitude distribution also showed organization with CME speed. The near-Sun CME speeds (<jats:italic>V</jats:italic> <jats:sub> <jats:italic>i</jats:italic> </jats:sub>) for these events ranged from ∼560 to 2650 km s<jats:sup>−1</jats:sup> while the average CME transit speeds to 1 au were significantly slower. The angular width of the events had a clear threshold at <jats:italic>V</jats:italic> <jats:sub> <jats:italic>i</jats:italic> </jats:sub> of ∼1300 km s<jats:sup>−1</jats:sup>, above which events showed significantly larger angular extension compared to events with speeds below. High-speed events also showed larger heavy ion peak intensities near the nose of the shock compared to the flanks while their spectral index was smaller near the nose and larger near the flanks. This organization for events with <jats:italic>V</jats:italic> <jats:sub> <jats:italic>i</jats:italic> </jats:sub> &lt; 1300 km s<jats:sup>−1</jats:sup> was not as clear. These ESP events were observed over a narrower range of longitudes though the heavy ion peak intensities still appeared largest near the nose of the shock. Their heavy ion spectra showed no clear organization with longitude. These observations highlight the impact of spacecraft position relative to the CME source longitude and <jats:italic>V</jats:italic> <jats:sub> <jats:italic>i</jats:italic> </jats:sub> on the properties of ESP events at 1 au.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the properties of oscillatory double-diffusive convection (ODDC) in the presence of a uniform vertical background magnetic field. ODDC takes place in stellar regions that are unstable according to the Schwarzschild criterion and stable according to the Ledoux criterion (sometimes called semiconvective regions), which are often predicted to reside just outside the core of intermediate-mass main-sequence stars. Previous hydrodynamic studies of ODDC have shown that the basic instability saturates into a state of weak wave-like convection, but that a secondary instability can sometimes transform it into a state of layered convection, where layers then rapidly merge and grow until the entire region is fully convective. We find that magnetized ODDC has very similar properties overall, with some important quantitative differences. A linear stability analysis reveals that the fastest-growing modes are unaffected by the field, but that other modes are. Numerically, the magnetic field is seen to influence the saturation of the basic instability, overall reducing the turbulent fluxes of temperature and composition. This in turn affects layer formation, usually delaying it, and occasionally suppressing it entirely for sufficiently strong fields. Further work will be needed, however, to determine the field strength above which layer formation is actually suppressed in stars. Potential observational implications are briefly discussed.</jats:p>