Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Similarly to light, gravitational waves can be gravitationally lensed as they propagate near massive astrophysical objects such as galaxies, stars, or black holes. In recent years, forecasts have suggested a reasonable chance of strong gravitational-wave lensing detections with the LIGO–Virgo–KAGRA detector network at design sensitivity. As a consequence, methods to analyze lensed detections have seen rapid development. However, the impact of higher-order modes on the lensing analyses is still under investigation. In this work, we show that the presence of higher-order modes enables the identification of individual image types for the observed gravitational-wave events when two lensed images are detected, which would lead to unambiguous confirmation of lensing. In addition, we show that higher-order mode content can be analyzed more accurately with strongly lensed gravitational-wave events.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Prominence bubbles and plumes often form near the lower prominence–corona boundary. They are believed to play an important role in mass supply and evolution of solar prominences. However, how they form is still an open question. In this Letter we present a unique high-resolution H<jats:italic>α</jats:italic> observation of a quiescent prominence by the New Vacuum Solar Telescope. Two noteworthy bubble–plume events are studied in detail. The two events are almost identical, except that an erupting mini filament appeared below the prominence–bubble interface in the second event, unlike the first one or any of the reported bubble observations. Analysis of the H<jats:italic>α</jats:italic> and extreme-ultraviolet data indicates that the rising magnetic flux rope (MFR) in the mini filament is the cause of bubble expansion and that the interaction between the prominence and MFR results in plume formation. These observations provided clear evidence that emerging MFR may be a common trigger of bubbles and suggested a new mechanism of plumes in addition to Rayleigh–Taylor instability and reconnection.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the first direct detection of molecular hydrogen associated with the Galactic nuclear wind. The Far-Ultraviolet Spectroscopic Explorer spectrum of LS 4825, a B1 Ib–II star at <jats:italic>l</jats:italic>, <jats:italic>b</jats:italic> = 1.67°,−6.63° lying <jats:italic>d</jats:italic> = 9.9<jats:inline-formula> <jats:tex-math> <?CDATA ${}_{-0.8}^{+1.4}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow /> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.4</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac3cbcieqn1.gif" xlink:type="simple" /> </jats:inline-formula> kpc from the Sun, ∼1 kpc below the Galactic plane near the Galactic center, shows two high-velocity H<jats:sub>2</jats:sub> components at <jats:italic>v</jats:italic> <jats:sub>LSR</jats:sub> = −79 and −108 km s<jats:sup>−1</jats:sup>. In contrast, the FUSE spectrum of the nearby (∼0.6° away) foreground star HD 167402 at <jats:italic>d</jats:italic> = 4.9<jats:inline-formula> <jats:tex-math> <?CDATA ${}_{-0.7}^{+0.8}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow /> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.8</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac3cbcieqn2.gif" xlink:type="simple" /> </jats:inline-formula> kpc reveals no H<jats:sub>2</jats:sub> absorption at these velocities. Over 60 lines of H<jats:sub>2</jats:sub> from rotational levels <jats:italic>J</jats:italic> = 0 to 5 are identified in the high-velocity clouds. For the <jats:italic>v</jats:italic> <jats:sub>LSR</jats:sub> = −79 km s<jats:sup>−1</jats:sup> cloud we measure total log <jats:italic>N</jats:italic>(H<jats:sub>2</jats:sub>) ≥ 16.75 cm<jats:sup>−2</jats:sup>, molecular fraction <jats:inline-formula> <jats:tex-math> <?CDATA ${f}_{{{\rm{H}}}_{2}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>f</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac3cbcieqn3.gif" xlink:type="simple" /> </jats:inline-formula> ≥ 0.8%, and <jats:italic>T</jats:italic> <jats:sub>01</jats:sub> ≥ 97 and <jats:italic>T</jats:italic> <jats:sub>25</jats:sub> ≤ 439 K for the ground- and excited-state rotational excitation temperatures. At <jats:italic>v</jats:italic> <jats:sub>LSR</jats:sub> = −108 km s<jats:sup>−1</jats:sup>, we measure log <jats:italic>N</jats:italic>(H<jats:sub>2</jats:sub>) = 16.13 ± 0.10 cm<jats:sup>−2</jats:sup>, <jats:inline-formula> <jats:tex-math> <?CDATA ${f}_{{{\rm{H}}}_{2}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>f</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac3cbcieqn4.gif" xlink:type="simple" /> </jats:inline-formula> ≥ 0.5%, and <jats:italic>T</jats:italic> <jats:sub>01</jats:sub> = 77<jats:inline-formula> <jats:tex-math> <?CDATA ${}_{-18}^{+34}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow /> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>18</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>34</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac3cbcieqn5.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:italic>T</jats:italic> <jats:sub>25</jats:sub> = 1092<jats:inline-formula> <jats:tex-math> <?CDATA ${}_{-117}^{+149}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow /> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>117</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>149</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac3cbcieqn6.gif" xlink:type="simple" /> </jats:inline-formula> K, for which the excited-state ortho- to para-H<jats:sub>2</jats:sub> is <jats:inline-formula> <jats:tex-math> <?CDATA ${1.0}_{-0.1}^{+0.3}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>1.0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.3</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac3cbcieqn7.gif" xlink:type="simple" /> </jats:inline-formula>, much less than the equilibrium value of 3 expected for gas at this temperature. This nonequilibrium ratio suggests that the −108 km s<jats:sup>−1</jats:sup> cloud has been recently excited and has not yet had time to equilibrate. As the LS 4825 sight line passes close by a tilted section of the Galactic disk, we propose that we are probing a boundary region where the nuclear wind is removing gas from the disk.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Calcium–aluminum-rich inclusions (CAIs) are the oldest materials that formed in the protosolar disk. Igneous CAIs experienced melting and subsequent crystallization in the disk during which the evaporation of relatively volatile elements such as Mg and Si occurred. Evaporation from the melt would have played a significant role in the variation of chemical, mineralogical, and petrologic characteristics of the igneous CAIs. In this study, we investigated crystallization of CAI analog melt under disk-like low-pressure hydrogen (<jats:italic>P</jats:italic> <jats:sub>H2</jats:sub>) conditions of 0.1, 1, and 10 Pa to constrain the pressure condition of the early solar system in which type B CAIs were formed. At <jats:italic>P</jats:italic> <jats:sub>H2</jats:sub> = 10 Pa, the samples were mantled by melilite crystals, as observed for type B1 CAIs. However, the samples heated at <jats:italic>P</jats:italic> <jats:sub>H2</jats:sub> = 0.1 Pa exhibited random distribution of melilite, as in type B2 CAIs. At the intermediate <jats:italic>P</jats:italic> <jats:sub>H2</jats:sub> of 1 Pa, type-B1-like structure formed when the cooling rate was 5°C hr<jats:sup>−1</jats:sup>, whereas the formation of type-B2-like structure required a cooling rate faster than 20°C hr<jats:sup>−1</jats:sup>. The compositional characteristics of melilite in type B1 and B2 CAIs could also be reproduced by experiments. The results of the present study suggest that <jats:italic>P</jats:italic> <jats:sub>H2</jats:sub> required for type-B1-like textural and chemical characteristics is greater than 1 Pa. The hydrogen pressure estimated in this study would impose an important constraint on the physical condition of the protosolar disk where type B CAIs were formed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present high-resolution 2D and 3D simulations of magnetized decaying turbulence in relativistic, resistive magnetohydrodynamics. The simulations show dynamic formation of large-scale intermittent long-lived current sheets being disrupted into plasmoid chains by the tearing instability. These current sheets are locations of enhanced magnetic-field dissipation and heating of the plasma. We find magnetic energy spectra ∝<jats:italic>k</jats:italic> <jats:sup>−3/2</jats:sup>, together with strongly pronounced dynamic alignment of Elsässer fields and of velocity and magnetic fields, for strong guide-field turbulence, whereas we retrieve spectra ∝<jats:italic>k</jats:italic> <jats:sup>−5/3</jats:sup> for the case of a weak guide-field.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Numerical models of collisionless shocks robustly predict an electron distribution composed of both thermal and nonthermal electrons. Here, we explore in detail the effect of thermal electrons on the emergent synchrotron emission from subrelativistic shocks. We present a complete “thermal + nonthermal” synchrotron model and derive properties of the resulting spectrum and light curves. Using these results, we delineate the relative importance of thermal and nonthermal electrons for subrelativistic shock-powered synchrotron transients. We find that thermal electrons are naturally expected to contribute significantly to the peak emission if the shock velocity is ≳0.2<jats:italic>c</jats:italic>, but would be mostly undetectable in nonrelativistic shocks. This helps explain the dichotomy between typical radio supernovae and the emerging class of “AT2018cow-like” events. The signpost of thermal electron synchrotron emission is a steep optically-thin spectral index and a <jats:italic>ν</jats:italic> <jats:sup>2</jats:sup> optically-thick spectrum. These spectral features are also predicted to correlate with a steep postpeak light-curve decline rate, broadly consistent with observed AT2018cow-like events. We expect that thermal electrons may be observable in other contexts where mildly relativistic shocks are present and briefly estimate this effect for gamma-ray burst afterglows and binary–neutron-star mergers. Our model can be used to fit spectra and light curves of events and accounts for both thermal and nonthermal electron populations with no additional physical degrees of freedom.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Condensable species are crucial to shaping planetary climate. A wide range of planetary climate systems involve understanding nondilute condensable substances and their influence on climate dynamics. There has been progress on large-scale dynamical effects and on 1D convection parameterization, but resolved 3D moist convection remains unexplored in nondilute conditions, though it can have a profound impact on temperature/humidity profiles and cloud structure. In this work, we tackle this problem for pure-steam atmospheres using three-dimensional, high-resolution numerical simulations of convection in postrunaway atmospheres. We show that the atmosphere is composed of two characteristic regions, an upper condensing region dominated by gravity waves and a lower noncondensing region characterized by convective overturning cells. Velocities in the condensing region are much smaller than those in the lower, noncondensing region, and the horizontal temperature variation is small. Condensation in the thermal photosphere is largely driven by radiative cooling and tends to be statistically homogeneous. Some condensation also happens deeper, near the boundary of the condensing region, due to triggering by gravity waves and convective penetrations and exhibits random patchiness. This qualitative structure is insensitive to varying model parameters, but quantitative details may differ. Our results confirm theoretical expectations that atmospheres close to the pure-steam limit do not have organized deep convective plumes in the condensing region. The generalized convective parameterization scheme discussed in Ding &amp; Pierrehumbert is appropriate for handling the basic structure of atmospheres near the pure-steam limit but cannot capture gravity waves and their mixing which appear in 3D convection-resolving models.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In spite of substantial advancements in simulating planet formation, the planet Mercury’s diminutive mass and isolated orbit and the absence of planets with shorter orbital periods in the solar system continue to befuddle numerical accretion models. Recent studies have shown that if massive embryos (or even giant planet cores) formed early in the innermost parts of the Sun’s gaseous disk, they would have migrated outward. This migration may have reshaped the surface density profile of terrestrial planet-forming material and generated conditions favorable to the formation of Mercury-like planets. Here we continue to develop this model with an updated suite of numerical simulations. We favor a scenario where Earth’s and Venus’s progenitor nuclei form closer to the Sun and subsequently sculpt the Mercury-forming region by migrating toward their modern orbits. This rapid formation of ∼0.5 <jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub> cores at ∼0.1–0.5 au is consistent with modern high-resolution simulations of planetesimal accretion. In successful realizations, Earth and Venus accrete mostly dry, enstatite chondrite–like material as they migrate, thus providing a simple explanation for the masses of all four terrestrial planets, the inferred isotopic differences between Earth and Mars, and Mercury’s isolated orbit. Furthermore, our models predict that Venus’s composition should be similar to the Earth’s and possibly derived from a larger fraction of dry material. Conversely, Mercury analogs in our simulations attain a range of final compositions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Recently, FRB 190520B, which has the largest extragalactic dispersion measure (DM), was discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The DM excess over the intergalactic medium and Galactic contributions is estimated as ∼900 pc cm<jats:sup>−3</jats:sup>, which is nearly ten times higher than that of other fast-radio-burst (FRB) host galaxies. The DM decreases with the rate ∼0.1 pc cm<jats:sup>−3</jats:sup> per day. It is the second FRB associated with a compact persistent radio source (PRS). The rotation measure (RM) is found to be larger than 1.8 × 10<jats:sup>5</jats:sup>rad m<jats:sup>−2</jats:sup>. In this Letter, we argue that FRB 190520B is powered by a young magentar formed by core collapse of massive stars, embedded in a composite of a magnetar wind nebula (MWN) and supernova remnant (SNR). The energy injection of the magnetar drives the MWN and SN ejecta to evolve together and the PRS is generated by the synchrotron radiation of the MWN. The magnetar has an interior magnetic field <jats:italic>B</jats:italic> <jats:sub>int</jats:sub> ∼ (2–4) × 10<jats:sup>16</jats:sup> G and an age <jats:italic>t</jats:italic> <jats:sub>age</jats:sub> ∼ 14–22 yr. The dense SN ejecta and the shocked shell contribute a large fraction of the observed DM and RM. Our model can naturally and simultaneously explain the luminous PRS, decreasing DM, and extreme RM of FRB 190520B.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Be star X-ray binaries are transient systems that show two different types of outbursts. Type I outbursts occur each orbital period while type II outbursts have a period and duration that are not related to any periodicity of the binary system. Type II outbursts may be caused by mass transfer to the neutron star from a highly eccentric Be star disk. A sufficiently misaligned Be star decretion disk undergoes secular Von Zeipel–Lidov–Kozai (ZLK) oscillations of eccentricity and inclination. Observations show that in some systems the type II outbursts come in pairs with the second being of lower luminosity. We use numerical hydrodynamical simulations to explore the dynamics of the highly misaligned disk that forms around the neutron star as a consequence of mass transfer from the Be star disk. We show that the neutron star disk may also be ZLK unstable and that the eccentricity growth leads to an enhancement in the accretion rate onto the neutron star that lasts for several orbital periods, resembling a type II outburst. We suggest that in a type II outburst pair, the first outburst is caused by mass transfer from the eccentric Be star disk while the second and smaller outburst is caused by the eccentric neutron star disk. We find that the timescale between outbursts in a pair may be compatible with the observed estimates.</jats:p>