Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The seven seconds’ gap in the Kamiokande-II SN1987A neutrino data is reexamined.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a new investigation of the intergalactic medium (IGM) near the end of reionization using “dark gaps” in the Ly<jats:italic>α</jats:italic> forest. Using spectra of 55 QSOs at <jats:italic>z</jats:italic> <jats:sub>em</jats:sub> &gt; 5.5, including new data from the XQR-30 VLT Large Programme, we identify gaps in the Ly<jats:italic>α</jats:italic> forest where the transmission averaged over 1 comoving <jats:italic>h</jats:italic> <jats:sup>−1</jats:sup> Mpc bins falls below 5%. Nine ultralong (<jats:italic>L</jats:italic> &gt; 80 <jats:italic>h</jats:italic> <jats:sup>−1</jats:sup> Mpc) dark gaps are identified at <jats:italic>z</jats:italic> &lt; 6. In addition, we quantify the fraction of QSO spectra exhibiting gaps longer than 30 <jats:italic>h</jats:italic> <jats:sup>−1</jats:sup> Mpc, <jats:italic>F</jats:italic> <jats:sub>30</jats:sub>, as a function of redshift. We measure <jats:italic>F</jats:italic> <jats:sub>30</jats:sub> ≃ 0.9, 0.6, and 0.15 at <jats:italic>z</jats:italic> = 6.0, 5.8, and 5.6, respectively, with the last of these long dark gaps persisting down to <jats:italic>z</jats:italic> ≃5.3. Comparing our results with predictions from hydrodynamical simulations, we find that the data are consistent with models wherein reionization extends significantly below redshift six. Models wherein the IGM is essentially fully reionized that retain large-scale fluctuations in the ionizing UV background at <jats:italic>z</jats:italic> ≲6 are also potentially consistent with the data. Overall, our results suggest that signatures of reionization in the form of islands of neutral hydrogen and/or large-scale fluctuations in the ionizing background remain present in the IGM until at least <jats:italic>z</jats:italic> ≃ 5.3.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Although the fast kink oscillation, as one of a few fundamental modes in coronal seismology, has received a lot of attention over the past two decades, observations of its frequency drift remain elusive. There is evidence that this phenomenon is related to the quasi-static evolution of loop density. We therefore consider analytically the effects of a quasi-static density evolution on the fast kink oscillation of coronal loops. From the analyses, we determine explicitly the analytic dependence of the oscillation period/frequency and amplitude on the evolving density of the oscillatory loop. The findings can well reconcile several key characters in some frequency drift observations, which are not understood. Models of fast kink oscillation in the thermal dynamic loop are also established to investigate the present effects in more detail. Our findings not only show us a possible explanation for the frequency drift of the coronal loop’s fast kink oscillation, but also a full new energy transformation mechanism where the internal energy and the kinetic energy of an oscillating coronal loop can be interchanged directly by the interaction of the loop’s oscillation and its density evolution, which we suggest may provide a new clue for the energy processes associated with a thermodynamic resonator in the space magnetic plasma.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use Atacama Cosmology Telescope (ACT) observations at 98 GHz (2015–2019), 150 GHz (2013–2019), and 229 GHz (2017–2019) to perform a blind shift-and-stack search for Planet 9. The search explores distances from 300 au to 2000 au and velocities up to 6.′3 per year, depending on the distance (<jats:italic>r</jats:italic>). For a 5 Earth-mass Planet 9 the detection limit varies from 325 au to 625 au, depending on the sky location. For a 10 Earth-mass planet the corresponding range is 425 au to 775 au. The predicted aphelion and most likely location of the planet corresponds to the shallower end of these ranges. The search covers the whole 18,000 square degrees of the ACT survey. No significant detections are found, which is used to place limits on the millimeter-wave flux density of Planet 9 over much of its orbit. Overall we eliminate roughly 17% and 9% of the parameter space for a 5 and 10 Earth-mass Planet 9, respectively. These bounds approach those of a recent INPOP19a ephemeris-based analysis, but do not exceed it. We also provide a list of the 10 strongest candidates from the search for possible follow-up. More generally, we exclude (at 95% confidence) the presence of an unknown solar system object within our survey area brighter than 4–12 mJy (depending on position) at 150 GHz with current distance 300 au &lt; <jats:italic>r</jats:italic> &lt; 600 au and heliocentric angular velocity <jats:inline-formula> <jats:tex-math> <?CDATA $1\buildrel{\,\prime}\over{.} 5\,{\mathrm{yr}}^{-1}\lt v\cdot \tfrac{500\,\mathrm{au}}{r}\lt 2\buildrel{\prime\prime}\over{.} 3\,{\mathrm{yr}}^{-1}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>1</mml:mn> <mml:mo>.′</mml:mo> <mml:mn>5</mml:mn> <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:mo>&lt;</mml:mo> <mml:mi>v</mml:mi> <mml:mo>·</mml:mo> <mml:mstyle displaystyle="false"> <mml:mfrac> <mml:mrow> <mml:mn>500</mml:mn> <mml:mspace width="0.25em" /> <mml:mi>au</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> </mml:mfrac> </mml:mstyle> <mml:mo>&lt;</mml:mo> <mml:mn>2</mml:mn> <mml:mo>.″</mml:mo> <mml:mn>3</mml:mn> <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="apjac2307ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, corresponding to low-to-moderate eccentricities. These limits worsen gradually beyond 600 au, reaching 5–15 mJy by 1500 au.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Acoustic waves excited in the photosphere and below might play an integral part in the heating of the solar chromosphere and corona. However, it is yet not fully clear how much of the initially acoustic wave flux reaches the corona and in what form. We investigate the wave propagation, damping, transmission, and conversion in the lower layers of the solar atmosphere using 3D numerical MHD simulations. A model of a gravitationally stratified expanding straight coronal loop, stretching from photosphere to photosphere, is perturbed at one footpoint by an acoustic driver with a period of 370 s. For this period, acoustic cutoff regions are present below the transition region (TR). About 2% of the initial energy from the driver reaches the corona. The shape of the cutoff regions and the height of the TR show a highly dynamic behavior. Taking only the driven waves into account, the waves have a propagating nature below and above the cutoff region, but are standing and evanescent within the cutoff region. Studying the driven waves together with the background motions in the model reveals standing waves between the cutoff region and the TR. These standing waves cause an oscillation of the TR height. In addition, fast or leaky sausage body-like waves might have been excited close to the base of the loop. These waves then possibly convert to fast or leaky sausage surface-like waves at the top of the main cutoff region, followed by a conversion to slow sausage body-like waves around the TR.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Propagating transverse waves are thought to be a key transporter of Poynting flux throughout the Sun’s atmosphere. Recent studies have shown that these transverse motions, interpreted as the magnetohydrodynamic kink mode, are prevalent throughout the corona. The associated energy estimates suggest the waves carry enough energy to meet the demands of coronal radiative losses in the quiescent Sun. However, it is still unclear how the waves deposit their energy into the coronal plasma. We present the results from a large-scale study of propagating kink waves in the quiescent corona using data from the Coronal Multi-channel Polarimeter (CoMP). The analysis reveals that the kink waves appear to be weakly damped, which would imply low rates of energy transfer from the large-scale transverse motions to smaller scales via either uniturbulence or resonant absorption. This raises questions about how the observed kink modes would deposit their energy into the coronal plasma. Moreover, these observations, combined with the results of Monte Carlo simulations, lead us to infer that the solar corona displays a spectrum of density ratios, with a smaller density ratio (relative to the ambient corona) in quiescent coronal loops and a higher density ratio in active-region coronal loops.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Small-scale brightenings in solar atmospheric observations are a manifestation of heating and/or energy transport events. We present statistical characteristics of brightenings from a new detection method applied to 1330, 1400, and 2796 Å IRIS slit-jaw image time series. A total of 2377 events were recorded that coexist in all three channels, giving high confidence that they are real. Of these, ≈1800 were spatially coherent, equating to event densities of ∼9.7 × 10<jats:sup>−5</jats:sup> arcsec<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup> within a 90″ × 100″ FOV over 34.5 minutes. Power-law indices estimates are determined for total brightness (2.78 &lt; <jats:italic>α</jats:italic> &lt; 3.71), maximum brightness (3.84 &lt; <jats:italic>α</jats:italic> &lt; 4.70), and average area (4.31 &lt; <jats:italic>α</jats:italic> &lt; 5.70) distributions. Duration and speed distributions do not obey a power law. A correlation is found between the events’ spatial fragmentation, area, and duration, and a weak relationship with total brightness, showing that larger/longer-lasting events are more likely to fragment during their lifetime. Speed distributions show that all events are in motion, with an average speed of ∼7 km s<jats:sup>−1</jats:sup>. The events’ spatial trajectories suggest that cooler 2796 Å events tend to appear slightly later and occupy a different position/trajectory than the hotter channel results. This suggests that either many of these are impulsive events caused by reconnection, with subsequent rapid cooling, or that the triggering event occurs near the TR, with a subsequent propagating disturbance to cooler atmospheric layers. The spatial distribution of events is not uniform, with broad regions devoid of events. A comparison of spatial distribution with properties of other atmospheric layers shows a tentative connection between high magnetic field strength, the corona’s multi-thermality, and high IRIS brightening activity.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Single-line spectroscopic binaries have recently contributed to stellar-mass black hole discovery, independently of the X-ray transient method. We report the identification of a single-line binary system, LTD064402+245919, with an orbital period of 14.50 days. The observed component is a subgiant with a mass of 2.77 ± 0.68 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, radius 15.5 ± 2.5 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub>, effective temperature <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> 4500 ± 200 K, and surface gravity log <jats:italic>g</jats:italic> 2.5 ± 0.25 dex. The discovery makes use of the Large Sky Area Multi-Object fiber Spectroscopic Telescope time-domain and Zwicky Transient Facility survey. Our general-purpose software pipeline applies a Lomb–Scargle periodogram to determine the orbital period and uses machine learning to classify the variable type from the folded light curves. We apply a combined model to estimate the orbital parameters from both the light and radial velocity curves, taking constraints on the primary star mass, mass function, and detection limit of secondary luminosity into consideration. We obtain a radial velocity semiamplitude of 44.6 ± 1.5 km s<jats:sup>−1</jats:sup>, mass ratio of 0.73 ± 0.07, and an undetected component mass of 2.02 ± 0.49 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> when the type of the undetected component is not set. We conclude that the inclination is not well constrained, and that the secondary mass is larger than 1 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> when the undetected component is modeled as a compact object. According to our investigations using a Monte Carlo Markov Chain simulation, increasing the spectra signal-to-noise ratio by a factor of 3 would enable the secondary light to be distinguished (if present). The algorithm and software in this work are able to serve as general-purpose tools for the identification of compact objects quiescent in X-rays.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We analyze the observations of EUV loop evolution associated with the filament eruption located at the border of an active region (AR). The event SOL2013-03-16T14:00 was observed with a large difference in view point by the Solar Dynamics Observatory and Solar Terrestrial Relations Observatory. The filament height is fitted with the sum of a linear and exponential function. These two phases point to different physical mechanisms such as tether-cutting reconnection and a magnetic instability. While no X-ray emission is reported, this event presents classical eruption features like separation of double ribbons and the growth of flare loops. We report the migration of the southern foot of the erupting filament flux rope due to the interchange reconnection with encountered magnetic loops of a neighboring AR. Parallel to the erupting filament, a stable filament remains in the core of the AR. The specificity of this eruption is that coronal loops, located above the nearly joining ends of the two filaments, first contract in phase, then expand and reach a new stable configuration close to the one present at the eruption onset. Both contraction and expansion phases last around 20 minutes. The main difference with previous cases is that the PIL bent about 180° around the end of the erupting filament because the magnetic configuration is at least tripolar. These observations are challenging for models that interpreted previous cases of loop contraction within a bipolar configuration. New simulations are required to broaden the complexity of the configurations studied.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The dynamics of magnetic reconnection in the solar current sheet (CS) is studied by high-resolution 2.5-dimensional MHD simulation. With the commencing of magnetic reconnection, a number of magnetic islands are formed intermittently and move quickly upward and downward along the CS. Upon collision with the semi-closed flux of the flare loops, the downflow islands cause a second reconnection with a rate comparable with that in the main CS. Though the time-integrated magnetic energy release is still dominated by the reconnection in the main CS, the second reconnection can release substantial magnetic energy, annihilating the main islands and generating secondary islands with various scales at the flare loop top. The distribution function of the flux of the secondary islands is found to follow a power law varying from <jats:inline-formula> <jats:tex-math> <?CDATA $f\left(\psi \right)\sim {\psi }^{-1}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>f</mml:mi> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi>ψ</mml:mi> </mml:mrow> </mml:mfenced> <mml:mo>∼</mml:mo> <mml:msup> <mml:mrow> <mml:mi>ψ</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="apjac3142ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> (small scale) to <jats:italic>ψ</jats:italic> <jats:sup>−2</jats:sup> (large scale), which seems to be independent to background plasma <jats:italic>β</jats:italic> and thermal conduction (TC). However, the spatial scale and the strength of the termination shocks driven by the main reconnection outflows or islands decrease if <jats:italic>β</jats:italic> increases or if TC is included. We suggest that the annihilation of magnetic islands at the flare loop top, which is not included in the standard flare model, plays a nonnegligible role in releasing magnetic energy to heat flare plasma and accelerate particles.</jats:p>