Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We present the turbulence spectra of magnetic and electron density fluctuations in situ measured by Voyager 1 in the local interstellar medium from 2012 to 2019. The magnetic spectrum shows a Kolmogorov power law with a one-dimensional power-law index −5/3 at m<jats:italic>k</jats:italic> ≤ 10<jats:sup>−8.8</jats:sup>, where <jats:italic>k</jats:italic> is a wavenumber and m is the unit meter. A bulge of enhanced magnetic power is found at m<jats:italic>k</jats:italic> = 10<jats:sup>−8.8</jats:sup>–10<jats:sup>−8.2</jats:sup>. Meanwhile, the electron density spectrum also shows a Kolmogorov power law with a one-dimensional power-law index −5/3 in the inertial range. A bulge of enhanced power is found around the kinetic scales of m<jats:italic>k</jats:italic> ≈ 10<jats:sup>−5</jats:sup>–10<jats:sup>−1</jats:sup>. Based on the observational data, the relationships between the outer scale of the turbulent system and the powers of electron density and magnetic fluctuations are obtained. We then calculate the spectra locally for six individual time periods, within which the electron density and magnetic fluctuations are simultaneously observed. It is found that the power of perpendicular magnetic fluctuations is usually higher than that of parallel magnetic fluctuations, which indicates the dominance of Alfvén waves in turbulence spectrum. Part of the observed turbulence spectra reveal that the normalized parallel magnetic power exhibits a much higher intensity than the normalized electron density power in the local interstellar medium of low to moderate plasma beta (<jats:italic>β</jats:italic> = 0.1–0.8). This dominance in the parallel magnetic power cannot be explained by the linear magnetohydrodynamic modes alone and may be associated with the arc/spherically polarized Alfvén mode.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Hierarchical triples are expected to be produced by the frequent binary-mediated interactions in the cores of globular clusters. In some of these triples, the tertiary companion can drive the inner binary to merger following large eccentricity oscillations, as a result of the eccentric Kozai–Lidov mechanism. In this paper, we study the dynamics and merger rates of black hole (BH) hierarchical triples, formed via binary–binary encounters in the <jats:monospace>CMC Cluster Catalog</jats:monospace>, a suite of cluster simulations with present-day properties representative of the Milky Way’s globular clusters. We compare the properties of the mergers from triples to the other merger channels in dense star clusters, and show that triple systems do not produce significant differences in terms of mass and effective spin distribution. However, they represent an important pathway for forming eccentric mergers, which could be detected by LIGO–Virgo/KAGRA (LVK), and future missions such as LISA and the DECi-hertz Interferometer Gravitational wave Observatory. We derive a conservative lower limit for the merger rate from this channel of 0.35 Gpc<jats:sup>−3</jats:sup> yr<jats:sup>−1</jats:sup> in the local universe and up to <jats:inline-formula> <jats:tex-math> <?CDATA $\sim 9 \% $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∼</mml:mo> <mml:mn>9</mml:mn> <mml:mo>%</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabba25ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> of these events may have a detectable eccentricity at LVK design sensitivity. Additionally, we find that triple systems could play an important role in retaining second-generation BHs, which can later merge again in the core of the host cluster.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the results of an extensive <jats:italic>γ</jats:italic>-ray data analysis of the emission from the blazar S5 0716+714 with the primary motivation to study its temporal and spectral variability behavior. In this work, we extract a 10 days binned <jats:italic>γ</jats:italic>-ray light curve from 2008 August 4 to 2016 April 27 in the energy range of 0.1–300 GeV and identify six outburst periods with peak flux of &gt;4 × 10<jats:sup>−7</jats:sup> ph cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup> from this highly variable source. The brightest flares are identified by zooming in these outburst periods to 1 day binning and using the Bayesian Blocks algorithm. The fastest variability timescale is found to be 1.5 ± 0.3  hr at MJD 57128.01 ± 0.01 with a peak flux above 100 MeV of (26.8 ± 6.9) × 10<jats:sup>−7</jats:sup> ph cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup>. No hint of periodic modulations has been detected for the light curve of S5 0716+714. During the outburst phases, the <jats:italic>γ</jats:italic>-ray spectrum shows an obvious spectral break with a break energy between 0.93 and 6.90 GeV energies, which may be caused by an intrinsic break in the energy distribution of radiating particles. The five highest-energy photons, with <jats:italic>E</jats:italic> &gt; 100 GeV, imply that the high-energy emission from this source may originate from a moving emission region in a helical path upstream in the jet. The spectral behavior and temporal characteristics of the individual flares indicate that the location of the emission region lies in the sub-parsec scale (<jats:italic>r</jats:italic> <jats:sub> <jats:italic>γ</jats:italic> </jats:sub> &lt; 0.85 pc).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Active region (AR) outflows have been studied in detail since the launch of Hinode/EIS and are believed to provide a possible source of mass and energy to the slow solar wind. In this work, we investigate the lower atmospheric counterpart of AR outflows using observations from the Interface Region Imaging Spectrograph (IRIS). We find that the IRIS Si <jats:sc>iv</jats:sc>, C <jats:sc>ii,</jats:sc> and Mg <jats:sc>ii</jats:sc> transition region (TR) and chromospheric lines exhibit different spectral features in the outflows as compared to neighboring regions at the footpoints (“moss”) of hot AR loops. The average redshift of Si <jats:sc>iv</jats:sc> in the outflow region (≈5.5 km s<jats:sup>−1</jats:sup>) is smaller than typical moss (≈12–13 km s<jats:sup>−1</jats:sup>) and quiet Sun (≈7.5 km s<jats:sup>−1</jats:sup>) values, while the C <jats:sc>ii</jats:sc> line is blueshifted (≈-1.1–1.5 km s<jats:sup>−1</jats:sup>), in contrast to the moss where it is observed to be redshifted by about ≈2.5 km s<jats:sup>−1</jats:sup>. Further, we observe that the low atmosphere underneath the coronal outflows is highly structured, with the presence of blueshifts in Si <jats:sc>iv</jats:sc> and positive Mg <jats:sc>ii</jats:sc> k2 asymmetries (which can be interpreted as signatures of chromospheric upflows) which are mostly not observed in the moss. These observations show a clear correlation between the coronal outflows and the chromosphere and TR underneath, which has not been shown before. Our work strongly suggests that these regions are not separate environments and should be treated together, and that current leading theories of AR outflows, such as the interchange reconnection model, need to take into account the dynamics of the low atmosphere.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The hardening and softening features in the DAMPE proton spectrum are very likely to have originated from a nearby supernova remnant (SNR). The proton spectrum from the nearby SNR is required to be very hard below ≈10 TeV. To reproduce this feature, we illustrate that an anomalously slow-diffusion zone for cosmic rays (CRs) must exist in the local interstellar medium (ISM) after also taking the dipole anisotropy of CRs into account. Assuming that the diffusion coefficient is homogeneous in the nearby ISM, we show that the diffusion coefficient is constrained to the magnitude of 10<jats:sup>26</jats:sup> cm<jats:sup>2</jats:sup> s<jats:sup>−1</jats:sup> when normalized to 1 GeV, which is about 100 times smaller than the average value in the Galaxy. We further discuss the spatial distribution of the slow diffusion and find two distinct possibilities. In one case, the SNR is several hundred parsecs away from the solar system, and both the SNR and the solar system must be included in a large slow-diffusion zone. In the other case, the SNR is very close with a distance of ∼50 pc and the slow-diffusion zone is only limited around the SNR, while the current multiwavelength observations do not indicate such a close source. This work provides a new way of studying the CR diffusion in the local ISM.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on a detailed study of the mode switching in pulsar J1326−6700 by analyzing the data acquired from the Parkes 64 m radio telescope at 1369 MHz. During the abnormal mode, the emission at the central and trailing components becomes extremely weak. Meanwhile, the leading emission shifts toward earlier longitude by almost 2°, and remains in this position for typically less than a minute. The mean flux density of the normal mode is almost five times that of the abnormal mode. Our data show that, for PSR J1326−6700, 85% of the time was spent in the normal mode and 15% was in the abnormal mode. The intrinsic distributions of mode timescales can be well described by Weibull distributions, which present a certain amount of memory in mode switching. Furthermore, a quasiperiodicity has been identified in the mode switching in pulsar J1326−6700. The estimated delay emission heights based on the kinematical effects indicate that the abnormal mode may have originated from higher altitude than the normal mode.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The flare produced when a star is tidally disrupted by a supermassive black hole holds potential as a diagnostic of both the black hole mass and the star mass. We propose a new method to realize this potential based upon a physical model of optical/UV light production in which shocks near the apocenters of debris orbits dissipate orbital energy, which is then radiated from that region. Measurement of the optical/UV luminosity and color temperature at the peak of the flare leads directly to the two masses. The black hole mass depends mostly on the temperature observed at peak luminosity, while the mass of the disrupted star depends mostly on the peak luminosity. We introduce TDE<jats:sc>mass</jats:sc>, a method to infer the black hole and stellar masses given these two input quantities. Using TDE<jats:sc>mass</jats:sc>, we find, for 21 well-measured events, black hole masses between 5 × 10<jats:sup>5</jats:sup> and 10<jats:sup>7</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and disrupted stars with initial masses between 0.6 and 13 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. An open-source <jats:sc>python</jats:sc>-based tool for TDE<jats:sc>mass</jats:sc> is available at <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://github.com/taehoryu/TDEmass.git" xlink:type="simple">https://github.com/taehoryu/TDEmass.git</jats:ext-link>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present <jats:inline-formula> <jats:tex-math> <?CDATA $\sim 10\mbox{--}40\,\mu {\rm{m}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbefbieqn1.gif" xlink:type="simple" /> </jats:inline-formula> SOFIA–FORCAST images of 14 intermediate-mass protostar candidates as part of the SOFIA Massive (SOMA) Star Formation Survey. We build spectral energy distributions, also using archival Spitzer, Herschel, and IRAS data. We then fit the spectral energy distributions with radiative transfer models of Zhang &amp; Tan, based on turbulent core accretion theory, to estimate key protostellar properties. With the addition of these intermediate-mass sources, based on average properties derived from SED fitting, SOMA protostars span luminosities from <jats:inline-formula> <jats:tex-math> <?CDATA $\sim {10}^{2}\,\mathrm{to}\,{10}^{6}\ {L}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbefbieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, current protostellar masses from <jats:inline-formula> <jats:tex-math> <?CDATA $\sim 0.5\,{\rm{t}}{\rm{o}}\,35\,{M}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbefbieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, and ambient clump mass surface densities, <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{\Sigma }}}_{\mathrm{cl}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbefbieqn4.gif" xlink:type="simple" /> </jats:inline-formula>, from <jats:inline-formula> <jats:tex-math> <?CDATA $0.1\,\mathrm{to}\,3\,{\rm{g}}\,{\mathrm{cm}}^{-2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbefbieqn5.gif" xlink:type="simple" /> </jats:inline-formula>. A wide range of evolutionary states of the individual protostars and of the protocluster environments is also probed. We have also considered about 50 protostars identified in infrared dark clouds that are expected to be at the earliest stages of their evolution. With this global sample, most of the evolutionary stages of high- and intermediate-mass protostars are probed. The best-fitting models show no evidence that a threshold value of the protocluster clump mass surface density is required to form protostars up to <jats:inline-formula> <jats:tex-math> <?CDATA $\sim 25\ {M}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbefbieqn6.gif" xlink:type="simple" /> </jats:inline-formula>. However, to form more massive protostars, there is tentative evidence that <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{\Sigma }}}_{\mathrm{cl}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbefbieqn7.gif" xlink:type="simple" /> </jats:inline-formula> needs to be <jats:inline-formula> <jats:tex-math> <?CDATA $\gtrsim 1\,{\rm{g}}\,{\mathrm{cm}}^{-2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabbefbieqn8.gif" xlink:type="simple" /> </jats:inline-formula>. We discuss how this is consistent with expectations from core accretion models that include internal feedback from the forming massive star.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present high spatial resolution (52 au) observations of the high-mass young stellar object (HMYSO) G345.4938+01.4677 made using the Atacama Large Millimeter/submillimeter Array. This O-type HMYSO is located at 2.38 kpc and is associated with a luminosity of 1.5 × 10<jats:sup>5 </jats:sup> <jats:italic>L</jats:italic> <jats:sub>☉</jats:sub>. We detect circumstellar emission from the H38<jats:italic>β</jats:italic> hydrogen recombination line showing a compact structure rotating perpendicularly to the previously detected radio jet. We interpret this emission as tracing a photoionized accretion disk around the HMYSO. While this disk-like structure seems currently too small to sustain continued accretion, the data present direct observational evidence of how disks can effectively survive the photoionization feedback from young high-mass stars. We also report the detection of a low-mass young stellar object in the vicinity of the HMYSO and suggest that it forms a high-mass and low-mass star binary system.</jats:p>