Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Theoretical models show that the power of relativistic jets of active galactic nuclei depends on the spin and mass of the central supermassive black holes, as well as the accretion. Here we report an analysis of archival observations of a sample of blazars. We find a significant correlation between jet kinetic power and the spin of supermassive black holes. At the same time, we use multiple linear regression to analyze the relationship between jet kinetic power and accretion, spin, and black hole mass. We find that the spin of supermassive black holes and accretion are the most important contributions to the jet kinetic power. The contribution rates of both the spin of supermassive black holes and accretion are more than 95%. These results suggest that the spin energy of supermassive black holes powers the relativistic jets. The jet production efficiency of almost all Fermi blazars can be explained by moderately thin, magnetically arrested accretion disks around rapidly spinning black holes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Utilizing the Atacama Large Millimeter/submillimeter Array, we present CS line maps in five rotational lines (<jats:italic>J</jats:italic> <jats:sub>u</jats:sub> = 7, 5, 4, 3, 2) toward the circumnuclear disk (CND) and streamers of the Galactic center. Our primary goal is to resolve the compact structures within the CND and the streamers, in order to understand the stability conditions of molecular cores in the vicinity of the supermassive black hole (SMBH) Sgr A*. Our data provide the first homogeneous high-resolution (1.″3 = 0.05 pc) observations aiming at resolving density and temperature structures. The CS clouds have sizes of 0.05–0.2 pc with a broad range of velocity dispersion (<jats:italic>σ</jats:italic> <jats:sub>FWHM</jats:sub> = 5–40 km s<jats:sup>−1</jats:sup>). The CS clouds are a mixture of warm (<jats:italic>T</jats:italic> <jats:sub>k</jats:sub> ≥ 50–500 K, <jats:inline-formula> <jats:tex-math> <?CDATA ${n}_{{{\rm{H}}}_{2}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>n</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="apjabf4cdieqn1.gif" xlink:type="simple" /> </jats:inline-formula> = 10<jats:sup>3</jats:sup>–10<jats:sup>5</jats:sup> cm<jats:sup>−3</jats:sup>) and cold gas (<jats:italic>T</jats:italic> <jats:sub>k</jats:sub> ≤ 50 K, <jats:inline-formula> <jats:tex-math> <?CDATA ${n}_{{{\rm{H}}}_{2}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>n</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="apjabf4cdieqn2.gif" xlink:type="simple" /> </jats:inline-formula> = 10<jats:sup>6</jats:sup>–10<jats:sup>8</jats:sup> cm<jats:sup>−3</jats:sup>). A stability analysis based on the unmagnetized virial theorem including tidal force shows that <jats:inline-formula> <jats:tex-math> <?CDATA ${84}_{-37}^{+16} \% $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>84</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>37</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>16</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>%</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabf4cdieqn3.gif" xlink:type="simple" /> </jats:inline-formula> of the total gas mass is tidally stable, which accounts for the majority of gas mass. Turbulence dominates the internal energy and thereby sets the threshold densities 10–100 times higher than the tidal limit at distance ≥1.5 pc to Sgr A*, and therefore it inhibits the clouds from collapsing to form stars near the SMBH. However, within the central 1 pc, the tidal force overrides turbulence and the threshold densities for a gravitational collapse quickly grow to ≥ 10<jats:sup>8</jats:sup> cm<jats:sup>−3</jats:sup>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Many theoretical studies have shown that external photoevaporation from massive stars can severely truncate, or destroy altogether, the gaseous protoplanetary disks around young stars. In tandem, several observational studies report a correlation between the mass of a protoplanetary disk and its distance to massive ionizing stars in star-forming regions, and cite external photoevaporation by the massive stars as the origin of this correlation. We present <jats:italic>N</jats:italic>-body simulations of the dynamical evolution of star-forming regions and determine the mass loss in protoplanetary disks from external photoevaporation due to far-ultraviolet and extreme-ultraviolet radiation from massive stars. We find that projection effects can be significant, in that low-mass disk-hosting stars that appear close to the ionizing sources may be fore- or background stars in the star-forming region. We find very little evidence in our simulations for a trend in increasing disk mass with increasing distance from the massive star(s), even when projection effects are ignored. Furthermore, the dynamical evolution of these young star-forming regions moves stars whose disks have been photoevaporated to far-flung locations, away from the ionizing stars, and we suggest that any correlation between disk mass and distance from the ionizing star is either coincidental, or due to some process other than external photoevaporation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This work proposes a thermophysical model for realistic surface layers on airless small bodies (RSTPM) for the use of interpreting their multiepoch thermal light curves (e.g., WISE/NEOWISE). RSTPM considers the real orbital cycle, rotation cycle, rough surface, temperature-dependent thermal parameters, as well as contributions of sunlight reflection to observations. It is thus able to produce a precise temperature distribution and thermal emission of airless small bodies regarding the variations on orbital timescales. Details of the physics, mathematics, and numerical algorithms of RSTPM are presented. When used to interpret multiepoch thermal light curves by WISE/NEOWISE, RSTPM can give constraints on the spin orientation and surface physical properties, such as the mean thermal inertia or the mean size of dust grains, the roughness fraction, and the albedo via a radiometric procedure. As an application example, we apply this model to the main-belt object (24) Themis, the largest object of the Themis family, which is believed to be the source region of many main-belt comets. We find multiepoch (2010, 2014–2018) observations of Themis by WISE/NEOWISE, yielding 18 thermal light curves. By fitting these data with RSTPM, the best-fit spin orientation of Themis is derived to be (<jats:italic>λ</jats:italic> = 137°, <jats:italic>β</jats:italic> = 59°) in ecliptic coordinates, and the mean radius of dust grains on the surface is estimated to be <jats:inline-formula> <jats:tex-math> <?CDATA $\tilde{b}=\,{140}_{-114}^{+500}(6\sim 640)$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>b</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>˜</mml:mo> </mml:mrow> </mml:mover> <mml:mo>=</mml:mo> <mml:mspace width="0.25em" /> <mml:msubsup> <mml:mrow> <mml:mn>140</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>114</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>500</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo stretchy="false">(</mml:mo> <mml:mn>6</mml:mn> <mml:mo>∼</mml:mo> <mml:mn>640</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabf4c9ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>μ</jats:italic>m, indicating that the surface thermal inertia varies from ∼3 Jm<jats:sup>−2</jats:sup> s<jats:sup>−0.5</jats:sup> K<jats:sup>−1</jats:sup> to ∼60 Jm<jats:sup>−2</jats:sup> <jats:italic>s</jats:italic> <jats:sup>−0.5</jats:sup> K<jats:sup>−1</jats:sup> due to seasonal temperature variation. A more detailed analysis found that the thermal light curves of Themis show a weak feature that depends on the rotation phase, which is indicative of heterogeneous thermal properties or imperfections of the light-curve inversion shape model.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Nonpotential magnetic energy promptly released in solar flares is converted to other forms of energy. This may include nonthermal energy of flare-accelerated particles, thermal energy of heated flaring plasma, and kinetic energy of eruptions, jets, upflows/downflows, and stochastic (turbulent) plasma motions. The processes or parameters governing partitioning of the released energy between these components are an open question. How these components are distributed between distinct flaring loops and what controls these spatial distributions are also unclear. Here, based on multiwavelength data and 3D modeling, we quantify the energy partitioning and spatial distribution in the well-observed SOL2014-02-16T064620 solar flare of class C1.5. Nonthermal emission of this flare displayed a simple impulsive single-spike light curve lasting about 20 s. In contrast, the thermal emission demonstrated at least three distinct heating episodes, only one of which was associated with the nonthermal component. The flare was accompanied by upflows and downflows and substantial turbulent velocities. The results of our analysis suggest that (i) the flare occurs in a multiloop system that included at least three distinct flux tubes; (ii) the released magnetic energy is divided unevenly between the thermal and nonthermal components in these loops; (iii) only one of these three flaring loops contains an energetically important amount of nonthermal electrons, while two other loops remain thermal; (iv) the amounts of direct plasma heating and that due to nonthermal electron loss are comparable; and (v) the kinetic energy in the flare footpoints constitutes only a minor fraction compared with the thermal and nonthermal energies.</jats:p>