Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Computer-assisted tomography (CAT) for interplanetary scintillation (IPS) observations enables the determination of the global distribution of solar wind speed. We compared solar wind speeds derived from the CAT analysis of IPS observations between 1985 and 2019 with in situ observations conducted by the near-Earth and Ulysses spacecraft. From this comparison, we found that solar wind speeds from the IPS observations for 2009–2019 were systematically higher than the in situ observations, whereas those for the period until 2008 were in good agreement with the in situ observations. Further, we found that the discrepancy between IPS and the in situ observations is improved by changing the power index of the empirical relation between the solar wind speed and density fluctuations. The CAT analysis using an optimal value for the power index determined from the comparison between IPS and in situ observations revealed long-term variations in the solar wind speed distribution over three cycles, leading to a better understanding of the time-varying global heliosphere. We found that polar solar winds become highly anisotropic at the Cycle 24/25 minimum, which is a peculiar aspect of this minimum. The IPS observations showed general agreement with the Parker Solar Probe observations around the perihelion of Orbit 1; this supports the reliability of the CAT analysis. The results of this study suggest that the physical properties of solar wind microturbulence may vary with a long-term decline in the solar activity, which provides important implication on the solar wind acceleration.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Stellar motions in the innermost parts of galactic nuclei, where the gravity of a supermassive black hole dominates, follow Keplerian ellipses to the first order of approximation. These orbits may be subject to periodic (Kozai–Lidov) oscillations of their orbital elements if some nonspherically distributed matter (e.g., a secondary massive black hole, coherent stellar subsystem, or large-scale gaseous structure) perturbs the gravity of the central supermassive black hole. These oscillations are, however, affected by the overall potential of the host nuclear star cluster. In this paper, we show that its influence strongly depends on the properties of the particular system, as well as the considered timescale. We demonstrate that for systems with astrophysically relevant parameters, the Kozai–Lidov oscillations of eccentricity can be enhanced by the extended potential of the cluster in terms of reaching significantly higher maximal values. In a more general statistical sense, the oscillations of eccentricity are typically damped. The efficiency of the damping, however, may be small to negligible for the suitable parameters of the system. This applies, in particular, in the case when the perturbing body is on an eccentric orbit.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present characterization of the planetary system architecture for V488 Per, the dustiest main-sequence star known with a fractional infrared luminosity of ≈16%. Far-infrared imaging photometry confirms the existence of an outer planetary system dust population with a blackbody-fit temperature of ≈130 K. Mid-infrared spectroscopy probing the previously identified ≈800 K inner planetary system dust population does not detect any obvious solid-state emission features, suggesting either large grain sizes that mute such emission and/or grain compositions dominated by species like amorphous carbon and metallic iron, which do not produce such features. In the latter case, the presence of significant quantities of iron-rich material could be indicative of the active formation of a Mercury-like planet around V488 Per. In any event, the absence of solid-state emission features is very unusual among main-sequence stars with copious amounts of warm orbiting dust particles; we know of no other such star whose mid-infrared spectrum lacks such features. Combined radial velocity monitoring and adaptive optics imaging find no evidence for stellar/substellar companions within several hundred astronomical units of V488 Per.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the third open gravitational-wave catalog (3-OGC) of compact-binary coalescences, based on the analysis of the public LIGO and Virgo data from 2015 through 2019 (O1, O2, O3a). Our updated catalog includes a population of 57 observations, including 4 binary black hole mergers that had not been previously reported. This consists of 55 binary black hole mergers and the 2 binary neutron star mergers, GW170817 and GW190425. We find no additional significant binary neutron star or neutron star–black hole merger events. The most confident new detection is the binary black hole merger GW190925_232845, which was observed by the LIGO–Hanford and Virgo observatories with <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal P }}_{\mathrm{astro}}\gt 0.99;$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mi>astro</mml:mi> </mml:mrow> </mml:msub> <mml:mo>&gt;</mml:mo> <mml:mn>0.99</mml:mn> <mml:mo>;</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac1c03ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> its primary and secondary component masses are <jats:inline-formula> <jats:tex-math> <?CDATA ${20.2}_{-2.5}^{+3.9}\,{M}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>20.2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>3.9</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em" /> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac1c03ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA ${15.6}_{-2.6}^{+2.1}\,{M}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>15.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2.1</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em" /> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac1c03ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, respectively. We estimate the parameters of all binary black hole events using an up-to-date waveform model that includes both subdominant harmonics and precession effects. To enable deep follow up as our understanding of the underlying populations evolves, we make available our comprehensive catalog of events, including the subthreshold population of candidates, and the posterior samples of our source parameter estimates.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this work, we search for signatures of gravitational millilensing in gamma-ray bursts (GRBs) in which the source−lens−observer geometry produces two images that manifest in the GRB light curve as superimposed peaks with identical temporal variability (or echoes), separated by the time delay between the two images. According to the sensitivity of our detection method, we consider millilensing events due to point-mass lenses in the range of 10<jats:sup>5</jats:sup> − 10<jats:sup>7</jats:sup> <jats:italic> M</jats:italic> <jats:sub>⊙</jats:sub> at lens redshift about half that of the GRB, with a time delay on the order of 10 s. Current GRB observatories are capable of resolving and constraining this lensing scenario if the above conditions are met. We investigated the Fermi/GBM GRB archive from the year 2008 to 2020 using the autocorrelation technique and found one millilensed GRB candidate out of 2137 GRBs searched, which we use to estimate the optical depth of millilensed GRBs by performing a Monte Carlo simulation to find the efficiency of our detection method. Considering a point-mass model for the gravitational lens, where the lens is a supermassive black hole, we show that the density parameter of black holes (Ω<jats:sub>BH</jats:sub>) with mass ≈ 10<jats:sup>6</jats:sup> <jats:italic> M</jats:italic> <jats:sub>⊙</jats:sub> is about 0.007 ± 0.004. Our result is one order of magnitude larger compared to previous work in the lower mass range of 10<jats:sup>2</jats:sup> − 10<jats:sup>3</jats:sup> <jats:italic> M</jats:italic> <jats:sub>⊙</jats:sub>, which gave a density parameter Ω<jats:sub>BH</jats:sub> ≈ 5 × 10<jats:sup>−4</jats:sup>, and recent work in the mass range of 10<jats:sup>2</jats:sup> − 10<jats:sup>7</jats:sup> <jats:italic> M</jats:italic> <jats:sub>⊙</jats:sub>, which reported Ω<jats:sub>BH</jats:sub> ≈ 4.6 × 10<jats:sup>−4</jats:sup>. The mass fraction of black holes in this mass range to the total mass of the universe would be <jats:italic>f</jats:italic> = Ω<jats:sub>BH</jats:sub>/Ω<jats:sub> <jats:italic>M </jats:italic> </jats:sub>≈ 0.027 ± 0.016.</jats:p>