Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We explore the electromagnetic counterparts that will associate with binary-neutron-star mergers for the case that remnant massive neutron stars survive for ≳0.5 s after the merger. For this study, we employ the outflow profiles obtained by long-term general-relativistic neutrino-radiation magnetohydrodynamics simulations with a mean-field dynamo effect. We show that a synchrotron afterglow with high luminosity can be associated with the merger event if the magnetic fields of the remnant neutron stars are significantly amplified by the dynamo effect. We also perform a radiative transfer calculation for kilonovae and find that, for the highly amplified magnetic field cases, the kilonovae can be bright in the early epoch (<jats:italic>t</jats:italic> ≤ 0.5 d), while it shows the optical emission which rapidly declines in a few days and the very bright near-infrared emission which lasts for ∼10 days. All these features have not been found in GW170817, indicating that the merger remnant neutron star formed in GW170817 might have collapsed to a black hole within several hundreds milliseconds or magnetic-field amplification might be a minor effect.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The stellar initial mass function (IMF) is predicted to depend upon the temperature of gas in star-forming molecular clouds. The introduction of an additional parameter, <jats:italic>T</jats:italic> <jats:sub>IMF</jats:sub>, into photometric template fitting suggests most galaxies obey an IMF top heavier than the Galactic IMF. The implications of the revised fit on mass function, quiescence, and turnoff are discussed. At all redshifts, the highest-mass galaxies become quiescent first with the turnoff mass decreasing toward the present. The synchronous turnoff mass across galaxies suggests quiescence is driven by universal mechanisms rather than by stochastic or environmental processes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>For revealing the first step of planet formation, it is important to understand how and when dust grains become larger in a disk around a protostar. To investigate the grain growth, we analyze dust continuum emission toward a disk around the Class I protostar L1489 IRS at 0.9 and 1.3 mm wavelengths obtained by the Atacama Large Millimeter/submillimeter Array. The dust continuum emission extends to a disk radius (<jats:italic>r</jats:italic>) of <jats:italic>r</jats:italic> ∼ 300 au, and the spectral index (<jats:italic>α</jats:italic>) is derived to be <jats:italic>α</jats:italic> ∼ 3.6 at a radius of <jats:italic>r</jats:italic> ∼ 100–300 au, similar to the interstellar dust. Therefore, the grain growth does not occur significantly in the outer disk (<jats:italic>r</jats:italic> ∼ 100–300 au). Furthermore, we tentatively identify a ring-like substructure at <jats:italic>r</jats:italic> ∼ 90 au even though the spatial resolution and sensitivity are not enough to determine this structure. If this is the real ring structure, the ring position and small dust in the disk outer part are consistent with the idea of the growth front. These results suggest that the L1489 protostellar disk may be the beginning of planet formation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present an analysis of the subpulse drift in PSR J1750−3503, which is characterized by abrupt transitions of drift direction. As the pulsar does not exhibit other mode changes or clear nulling, it is an ideal candidate system for studying the phenomenon of drift direction change. For ∼80% of the time, the subpulses are characterized by positive drift—from early to later longitudes—while the drift direction is negative in the other ∼20%. The subpulse separation for single pulses with positive drift, <jats:italic>P</jats:italic> <jats:sub>2</jats:sub> = (18.8 ± 0.1)°, is higher than for single pulses with negative drift, <jats:italic>P</jats:italic> <jats:sub>2</jats:sub> = (17.5 ± 0.2)°. When the drift is stable, the measured repetition time of the drift pattern is <jats:italic>P</jats:italic> <jats:sub>3</jats:sub> <jats:sup>obs</jats:sup> = (43.5 ± 0.4)<jats:italic>P</jats:italic>, where <jats:italic>P</jats:italic> is the pulsar period. We show that the observed data can be reproduced by a carousel models with subpulse rotation around the magnetic axis using a purely dipolar configuration of the surface magnetic field. The observed drift characteristics can be modeled assuming that the actual repetition time <jats:italic>P</jats:italic> <jats:sub>3</jats:sub> &lt; 2<jats:italic>P</jats:italic>, such that we observe its aliased value. A small variation in <jats:italic>P</jats:italic> <jats:sub>3</jats:sub>, of the order of 6% (or less assuming higher alias orders), is enough to reproduce the characteristic drift direction changes we observe.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Fourier transformation is an effective and efficient operation of Gaussianization at the one-point level. Using a set of <jats:italic>N</jats:italic>-body simulation data, we verified that the one-point distribution functions of the dark matter momentum divergence and density fields closely follow complex Gaussian distributions. The one-point distribution function of the quotient of two complex Gaussian variables is introduced and studied. Statistical theories are then applied to model one-point statistics about the growth of individual Fourier modes of the dark matter density field, which can be obtained by the ratio of two Fourier-transformed cosmic fields. Our simulation results proved that the models based on the Gaussian approximation are impressively accurate, and our analysis revealed many interesting aspects of the growth of dark matter’s density fluctuation in Fourier space.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this study, we report on a detailed single-pulse analysis of the radio emission from a rotating radio transient (RRAT) J1918−0449, which is discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The sensitive observations were carried out on 2021 April 30 using the FAST with a central frequency of 1250 MHz and a short time resolution of 49.152 <jats:italic>μ</jats:italic>s, which forms a reliable basis to probe single-pulse emission properties in detail. The source was successively observed for around 2 hr. A total of 83 dispersed bursts with significance above 6<jats:italic>σ</jats:italic> are detected over 1.8 hr. The source’s dispersion measure (DM) and rotational period are determined to be 116.1 ± 0.4 pc cm<jats:sup>−3</jats:sup> and 2479.21 ± 0.03 ms, respectively. The share of registered pulses from the total number of observed periods is 3.12%. No underlying emission is detected in the averaged off-pulse profile. For bursts with fluence larger than 10 Jy ms, the pulse energy follows a power-law distribution with an index of −3.1 ± 0.4, suggesting the existence of bright pulse emission. We find that the distribution of time between subsequent pulses is consistent with a stationary Poisson process and find no evidence of clustering over the 1.8 hr observations, giving a mean burst rate of one burst every 66 s. Close inspection of the detected bright pulses reveals that 21 pulses exhibit well-defined quasiperiodicities. The subpulse drifting is present in nonsuccessive rotations with periodicity of 2.51 ± 0.06 periods. Finally, possible physical mechanisms are discussed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present an updated prescription for the equilibrium tides suitable for population synthesis codes. A grid of 1D evolutionary models was created and the viscous timescale was calculated for each detailed model. A metallicity-dependent power-law relation was fitted to both the convective cores and convective envelopes of the models. The prescription was implemented into the population synthesis code Binary Star Evolution and predicts a 16.5% reduction in the overall number of merges, with those involving main-sequence stars most affected. The new prescription also reduces the overall supernova rate by 3.6% with individual channels being differently affected. The single degenerate Ia supernova occurrence is reduced by 12.8%. The merging of two carbon oxygen white dwarfs to cause a Ia supernova occurs 16% less frequently. The number of subsynchronously rotating stars in close binaries is substantially increased with our prescription, as is the number of noncircularized systems at the start of common-envelope evolution.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A recent hydrodynamic model, the<jats:italic> radiation-driven fountain model</jats:italic> (Wada et al. 2016), presented a dynamical picture that active galactic nuclei (AGNs) tori sustain their geometrical thickness by gas circulation around AGNs, and previous papers have confirmed that this picture is consistent with multiwavelength observations of nearby Seyfert galaxies. Recent near-infrared observations implied that CO rovibrational absorption lines (Δ<jats:italic>J</jats:italic> = ± 1, <jats:italic>v</jats:italic> = 0 − 1, <jats:italic>λ</jats:italic> ∼ 4.7 <jats:italic>μ</jats:italic>m) could probe the physical properties of the inside tori. However, the origin of the CO absorption lines has been under debate. In this paper, we investigate the origin of the absorption lines and conditions for detecting them by performing line radiative transfer calculations based on the radiation-driven fountain model. We find that CO rovibrational absorption lines are detected at inclination angles <jats:italic>θ</jats:italic> <jats:sub>obs</jats:sub> = 50°–80°. At the inclination angle <jats:italic>θ</jats:italic> <jats:sub>obs</jats:sub> = 77°, we observe multi-velocity components: inflow (<jats:italic>v</jats:italic> <jats:sub>LOS</jats:sub> = 30 km s<jats:sup>−1</jats:sup>), systemic (<jats:italic>v</jats:italic> <jats:sub>LOS</jats:sub> = 0 km s<jats:sup>−1</jats:sup>), and outflows (<jats:italic>v</jats:italic> <jats:sub>LOS</jats:sub> = −75, − 95, and −105 km s<jats:sup>−1</jats:sup>). The inflow and outflow components (<jats:italic>v</jats:italic> <jats:sub>LOS</jats:sub> = 30 and −95 km s<jats:sup>−1</jats:sup>) are collisionally excited at the excitation temperatures of 186 and 380 K up to <jats:italic>J</jats:italic> = 12 and 4, respectively. The inflow and outflow components originate from the accreting gas on the equatorial plane at 1.5 pc from the AGN center and the outflowing gas driven by AGN radiation pressure at 1.0 pc, respectively. These results suggest that CO rovibrational absorption lines can provide us with the velocities and kinetic temperatures of the inflow and outflow in the inner few parsec region of AGN tori, and the observations can probe the gas circulation inside the tori.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Long-term solar activity can be studied using several parameters. Some of the most used are based on the sunspot counting. The active day fraction (ADF) is the simplest index derived from this counting. It is reliable in periods of low solar activity such as the Maunder minimum (MM). In this work, we study the relationship between the ADF and the sunspot number. We have obtained that the optimal fit of that relationship is an exponential function whose exponent is a degree 3 polynomial including all data except those with ADF equal to 100%. Then, we use that fit to estimate the sunspot number during the MM from the ADF calculated from the most recent sunspot group number database. Our estimations of the annual sunspot numbers are below 15, except that for 1656, which is 40.8, whereas our estimations of the triennial sunspot numbers are below 10 from 1648 to 1714. We have found peaks of the solar cycle in the middle of the 1650s, 1670s, 1680s, and 1700s but no clear evidence of solar cycle in the 1660s and 1690s, likely due to the scarcity of the available data. Our results agree with previous works obtaining values significantly higher than those of the group sunspot number derived by Hoyt and Schatten in 1998 but still fully compatible with a grand minimum period.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present radio spectra spanning 0.1–10 GHz for the sample of heavily obscured luminous quasars with extremely red mid-infrared-optical colors and compact radio emission. The spectra are constructed from targeted 10 GHz observations and archival radio survey data that together yield 6–11 flux-density measurements for each object. Our primary result is that most (62%) of the sample have peaked or curved radio spectra and many (37%) could be classified as Gigahertz-Peaked Spectrum (GPS) sources. This indicates compact emission regions likely arising from recently triggered radio jets. Assuming synchrotron self-absorption (SSA) generates the peaks, we infer compact source sizes (3–100 pc) with strong magnetic fields (6–100 mG) and young ages (30–10<jats:sup>4</jats:sup> yr). Conversely, free-free absorption (FFA) could also create peaks due to the high column densities associated with the deeply embedded nature of the sample. However, we find no correlations between the existence or frequency of the peaks and any parameters of the MIR emission. The high-frequency spectral indices are steep (<jats:italic>α</jats:italic> ≈ −1) and correlate, weakly, with the ratio of MIR photon energy density to magnetic energy density, suggesting that the spectral steepening could arise from inverse Compton scattering off the intense MIR photon field. This study provides a foundation for combining multifrequency and mixed-resolution radio survey data for understanding the impact of young radio jets on the ISM and star-formation rates of their host galaxies. <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://github.com/paloween/Radio_Spectral_Fitting" xlink:type="simple">faGithub</jats:ext-link> </jats:p>