Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Observations of the most luminous quasars at high redshifts (<jats:italic>z</jats:italic> &gt; 6) have revealed that the largest supermassive black holes (SMBHs) at those epochs tend to be substantially overmassive relative to their host galaxies compared to the local relations, suggesting they experienced rapid early growth phases. We propose an assembly model for the SMBHs that end up in rare massive ∼10<jats:sup>12</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> host halos at <jats:italic>z</jats:italic> ∼ 6–7, applying a kinetic feedback prescription for BHs accreting above the Eddington rate, provided by radiation hydrodynamic simulations for the long-term evolution of the accretion-flow structure. The large inflow rates into these halos during their assembly enable the formation of &gt;10<jats:sup>9</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> SMBHs by <jats:italic>z</jats:italic> ∼ 6, even starting from stellar-mass seeds at <jats:italic>z</jats:italic> ∼ 30, and even in the presence of outflows that reduce the BH feeding rate, especially at early times. This mechanism also naturally yields a high BH-to-galaxy mass ratio of &gt;0.01 before the SMBH mass reaches <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub> &gt; 10<jats:sup>9</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> by <jats:italic>z</jats:italic> ∼ 6. These fast-growing SMBH progenitors are bright enough to be detected by upcoming observations with the James Webb Space Telescope over a wide range of redshift (7 &lt; <jats:italic>z</jats:italic> &lt; 15), regardless of how they were seeded.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Mechanisms have been proposed to enhance the merger rate of stellar-mass black hole binaries, such as the Von Zeipel–Lidov–Kozai mechanism (vZLK). However, high inclinations are required in order to greatly excite the eccentricity and to reduce the merger time through vZLK. Here, we propose a novel pathway through which compact binaries could merge due to eccentricity increase in general, including in a near coplanar configuration. Specifically, a compact binary migrating in an active galactic nucleus disk could be captured in an evection resonance, when the precession rate of the binary equals the orbital period around the supermassive black hole. In our study we include precession due to first-order post-Newtonian precession as well as that due to disk around one or both components of the binary. Eccentricity is excited when the binary sweeps through the resonance, which happens only when it migrates on a timescale 10–100 times the libration timescale of the resonance. Libration timescale decreases as the mass of the disk increases. The eccentricity excitation of the binary can reduce the merger timescale by up to a factor of ∼10<jats:sup>3−5</jats:sup>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>To fully leverage the statistical strength of the large number of planets found by projects such as the Kepler survey, the properties of planets and their host stars must be measured as accurately as possible. One key population for planet demographic studies is circumstellar planets in close binaries (<jats:italic>ρ</jats:italic> &lt; 50 au), where the complex dynamical environment of the binary inhibits most planet formation, but some planets nonetheless survive. Accurately characterizing the stars and planets in these complex systems is a key factor in better understanding the formation and survival of planets in binaries. Toward that goal, we have developed a new Markov Chain Monte Carlo fitting algorithm to retrieve the properties of binary systems using unresolved spectra, unresolved photometry, and resolved contrasts. We have analyzed eight Kepler Objects of Interest in M-star binary systems using literature data, and have found that the temperatures of the primary stars (and presumed planet hosts) are revised upward by an average of 200 K. The planetary radii should be revised upward by an average of 20% if the primary star is the host, and 80% if the secondary star is the planet host. The average contrast between stellar components in the Kepler band is 0.75 mag, which is small enough that neither star in any of the binaries can be conclusively ruled out as a potential planet host. Our results emphasize the importance of accounting for multiplicity when measuring stellar parameters, especially in the context of exoplanet characterization.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the discovery of 1RXH J082623.6−505741, a 10.4 hr orbital period compact binary. Modeling extensive optical photometry and spectroscopy reveals a ∼0.4 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> K-type secondary transferring mass through a low-state accretion disk to a nonmagnetic ∼0.8 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> white dwarf. The secondary is overluminous for its mass and dominates the optical spectra at all epochs and must be evolved to fill its Roche Lobe at this orbital period. The X-ray luminosity <jats:italic>L</jats:italic> <jats:sub> <jats:italic>X</jats:italic> </jats:sub> ∼ 1–2 × 10<jats:sup>32</jats:sup> erg s<jats:sup>−1</jats:sup> derived from both new XMM-Newton and archival observations, although high compared to most CVs, still only requires a modest accretion rate onto the white dwarf of <jats:inline-formula> <jats:tex-math> <?CDATA $\dot{M}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac7b25ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> ∼ 3 × 10<jats:sup>−11</jats:sup> to 3 × 10<jats:sup>−10</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>, lower than expected for a cataclysmic variable with an evolved secondary. No dwarf nova outbursts have yet been observed from the system, consistent with the low derived mass-transfer rate. Several other cataclysmic variables with similar orbital periods also show unexpectedly low mass-transfer rates, even though selection effects disfavor the discovery of binaries with these properties. This suggests the abundance and evolutionary state of long-period, low mass-transfer rate cataclysmic variables are worthy of additional attention.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We hereby report a low-speed (about 21 km s<jats:sup>−1</jats:sup> with respect to the Sun) intruder member in the Hyades cluster based on the data in the literature. The results show that the star is a nonnative member star for Hyades, with its radial velocity being smaller than the radial velocity of the Hyades cluster, even exceeding the standard deviation of the radial velocity of the cluster by a factor of 9. Furthermore, by analyzing and comparing the orbits of this star and its host, it may have intruded into its host in the past 2 Myr. If the star’s current motion orbit remains unchanged, it may leave its host in the next 2 Myr. This implies that the intruder star may be temporarily residing in the cluster. This study presents the first observational evidence of a star intrusion into a cluster, which suggests that more evidence may be found.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Parker Solar Probe (PSP) and SolO data are utilized to investigate magnetic field intermittency in the solar wind (SW). Small-scale intermittency (20−100 <jats:italic>d</jats:italic> <jats:sub> <jats:italic>i</jats:italic> </jats:sub>) is observed to radially strengthen when methods relying on higher-order moments are considered (SF<jats:sub> <jats:italic>q</jats:italic> </jats:sub>; SDK), but no clear trend is observed at larger scales. However, lower-order moment-based methods (e.g., partial variance of increments; PVI) are deemed more appropriate for examining the evolution of the bulk of coherent structures (CSs), PVI ≥ 3. Using PVI, we observe a scale-dependent evolution in the fraction of the data set occupied by CSs, <jats:italic>f</jats:italic> <jats:sub>PVI≥3</jats:sub>. Specifically, regardless of the SW speed, a subtle increase is found in <jats:italic>f</jats:italic> <jats:sub>PVI≥3</jats:sub> for <jats:italic>ℓ</jats:italic> = 20 <jats:italic>d</jats:italic> <jats:sub> <jats:italic>i</jats:italic> </jats:sub>, in contrast to a more pronounced radial increase in CSs observed at larger scales. Intermittency is investigated in relation to plasma parameters. Though, slower SW speed intervals exhibit higher <jats:italic>f</jats:italic> <jats:sub>PVI≥6</jats:sub> and higher kurtosis maxima, no statistical differences are observed for <jats:italic>f</jats:italic> <jats:sub>PVI≥3</jats:sub>. Highly Alfvénic intervals display lower levels of intermittency. The anisotropy with respect to the angle between the magnetic field and SW flow, Θ<jats:sub>VB</jats:sub> is investigated. Intermittency is weaker at Θ<jats:sub>VB</jats:sub> ≈ 0° and is strengthened at larger angles. Considering the evolution at a constant alignment angle, a weakening of intermittency is observed with increasing advection time of the SW. Our results indicate that the strengthening of intermittency in the inner heliosphere is driven by the increase in comparatively highly intermittent perpendicular intervals sampled by the probes with increasing distance, an effect related directly to the evolution of the Parker spiral.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper, we study stellar light curves from the Transiting Exoplanet Survey Satellite (TESS) for the presence of stellar flares. The main aim is to detect stellar flares using 2 minute cadence data and to perform a statistical analysis. To find and analyze stellar flares, we prepared the automatic software WARPFINDER. We implemented three methods described in this paper: trend, difference, and profile fitting. Automated searches for flares was accompanied by visual inspection. Using our software we analyzed the 2 minute cadence light curves of 330,000 stars located in the first 39 sectors of TESS observations. As a result, we detected over 25,000 stars showing flare activity with the total number of more than 140,000 flares. This means that about 7.7% of all the analyzed objects are flaring stars. The estimated flare energies range between 10<jats:sup>31</jats:sup> and 10<jats:sup>36</jats:sup> erg. We prepared a preliminary preview of the statistical distribution of parameters such as the flare duration, amplitude, and energy, and compared it with previous results. The relationship between stellar activity and spectral type, temperature, and mass was also statistically analyzed. Based on the scaling laws, we estimated the average values of the magnetic field strength and length of the flare loops. In our work, we used both single (about 60%), and double (about 40%) flare profiles to fit the observational data. The components of the double profile are supposed to be related to the direct heating of the photosphere by nonthermal electrons and back-warming processes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the average [C <jats:sc>ii</jats:sc>] 158 <jats:italic>μ</jats:italic>m emission line sizes of UV-bright star-forming galaxies at <jats:italic>z</jats:italic> ∼ 7. Our results are derived from a stacking analysis of [C <jats:sc>ii</jats:sc>] 158 <jats:italic>μ</jats:italic>m emission lines and dust continua observed by the Atacama Large Millimeter/submillimeter Array (ALMA), taking advantage of the large program Reionization Era Bright Emission Line Survey. We find that the average [C <jats:sc>ii</jats:sc>] emission at <jats:italic>z</jats:italic> ∼ 7 has an effective radius <jats:italic>r</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> of 2.2 ± 0.2 kpc. It is ≳2× larger than the dust continuum and the rest-frame UV emission, in agreement with recently reported measurements for <jats:italic>z</jats:italic> ≲ 6 galaxies. Additionally, we compared the average [C <jats:sc>ii</jats:sc>] size with 4 &lt; <jats:italic>z</jats:italic> &lt; 6 galaxies observed by the ALMA Large Program to INvestigate [C <jats:sc>ii</jats:sc>] at Early times (ALPINE). By analyzing [C <jats:sc>ii</jats:sc>] sizes of 4 &lt; <jats:italic>z</jats:italic> &lt; 6 galaxies in two redshift bins, we find an average [C <jats:sc>ii</jats:sc>] size of <jats:italic>r</jats:italic> <jats:sub>e</jats:sub> = 2.2 ± 0.2 kpc and <jats:italic>r</jats:italic> <jats:sub>e</jats:sub> = 2.5 ± 0.2 kpc for <jats:italic>z</jats:italic> ∼ 5.5 and <jats:italic>z</jats:italic> ∼ 4.5 galaxies, respectively. These measurements show that star-forming galaxies, on average, show no evolution in the size of the [C <jats:sc>ii</jats:sc>] 158 <jats:italic>μ</jats:italic>m emitting regions at redshift between <jats:italic>z</jats:italic> ∼ 7 and <jats:italic>z</jats:italic> ∼ 4. This finding suggests that the star-forming galaxies could be morphologically dominated by gas over a wide redshift range.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Voyager 2 (V2) observed that pickup ions (PUIs) and anomalous cosmic rays (ACRs) have a significant influence on the solar wind structures in the outer heliosphere. In particular, the maxima in energetic particle intensities often lagged behind the shock front, while the flow velocity in some cases featured a precursor in front of the shock. These two effects are believed to be caused by the cease of ACR injection from PUIs at large heliocentric distances, and the backward diffusion of ACRs, respectively. This paper investigates the dynamical coupling between the ACRs and the solar wind in the outer heliosphere by means of a time-dependent numerical MHD simulation, in which the ACRs are treated as a massless fluid that only contributes its pressure to the system. Two types of inner boundary conditions were used, namely a synthetic short-term shock event and an extended period of data-driven solar wind variability based on the OMNI database. The lag of the ACR pressure maximum relative to the shock front, and the extended shock precursor were reproduced by the numerical results. The increase rate of the lag is related to the corresponding diffusion coefficient and the injection efficiency from PUIs to ACRs. The model was also applied to the termination shock, where simulations likewise showed that the peak in the ACR distribution can be located a short distance downstream of the shock front, indicating that the time-dependent diffusive shock acceleration mechanism is a candidate to interpret the lag between the ACR pressure peak and the shock front observed by V2.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The blazar J1924–2914 is a primary Event Horizon Telescope (EHT) calibrator for the Galactic center’s black hole Sagittarius A*. Here we present the first total and linearly polarized intensity images of this source obtained with the unprecedented 20 <jats:italic>μ</jats:italic>as resolution of the EHT. J1924–2914 is a very compact flat-spectrum radio source with strong optical variability and polarization. In April 2017 the source was observed quasi-simultaneously with the EHT (April 5–11), the Global Millimeter VLBI Array (April 3), and the Very Long Baseline Array (April 28), giving a novel view of the source at four observing frequencies, 230, 86, 8.7, and 2.3 GHz. These observations probe jet properties from the subparsec to 100 pc scales. We combine the multifrequency images of J1924–2914 to study the source morphology. We find that the jet exhibits a characteristic bending, with a gradual clockwise rotation of the jet projected position angle of about 90° between 2.3 and 230 GHz. Linearly polarized intensity images of J1924–2914 with the extremely fine resolution of the EHT provide evidence for ordered toroidal magnetic fields in the blazar compact core.</jats:p>