Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We present first prominence observations obtained with Atacama Large Millimeter Array (ALMA) in Band 3 at the wavelength of 3 mm. High-resolution observations have been coaligned with the MSDP H<jats:italic>α</jats:italic> data from Wrocław–Białków large coronagraph at similar spatial resolution. We analyze one particular cotemporal snapshot, first calibrating both ALMA and MSDP data and then demonstrating a reasonable correlation between both. In particular, we can see quite similar fine-structure patterns in both ALMA brightness-temperature maps and MSDP maps of H<jats:italic>α</jats:italic> intensities. Using ALMA, we intend to derive the prominence kinetic temperatures. However, having current observations only in one band, we use an independent diagnostic constraint, which is the H<jats:italic>α</jats:italic> line integrated intensity. We develop an inversion code and show that it can provide realistic temperatures for brighter parts of the prominence where one gets a unique solution, while within faint structures, such inversion is ill conditioned. In brighter parts, ALMA serves as a prominence thermometer, provided that the optical thickness in Band 3 is large enough. In order to find a relation between brightness and kinetic temperatures for a given observed H<jats:italic>α</jats:italic> intensity, we constructed an extended grid of non-LTE prominence models covering a broad range of prominence parameters. We also show the effect of the plane-of-sky filling factor on our results.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The intuition suggested by the Drake equation implies that technology should be less prevalent than biology in the galaxy. However, it has been appreciated for decades in the SETI community that technosignatures could be more abundant, longer-lived, more detectable, and less ambiguous than biosignatures. We collect the arguments for and against technosignatures’ ubiquity and discuss the implications of some properties of technological life that fundamentally differ from nontechnological life in the context of modern astrobiology: It can spread among the stars to many sites, it can be more easily detected at large distances, and it can produce signs that are unambiguously technological. As an illustration in terms of the Drake equation, we consider two Drake-like equations, for technosignatures (calculating <jats:italic>N</jats:italic>(tech)) and biosignatures (calculating <jats:italic>N</jats:italic>(bio)). We argue that Earth and humanity may be poor guides to the longevity term <jats:italic>L</jats:italic> and that its maximum value could be very large, in that technology can outlive its creators and even its host star. We conclude that while the Drake equation implies that <jats:italic>N</jats:italic>(bio) ≫ <jats:italic>N</jats:italic>(tech), it is also plausible that <jats:italic>N</jats:italic>(tech) ≫ <jats:italic>N</jats:italic>(bio). As a consequence, as we seek possible indicators of extraterrestrial life, for instance, via characterization of the atmospheres of habitable exoplanets, we should search for both biosignatures and technosignatures. This exercise also illustrates ways in which biosignature and technosignature searches can complement and supplement each other and how methods of technosignature search, including old ideas from SETI, can inform the search for biosignatures and life generally.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>GW190521 was the most massive black hole merger discovered by LIGO/Virgo so far, with masses in tension with stellar evolution models. A possible explanation of such heavy black holes is that they themselves are the remnants of previous mergers of lighter black holes. Here we estimate the masses of the ancestral black holes of GW190521, assuming it is the end product of previous mergers. We find that the heaviest parental black holes has a mass of <jats:inline-formula> <jats:tex-math> <?CDATA ${56}_{-18}^{+20}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>56</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>18</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>20</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac5f47ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> (90% credible level). We find 70% probability that it is in the 50 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>–120 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> mass gap, indicating that it may also be the end product of a previous merger. We therefore also compute the expected mass distributions of the “grandparent” black holes of GW190521, assuming they existed. Ancestral black hole masses could represent an additional puzzle piece in identifying the origin of LIGO/Virgo/KAGRA’s heaviest black holes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The subject of switchbacks, defined either as large angular deflections or polarity reversals of the magnetic field, has generated substantial interest in the space physics community since the launch of the Parker Solar Probe (PSP) in 2018. Previous studies have characterized switchbacks in several different ways and have been restricted to data available from the first few orbits. Here, we analyze the frequency of occurrence of switchbacks per unit distance for the first full eight orbits of PSP. In this work, events that reverse the sign of the magnetic field relative to a regional average are considered switchbacks. A significant finding is that the rate of occurrence falls off sharply approaching the Sun near 0.2 au (40 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub>) and rises gently from 0.2 au outward. The analysis is varied for different magnetic field cadences and for different local averages of the ambient field, confirming the robustness of the results. We discuss implications for the mechanisms of switchback generation. A publicly available database has been created with the identified reversals.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the first detection of (<jats:italic>Z</jats:italic>)-1,2-ethenediol, (CHOH)<jats:sub>2</jats:sub>, the enol form of glycolaldehyde, in the interstellar medium toward the G+0.693−0.027 molecular cloud located in the Galactic Center. We have derived a column density of (1.8 ± 0.1) × 10<jats:sup>13</jats:sup> cm<jats:sup>−2</jats:sup>, which translates into a molecular abundance with respect to molecular hydrogen of 1.3 × 10<jats:sup>−10</jats:sup>. The abundance ratio between glycolaldehyde and (<jats:italic>Z</jats:italic>)-1,2-ethenediol is ∼5.2. We discuss several viable formation routes through chemical reactions from precursors such as HCO, H<jats:sub>2</jats:sub>CO, CHOH, or CH<jats:sub>2</jats:sub>CHOH. We also propose that this species might be an important precursor in the formation of glyceraldehyde (HOCH<jats:sub>2</jats:sub>CHOHCHO) in the interstellar medium through combination with the hydroxymethylene (CHOH) radical.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a high-resolution observation of the distant comet C/2014 UN<jats:sub>271</jats:sub> (Bernardinelli–Bernstein) using the Hubble Space Telescope on 2022 January 8. The signal of the nucleus was successfully isolated by means of a nucleus extraction technique, with an apparent <jats:italic>V</jats:italic>-band magnitude measured to be 21.65 ± 0.11, corresponding to an absolute magnitude of 8.63 ± 0.11. The product of the visual geometric albedo with the effective radius squared is <jats:inline-formula> <jats:tex-math> <?CDATA ${p}_{V}{R}_{{\rm{n}}}^{2}=157\pm 16$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>p</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>V</mml:mi> </mml:mrow> </mml:msub> <mml:msubsup> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">n</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>157</mml:mn> <mml:mo>±</mml:mo> <mml:mn>16</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac626aieqn1.gif" xlink:type="simple" /> </jats:inline-formula> km<jats:sup>2</jats:sup>. If the ALMA observation by Lellouch et al. refers to a bare nucleus, we derived a visual geometric albedo of 0.033 ± 0.009. If dust contamination of the ALMA signal is present at the maximum allowed level (24%), we found an albedo of 0.044 ± 0.012 for the nucleus having an effective diameter of 119 ± 15 km. In either case, we confirm that C/2014 UN<jats:sub>271</jats:sub> is the largest long-period comet ever detected. Judging from the measured surface brightness profile of the coma, whose logarithmic gradient varies azimuthally between ∼1.0 and 1.7 as a consequence of solar radiation pressure, the mass production is consistent with steady-state production but not with impulsive ejection, as would be produced by an outburst. Using aperture photometry, we estimated an enormous (albeit uncertain) mass-loss rate of ∼10<jats:sup>3</jats:sup> kg s<jats:sup>−1</jats:sup> at a heliocentric distance of ∼20 au.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The study of the interaction of a massive black hole binary with its gaseous environment is crucial in order to be able to predict merger rates and possible electromagnetic counterparts of gravitational-wave signals. The evolution of the binary semimajor axis resulting from this interaction has been recently debated, and a clear consensus is still missing because of several numerical limitations, i.e., fixed orbit binaries or lack of resolution inside the cavity carved by the binary in its circumbinary disk. Using on-the-fly particle splitting in the 3D meshless code <jats:sc>gizmo</jats:sc>, we achieve hyper-Lagrangian resolution, which allows us to properly resolve the dynamics inside the cavity—in particular, for the first time, the disks that form around the two components of a live binary surrounded by a locally isothermal gaseous circumbinary disk. We show that the binary orbit decays with time for very cold and very warm disks and that the result of the interaction in the intermediate regime is strongly influenced by the disk viscosity, as this essentially regulates the fraction of mass contained in the disks around the binary components, as well as the fraction that is accreted by the binary. We find the balance between these two quantities to determine whether the binary semimajor axis decreases with time.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) medium-resolution spectroscopic survey (MRS), we report the discovery of nine super Li-rich unevolved stars with A(Li) &gt; 3.8 dex. These objects show unusually high levels of lithium abundances, up to three times higher than the meteoritic value of 3.3 dex, which indicates that they must have experienced a history of lithium enrichment. It is found that seven of our program stars are fast rotators with <jats:italic>v</jats:italic> sin <jats:italic>i</jats:italic> &gt; 9 km s<jats:sup>−1</jats:sup>, which suggests that the accretion of circumstellar matter may be the main contributor to the lithium enhancement of these unevolved stars; however, other sources cannot be excluded.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This Letter presents the detection of a source at the position of the Type Ib/c supernova (SN) 2013ge more than four years after the radioactive component is expected to have faded. This source could mark the first post-SN direct detection of a surviving companion to a stripped-envelope Type Ib/c explosion. We test this hypothesis and find the shape of the source’s spectral energy distribution is most consistent with that of a B5 I supergiant. While binary models tend to predict OB-type stars for stripped-envelope companions, the location of the source on a color–magnitude diagram places it redward of its more likely position on the main sequence (MS). The source may be temporarily out of thermal equilibrium, or a cool and inflated non-MS companion, which is similar to the suggested companion of Type Ib SN 2019yvr that was constrained from pre-SN imaging. We also consider other possible physical scenarios for the source, including a fading SN, circumstellar shock interaction, line-of-sight coincidence, and an unresolved host star cluster, all of which will require future observations to more definitively rule out. Ultimately, the fraction of surviving companions (“binary fraction”) will provide necessary constraints on binary evolution models and the underlying physics.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A dark energy–like component in the early universe, known as early dark energy (EDE), is a proposed solution to the Hubble tension. Currently, there is no consensus in the literature as to whether EDE can simultaneously solve the Hubble tension and provide an adequate fit to the data from the cosmic microwave background (CMB) and large-scale structure of the universe. In this work, we deconstruct the current constraints from the Planck CMB and the full-shape clustering data of the Baryon Oscillation Spectroscopic Survey to understand the origin of different conclusions in the literature. We use two different analyses, a grid sampling and a profile likelihood, to investigate whether the current constraints suffer from volume effects upon marginalization and are biased toward some values of the EDE fraction, <jats:italic>f</jats:italic> <jats:sub>EDE</jats:sub>. We find that the <jats:italic>f</jats:italic> <jats:sub>EDE</jats:sub> allowed by the data strongly depends on the particular choice of the other parameters of the model, and that several choices of these parameters prefer larger values of <jats:italic>f</jats:italic> <jats:sub>EDE</jats:sub> than in the Markov Chain Monte Carlo analysis. This suggests that volume effects are the reason behind the disagreement in the literature. Motivated by this, we use a profile likelihood to analyze the EDE model and compute a confidence interval for <jats:italic>f</jats:italic> <jats:sub>EDE</jats:sub>, finding <jats:italic>f</jats:italic> <jats:sub>EDE</jats:sub> = 0.072 ± 0.036 (68% C.L.). Our approach gives a confidence interval that is not subject to volume effects and provides a powerful tool to understand whether EDE is a possible solution to the Hubble tension.</jats:p>