Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We report the discovery of a circumplanetary disk (CPD) candidate embedded in the circumstellar disk of the T Tauri star AS 209 at a radial distance of about 200 au (on-sky separation of 1.″4 from the star at a position angle of 161°), isolated via <jats:sup>13</jats:sup>CO <jats:italic>J</jats:italic> = 2−1 emission. This is the first instance of CPD detection via gaseous emission capable of tracing the overall CPD mass. The CPD is spatially unresolved with a 117 × 82 mas beam and manifests as a point source in <jats:sup>13</jats:sup>CO, indicating that its diameter is ≲14 au. The CPD is embedded within an annular gap in the circumstellar disk previously identified using <jats:sup>12</jats:sup>CO and near-infrared scattered-light observations and is associated with localized velocity perturbations in <jats:sup>12</jats:sup>CO. The coincidence of these features suggests that they have a common origin: an embedded giant planet. We use the <jats:sup>13</jats:sup>CO intensity to constrain the CPD gas temperature and mass. We find that the CPD temperature is ≳35 K, higher than the circumstellar disk temperature at the radial location of the CPD, 22 K, suggesting that heating sources localized to the CPD must be present. The CPD gas mass is ≳0.095 <jats:italic>M</jats:italic> <jats:sub>Jup</jats:sub> ≃ 30 <jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub> adopting a standard <jats:sup>13</jats:sup>CO abundance. From the nondetection of millimeter continuum emission at the location of the CPD (3<jats:italic>σ</jats:italic> flux density ≲26.4 <jats:italic>μ</jats:italic>Jy), we infer that the CPD dust mass is ≲0.027 <jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub> ≃ 2.2 lunar masses, indicating a low dust-to-gas mass ratio of ≲9 × 10<jats:sup>−4</jats:sup>. We discuss the formation mechanism of the CPD-hosting giant planet on a wide orbit in the framework of gravitational instability and pebble accretion.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the discovery of a new 5.78 ms period millisecond pulsar (MSP), PSR J1740−5340B (NGC 6397B), in an eclipsing binary system discovered with the Parkes radio telescope (now also known as Murriyang) in Australia and confirmed with the MeerKAT radio telescope in South Africa. The measured orbital period, 1.97 days, is the longest among all eclipsing binaries in globular clusters (GCs) and consistent with that of the coincident X-ray source U18, previously suggested to be a “hidden MSP.” Our XMM-Newton observations during NGC 6397B’s radio-quiescent epochs detected no X-ray flares. NGC 6397B is either a transitional MSP or an eclipsing binary in its initial stage of mass transfer after the companion star left the main sequence. The discovery of NGC 6397B potentially reveals a subgroup of extremely faint and heavily obscured binary pulsars, thus providing a plausible explanation for the apparent dearth of binary neutron stars in core-collapsed GCs as well as a critical constraint on the evolution of GCs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report a very bright, long-duration gamma-ray burst (GRB), GRB 220426A, observed by the Fermi satellite. GRB 220426A, with a total duration of <jats:italic>T</jats:italic> <jats:sub>90</jats:sub> = 6 s, is composed of two main pulses and some subpeaks. The spectral analysis of this burst with a Band function reveals that both the time-integrated and the time-resolved spectra are very narrow with a high <jats:italic>α</jats:italic> ≳ 0.2 and low <jats:italic>β</jats:italic> ≲ −3.1. It is highly reminiscent of GRB 090902B, a special GRB with a photospheric emission identification. Then, we perform the spectral analysis of this burst based on nondissipated photospheric emission, which can be well modeled by a multicolor blackbody with a cutoff power-law distribution of the thermal temperature. The spectral fittings reveal that the photospheric emission can well describe the radiation spectrum of this burst. We conclude that this burst would be a second burst in the class of GRB 090902B observed by the Fermi satellite. We also discuss the physics of the photosphere and the origin of the high-energy component in GRB 220426A.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Surfaces of the Sun and other cool stars are filled with magnetic fields, which are either seen as dark compact spots or more diffuse bright structures like faculae. Both hamper detection and characterization of exoplanets, affecting stellar brightness and spectra, as well as transmission spectra. However, the expected facular and spot signals in stellar data are quite different, for instance, they have distinct temporal and spectral profiles. Consequently, corrections of stellar data for magnetic activity can greatly benefit from the insight on whether the stellar signal is dominated by spots or faculae. Here, we utilize a surface flux transport model to show that more effective cancellation of diffuse magnetic flux associated with faculae leads to spot area coverages increasing faster with stellar magnetic activity than that by faculae. Our calculations explain the observed dependence between solar spot and facular area coverages and allow its extension to stars that are more active than the Sun. This extension enables anticipating the properties of stellar signal and its more reliable mitigation, leading to a more accurate characterization of exoplanets and their atmospheres.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A decade ago, the archetypal Seyfert-1 galaxy NGC 5548 was discovered to have undergone major spectral changes. The soft X-ray flux had dropped by a factor of 30 while new broad and blueshifted UV absorption lines appeared. This was explained by the emergence of a new obscuring wind from the accretion disk. Here we report on the striking long-term variability of the obscuring disk wind in NGC 5548 including new observations taken in 2021–2022 with the Swift Observatory and the Hubble Space Telescope’s Cosmic Origins Spectrograph. The X-ray spectral hardening as a result of obscuration has declined over the years, reaching its lowest in 2022, at which point we find the broad C <jats:sc>iv</jats:sc> UV absorption line to have nearly vanished. The associated narrow low-ionization UV absorption lines, produced previously when shielded from the X-rays, are also remarkably diminished in 2022. We find a highly significant correlation between the variabilities of the X-ray hardening and the equivalent width of the broad C <jats:sc>iv</jats:sc> absorption line, demonstrating that X-ray obscuration is inherently linked to disk winds. We derive for the first time a relation between the X-ray and UV covering fractions of the obscuring wind using its long-term evolution. The diminished X-ray obscuration and UV absorption are likely caused by an increasingly intermittent supply of outflowing streams from the accretion disk. This results in growing gaps and interstices in the clumpy disk wind, thereby reducing its covering fractions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The chemical composition of the inner region of protoplanetary disks can trace the composition of planetary-building material. The exact elemental composition of the inner disk has not yet been measured and tensions between models and observations still exist. Recent advancements have shown UV shielding to be able to increase the emission of organics. Here, we expand on these models and investigate how UV shielding may impact chemical composition in the inner 5 au. In this work, we use the model from Bosman et al. and expand it with a larger chemical network. We focus on the chemical abundances in the upper disk atmosphere where the effects of water UV shielding are most prominent and molecular lines originate. We find rich carbon and nitrogen chemistry with enhanced abundances of C<jats:sub>2</jats:sub>H<jats:sub>2</jats:sub>, CH<jats:sub>4</jats:sub>, HCN, CH<jats:sub>3</jats:sub>CN, and NH<jats:sub>3</jats:sub> by &gt;3 orders of magnitude. This is caused by the self-shielding of H<jats:sub>2</jats:sub>O, which locks oxygen in water. This subsequently results in a suppression of oxygen-containing species like CO and CO<jats:sub>2</jats:sub>. The increase in C<jats:sub>2</jats:sub>H<jats:sub>2</jats:sub> seen in the model with the inclusion of water UV shielding allows us to explain the observed C<jats:sub>2</jats:sub>H<jats:sub>2</jats:sub> abundance without resorting to elevated C/O ratios as water UV shielding induced an effectively oxygen-poor environment in oxygen-rich gas. Thus, water UV shielding is important for reproducing the observed abundances of hydrocarbons and nitriles. From our model result, species like CH<jats:sub>4</jats:sub>, NH<jats:sub>3</jats:sub>, and NO are expected to be observable with the James Webb Space Telescope (JWST).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present extended Ly<jats:italic>α </jats:italic>emission out to 800 kpc of 1034 [O <jats:sc>iii</jats:sc>]-selected galaxies at redshifts 1.9 &lt; <jats:italic>z</jats:italic> &lt; 2.35 using the Hobby–Eberly Telescope Dark Energy Experiment. The locations and redshifts of the galaxies are taken from the 3D-HST survey. The median-stacked surface brightness profile of the Ly<jats:italic>α</jats:italic> emission of the [O <jats:sc>iii</jats:sc>]-selected galaxies agrees well with that of 968 bright Ly<jats:italic>α</jats:italic>-emitting galaxies (LAEs) at <jats:italic>r</jats:italic> &gt; 40 kpc from the galaxy centers. The surface brightness in the inner parts (<jats:italic>r</jats:italic> &lt; 10 kpc) around the [O <jats:sc>iii</jats:sc>]-selected galaxies, however, is 10 times fainter than that of the LAEs. Our results are consistent with the notion that photons dominating the outer regions of the Ly<jats:italic>α</jats:italic> halos are not produced in the central galaxies but originate outside of them.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The neutral atomic gas content of individual galaxies at large cosmological distances has until recently been difficult to measure due to the weakness of the hyperfine H <jats:sc>i</jats:sc> 21 cm transition. Here we estimate the H <jats:sc>i</jats:sc> gas mass of a sample of main-sequence star-forming galaxies at <jats:italic>z</jats:italic> ∼ 6.5–7.8 surveyed for [C <jats:sc>ii</jats:sc>] 158 <jats:italic>μ</jats:italic>m emission as part of the Reionization Era Bright Emission Line Survey (REBELS), using a recent calibration of the [C <jats:sc>ii</jats:sc>]-to-H <jats:sc>i</jats:sc> conversion factor. We find that the H <jats:sc>i</jats:sc> gas mass excess in galaxies increases as a function of redshift, with an average of <jats:italic>M</jats:italic> <jats:sub>H<jats:sc>i</jats:sc> </jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> ≈ 10, corresponding to H <jats:sc>i</jats:sc> gas mass fractions of <jats:italic>f</jats:italic> <jats:sub>H<jats:sc>i</jats:sc> </jats:sub> = <jats:italic>M</jats:italic> <jats:sub>H<jats:sc>i</jats:sc> </jats:sub>/(<jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> + <jats:italic>M</jats:italic> <jats:sub>H<jats:sc>i</jats:sc> </jats:sub>) = 90%, at <jats:italic>z</jats:italic> ≈ 7. Based on the [C <jats:sc>ii</jats:sc>] 158 <jats:italic>μ</jats:italic>m luminosity function (LF) derived from the same sample of galaxies, we further place constraints on the cosmic H <jats:sc>i</jats:sc> gas mass density in galaxies (<jats:italic>ρ</jats:italic> <jats:sub>H<jats:sc>i</jats:sc> </jats:sub>) at this redshift, which we measure to be <jats:inline-formula> <jats:tex-math> <?CDATA ${\rho }_{{\rm{H}}{\rm\small{I}}}={7.1}_{-3.0}^{+6.4}\times {10}^{6}\,{M}_{\odot }\,{\mathrm{Mpc}}^{-3}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>ρ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mi mathsize="small" mathvariant="normal">I</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>7.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3.0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>6.4</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>6</mml:mn> </mml:mrow> </mml:msup> <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:mspace width="0.25em" /> <mml:msup> <mml:mrow> <mml:mi>Mpc</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac8057ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. This estimate is substantially lower by a factor of ≈10 than that inferred from an extrapolation of damped Ly<jats:italic>α</jats:italic> absorber (DLA) measurements and largely depends on the exact [C <jats:sc>ii</jats:sc>] LF adopted. However, we find this decrease in <jats:italic>ρ</jats:italic> <jats:sub>H<jats:sc>i</jats:sc> </jats:sub> to be consistent with recent simulations and argue that this apparent discrepancy is likely a consequence of the DLA sight lines predominantly probing the substantial fraction of H <jats:sc>i</jats:sc> gas in high-<jats:italic>z</jats:italic> galactic halos, whereas [C <jats:sc>ii</jats:sc>] traces the H <jats:sc>i</jats:sc> in the ISM associated with star formation. We make predictions for this buildup of neutral gas in galaxies as a function of redshift, showing that at <jats:italic>z</jats:italic> ≳ 5, only ≈10% of the cosmic H <jats:sc>i</jats:sc> gas content is confined in galaxies and associated with the star-forming ISM.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Electromagnetic emissions <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal H }}_{3}$?> </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:mn>3</mml:mn> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac7f28ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal H }}_{4}$?> </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:mn>4</mml:mn> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac7f28ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> at the third and fourth harmonics of the plasma frequency <jats:italic>ω</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub> were observed during the occurrence of type II and type III solar radio bursts. Two-dimensional particle-in-cell simulations are performed using a weak beam, high space and time resolutions, and a plasma with density fluctuations of a few percent, for parameters relevant to regions of type III bursts. For the first time, a detailed study of the different wave coalescence processes involved in the generation of <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal H }}_{3}$?> </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:mn>3</mml:mn> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac7f28ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal H }}_{4}$?> </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:mn>4</mml:mn> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac7f28ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> waves is presented and the impact of density fluctuations on the wave interaction mechanisms is demonstrated. Energy ratios between the second, third, and fourth harmonics <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal H }}_{2}$?> </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:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac7f28ieqn5.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal H }}_{3}$?> </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:mn>3</mml:mn> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac7f28ieqn6.gif" xlink:type="simple" /> </jats:inline-formula>, and <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal H }}_{4}$?> </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:mn>4</mml:mn> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac7f28ieqn7.gif" xlink:type="simple" /> </jats:inline-formula> are consistent with space observations. It is shown that, in both homogeneous and inhomogeneous plasmas, the dominant processes generating <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal H }}_{3}$?> </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:mn>3</mml:mn> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac7f28ieqn8.gif" xlink:type="simple" /> </jats:inline-formula> (<jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal H }}_{4}$?> </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:mn>4</mml:mn> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac7f28ieqn9.gif" xlink:type="simple" /> </jats:inline-formula>) are the coalescence of <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal H }}_{2}$?> </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:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac7f28ieqn10.gif" xlink:type="simple" /> </jats:inline-formula> (<jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal H }}_{3}$?> </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:mn>3</mml:mn> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac7f28ieqn11.gif" xlink:type="simple" /> </jats:inline-formula>) with a Langmuir wave, in spite of the random density fluctuations modifying the waves’ resonance conditions by energy transport in the wavevector space and of the damping of Langmuir waves. The role of the backscattered (forward-propagating) Langmuir waves coming from the first (second) cascade of the electrostatic decay of beam-driven Langmuir waves is determinant in these processes. Understanding such wave coalescence mechanisms can provide indirect information on Langmuir and ion acoustic wave turbulence, the average level of density inhomogeneities, and suprathermal electron fluxes generated in solar wind regions where the harmonics manifest. Causes for the rarity of their observations are discussed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Recently, an association between an optical transient, AT2020hur, and a repeating fast radio burst, FRB 20180916b, has been suggested, based on a strong positional coincidence on the sky and the temporal coincidence with one of the fast radio burst’s activity periods (∼6 days duration every ∼16 days). This suggestion is explored further and tested in this paper, utilizing full-frame images from the Transiting Exoplanet Survey Satellite (TESS) across three of its observing periods in 2019 and 2020 (Sectors 18, 24, and 25). The discovery observations of AT2020hur took place between Sectors 18 and 24, within 5 days of the commencement of Sector 24 observations. The TESS observations cover at least six activity periods for the FRB. Thus, the TESS data provide excellent temporal coverage close in time to the discovery of AT2020hur and at known times of FRB activity and radio detection. From the TESS data, no evidence is found for repeating optical transients with the suspected emission timescale of ⪆1000 s.</jats:p>