Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We present the detectability of strong mid-infrared (MIR) light echoes from faint debris disks illuminated by bright superflares of M-dwarf stars. Circumstellar dust grains around an M-dwarf star are simultaneously heated by superflare radiation. One can thus expect their re-emission in the MIR wavelength regime. According to our model calculations for the Proxima Centauri system, the nearest M-dwarf star system, thermal emission echoes from an inner (<jats:italic>r</jats:italic> &lt; 1 au) debris disk with a total mass down to that of the solar system’s zodiacal dust are expected to emerge at wavelengths longer than ∼10 <jats:italic>μ</jats:italic>m with a strength comparable to or greater than a white-light superflare. Also, observable echoes from inner- (<jats:italic>r</jats:italic> ≲ 0.5 au) debris disks irradiated by energetic ( ≳10<jats:sup>33.5</jats:sup> erg) superflares of nearby (<jats:italic>D</jats:italic> &lt; 3 pc) M dwarfs are expected. Our simulation results indicate that superflare monitoring using high-speed optical instruments like OASES and its prompt follow-up using ground-based MIR instruments, such as TAO/MIMIZUKU, can detect these MIR light echoes from debris disks around solar neighborhood flare stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Solar energetic particles (SEPs) associated with flares and/or coronal mass ejection (CME)-driven shocks can impose acute radiation hazards on space explorations. To measure energetic particles in near-Mars space, the Mars Energetic Particle Analyzer (MEPA) instrument on board China's Tianwen-1 (TW-1) mission was designed. Here, we report the first MEPA measurements of the widespread SEP event occurring on 2020 November 29 when TW-1 was in transit to Mars. This event occurred when TW-1 and Earth were magnetically well connected, known as the Hohmann–Parker effect, thus offering us a rare opportunity to understand the underlying particle acceleration and transport process. Measurements from TW-1 and near-Earth spacecraft show similar double-power-law spectra and a radial dependence of the SEP peak intensities. Moreover, the decay phases of the time–intensity profiles at different locations clearly show the reservoir effect. We conclude that the double-power-law spectrum is likely generated at the acceleration site and that a small but finite cross-field diffusion is crucial to understanding the formation of the SEP reservoir phenomenon. These results provide insight into particle acceleration and transport associated with CME-driven shocks, which may contribute to the improvement of relevant physical models.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The detection of cyclotron resonance scattering features (CRSFs) is the only way to directly and reliably measure the magnetic field near the surface of a neutron star (NS). The broad energy coverage and large collection area of Insight-HXMT in the hard X-ray band allowed us to detect the CRSF with the highest energy known to date, reaching about 146 keV during the 2017 outburst of the first galactic pulsing ultraluminous X-ray source (pULX) Swift J0243.6+6124. During this outburst, the CRSF was only prominent close to the peak luminosity of ∼2 × 10<jats:sup>39</jats:sup> erg s<jats:sup>−1</jats:sup>, the highest to date in any of the Galactic pulsars. The CRSF is most significant in the spin-phase region corresponding to the main pulse of the pulse profile, and its centroid energy evolves with phase from 120 to 146 keV. We identify this feature as the fundamental CRSF because no spectral feature exists at 60–70 keV. This is the first unambiguous detection of an electron CRSF from an ULX. We also estimate a surface magnetic field of ∼1.6 × 10<jats:sup>13</jats:sup> G for Swift J0243.6+6124. Considering that the dipole magnetic field strengths, inferred from several independent estimates of magnetosphere radius, are at least an order of magnitude lower than our measurement, we argue that the detection of the highest-energy CRSF reported here unambiguously proves the presence of multipole field components close to the surface of the neutron star. Such a scenario has previously been suggested for several pulsating ULXs, including Swift J0243.6+6124, and our result represents the first direct confirmation of this scenario.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The interpretation of molecular-line data using hydrodynamical simulations of planet–disk interactions fosters new hope for the indirect detection of protoplanets. In a model-independent approach, embedded protoplanets should be found at the roots of abrupt Doppler flips in velocity centroid maps. However, the largest velocity perturbation known for an unwarped disk, in the disk of HD 100546, leads to a conspicuous Doppler flip that coincides with a thick dust ring, in contradiction with an interpretation in terms of a ≳1 <jats:italic>M</jats:italic> <jats:sub>jup</jats:sub> body. Here we present new ALMA observations of the <jats:sup>12</jats:sup>CO(2–1) kinematics in HD 100546, with a factor of 2 finer angular resolutions. We find that the disk rotation curve is consistent with a central mass 2.1 &lt; <jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> &lt; 2.3 and that the blueshifted side of the Doppler flip is due to vertical motions, reminiscent of the disk wind proposed previously from blueshifted SO lines. We tentatively propose a qualitative interpretation in terms of a surface disturbance to the Keplerian flow, i.e., a disk eruption, driven by an embedded outflow launched by a ∼10 <jats:italic>M</jats:italic> <jats:sub>earth</jats:sub> body. Another interpretation involves a disk-mass-loading hot spot at the convergence of an envelope accretion streamer.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>It is believed that millisecond pulsars attain their fast spins by accreting matter and angular momentum from companion stars. Theoretical modeling of the accretion process suggests a spin-up line in the period–period derivative (<jats:italic>P</jats:italic>-<jats:inline-formula> <jats:tex-math> <?CDATA $\dot{P}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>P</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="apjlac7eb6ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>) diagram of millisecond pulsars, which plays an important role in population studies of radio millisecond pulsars and accreting neutron stars in X-ray binaries. Here we present observational evidence for such a spin-up line using a sample of 143 radio pulsars with <jats:italic>P</jats:italic> &lt; 30 ms. We also find that PSRs J1823−3021A and J1824−2452A, located near the classic spin-up line, are consistent with the broad population of millisecond pulsars. Finally, we show that our approach of Bayesian inference can probe accretion physics, allowing constraints to be placed on the accretion rate and the disk–magnetosphere interaction.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the detection of an optical impact flash on Jupiter on 2021 October 15 by a dedicated telescope, Planetary ObservatioN Camera for Optical Transient Surveys, for the first time. Our temporally resolved three-band observations of the flash allowed investigations of its optical energy without the need for approximations on the impact brightness temperature. The kinetic energy of the impactor was equivalent to approximately two megatons of TNT, an order of magnitude greater than that of previously detected flashes on Jupiter and comparable with the Tunguska impact on Earth in 1908. This detection indicates that Tunguska-like impact events on Jupiter occur approximately once per year, two to three orders of magnitude more frequently than terrestrial impacts. The observed flash displayed a single-temperature blackbody spectrum with an effective temperature of approximately 8300 K without clear temporal variation, possibly representing common radiative features of terrestrial Tunguska-class superbolides.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We unify the power laws of size distributions of solar flare and nanoflare energies. We present three models that predict the power-law slopes <jats:italic>α</jats:italic> <jats:sub> <jats:italic>E</jats:italic> </jats:sub> of flare energies defined in terms of the 2D and 3D fractal dimensions (<jats:italic>D</jats:italic> <jats:sub> <jats:italic>A</jats:italic> </jats:sub>, <jats:italic>D</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub>): (i) the spatiotemporal standard self-organized criticality model, defined by the power-law slope <jats:italic>α</jats:italic> <jats:sub> <jats:italic>E</jats:italic>1</jats:sub> =1 + 2/(<jats:italic>D</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> + 2) = (13/9) ≈ 1.44; (ii) the 2D thermal energy model, <jats:italic>α</jats:italic> <jats:sub> <jats:italic>E</jats:italic>2</jats:sub> = 1 + 2/<jats:italic>D</jats:italic> <jats:sub> <jats:italic>A</jats:italic> </jats:sub> = (7/3) ≈ 2.33; and (iii) the 3D thermal energy model, <jats:italic>α</jats:italic> <jats:sub> <jats:italic>E</jats:italic>3</jats:sub> = 1 + 2/<jats:italic>D</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> = (9/5) ≈ 1.80. The theoretical predictions of energies are consistent with the observational values of these three groups, i.e., <jats:italic>α</jats:italic> <jats:sub> <jats:italic>E</jats:italic>1</jats:sub> = 1.47 ± 0.07, <jats:italic>α</jats:italic> <jats:sub> <jats:italic>E</jats:italic>2</jats:sub> = 2.38 ± 0.09, and <jats:italic>α</jats:italic> <jats:sub> <jats:italic>E</jats:italic>3</jats:sub> = 1.80 ± 0.18. These results corroborate that the energy of nanoflares does not diverge at small energies, since (<jats:italic>α</jats:italic> <jats:sub> <jats:italic>E</jats:italic>1</jats:sub> &lt; 2) and (<jats:italic>α</jats:italic> <jats:sub> <jats:italic>E</jats:italic>3</jats:sub> &lt; 2), except for the 2D model (<jats:italic>α</jats:italic> <jats:sub> <jats:italic>E</jats:italic>2</jats:sub> &gt; 2). Thus, while this conclusion does not support nanoflare scenarios of coronal heating from a dimensionality point of view, magnetic reconnection processes with quasi-1D or quasi-2D current sheets cannot be ruled out.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We consider the propagation of polarization in the inner parts of pair-symmetric magnetar winds, close to the light cylinder. Pair plasmas in magnetic field is birefringent, a ∝ <jats:italic>B</jats:italic> <jats:sup>2</jats:sup> effect. As a result, such plasmas work as phase retarders: Stokes parameters follow a circular trajectory on the Poincare sphere. In the highly magnetized regime, <jats:italic>ω</jats:italic>, <jats:italic>ω</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub> ≪ <jats:italic>ω</jats:italic> <jats:sub> <jats:italic>B</jats:italic> </jats:sub>, the corresponding rotation rates are independent of the magnetic field. A plasma screen with dispersion measure DM ∼ 10<jats:sup>−6</jats:sup> pc cm<jats:sup>−3</jats:sup> can induce large polarization changes, including large effective rotation measures (RMs). The frequency scaling of the (generalized) RM, ∝ <jats:italic>λ</jats:italic> <jats:sup> <jats:italic>α</jats:italic> </jats:sup>, mimics the conventional RM with <jats:italic>α</jats:italic> = 2 for small phase shifts, but can be as small as <jats:italic>α</jats:italic> = 1. In interpreting observations, the frequency scaling of polarization parameters should be fitted independently. The model offers explanations for (i) the large circular polarization component observed in FRBs, with right–left switching; (ii) large RM, with possible sign changes (when the observation bandwidth is small); and (iii) time-dependent variable polarization. A relatively dense and slow wind is needed—the corresponding effect in regular pulsars is small.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The observation of global acoustic waves (<jats:italic>p</jats:italic> modes) in the Sun has been key to unveiling its internal structure and dynamics. A different kind of wave, known as sectoral Rossby modes, has been observed and identified, which potentially opens the door to probing internal processes that are inaccessible through <jats:italic>p</jats:italic>-mode helioseismology. Yet another set of waves, appearing as retrograde-propagating, equatorially antisymmetric vorticity waves, has also been observed but their identification remained elusive. Here, through a numerical model implemented as an eigenvalue problem, we provide evidence supporting the identification of those waves as a class of inertial eigenmodes, distinct from the Rossby-mode class, with radial velocities comparable to the horizontal ones deep in the convective zone but still small compared to the horizontal velocities toward the surface. We also suggest that the signature of tesseral-like Rossby modes might be present in recent observational data.</jats:p>