Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We performed a systematic search for X-ray bursts of the SGR J1935+2154 using the Fermi Gamma-ray Burst Monitor continuous data dated from 2013 January to 2021 October. Eight bursting phases, which consist of a total of 353 individual bursts, are identified. We further analyze the periodic properties of our sample using the Lomb–Scargle periodogram. The result suggests that those bursts exhibit a period of ∼238 days with a ∼63.2% duty cycle. Based on our analysis, we further predict two upcoming active windows of the X-ray bursts. Since 2021 July, the beginning date of our first prediction has been confirmed by the ongoing X-ray activities of the SGR J1935+2154.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A stellar occultation by Pluto was observed on 2020 June 6 with the 1.3 m and 3.6 m telescopes located at Devasthal, Nainital, India, using imaging systems in the <jats:italic>I</jats:italic> and <jats:italic>H</jats:italic> bands, respectively. From this event, we derive a surface pressure for Pluto’s atmosphere of <jats:inline-formula> <jats:tex-math> <?CDATA ${p}_{\mathrm{surf}}={12.23}_{-0.38}^{+0.65}$?> </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>surf</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>12.23</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.38</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.65</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac4249ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>μ</jats:italic>bar. This shows that Pluto’s atmosphere has been in a plateau phase since mid-2015, a result which is in excellent agreement with the Pluto volatile transport model of Meza et al. This value does not support the pressure decrease reported by independent teams, based on occultations observed in 2018 and 2019 by Young et al. and Arimatsu et al., respectively.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the results of our follow-up campaign for the neutron-star—black-hole (NSBH) merger GW200115 detected during the O3 run of the Advanced LIGO and Advanced Virgo detectors. We obtained wide-field observations with the Deca-Degree Optical Transient Imager covering ∼20% of the total probability area down to a limiting magnitude of <jats:italic>w</jats:italic> = 20.5 AB at ∼23 hr after the merger. Our search for counterparts returns a single candidate (AT2020aeo), likely not associated with the merger. In total, only 25 sources of interest were identified by the community and later discarded as unrelated to the GW event. We compare our upper limits with the emission predicted by state-of-the-art kilonova simulations and disfavor high-mass ejecta (&gt;0.1 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>), indicating that the spin of the system is not particularly high. By combining our optical limits with gamma-ray constraints from Swift and Fermi, we disfavor the presence of a standard short-duration burst for viewing angles ≲15° from the jet axis. Our conclusions are, however, limited by the large localization region of this GW event, and accurate prompt positions remain crucial to improving the efficiency of follow-up efforts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the first multiwavelength simultaneous detection of quasi-periodic pulsations (QPPs) in a superflare (more than a thousand times stronger than known solar flares) on a cool star, in soft X-rays (SXRs, with XMM-Newton) and white light (WL, with Kepler). It allowed for the first ever analysis of oscillatory processes in a stellar flare simultaneously in thermal and nonthermal emissions, conventionally considered to come from the corona and chromosphere of the star, respectively. The observed QPPs have periods 1.5 ± 0.15 hr (SXR) and 3 ± 0.6 hr (WL), and correlate well with each other. The unique relationship between the observed parameters of QPPs in SXR and WL allowed us to link them with oscillations of the electric current in the flare loop, which directly affect the dynamics of nonthermal electrons and indirectly (via ohmic heating) the thermal plasma. These findings could be considered in favor of the equivalent LCR contour model of a flare loop, at least in the extreme conditions of a stellar superflare.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The recently proposed “dynamically driven double-degenerate double-detonation” (D<jats:sup>6</jats:sup>) scenario posits that Type Ia supernovae (SNe) may occur during dynamically unstable mass transfer between two white dwarfs (WDs) in a binary. This scenario predicts that the donor WD may then survive the explosion and be released as a hypervelocity runaway, opening up the exciting possibility of identifying remnant stars from D<jats:sup>6</jats:sup> SNe and using them to study the physics of detonations that produce Type Ia SNe. Three candidate D<jats:sup>6</jats:sup> runaway objects have been identified in Gaia data. The observable runaway velocity of these remnant objects represents their orbital speed at the time of SN detonation. The orbital dynamics and Roche lobe geometry required in the D<jats:sup>6</jats:sup> scenario place specific constraints on the radius and mass of the donor WD that becomes the hypervelocity runaway. In this Letter, we calculate the radii required for D<jats:sup>6</jats:sup> donor WDs as a function of the runaway velocity. Using mass–radius relations for WDs, we then constrain the masses of the donor stars as well. With measured velocities for each of the three D<jats:sup>6</jats:sup> candidate objects based on <jats:italic>Gaia </jats:italic>EDR3, this work provides a new probe of the masses and mass ratios in WD binary systems that produce SN detonations and hypervelocity runaways.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We utilize the data from the Parker Solar Probe mission at its first perihelion to investigate the three-dimensional (3D) anisotropies and scalings of solar wind turbulence for the total, perpendicular, and parallel magnetic-field fluctuations at kinetic scales in the inner heliosphere. By calculating the five-point second-order structure functions, we find that the three characteristic lengths of turbulence eddies for the total and the perpendicular magnetic-field fluctuations in the local reference frame <jats:inline-formula> <jats:tex-math> <?CDATA $({\hat{L}}_{\perp },{\hat{l}}_{\perp },{\hat{l}}_{| | })$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>ˆ</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mo>⊥</mml:mo> </mml:mrow> </mml:msub> <mml:mo>,</mml:mo> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>l</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>ˆ</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mo>⊥</mml:mo> </mml:mrow> </mml:msub> <mml:mo>,</mml:mo> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>l</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>ˆ</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mo stretchy="false">∣</mml:mo> <mml:mo stretchy="false">∣</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac4027ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> defined with respect to the local mean magnetic field <jats:bold> <jats:italic>B</jats:italic> </jats:bold> <jats:sub>local</jats:sub> feature as <jats:italic>l</jats:italic> <jats:sub>∣∣</jats:sub> &gt; <jats:italic>L</jats:italic> <jats:sub>⊥</jats:sub> &gt; <jats:italic>l</jats:italic> <jats:sub>⊥</jats:sub> in both the transition range and the ion-to-electron scales, but <jats:italic>l</jats:italic> <jats:sub>∣∣</jats:sub> &gt; <jats:italic>L</jats:italic> <jats:sub>⊥</jats:sub> ≈ <jats:italic>l</jats:italic> <jats:sub>⊥</jats:sub> for the parallel magnetic-field fluctuations. For the total magnetic-field fluctuations, the wave-vector anisotropy scalings are characterized by <jats:inline-formula> <jats:tex-math> <?CDATA ${l}_{| | }\propto {{l}_{\perp }}^{0.78}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>l</mml:mi> </mml:mrow> <mml:mrow> <mml:mo stretchy="false">∣</mml:mo> <mml:mo stretchy="false">∣</mml:mo> </mml:mrow> </mml:msub> <mml:mo>∝</mml:mo> <mml:msup> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>l</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊥</mml:mo> </mml:mrow> </mml:msub> </mml:mrow> <mml:mrow> <mml:mn>0.78</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac4027ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA ${L}_{\perp }\propto {{l}_{\perp }}^{1.02}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊥</mml:mo> </mml:mrow> </mml:msub> <mml:mo>∝</mml:mo> <mml:msup> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>l</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊥</mml:mo> </mml:mrow> </mml:msub> </mml:mrow> <mml:mrow> <mml:mn>1.02</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac4027ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> in the transition range, and they feature as <jats:inline-formula> <jats:tex-math> <?CDATA ${l}_{| | }\propto {{l}_{\perp }}^{0.44}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>l</mml:mi> </mml:mrow> <mml:mrow> <mml:mo stretchy="false">∣</mml:mo> <mml:mo stretchy="false">∣</mml:mo> </mml:mrow> </mml:msub> <mml:mo>∝</mml:mo> <mml:msup> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>l</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊥</mml:mo> </mml:mrow> </mml:msub> </mml:mrow> <mml:mrow> <mml:mn>0.44</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac4027ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA ${L}_{\perp }\propto {{l}_{\perp }}^{0.73}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊥</mml:mo> </mml:mrow> </mml:msub> <mml:mo>∝</mml:mo> <mml:msup> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>l</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊥</mml:mo> </mml:mrow> </mml:msub> </mml:mrow> <mml:mrow> <mml:mn>0.73</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac4027ieqn5.gif" xlink:type="simple" /> </jats:inline-formula> in the ion-to-electron scales. Still, we need more complete kinetic-scale turbulence models to explain all these observational results.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Plasma heating at thin current sheets in the solar wind is examined using magnetic field and plasma data obtained by the WIND spacecraft in the past 17 years from 2004 to 2019. In this study, a thin current sheet is defined by an abrupt rotation (larger than 45°) of the magnetic field direction in 3 s. A total of 57,814 current sheets have been identified, among which 25,018 current sheets are located in the slow wind and 19,842 current sheets are located in the fast wind. Significant plasma heating is found at current sheets in both slow and fast wind. Proton temperature increases more significantly at current sheets in the fast wind than in the slow wind, while the enhancement in electron temperature is less remarkable at current sheets in the fast wind. The results reveal that plasma heating commonly exists at thin current sheets in the solar wind regardless of the wind speed, but the underlying heating mechanisms might be different.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>At least half of a protostar’s mass is accreted in the Class 0 phase, when the central protostar is deeply embedded in a dense, infalling envelope. We present the first systematic search for outbursts from Class 0 protostars in the Orion clouds. Using photometry from Spitzer/IRAC spanning 2004 to 2017, we detect three outbursts from Class 0 protostars with ≥2 mag changes at 3.6 or 4.5 <jats:italic>μ</jats:italic>m. This is comparable to the magnitude change of a known protostellar FU Ori outburst. Two are newly detected bursts from the protostars HOPS 12 and 124. The number of detections implies that Class 0 protostars burst every 438 yr, with a 95% confidence interval of 161 to 1884 yr. Combining Spitzer and WISE/NEOWISE data spanning 2004–2019, we show that the bursts persist for more than nine years with significant variability during each burst. Finally, we use 19–100 <jats:italic>μ</jats:italic>m photometry from SOFIA, Spitzer, and Herschel to measure the amplitudes of the bursts. Based on the burst interval, a duration of 15 yr, and the range of observed amplitudes, 3%–100% of the mass accretion during the Class 0 phase occurs during bursts. In total, we show that bursts from Class 0 protostars are as frequent, or even more frequent, than those from more evolved protostars. This is consistent with bursts being driven by instabilities in disks triggered by rapid mass infall. Furthermore, we find that bursts may be a significant, if not dominant, mode of mass accretion during the Class 0 phase.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The generation of Langmuir wave turbulence by a weak electron beam in a randomly inhomogeneous plasma and its subsequent electromagnetic radiation are studied owing to two-dimensional particle-in-cell simulations in conditions relevant to type III solar radio bursts. The essential impact of random density fluctuations of average levels of a few percents of the background plasma on the characteristics of the electromagnetic radiation at the fundamental plasma frequency <jats:italic>ω</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub> is shown. Not only wave nonlinear interactions but also processes of Langmuir waves’ transformations on the density fluctuations contribute to the generation of such emissions. During the beam relaxation, the amount of electromagnetic energy radiated at <jats:italic>ω</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub> in a plasma with density fluctuations strongly exceeds that observed when the plasma is homogeneous. The fraction of Langmuir wave energy involved in the generation of electromagnetic emissions at <jats:italic>ω</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub> saturates around 10<jats:sup>−4</jats:sup>, i.e., one order of magnitude above that reached when the plasma is uniform. Moreover, whereas harmonic emission at 2<jats:italic>ω</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub> dominates over fundamental emission during the time evolution in a homogeneous plasma, fundamental emission is strongly dominant when the plasma contains density fluctuations, at least during several thousands of plasma periods before being overcome by harmonic emission when the total electromagnetic energy begins to saturate.</jats:p>