Sazuna/UAT_keywords huggingface dataset:
Probing the Origin of Cosmic Rays in Cygnus Cocoon Using Ultrahigh-energy Gamma-Ray and Neutrino Observations. Recent ultrahigh-energy gamma-ray observations by the High Altitude Water Cherenkov Observatory up to 100 TeV and LHAASO observatories up to 1.4 PeV energies from the direction of Fermi Large Area Telescope 4FGL source 4FGL J2028.6 + 4110e (Cygnus Cocoon) are indicative of a hadronic origin over a leptonic process for their creation. The IceCube Neutrino Observatory has reported IceCube-201120A, a neutrino event coming from the same direction, suggesting that the Cygnus Cocoon may correspond to one of the most plausible sources of high-energy cosmic rays. The apparent relationship of the neutrino event with the observed ultrahigh-energy gamma rays from the Cygnus Cocoon is investigated in this work to study if it can be explained consistently in hadronic interactions of accelerated cosmic rays with ambient matter. Our findings reveal that leptonic mechanisms, together with pure hadronic mechanisms, make a considerable contribution to the understanding of the total electromagnetic spectrum as well as the observed neutrino event. The estimate of expected muon neutrino events from the Cygnus Cocoon agrees with the one muon neutrino event detected so far in IceCube multiyear observations. Thus, our results are indicative of the potential of the Cygnus Cocoon to be a Galactic cosmic-ray source capable of accelerating at least up to PeV energies.

Keywords: Cosmic ray sources, Cosmic rays
Discovery of a 500 au Protobinary in the Massive Prestellar Core G11.92-0.61 MM2. We present high-resolution (≲160 au) Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm observations of the high-mass prestellar core candidate G11.92-0.61 MM2, which reveal that this source is in fact a protobinary system with a projected separation of 505 au. The binary components, MM2E and MM2W, are compact (radii &lt;140 au) sources within the partially optically thick dust emission with α 0.9 cm-1.3 mm = 2.47-2.94. The 1.3 mm brightness temperatures, T b = 68.4/64.6 K for MM2E/MM2W, imply internal heating and minimum luminosities L * &gt; 24.7 L ☉ for MM2E and L * &gt; 12.6 L ☉ for MM2W. The compact sources are connected by a "bridge" of lower-surface-brightness dust emission and lie within more extended emission that may correspond to a circumbinary disk. The circumprotostellar gas mass, estimated from ~0.″2 resolution VLA 0.9 cm observations assuming optically thin emission, is 6.8 ± 0.9 M ☉. No line emission is detected toward MM2E and MM2W in our high-resolution 1.3 mm ALMA observations. The only line detected is 13CO J = 2-1, in absorption against the 1.3 mm continuum, which likely traces a layer of cooler molecular material surrounding the protostars. We also report the discovery of a highly asymmetric bipolar molecular outflow that appears to be driven by MM2E and/or MM2W in new deep, ~0.″5 resolution (1685 au) ALMA 0.82 mm observations. This outflow, traced by low-excitation CH3OH emission, indicates ongoing accretion onto the protobinary system. Overall, the super-Alfvénic models of Mignon-Risse et al. agree well with the observed properties of the MM2E/MM2W protobinary, suggesting that this system may be forming in an environment with a weak magnetic field.

Keywords: Binary stars, Star forming regions, Star formation, Stellar accretion, Stellar accretion disks, Protostars
Current-sheet Oscillations Caused by the Kelvin-Helmholtz Instability at the Loop Top of Solar Flares. Current sheets (CSs), long stretching structures of magnetic reconnection above solar flare loops, are usually observed to oscillate; their origins, however, are still puzzled at present. Based on a high-resolution 2.5D MHD simulation of magnetic reconnection, we explore the formation mechanism of CS oscillations. We find that large-amplitude transverse waves are excited by the Kelvin-Helmholtz instability at the highly turbulent cusp-shaped region. The perturbations propagate upward along the CS with a phase speed close to local Alfvén speed thus resulting in the CS oscillations we observe. Though the perturbations damp after propagating for a long distance, the CS oscillations are still detectable. In terms of detected CS oscillations, with a combination of differential emission measure techniques, we propose a new method for measuring the magnetic field strength of the CS and its distribution in height.

Keywords: Solar flares, Solar magnetic reconnection, Magnetohydrodynamical simulations
First Experimental Confirmation of the CH<SUB>3</SUB>O + H<SUB>2</SUB>CO → CH<SUB>3</SUB>OH + HCO Reaction: Expanding the CH<SUB>3</SUB>OH Formation Mechanism in Interstellar Ices. The successive addition of H atoms to CO in the solid phase has been hitherto regarded as the primary route to form methanol in dark molecular clouds. However, recent Monte Carlo simulations of interstellar ices alternatively suggested the radical-molecule H-atom abstraction reaction CH3O + H2CO → CH3OH + HCO, in addition to CH3O + H → CH3OH, as a very promising and possibly dominating (70%-90%) final step to form CH3OH in those environments. Here, we compare the contributions of these two steps leading to methanol by experimentally investigating hydrogenation reactions on H2CO and D2CO ices, which ensures comparable starting points between the two scenarios. The experiments are performed under ultrahigh vacuum conditions and astronomically relevant temperatures, with H:H2CO (or D2CO) flux ratios of 10:1 and 30:1. The radical-molecule route in the partially deuterated scenario, CHD2O + D2CO → CHD2OD + DCO, is significantly hampered by the isotope effect in the D-abstraction process, and can thus be used as an artifice to probe the efficiency of this step. We observe a significantly smaller yield of D2CO + H products in comparison to H2CO + H, implying that the CH3O-induced abstraction route must play an important role in the formation of methanol in interstellar ices. Reflection-absorption infrared spectroscopy and temperature-programmed desorption-quadrupole mass spectrometry analyses are used to quantify the species in the ice. Both analytical techniques indicate constant contributions of ~80% for the abstraction route in the 10-16 K interval, which agrees well with the Monte Carlo calculations. Additional H2CO + D experiments confirm these conclusions.

Keywords: Laboratory astrophysics, Dark interstellar clouds, Astrochemistry
Insufficient Gas Accretion Caused the Decline in Cosmic Star-formation Activity Eight Billion Years Ago. Measurements of the atomic hydrogen (HI) properties of high-redshift galaxies are critical to understanding the decline in the star formation rate (SFR) density of the universe after its peak ≈8-11 Gyr ago. Here, we use ≈510 hr of observations with the upgraded Giant Metrewave Radio Telescope to measure the dependence of the average HI mass of star-forming galaxies at z = 0.74-1.45 on their average stellar mass and redshift by stacking their HI 21 cm emission signals. We divide our sample of 11,419 main-sequence galaxies at z = 0.74-1.45 into two stellar-mass (M *) subsamples, with M * &gt; 1010 M ⊙ and M * &lt; 1010 M ⊙, and obtain clear detections, at &gt;4.6σ significance, of the stacked HI 21 cm emission in both subsamples. We find that galaxies with M * &gt; 1010 M ⊙, which dominate the decline in the cosmic SFR density at z ≲ 1, have HI reservoirs that can sustain their SFRs for only a short period, 0.86 ± 0.20 Gyr, unless their HI is replenished via accretion. We also stack the HI 21 cm emission from galaxies in two redshift subsamples, at z = 0.74-1.25 and z = 1.25-1.45, again obtaining clear detections of the stacked HI 21 cm emission signals, at &gt;5.2σ significance in both subsamples. We find that the average HI mass of galaxies with &lt;M *&gt; ≈ 1010 M ⊙ declines steeply over a period of ≈1 billion years, from (33.6 ± 6.4) × 109 M ⊙ at &lt;z&gt; ≈ 1.3 to (10.6 ± 1.9) × 109 M ⊙ at &lt;z&gt; ≈ 1.0, i.e., by a factor ≳3. We thus find direct evidence that accretion of HI onto star-forming galaxies at z ≈ 1 is insufficient to replenish their HI reservoirs and sustain their SFRs, thus resulting in the decline in the cosmic SFR density 8 billion years ago.

Keywords: Radio spectroscopy, Neutral hydrogen clouds, Galaxy evolution
The Peculiar Short-duration GRB 200826A and Its Supernova. Gamma-ray bursts (GRBs) are classified into long and short events. Long GRBs (LGRBs) are associated with the end states of very massive stars, while short GRBs (SGRBs) are linked to the merger of compact objects. GRB 200826A was a peculiar event, because by definition it was an SGRB, with a rest-frame duration of ~0.5 s. However, this event was energetic and soft, which is consistent with LGRBs. The relatively low redshift (z = 0.7486) motivated a comprehensive, multiwavelength follow-up campaign to characterize its host, search for a possible associated supernova (SN), and thus understand the origin of this burst. To this aim we obtained a combination of deep near-infrared (NIR) and optical imaging together with spectroscopy. Our analysis reveals an optical and NIR bump in the light curve whose luminosity and evolution are in agreement with several SNe associated to LGRBs. Analysis of the prompt GRB shows that this event follows the E p,i-E iso relation found for LGRBs. The host galaxy is a low-mass star-forming galaxy, typical of LGRBs, but with one of the highest star formation rates, especially with respect to its mass ( $\mathrm{log}{M}_{* }/{M}_{\odot }=8.6$ , SFR ~ 4.0 M ☉ yr-1). We conclude that GRB 200826A is a typical collapsar event in the low tail of the duration distribution of LGRBs. These findings support theoretical predictions that events produced by collapsars can be as short as 0.5 s in the host frame and further confirm that duration alone is not an efficient discriminator for the progenitor class of a GRB. * Based on data obtained with the LBT programs: LBT-2019B-18 (PI A. Rossi), DDT-2019B-9 (PI P. D'Avanzo), and LD-2020B-0100 (PI. B. Rothberg); and the TNG programme A41 TAC15 (PI V. D'Elia).

Keywords: Gamma-ray bursts, Supernovae, Core-collapse supernovae
Effects of Total Solar Eclipse on Ionospheric Total Electron Content over Antarctica on 2021 December 4. The effects of a total solar eclipse that occurred on 2021 December 4 on ionospheric total electron content (TEC) over Antarctic stations were studied. The study was based on GPS data obtained over Antarctica on the day of the eclipse and the days before and after the eclipse over six GPS stations. The findings of this study show that a total solar eclipse lowers the amount of ionization reaching the Earth's surface with TEC values dropping across the stations. Finally, the enhancement of ΔTEC is quite different from one station to another station. This may also be due to the effect of solar heating conditions and the density of the Sun as exerted over the stations with the Sun side over one station and the clouded part over the others.

Keywords: Solar eclipses
Non-LTE Inversion of Prominence Spectroscopic Observations in Hα and Mg II h&amp;k lines. We continued our investigation of the plasma characteristics of a quiescent prominence that occurred on 2017 March 30. The prominence was observed simultaneously by several instruments, including the Interface Region Imaging Spectrograph (IRIS) and the Multichannel Subtractive Double Pass (MSDP) spectrograph operating at the Meudon solar tower. We focused on IRIS Mg II h&amp;k and MSDP Hα spectra, selecting 55 well-coaligned points within the prominence. We computed an extensive grid of 63,000 isothermal and isobaric 1D-slab prominence models with a non-LTE (i.e., departures from the local thermodynamic equilibrium) radiative transfer code. We then performed a 1.5D spectral inversion searching for an optimal model that best fits five parameters of the observed profiles (observables), namely, the integrated intensity of the Hα and Mg II k lines, the FWHM of both lines, and the ratio of intensities of the Mg II k and Mg II h lines. The latter is sensitive to temperature. Our results show that the prominence is a low-temperature structure, mostly below 10,000 K, with some excursions to higher values (up to 18,000 K) but also rather low temperatures (around 5000 K). The microturbulent velocity is typically low, peaking around 8 km s-1, and electron density values are of the order of 1010 cm-3. The peak effective thickness is 500 km, although the values range up to 5000 km. The studied prominence is rather optically thin in the Hα line and optically thick in the Mg II h&amp;k lines.

Keywords: Quiescent solar prominence, Radiative transfer, Spectroscopy
Absorption Spectra of Electrified Hydrogen Molecules. Molecular hydrogen normally has only weak, quadrupole transitions between its rovibrational states, but in a static electric field it acquires a dipole moment and a set of allowed transitions. Here we use published ab initio calculations of the static electrical response tensors of the H2 molecule to construct the perturbed rovibrational eigensystem and its ground state absorptions. We restrict attention to two simple field configurations that are relevant to condensed hydrogen molecules in the interstellar medium (ISM): a uniform electric field and the field of a pointlike charge. The energy eigenstates are mixtures of vibrational and angular momentum eigenstates so there are many transitions that satisfy the dipole selection rules. We find that mixing is strongest among the states with high vibrational excitation, leading to hundreds of absorption lines across the optical and near-infrared. These spectra are very different from that of the field-free molecule, so if they appeared in astronomical data they would be difficult to assign. Furthermore, in a condensed environment the excited states likely have short lifetimes to internal conversion, giving the absorption lines a diffuse appearance. We therefore suggest electrified H2 as a possible carrier of the diffuse interstellar bands (DIBs). We further argue that in principle it may be possible to account for all of the DIBs with this one carrier. However, despite electrification, the transitions are not very strong and a large column of condensed H2 would be required, making it difficult to reconcile this possibility with our current understanding of the ISM.

Keywords: Interstellar dust, Diffuse interstellar bands, Interstellar line absorption, Molecular spectroscopy, Interstellar dust extinction, Molecular physics
Spectral-line Survey of the Region of Massive Star Formation W51e1/e2 in the 4 mm Wavelength Range. We present the results of a spectral-line survey of the W51e1/e2 star-forming region at 68-88 GHz. 79 molecules and their isotopologues were detected, from simple diatomic or triatomic molecules, such as SO, SiO, and CCH, to complex organic compounds, such as CH3OCH3 or CH3COCH3. A number of lines that are absent from the Lovas list of molecular lines observed in space were detected, and most of these were identified. A significant number of the detected molecules are typical for hot cores. These include the neutral molecules HCOOCH3, CH3CH2OH, and CH3COCH3, which are currently believed to exist in the gas phase only in hot cores and shock-heated gas. In addition, vibrationally excited C4H and HC3N lines with upper-level energies of several hundred Kelvins were found. Such lines can arise only in hot gas with temperatures on the order of 100 K or higher. Apart from neutral molecules, various molecular ions were also detected. Some of these (HC18O+, H13CO+, and HCS+) usually exist in molecular clouds with high visual extinctions. Potential formation pathways of complex organic molecules and hydrocarbons, along with nitriles, are considered. These formation routes are first discussed in the context of laboratory experiments elucidating the synthesis of organic molecules in interstellar ices in cold molecular clouds, followed by sublimation into the gas phase in the hot core stage. Thereafter, we discuss the predominant formation of hydrocarbons and their nitriles in the gas phase through bimolecular neutral-neutral reactions.

Keywords: Star forming regions, Interstellar medium, Pre-biotic astrochemistry
The Young Embedded Disk L1527 IRS: Constraints on the Water Snowline and Cosmic-Ray Ionization Rate from HCO+ Observations. The water snowline in circumstellar disks is a crucial component in planet formation, but direct observational constraints on its location remain sparse owing to the difficulty of observing water in both young embedded and mature protoplanetary disks. Chemical imaging provides an alternative route to locate the snowline, and HCO+ isotopologues have been shown to be good tracers in protostellar envelopes and Herbig disks. Here we present ~0.″5 resolution (~35 au radius) Atacama Large Millimeter/submillimeter Array (ALMA) observations of HCO+ J = 4 - 3 and H13CO+ J = 3 - 2 toward the young (Class 0/I) disk L1527 IRS. Using a source-specific physical model with the midplane snowline at 3.4 au and a small chemical network, we are able to reproduce the HCO+ and H13CO+ emission, but for HCO+ only when the cosmic-ray ionization rate is lowered to 10-18 s-1. Even though the observations are not sensitive to the expected HCO+ abundance drop across the snowline, the reduction in HCO+ above the snow surface and the global temperature structure allow us to constrain a snowline location between 1.8 and 4.1 au. Deep observations are required to eliminate the envelope contribution to the emission and to derive more stringent constraints on the snowline location. Locating the snowline in young disks directly with observations of H2O isotopologues may therefore still be an alternative option. With a direct snowline measurement, HCO+ will be able to provide constraints on the ionization rate.

Keywords: Interstellar molecules, Protostars, Astrochemistry
The Accretion Flow Geometry of MAXI J1820+070 through Broadband Noise Research with Insight Hard X-ray Modulation Telescope. Here we present a detailed study of the broadband noise in the power density spectra of the black hole X-ray binary MAXI J1820+070 during the hard state of its 2018 outburst, using Hard X-ray Modulation Telescope observations. The broadband noise shows two main humps, which might separately correspond to variability from a variable disk and two Comptonization regions. We fitted the two humps with multiple Lorentzian functions and studied the energy-dependent properties of each component up to 90-150 keV and their evolution with spectral changes. The lowest-frequency component is considered as the subharmonic of the quasiperiodic oscillation component and shows a different energy dependence compared with other broadband noise components. We found that although the fractional rms of all the broadband noise components mainly decreases with the energy, their rms spectra are different in shape. Above ~20-30 keV, the characteristic frequencies of these components increase sharply with the energy, meaning that the high-energy component is more variable on short timescales. Our results suggest that the hot inner flow in MAXI J1820+070 is likely to be inhomogeneous. We propose a geometry with a truncated accretion disk and two Comptonization regions.

Keywords: Accretion, Low-mass x-ray binary stars, Stellar mass black holes, Astrophysical black holes
Compressible Test-field Method and Its Application to Shear Dynamos. In this study, we present a compressible test-field method (CTFM) for computing α-effect and turbulent magnetic diffusivity tensors, as well as those relevant for the mean ponderomotive force and mass source, applied to the full MHD equations. We describe the theoretical background of the method and compare it to the quasi-kinematic test-field method and to the previously studied variant working in simplified MHD (SMHD). We present several test cases using velocity and magnetic fields of the Roberts geometry and also compare with the imposed-field method. We show that, for moderate imposed-field strengths, the nonlinear CTFM (nCTFM) gives results in agreement with the imposed-field method. A comparison of different flavors of the nCTFM in the shear dynamo case also yields agreement up to equipartition field strengths. Some deviations between the CTFM and SMHD variants exist. As a relevant physical application, we study nonhelically forced shear flows, which exhibit large-scale dynamo action, and present a reanalysis of low-Reynolds-number, moderate shear systems, where we previously ignored the pressure gradient in the momentum equation and found no coherent shear-current effect. Another key difference is that in the earlier study we used magnetic forcing to mimic small-scale dynamo action, while here it is self-consistently driven by purely kinetic forcing. The kinematic CTFM with general validity forms the core of our analysis. We still find no coherent shear-current effect, but do recover strong large-scale dynamo action that, according to our analysis, is driven by incoherent effects.

Keywords: Astrophysical magnetism, Cosmic magnetic fields theory, Astrophysical processes
Toward RNA Life on Early Earth: From Atmospheric HCN to Biomolecule Production in Warm Little Ponds. The origin of life on Earth involves the early appearance of an information-containing molecule such as RNA. The basic building blocks of RNA could have been delivered by carbon-rich meteorites or produced in situ by processes beginning with the synthesis of hydrogen cyanide (HCN) in the early Earth's atmosphere. Here, we construct a robust physical and nonequilibrium chemical model of the early Earth's atmosphere. The atmosphere is supplied with hydrogen from impact degassing of meteorites, water evaporated from the oceans, carbon dioxide from volcanoes, and methane from undersea hydrothermal vents, and in it lightning and external UV-driven chemistry produce HCN. This allows us to calculate the rain-out of HCN into warm little ponds (WLPs). We then use a comprehensive numerical model of sources and sinks to compute the resulting abundances of nucleobases, ribose, and nucleotide precursors such as 2-aminooxazole resulting from aqueous and UV-driven chemistry within them. We find that 4.4 billion years ago the limit of adenine concentrations in ponds for habitable surfaces is 0.05 μM in the absence of seepage. Meteorite delivery of adenine to WLPs can provide boosts in concentration by 2-3 orders of magnitude, but these boosts deplete within months by UV photodissociation, seepage, and hydrolysis. The early evolution of the atmosphere is dominated by the decrease in hydrogen due to falling impact rates and atmospheric escape, and the rise of oxygenated species such as OH from H2O photolysis. The source of HCN is predominantly from UV radiation rather than lightning. Our work points to an early origin of RNA on Earth within ~200 Myr of the Moon-forming impact.

Keywords: Planetary atmospheres, Earth (planet), Astrobiology, Pre-biotic astrochemistry, Lightning