Sazuna/UAT_keywords huggingface dataset:
The Nucleus of Interstellar Comet 2I/Borisov. We present high-resolution imaging observations of interstellar comet 2I/Borisov (formerly C/2019 Q4) obtained using the Hubble Space Telescope. Scattering from the comet is dominated by a coma of large particles (characteristic size ∼0.1 mm) ejected anisotropically. Convolution modeling of the coma surface brightness profile sets a robust limit to the spherical-equivalent nucleus radius rn ≤ 0.5 km (geometric albedo 0.04 assumed). We obtain an independent constraint based on the nongravitational acceleration of the nucleus, finding rn &gt; 0.2 km (nucleus density ρ = 500 kg m-3 assumed). The profile and the nongravitational constraints cannot be simultaneously satisfied if ρ ≤ 25 kg m-3; the nucleus of comet Borisov cannot be a low-density fractal assemblage of the type proposed elsewhere for the nucleus of 1I/'Oumuamua. We show that the spin-up timescale to outgassing torques, even at the measured low production rates, is comparable to or shorter than the residence time in the Sun's water sublimation zone. The spin angular momentum of the nucleus should be changed significantly during the current solar flyby. Lastly, we find that the differential interstellar size distribution in the 0.5 mm to 100 m size range can be represented by power laws with indices &lt;4 and that interstellar bodies of 100 m size scale strike Earth every one to two hundred million years.

Keywords: Long period comets, Comets
The Nearby Luminous Transient AT2018cow: A Magnetar Formed in a Subrelativistically Expanding Nonjetted Explosion. The fast-rising blue optical transient AT2018cow indicated unusual early-phase characteristics unlike relatively better studied explosive transients. Its afterglow may be produced by either a relativistically beamed (jetted) or intrinsically luminous (nonjetted) ejecta and carries observational signatures of the progenitor and environment. High-resolution monitoring can distinguish between these scenarios and clarify the progenitor nature. We present very long baseline interferometry (VLBI) observations of AT2018cow at 5 GHz involving 21 radio telescopes from the European VLBI Network with five sessions spanning ≈1 yr. With an astrometric precision up to 25 μas per epoch, the rapidly fading compact mas-scale source is found to be nonjetted with a proper motion of ≤0.15 mas yr-1 (0.14 c). This and a dense (number density ≈104-105 cm-3) magnetized environment (magnetic field strength ≥0.84 G) are characteristic of a newly formed magnetar driven central engine, originating in the successful explosion of a low-mass star.

Keywords: High energy astrophysics, Very long baseline interferometry, Transient sources, Burst astrophysics, Magnetars
Precise Measurements of the Speed of Light with High-redshift Quasars: Ultra-compact Radio Structure and Strong Gravitational Lensing. Although the speed of light has been measured with very high precision, most of these measurements were carried out on Earth or in our close cosmic surroundings. In this Letter, we propose an original idea to combine the observations of ultra-compact structure in radio quasars and strong gravitational lensing with quasars acting as background sources to estimate the speed of light. The method will provide precise measurements of the speed of light using extragalactic objects at different redshifts. We evaluate if current or future missions such as the Large Synoptic Survey Telescope (LSST) and Dark Energy Survey (DES) can be sensitive enough to detect any variation of c. Our results show that strongly lensed quasars observed by LSST would produce robust constraints on Δc/c at the level of 10-4, if the compact radio structure measurements are available.

Keywords: Strong gravitational lensing, Radio sources, Cosmological parameters, Quasars
Duffing Oscillator Model of Solar Cycles. We propose that the solar cycle variability could be described in the framework of an external quasi-sinusoidal influence on an oscillator with cubic nonlinearity and linear damping (Duffing oscillator). To demonstrate this, we compare the empirical amplitude-frequency dependence with the theoretical one obtained by the Krylov-Bogolyubov averaging method. The empirical data are a composite time series of 2.0 version of sunspot number series, which starts in 1700, and the sunspot group number series by Svalgaard &amp; Schatten, scaled to sunspot number, for 1610-1699 interval. We find that while this interpretation of solar cycle is a mathematical approximation, it explains several properties of solar cycle variability.

Keywords: Solar cycle, Analytical mathematics, Maunder minimum
Spatial Segregation of Massive Clusters in Dwarf Galaxies. The relative average minimum projected separations of star clusters in the Legacy ExtraGalactic UV Survey (LEGUS) and in tidal dwarfs around the interacting galaxy NGC 5291 are determined as a function of cluster mass to look for cluster-cluster mass segregation. Class 2 and 3 LEGUS clusters, which have a more irregular internal structure than the compact and symmetric class 1 clusters, are found to be mass-segregated in low-mass galaxies, which means that the more massive clusters are systematically bunched together compared to the lower-mass clusters. This mass segregation is not present in high-mass galaxies or class 1 clusters. We consider possible causes for this segregation, including differences in cluster formation and scattering in the shallow gravitational potentials of low-mass galaxies.

Keywords: Star formation, Galaxies, Star clusters
Estimating the Temperature and Density of a Spicule from 100 GHz Data Obtained with ALMA. We succeeded in observing two large spicules simultaneously with the Atacama Large Millimeter/submillimeter Array (ALMA), the Interface Region Imaging Spectrograph (IRIS), and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. One is a spicule seen in the IRIS Mg II slit-jaw images and AIA 304 Å images (Mg II/304 Å spicule). The other one is a spicule seen in the 100 GHz images obtained with ALMA (100 GHz spicule). Although the 100 GHz spicule overlapped with the Mg II/304 Å spicule in the early phase, it did not show any corresponding structures in the IRIS Mg II and AIA 304 Å images after the early phase. It suggests that the spicules are individual events and do not have a physical relationship. To obtain the physical parameters of the 100 GHz spicule, we estimate the optical depths as a function of temperature and density using two different methods. One is using the observed brightness temperature by assuming a filling factor, and the other is using an emission model for the optical depth. As a result of comparing them, the kinetic temperature of the plasma and the number density of ionized hydrogen in the 100 GHz spicule are ∼6800 K and 2.2 × 1010 cm-3. The estimated values can explain the absorbing structure in the 193 Å image, which appear as a counterpart of the 100 GHz spicule. These results suggest that the 100 GHz spicule presented in this Letter is classified to a macrospicule without a hot sheath in former terminology.

Keywords: Solar ultraviolet emission, The Sun, Solar spicules, Solar radio emission, Solar chromosphere
Symmetries of CMB Temperature Correlation at Large Angular Separations. A new analysis is presented of the angular correlation function C(Θ) of cosmic microwave background temperature at large angular separation, based on published maps derived from Wilkinson Microwave Anisotropy Probe and Planck satellite data, using different models of astrophysical foregrounds. It is found that using a common analysis, the results from the two satellites are very similar. In particular, it is found that previously published differences between measured values of C(Θ) near Θ = 90° arise mainly from different choices of masks in regions of largest Galactic emissions, and that demonstrated measurement biases are reduced by eliminating masks altogether. Maps from both satellites are shown to agree with C(90°) = 0 to within estimated statistical and systematic errors, consistent with an exact symmetry predicted in a new holographic quantum model of inflation.

Keywords: Cosmic anisotropy, Cosmic microwave background radiation, Quantum gravity, Cosmic inflation
A Retrograde Spin of the Black Hole in MAXI J1659-152. We present the results of spectral analysis of the galactic black hole binary MAXI J1659-152 in the rising phase of the outburst that lasted for about 65 days starting on 2010 September 25. The presence of a broad Fe line, verified by Monte Carlo simulations, and coverage of a wide energy band by utilizing the combined spectral capabilities of XMM-Newton/EPIC-pn and RXTE/PCA allowed us to use a combination of reflection spectroscopy and continuum fitting methods to estimate the spin of the black hole. We explored the entire parameter range allowed by the present uncertainties on black hole mass, inclination, and distance as well as the accretion rate. We show that for about 95% of parameter space and very reasonable upper limits on $\dot{M}$ , the spin of the black hole has to be negative. This is the first clear detection of negative spin in a galactic black hole binary.

Keywords: Low-mass x-ray binary stars, Stellar accretion disks, Kerr black holes
Turbulent Viscosity Acting on the Equilibrium Tidal Flow in Convective Stars. Convection is thought to act as a turbulent viscosity in damping tidal flows and in driving spin and orbital evolution in close convective binary systems. This turbulent viscosity should be reduced, compared to mixing-length predictions, when the forcing (tidal) frequency $| {\omega }_{t}| $ exceeds the turnover frequency ωcv of the dominant convective eddies. However, two contradictory scaling laws have been proposed and this issue remains highly disputed. To revisit this controversy, we conduct the first direct numerical simulations of convection interacting with the equilibrium tidal flow in an idealized global model of a low-mass star. We present direct computations of the turbulent effective viscosity, νE, acting on the equilibrium tidal flow. We unexpectedly report the coexistence of the two disputed scaling laws, which reconciles previous theoretical (and numerical) findings. We recover the universal quadratic scaling ${\nu }_{E}\propto {(| {\omega }_{t}| /{\omega }_{{cv}})}^{-2}$ in the high-frequency regime $| {\omega }_{t}| /{\omega }_{{cv}}\gg 1$ . Our results also support the linear scaling ${\nu }_{E}\propto {(| {\omega }_{t}| /{\omega }_{{cv}})}^{-1}$ in an intermediate regime with $1\leqslant | {\omega }_{t}| /{\omega }_{{cv}}\lesssim { \mathcal O }(10)$ . Both regimes may be relevant to explain the observed properties of close binaries, including spin synchronization of solar-type stars and the circularization of low-mass stars. The robustness of these two regimes of tidal dissipation, and the transition between them, should be explored further in more realistic models. A better understanding of the interaction between convection and tidal flows is indeed essential to correctly interpret observations of close binary stars and short-period planetary orbits.

Keywords: Stellar convective zones, Stellar convection envelopes, Hydrodynamics, Close binary stars, Planet hosting stars, Astrophysical fluid dynamics
Relations between Coronal Mass Ejections and the Photospheric Magnetic Field in Cycles 23 and 24. The number of coronal mass ejections (CMEs) and their parameters and cycle variations were investigated and compared to the photospheric magnetic field evolution in cycles 23 and 24. The Coordinated Data Analysis Workshops (CDAW) catalog of white-light CMEs detected by the Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph coronagraphs and the data on the photospheric magnetic fields from the Kitt Peak Vacuum Telescope Spectromagnetograph (KPVT/Spectromagnetograph) and the Synoptic Optical Long-term Investigations of the Sun Vector-Spectromagnetograph (SOLIS/VSM) were used. The results suggest that not only did the number of CMEs increase in cycle 24, but that their parameters, cycle variations, distributions, and dependencies on the photospheric magnetic fields were also different. Various CME categories behave in different ways during solar cycles. The differences in the number and parameters of CMEs and their cycle variations may be related to the differences in the photospheric magnetic fields during the cycles. The strong photospheric magnetic fields maintained approximately the same strength from cycle 23 to cycle 24, whereas the weak fields became weaker and the area they occupied increased. Taking into account that the global magnetic field diminished from cycle 23 to cycle 24, the increase in the number of CMEs in cycle 24 can be understood. A detailed analysis of the similarities and differences in CME parameters and their cycle evolution indicates that, along with the influence of changes in the CME detection mode in 2004 and 2010, the changes in CME rate and parameters were also associated with real differences in the behavior of strong and weak photospheric magnetic fields in cycles 23 and 24.

Keywords: Solar cycle, Active solar corona, Solar coronal mass ejections, Solar magnetic fields
Line Formation of Raman-scattered He II λ 4851 in an Expanding Spherical H I Shell in Young Planetary Nebulae. We investigate line formation of Raman-scattered He II at 4851 Å in an expanding neutral, spherical shell that surrounds a point-like He II source located at the center. A new grid-based Monte Carlo code is used to take into consideration the H I density variation along each photon path. In the case of a monochromatic He II emission source, the resultant line profiles are characterized by an asymmetric double-peak structure with a tertiary peak and a significant red tail that may extend to the line centers of He IIλ4859 and Hβ. The peak separation corresponds to the expansion velocity, which we consider is in the range 20-40 km s-1 in this work. Tertiary red peaks are formed as a result of multiple Rayleigh reflections at the inner surface of a hollow, spherical shell of H I. Due to a sharp increase of scattering cross section near resonance, the overall Raman conversion efficiency is significantly enhanced as the expansion speed increases. In the case of a He II line source with a Gaussian line profile with an FWHM of 30-70 km s-1, we obtain distorted redward profiles that are due to the increasing redward cross section of H I. A simple application to the young planetary nebula IC 5117 is consistent with a neutral shell expanding with a speed ∼30 km s-1.

Keywords: Planetary nebulae, Radiative transfer, Stellar mass loss
Implications for Extraterrestrial Hydrocarbon Chemistry: Analysis of Acetylene (C<SUB>2</SUB>H<SUB>2</SUB>) and D2-acetylene (C<SUB>2</SUB>D<SUB>2</SUB>) Ices Exposed to Ionizing Radiation via Ultraviolet-Visible Spectroscopy, Infrared Spectroscopy, and Reflectron Time-of-flight Mass Spectrometry. The processing of the simple hydrocarbon ice, acetylene (C2H2/C2D2), via energetic electrons, thus simulating the processes in the track of galactic cosmic-ray particles penetrating solid matter, was carried out in an ultrahigh vacuum surface apparatus. The chemical evolution of the ices was monitored online and in situ utilizing Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy and, during temperature programmed desorption, via a quadrupole mass spectrometer with an electron impact ionization source (EI-QMS) and a reflectron time-of-flight mass spectrometer utilizing single-photon photoionization (SPI-ReTOF-MS) along with resonance-enhanced multiphoton photoionization (REMPI-ReTOF-MS). The confirmation of previous in situ studies of ethylene ice irradiation using FTIR was accomplished with the detection of five products: ethane (C2H6/C2D6), ethylene (C2H4/C2D4), diacetylene (C4H2/C4D2), vinylacetylene (C4H4/C4D4), and benzene (C6H6/C6D6). Alternatively to previous gas-phase analytical studies, the sensitive SPI-ReTOF-MS analysis detected 10 hydrocarbon groups of distinct degrees of saturation: CnH2n+2 (n = 4, 6-16), CnH2n (n = 2, 3, 6, 8-16), CnH2n-2 (n = 3, 4, 6, 8, 10-15), CnH2n-4 (n = 4-8, 10-14), CnH2n-6 (n = 4-10, 12-16), CnH2n-8 (n = 6-10, 12, 14-17), CnH2n-10 (n = 6-12, 14-17), CnH2n-12 (n = 8-14), CnH2n-14 (n = 8-16), and CnH2n-16 (n = 10-16). From these detected groups the REMPI-ReTOF-MS method was able to assign the isomer-specific production of five aromatic hydrocarbons: benzene (C6H6), phenylacetylene (C8H6), styrene (C8H8), naphthalene (C10H8), and phenanthrene (C14H10).

Keywords: Interstellar dust, Polycyclic aromatic hydrocarbons, Mass spectrometry, Astrochemistry, Spectroscopy, Saturnian satellites
Galactic Archaeology at High Redshift: Inferring the Nature of GRB Host Galaxies from Abundances. We identify the nature of high-redshift long gamma-ray burst (LGRB) host galaxies by comparing the observed abundance ratios in the interstellar medium with detailed chemical evolution models accounting for the presence of dust. We compare abundance data from LGRB afterglow spectra to abundance patterns as predicted by our models for different galaxy types. We analyze [X/Fe] abundance ratios (where X is C, N, O, Mg, Si, S, Ni, Zn) as functions of [Fe/H]. Different galaxies (irregulars, spirals, spheroids) are, in fact, characterized by different star formation histories, which produce different [X/Fe] versus [Fe/H] relations ("time-delay model"). This allows us to identify the star formation history of the host galaxies and to infer their age (I.e., the time elapsed from the beginning of star formation) at the time of the GRB events. Unlike previous works, we use newer models in which we adopt updated stellar yields and prescriptions for dust production, accretion, and destruction. We consider a sample of seven LGRB host galaxies. Our results suggest that two of them (GRB 050820, GRB 120815A) are star-forming spheroids, two (GRB 081008, GRB 161023A) are spirals, and three (GRB 090926A, GRB 050730, GRB 120327A) are irregulars. The inferred ages of the considered host galaxies span from 10 Myr to slightly more than 1 Gyr.

Keywords: Interstellar dust, Gamma-ray bursts, Interstellar abundances, Galaxy evolution, High-redshift galaxies
Hubble Space Telescope Observations of Mira Variables in the SN Ia Host NGC 1559: An Alternative Candle to Measure the Hubble Constant. We present year-long, near-infrared Hubble Space Telescope (HST) WFC3 observations used to search for Mira variables in NGC 1559, the host galaxy of the Type Ia supernova (SN Ia) SN 2005df. This is the first dedicated search for Miras, highly evolved low-mass stars, in an SN Ia host, and subsequently the first calibration of the SN Ia luminosity using Miras in a role historically played by Cepheids. We identify a sample of 115 O-rich Miras with P &lt; 400 days based on their light-curve properties. We find that the scatter in the Mira period-luminosity relation (PLR) is comparable to Cepheid PLRs seen in SN Ia host galaxies. Using a sample of O-rich Miras discovered in NGC 4258 with HSTF160W and its maser distance, we measure a distance modulus for NGC 1559 of ${\mu }_{1559}=31.41\pm 0.050$ (statistical) $\pm 0.060$ (systematic) mag. Based on the light curve of the normal, well-observed, low-reddening SN 2005df, we obtain a measurement of the fiducial SN Ia absolute magnitude of ${M}_{B}^{0}=-19.27\pm 0.13$ mag. With the Hubble diagram of SNe Ia we find ${H}_{0}=72.7\pm 4.6$ km s-1 Mpc-1. Combining the calibration from the NGC 4258 megamaser and the Large Magellanic Cloud detached eclipsing binaries gives a best value of ${H}_{0}=73.3\pm 4.0$ km s-1 Mpc-1. This result is within 1σ of the Hubble constant derived using Cepheids and multiple calibrating SNe Ia. This is the first of four expected calibrations of the SN Ia luminosity from Miras that should reduce the error in H0 via Miras to ∼3%. In light of the present Hubble tension and JWST, Miras have utility in the extragalactic distance scale to check Cepheid distances or calibrate nearby SNe in early-type host galaxies that would be unlikely targets for Cepheid searches.

Keywords: Cosmology, Galaxy distances, Cosmological parameters, Distance indicators, Hubble constant, Mira variable stars
Probing the Emission States of PSR J1107-5907. The emission from PSR J1107-5907 is erratic. Sometimes the radio pulse is undetectable, at other times the pulsed emission is weak, and for short durations the emission can be very bright. In order to improve our understanding of these state changes, we have identified archival data sets from the Parkes radio telescope in which the bright emission is present, and find that the emission never switches from the bright state to the weak state, but instead always transitions to the "off" state. Previous work had suggested the identification of the "off" state as an extreme manifestation of the weak state. However, the connection between the "off" and bright emission reported here suggests that the emission can be interpreted as undergoing only two emission states: a "bursting" state consisting of both bright pulses and nulls, and the weak emission state.

Keywords: Observational astronomy, Astronomy data analysis, Radio pulsars
Mirror and Proton-cyclotron Instabilities Coexisting with Ambient Turbulence in a Proton-Alpha Plasma. We investigate the effect of ambient turbulence on the mirror and proton-cyclotron instabilities in a proton-alpha particle plasma. We perform three-dimensional hybrid simulations with particle-in-cell ions and a quasi-neutralizing electron fluid. The instabilities are driven by the protons with temperature perpendicular to the mean magnetic field larger than the parallel temperature. The description of these instabilities is usually based on the assumption of a uniform and stationary background. However, this assumption is violated by the ambient turbulence. In particular, the turbulent fluctuations modify the particle distribution function by making it spatially inhomogeneous and time-dependent. We compare the properties of the instabilities to the case of a uniform and stationary background and the same average temperature anisotropy and plasma beta. We find that the initial growth rates of the mirror mode are close, but the saturation level is significantly reduced when the turbulence is present. The saturation level of the proton-cyclotron mode is not affected as strongly.

Keywords: Interplanetary turbulence, Space plasmas, Solar wind