Sazuna/UAT_keywords huggingface dataset:
Incorporating Inner Magnetosphere Current-driven Electron Acceleration in Numerical Simulations of Exoplanet Radio Emission. We present calculations of auroral radio emission for an Earth-like planet produced by field-aligned current (FAC) driven electron acceleration using a coupled global magnetohydrodynamic (MHD) and inner magnetosphere model, extending the capabilities of previous works which focus solely on the direct transmission of magnetic energy between the stellar wind and ionosphere. Magnetized exoplanets are expected to produce radio emission via interaction between the host star's stellar wind and planetary magnetosphere-ionosphere system. The empirically derived Radiometric Bode's Law (RBL) is a linear relation between the magnetic solar wind power and total emitted radio power from magnetized Solar System planets, and is often extrapolated to extreme exoplanet systems. It has been shown that the magnitudes of the FACs coupling the stellar wind to planetary ionospheres are likely to be significantly limited (often referred to as ionospheric saturation), resulting in an estimated radio power up to several orders of magnitude less than that predicted by RBL. In this paper, we demonstrate the significance of intense, sporadic FACs, driven by nightside magnetic reconnection and inner magnetosphere plasma flow, to the total radio power produced by wind-ionosphere interaction in terrestrial planets. During periods of strong stellar wind variability, the contribution from these secondary currents can be over an order of magnitude greater than the primary current systems that previous models describe. The results highlight the role of the variability of the stellar wind on the magnitude and location of the resulting emission, subsequently affecting the conditions for detectability.

Keywords: Solar-terrestrial interactions, Magnetospheric radio emissions
Discovery of Beryllium in White Dwarfs Polluted by Planetesimal Accretion. The element beryllium is detected for the first time in white dwarf stars. This discovery in the spectra of two helium-atmosphere white dwarfs was made possible only because of the remarkable overabundance of Be relative to all other elements, heavier than He, observed in these stars. The measured Be abundances, relative to chondritic, are by far the largest ever seen in any astronomical object. We anticipate that the Be in these accreted planetary bodies was produced by spallation of one or more of O, C, and N in a region of high fluence of particles of MeV or greater energy.

Keywords: High resolution spectroscopy, Extrasolar rocky planets, Abundance ratios, White dwarf stars, Stellar accretion, Planetesimals, Overabundances, Stellar spectral lines
Construction of Explicit Symplectic Integrators in General Relativity. IV. Kerr Black Holes. In previous papers, explicit symplectic integrators were designed for nonrotating black holes, such as a Schwarzschild black hole. However, they fail to work in the Kerr spacetime because not all variables can be separable, or not all splitting parts have analytical solutions as explicit functions of proper time. To cope with this difficulty, we introduce a time transformation function to the Hamiltonian of Kerr geometry so as to obtain a time-transformed Hamiltonian consisting of five splitting parts, whose analytical solutions are explicit functions of the new coordinate time. The chosen time transformation function can cause time steps to be adaptive, but it is mainly used to implement the desired splitting of the time-transformed Hamiltonian. In this manner, new explicit symplectic algorithms are easily available. Unlike Runge-Kutta integrators, the newly proposed algorithms exhibit good long-term behavior in the conservation of Hamiltonian quantities when appropriate fixed coordinate time steps are considered. They are better than same-order implicit and explicit mixed symplectic algorithms and extended phase-space explicit symplectic-like methods in computational efficiency. The proposed idea on the construction of explicit symplectic integrators is suitable for not only the Kerr metric but also many other relativistic problems, such as a Kerr black hole immersed in a magnetic field, a Kerr-Newman black hole with an external magnetic field, axially symmetric core-shell systems, and five-dimensional black ring metrics.

Keywords: Celestial mechanics, Black hole physics, Computational methods, Computational astronomy
Multiwavelength View of the Type IIn Zoo: Optical to X-Ray Emission Model of Interaction-powered Supernovae. Transients powered by interaction with the circumstellar medium (CSM) are often observed in wavelengths other than the optical, and multiwavelength modeling can be important when inferring the properties of the explosion and CSM, or for distinguishing from other powering mechanisms. We develop a model calculating the time-dependent emission spectrum of interaction-powered transients. We solve the energy equations of electron-proton plasma in the shocked supernova ejecta and CSM and the radiation transfer equation out to the outer edge of the CSM, incorporating collisional relaxation and the Comptonization of bremsstrahlung radiation. We compare our model to observations of Type IIn supernovae covering a frequency range from the optical to X-rays. For SN 2010jl the observed optical and X-ray light curves can be consistently explained if a clumpy or asymmetric structure in the CSM is assumed, in agreement with previous studies. For SN 2014C our model successfully reproduces the X-ray bremsstrahlung component and the emergence of Hα emission at 400 days after explosion. Finally we find a parameter space where the supernova is extremely X-ray bright, reaching 1043-1044 erg s-1, for up to 100 days. Such X-ray transients are likely to be detectable with all-sky surveys by, e.g., eROSITA.

Keywords: Type II supernovae, X-ray sources, Stellar mass loss
Sensitivity of Cosmological Parameter Estimation to Nonlinear Prescription from Galaxy Clustering. Next-generation large-scale surveys will probe the nonlinear regime with high resolution. Making viable cosmological inferences based on these observations requires accurate theoretical modeling of the mildly nonlinear regime. In this work we investigate the sensitivity of cosmological parameter measurements from future probes of galaxy clustering to the choice of nonlinear prescription up to ${k}_{\max }=0.3\,h\,{\mathrm{Mpc}}^{-1}$ . In particular, we calculate the induced parameter bias when the mildly nonlinear regime is modeled by the Halofit fitting scheme. We find significant (~5σ) bias for some parameters with a future Euclid-like survey. We also explore the contribution of different scales to the parameter estimation for different observational setups and cosmological scenarios, compared for the two nonlinear prescriptions of Halofit and EFTofLSS. We include in the analysis the free parameters of the nonlinear theory and a blind parameterization for the galaxy bias. We find that marginalization over these nuisance parameters significantly boosts the errors of the standard cosmological parameters. This renders the differences in the predictions of the various nonlinear prescriptions less effective when transferred to the parameter space. More accurate modeling of these nuisance parameters would therefore greatly enhance the cosmological gain from the mildly nonlinear regime.

Keywords: Large-scale structure of the universe, Fisher's Information, Astronomy data analysis, Cosmological parameters from large-scale structure, Dark energy
Probing Feedback via IGM tomography and the Lyα Forest with Subaru PFS, TMT/ELT, and JWST. In preparation for the tomography study of the intergalactic medium (IGM) by Subaru Prime Focus Spectrograph (PFS) survey and other large future telescopes such as TMT/ELT/GMT, we present the results of our pilot study on Lyα forest and IGM tomography statistics using the GADGET3-OSAKA cosmological smoothed particle hydrodynamical simulation. Our simulation includes models for star formation and supernova feedback, which enables more realistic cross-correlation studies between galaxies, neutral hydrogen (H I), and metals in circumgalactic and intergalactic medium. We create a light-cone data set at z = 2-3 from our simulations and generate mock Lyα forest data. As a first step, in this paper, we focus on the distribution of H I and galaxies, and present statistical results on 1D flux probability distribution function, 1D power spectrum, flux contrast versus impact parameter, and H I-galaxy cross-correlations. Our results show overall agreement with current observational data, with some interesting discrepancies on small scales that are due to either feedback effects or varying observational conditions. Our simulation shows stronger H I absorption with decreasing transverse distance from galaxies. We find that massive galaxies with M⋆ ≥ 1010 M⊙ contribute strongly to the flux contrast signal, and that lower-mass galaxies with M⋆ ~ 108-1010 M⊙ tend to dilute the flux contrast signal from massive galaxies. On large scales, the average flux contrast smoothly connects to the IGM level, supporting the concordance Λ cold dark matter model. We also find an increase in the H I absorption toward the center of a protocluster.

Keywords: Cosmology, Hydrodynamical simulations, Galaxy formation, Stellar feedback, Quasar absorption line spectroscopy, Protoclusters, Neutral hydrogen clouds, Chemical enrichment, Star formation, Active galactic nuclei, Intergalactic medium, N-body simulations
A Deep Learning Method for AGILE-GRID Gamma-Ray Burst Detection. The follow-up of external science alerts received from gamma-ray burst (GRB) and gravitational wave detectors is one of the AGILE Team's current major activities. The AGILE team developed an automated real-time analysis pipeline to analyze AGILE Gamma-Ray Imaging Detector (GRID) data to detect possible counterparts in the energy range 0.1-10 GeV. This work presents a new approach for detecting GRBs using a convolutional neural network (CNN) to classify the AGILE-GRID intensity maps by improving the GRB detection capability over the Li &amp; Ma method, currently used by the AGILE team. The CNN is trained with large simulated data sets of intensity maps. The AGILE complex observing pattern due to the so-called "spinning mode" is studied to prepare data sets to test and evaluate the CNN. A GRB emission model is defined from the second Fermi-LAT GRB catalog and convoluted with the AGILE observing pattern. Different p-value distributions are calculated, evaluating, using the CNN, millions of background-only maps simulated by varying the background level. The CNN is then used on real data to analyze the AGILE-GRID data archive, searching for GRB detections using the trigger time and position taken from the Swift-BAT, Fermi-GBM, and Fermi-LAT GRB catalogs. From these catalogs, the CNN detects 21 GRBs with a significance of ≥3&amp;sgr;, while the Li &amp; Ma method detects only two GRBs. The results shown in this work demonstrate that the CNN is more effective in detecting GRBs than the Li &amp; Ma method in this context and can be implemented into the AGILE-GRID real-time analysis pipeline.

Keywords: Gamma-ray astronomy, Gamma-ray bursts, Convolutional neural networks, Neural networks
Impact of Dust on Spectral Distortion Measurements of the Cosmic Microwave Background. Spectral distortions of the cosmic microwave background (CMB) are sensitive to energy injection by exotic physics in the early universe. The proposed Primordial Inflation Explorer (PIXIE) mission has the raw sensitivity to provide meaningful limits on new physics, but only if foreground emission can be adequately modeled. We quantify the impact of interstellar dust on Compton y and μ measurements by considering a range of grain size distributions and compositions constrained by theoretical and observational priors. We find that PIXIE can marginalize over a modest number of dust parameters and still recover y and μ estimates, though with increased uncertainty. As more foreground components are included (synchrotron, free-free), estimates of y degrade, and measurement of μ in the range sometimes considered for the standard ΛCDM of 2 × 10-8 becomes infeasible without ancillary low-frequency foreground information. An additional concern is dust absorption of the CMB monopole, a subtle effect that must be included. We quantify one form of model discrepancy error, finding that the error introduced by fitting our interstellar medium dust model with a modified blackbody is too large for CMB spectral distortions to be detectable. The greatest challenge may be the cosmic infrared background (CIB). We find that μ and y are extremely sensitive to modeling choices for the CIB, and quantify biases expected for a range of assumptions.

Keywords: Interstellar dust, Cosmology, Astrosphere interstellar medium interactions, Cosmic microwave background radiation, Observational cosmology, Interstellar dust extinction, Infrared astronomy, CMBR detectors, Interstellar medium
Light Curves of Partial Tidal Disruption Events. Tidal disruption events (TDEs) can uncover the quiescent black holes (BHs) at the center of galaxies and also offer a promising method to study them. In a partial TDE (PTDE), the BH's tidal force cannot fully disrupt the star, so the stellar core survives and only a varied portion of the stellar mass is bound to the BH and feeds it. We calculate the event rate of PTDEs and full TDEs (FTDEs). In general, the event rate of PTDEs is higher than that of FTDEs, especially for the larger BHs, and the detection rate of PTDEs is approximately dozens per year, as observed by the Zwicky Transient Factory. During the circularization process of the debris stream in PTDEs, no outflow can be launched due to the efficient radiative diffusion. The circularized debris ring then experiences viscous evolution and forms an accretion disk. We calculate the light curves of PTDEs contributed by these two processes, along with their radiation temperature evolution. The light curves have double peaks and peak in the UV spectra. Without obscuration or reprocessing of the radiation by an outflow, PTDEs provide a clean environment to study the circularization and transient disk formation in TDEs.

Keywords: Accretion, Black hole physics, Galaxy nuclei
Magnetic Connections across the Chromosphere-Corona Transition Region. The plasma contributing to emission from the Sun between the cool chromosphere (≤104 K) and hot corona (≥106 K) has been subjected to many different interpretations. Here we look at the magnetic structure of this transition region (TR) plasma, based upon the implications of CLASP2 data of an active region recently published by Ishikawa et al., and earlier Interface Region Imaging Spectrograph (IRIS) and Solar Dynamics Observatory (SDO) data of quiet regions. Ishikawa et al. found that large areas of sunspot plages are magnetically unipolar as measured in the cores of Mg II resonance lines, formed in the lower TR under low plasma-β conditions. Here we show that IRIS images in the line cores have fibrils that are well aligned with the overlying coronal loop segments seen in the 171 Å channel of SDO. When the TR emission in active regions arises from plasma magnetically and thermally connected to the corona, then the line cores can provide the first credible magnetic boundary conditions for force-free calculations extended to the corona. We also re-examine IRIS images of dynamic TR cool loops previously reported as a major contributor to TR emission from the quiet Sun. Dynamic cool loops contribute only a small fraction of the total TR emission from the quiet Sun.

Keywords: Quiet solar corona, Solar corona, Solar transition region, Active solar corona, Stellar coronae
An MHD Modeling of the Successive X2.2 and X9.3 Solar Flares of 2017 September 6. The solar active region 12673 produced two successive X-class flares (X2.2 and X9.3) approximately 3 hr apart in 2017 September. The X9.3 flare was the largest recorded solar flare in Solar Cycle 24. In this study we perform a data-constrained magnetohydrodynamic simulation taking into account the observed photospheric magnetic field to reveal the initiation and dynamics of the X2.2 and X9.3 flares. According to our simulation, the X2.2 flare is first triggered by magnetic reconnection at a local site where at the photosphere the negative polarity intrudes into the opposite-polarity region. This magnetic reconnection expels the innermost field lines upward, beneath which the magnetic flux rope is formed through continuous reconnection with external twisted field lines. Continuous magnetic reconnection after the X2.2 flare enhances the magnetic flux rope, which is lifted up and eventually erupts via the torus instability. This gives rise to the X9.3 flare.

Keywords: Solar active regions, Solar flares, Solar magnetic fields, Magnetohydrodynamical simulations
Observational Evidence for a Thick Disk of Dark Molecular Gas in the Outer Galaxy. We present the serendipitous discovery of an extremely broad (ΔVLSR ~ 150 km s-1), faint (Tmb &lt; 10 mK), and ubiquitous 1667 and 1665 MHz ground-state thermal OH emission toward the second quadrant of the outer Galaxy (Rgal &gt; 8 kpc) with the Green Bank Telescope. Originally discovered in 2015, we describe the redundant experimental, observational, and data quality tests of this result over the last five years. The longitude-velocity distribution of the emission unambiguously suggests large-scale Galactic structure. We observe a smooth distribution of OH in radial velocity that is morphologically similar to the H I radial velocity distribution in the outer Galaxy, showing that molecular gas is significantly more extended in the outer Galaxy than previously expected. Our results imply the existence of a thick (-200 pc &lt; z &lt; 200 pc) disk of diffuse ( ${n}_{{{\rm{H}}}_{2}}$ ~ 5 × 10-3 cm-3) molecular gas in the outer Galaxy previously undetected in all-sky 12CO surveys.

Keywords: Interstellar molecules, Molecular gas, Interstellar phases, Interstellar atomic gas, Galaxy structure, Galaxy physics, Molecular clouds, Galaxy disks, Spiral arms, Interstellar clouds, Interstellar medium, Diffuse interstellar clouds
How Merger-driven Gas Motions in Galaxy Clusters Can Turn AGN Bubbles into Radio Relics. Radio relics in galaxy clusters are extended synchrotron sources produced by cosmic-ray electrons in the microgauss magnetic field. Many relics are found in the cluster periphery and have a cluster-centric, narrow arc-like shape, which suggests that the electrons are accelerated or reaccelerated by merger shock fronts propagating outward in the intracluster plasma. In the X-ray, some relics do exhibit such shocks at the location of the relic, but many do not. We explore the possibility that radio relics trace not the shock fronts but the shape of the underlying distribution of seed relativistic electrons, lit up by a recent shock passage. We use magnetohydrodynamic simulations of cluster mergers and include bubbles of relativistic electrons injected by jets from the central active galactic nucleus or from an off-center radio galaxy. We show that the merger-driven gas motions (a) can advect the bubble cosmic rays to very large radii and (b) spread the relativistic seed electrons preferentially in the tangential direction-along the gravitational equipotential surfaces-producing extended, filamentary, or sheet-like regions of intracluster plasma enriched with aged cosmic rays, which resemble radio relics. Once a shock front passes across such a region, the sharp radio emission edges would trace the sharp boundaries of these enriched regions rather than the front. We also show that these elongated cosmic-ray features are naturally associated with magnetic fields stretched tangentially along their long axis, which could help explain the high polarization of relics.

Keywords: Galaxy clusters, Extragalactic radio sources, Intracluster medium, Magnetohydrodynamical simulations
Eccentricity without Measuring Eccentricity: Discriminating among Stellar Mass Black Hole Binary Formation Channels. We show how the observable number of binaries in LISA is affected by eccentricity through its influence on the peak gravitational-wave frequency, enhanced binary number density required to produce the LIGO observed rate, and the reduced signal-to-noise ratio (S/N) for an eccentric event. We also demonstrate how these effects should make it possible to learn about the eccentricity distribution and formation channels by counting the number of binaries as a function of frequency, even with no explicit detection of eccentricity. We also provide a simplified calculation for S/N of eccentric binaries.

Keywords: Gravitational wave astronomy
Extension of the Synchrotron Radiation of Electrons to Very High Energies in Clumpy Environments. The synchrotron cooling of relativistic electrons is one of the most effective radiation mechanisms in astrophysics. It not only accompanies the process of particle acceleration, but also has feedback on the formation of the energy distribution of the parent electrons. The radiative cooling time of electrons decreases with energy as tSYN ∝ 1/E; correspondingly, the overall radiation efficiency increases with energy. However, this effect strictly limits the maximum energy of individual photons. Even in the so-called extreme accelerators, where the acceleration proceeds at the highest possible rate, ${t}_{{\rm\small{ACC}}}^{-1}={eBc}/E$ , allowed in an ideal magnetohydrodynamic plasma, the synchrotron radiation cannot extend well beyond the characteristic energy determined by the electron mass and the fine-structure constant: $h{\nu }^{{\rm\small{MAX}}}\sim {m}_{{\rm{e}}}{c}^{2}/\alpha \sim 70\,\mathrm{MeV}$ . In this paper, we propose a model in which the formation of synchrotron radiation takes place in compact magnetic blobs located inside the particle accelerator and develop a formalism for calculations of synchrotron radiation emerging from such systems. We demonstrate that for certain combinations of parameters characterizing the accelerator and the magnetic blobs, the synchrotron radiation can extend beyond this limit by a several orders of magnitude. This scenario requires a weak magnetization of the particle accelerator, and an efficient conversion of gas internal energy into magnetic energy in sufficiently small blobs. The required size of the blobs is constrained by the magnetic mirroring effect, which can prevent particle penetration into the regions of strong magnetic field under certain conditions.

Keywords: Gamma-ray sources, Non-thermal radiation sources, Theoretical models