Sazuna/UAT_keywords huggingface dataset:
Search for Gravitational Waves from the Coalescence of Subsolar Mass and Eccentric Compact Binaries. We present a search for gravitational waves from subsolar mass compact-binary mergers that allows for nonnegligible orbital eccentricity. Subsolar mass black holes are a signature of primordial origin black holes, which may be a component of dark matter. To produce binary coalescences, primordial black holes may form close binaries either in the early universe or more recently through dynamical interactions. A signature of dynamical formation would be the observation of noncircularized orbits. We search for black hole mergers where the primary mass is 0.1-7M⊙ and the secondary mass is 0.1-1M⊙. We allow for eccentricity up to ~0.3 at a dominant-mode gravitational-wave frequency of 10 Hz for binaries with component masses &gt;0.5M⊙. We find no convincing candidates in the public LIGO data from 2015-2017. The two most promising candidates have a false alarm rate of 1 per 3 and 4 yr, respectively, which combined is only a ~2.4σ deviation from the expected Poisson rate. Given the marginal statistical significance, we place upper limits on the rate of subsolar mass mergers under the assumption of a null observation and compare how these limits may inform the possible dark matter contribution.

Keywords: Elliptical orbits, Gravitational waves, Primordial black holes
Tether-cutting and Overlying Magnetic Reconnections in an MHD Simulation of Prominence-cavity System. We investigate the magnetic reconnection in an MHD simulation of a coronal magnetic flux rope (MFR) confined by a helmet streamer, where a prominence-cavity system forms. This system includes a hot cavity surrounding a prominence with prominence horns and a central hot core above the prominence. The evolution of the system from quasi-equilibrium to eruption can be divided into four phases: quasi-static, slow-rise, fast-rise, and propagation phases. The emerged MFR initially stays quasi-static and magnetic reconnection occurs at the overlying high-Q (squashing factor) apex region, which gradually evolves into a hyperbolic flux tube (HFT). The decrease of the integrated magnetic tension force (above the location of the overlying reconnection) is due to the removal of overlying confinement by the enhanced overlying reconnection between the MFR and the overlying fields at the apex HFT, thus engines the slow rise of the MFR with a nearly constant velocity. Once the MFR reaches the regime of torus instability, another HFT immediately forms at the dip region under the MFR, followed by the explosive flare reconnection. The integrated resultant force (above the location of the flare reconnection) exponentially increases, which drives the exponential fast rise of the MFR. The system enters the propagation phase, once its apex reaches the height of about one solar radius above the photosphere. The simulation reproduces the main processes of one group of prominence eruptions especially those occurring on the quiet Sun.

Keywords: Solar prominences, Solar magnetic reconnection, Solar filaments, Solar magnetic fields, Solar coronal mass ejections, Magnetohydrodynamical simulations
High Mass but Low Spin: An Exclusion Region to Rule Out Hierarchical Black Hole Mergers as a Mechanism to Populate the Pair-instability Mass Gap. The occurrence of pair-instability supernovae is predicted to prevent the formation of black holes with masses ≳50 M⊙. Recent gravitational-wave detections in this mass range require an explanation beyond that of standard stellar collapse. Current modeling strategies include the hierarchical assembly of previous generations of black hole mergers as well as other mechanisms of astrophysical nature (lowered nuclear-reaction rates, envelope retention, stellar mergers, accretion, dredge-up episodes). In this paper, we point out the occurrence of an exclusion region that cannot be easily populated by hierarchical black hole mergers. A future gravitational-wave detection of a black hole with mass ≳50 M⊙ and spin ≲0.2 will indicate that the pair-instability mass gap is polluted in some other way. Such a putative outlier can be explained using hierarchical mergers only with considerable fine-tuning of both mass ratio and spins of the preceding black hole merger-an assumption that can then be cross-checked against the bulk of the gravitational-wave catalog.

Keywords: LIGO, Gravitational waves, Stellar mass black holes, Core-collapse supernovae
A Deep Census of Outlying Star Formation in the M101 Group. We present deep, narrowband imaging of the nearby spiral galaxy M101 and its group environment to search for star-forming dwarf galaxies and outlying H II regions. Using the Burrell Schmidt telescope, we target the brightest emission lines of star-forming regions, Hα, Hβ, and [O III], to detect potential outlying star-forming regions. Our survey covers ~6 deg2 around M101, and we detect objects in emission down to an Hα flux level of 5.7 × 10-17 erg s-1 cm-2 (equivalent to a limiting star formation rate of 1.7 × 10-6 M⊙ yr-1 at the distance of M101). After careful removal of background contaminants and foreground M stars, we detect 19 objects in emission in all three bands and 8 objects in emission in Hα and [O III]. We compare the structural and photometric properties of the detected sources to Local Group dwarf galaxies and star-forming galaxies in the 11HUGS and SINGG surveys. We find no large population of outlying H II regions or undiscovered star-forming dwarfs in the M101 Group, as most sources (93%) are consistent with being M101 outer-disk H II regions. Only two sources were associated with other galaxies: a faint star-forming satellite of the background galaxy NGC 5486 and a faint outlying H II region near the M101 companion NGC 5474. We also find no narrowband emission associated with recently discovered ultradiffuse galaxies and starless H I clouds near M101. The lack of any hidden population of low-luminosity star-forming dwarfs around M101 suggests a rather shallow faint-end slope (as flat as α ~ -1.0) for the star-forming luminosity function in the M101 Group. We discuss our results in the context of tidally triggered star formation models and the interaction history of the M101 Group.

Keywords: Narrow band photometry, Star formation, Star forming regions, Galaxy environments
A Deep Polarimetric Study of the Asymmetrical Debris Disk HD 106906. Located in the Lower Centaurus Crux group, HD 106906 is a young, binary stellar system. This system is unique among discovered systems in that it contains an asymmetrical debris disk, as well as an 11 MJup planet companion, at a separation of ~735 au. Only a handful of other systems are known to contain both a disk and a directly imaged planet, where HD 106906 is the only one in which the planet has apparently been scattered. The debris disk is nearly edge-on and extends to roughly &gt;500 au, where previous studies with the Hubble Space Telescope have shown the outer regions to have high asymmetry. To better understand the structure and composition of the disk, we have performed a deep polarimetric study of HD 106906's asymmetrical debris disk using newly obtained H-, J-, and K1-band polarimetric data from the Gemini Planet Imager. An empirical analysis of our data supports a disk that is asymmetrical in surface brightness and structure, where fitting an inclined ring model to the disk spine suggests that the disk may be highly eccentric (e ≳ 0.16). A comparison of the disk flux with the stellar flux in each band suggests a blue color that also does not significantly vary across the disk. We discuss these results in terms of possible sources of asymmetry, where we find that dynamical interaction with the planet companion, HD 106906b, is a likely candidate.

Keywords: Planetary-disk interactions, Infrared astronomy, Starlight polarization, Circumstellar disks, Circumstellar dust, Debris disks, Planetesimals
The Intrinsic Properties of Multiwavelength Energy Spectra for Fermi Teraelectronvolt Blazars. In this paper, we have selected a sample of 64 teraelectronvolt blazars, with redshift, from those classified in the fourth Fermi Large Area Telescope source catalog.3 We have obtained the values of the relevant physical parameters by performing a log-parabolic fitting of the average-state multiwavelength spectral energy distributions. We estimate the range of the radiation zone parameters, such as the Doppler factor (D), the magnetic field strength (B), the radiative zone radius (R), and the peak Lorentz factor (γp) of nonthermal electrons. Here, we show that (1) there is a strong linear positive correlation between the intrinsic synchrotron peak frequency and the intrinsic inverse Compton scattering (ICs) peak frequency among different types of blazars; (2) if radio bands are excluded, the spectral index of each band is negatively correlated with the intrinsic peak frequency; (3) there is a strong linear negative correlation between the curvature at the peak and the intrinsic peak frequency of the synchrotron bump, and a weak positive correlation between the curvature at the peak and the intrinsic peak frequency of the ICs bump; (4) there is a strong linear positive correlation between the intrinsic ICs peak luminosity and intrinsic γ-ray luminosity and between the intrinsic ICs peak frequency and peak Lorentz factor; (5) there is a strong negative linear correlation between $\mathrm{log}\,B$ and $\mathrm{log}\,{\gamma }_{{\rm{p}}}$ ; and (6) there is no correlation between $\mathrm{log}\,R$ and $\mathrm{log}\,{\gamma }_{{\rm{p}}}$ .

Keywords: Blazars, BL Lacertae objects
Amplitude of the Usual Cosmic Ray Diurnal and Enhanced Anisotropies: Implications for the Observed Magnitude, Timing, and Ranking of Forbush Decreases. Cosmic ray (CR) diurnal anisotropy and Forbush decreases (FDs), as well as the relationship between them, have received considerable study. Several astrophysicists have focused on the speculated impact of FDs on the amplitude of the diurnal CR variations on different timescales. In an attempt to disentangle the contribution of FDs, days of Forbush events are traditionally excluded while calculating the diurnal amplitude in individual neutron monitor (NM) data. But the implications of CR diurnal anisotropy on the magnitude of FDs are rarely investigated in detail. Recently, an effort was made, using a combination of Fast Fourier transform and FD-location algorithms, to account for the contribution of CR diurnal anisotropy on the number, magnitude, and timing of FDs. With some technical advancements, the efficiency of the software is tested in the current work using CR data measured by the oldest CR observatory (Climax) from 1953 to 2006. We find strong and statistically significant correlations between FD magnitude calculated from raw and Fourier transformed CR data and the amplitude of diurnal anisotropy. The relationship is stronger in the case of the Fourier transformed signal, lending credence to the idea that CR anisotropy is a part of Forbush events. In order to validate the observed relationship between the amplitude of CR diurnal variations, magnitude, and timing of FDs, large volumes of data from the Moscow, McMurdo, and Potchefstroom NMs were also analyzed. The significant CR intensity decreases (FD magnitude &gt;5%) at the four stations were ranked according to their magnitudes.

Keywords: Galactic cosmic rays, Cosmic ray sources
NuSTAR Observation of LS 5039. LS 5039 is a high-mass γ-ray binary hosting a compact object of unknown type. NuSTAR observed LS 5039 during the entire 3.9-day binary period. We performed a periodic signal search up to 1000 Hz, which did not produce credible period candidates. We do see the 9.05 s period candidate, originally reported by Yoneda et al. using the same data, in the Fourier power spectrum, but we find that the statistical significance of this feature is too low to claim it as a real detection. We did not find significant bursts or quasiperiodic variability either. The modulation with orbital period is clearly seen and remains unchanged over a timescale of 10 years when compared to the earlier Suzaku light curve. The joint analysis of the NuSTAR and Suzaku XIS data shows that the 0.7-70 keV spectrum can be satisfactory described by a single absorbed power-law model with no evidence of a cutoff at higher energies. The slope of the spectrum is anticorrelated with the flux during the binary orbit. If LS 5039 hosts a young neutron star, its X-ray pulsations therefore appear to be outshone by the intrabinary shock emission. The lack of spectral lines and/or an exponential cutoff at higher energies suggests that the putative neutron star is not actively accreting. Although a black hole scenario still remains a possibility, the lack of variability or Fe Kα lines, which typically accompany accretion, makes it less likely.

Keywords: X-ray point sources, High mass x-ray binary stars, Gamma-rays, Compact objects
The Effect of a Strong Pressure Bump in the Sun's Natal Disk: Terrestrial Planet Formation via Planetesimal Accretion Rather than Pebble Accretion. Mass-independent isotopic anomalies of carbonaceous and noncarbonaceous meteorites show a clear dichotomy suggesting an efficient separation of the inner and outer solar system. Observations show that ring-like structures in the distribution of millimeter-sized pebbles in protoplanetary disks are common. These structures are often associated with drifting pebbles being trapped by local pressure maxima in the gas disk. Similar structures may also have existed in the Sun's natal disk, which could naturally explain the meteorite/planetary isotopic dichotomy. Here, we test the effects of a strong pressure bump in the outer disk (e.g., ~5 au) on the formation of the inner solar system. We model dust coagulation and evolution, planetesimal formation, as well as embryo growth via planetesimal and pebble accretion. Our results show that terrestrial embryos formed via planetesimal accretion rather than pebble accretion. In our model, the radial drift of pebbles fosters planetesimal formation. However, once a pressure bump forms, pebbles in the inner disk are lost via drift before they can be efficiently accreted by embryos growing at ⪆1 au. Embryos inside ~0.5-1.0 au grow relatively faster and can accrete pebbles more efficiently. However, these same embryos grow to larger masses so they should migrate inwards substantially, which is inconsistent with the current solar system. Therefore, terrestrial planets most likely accreted from giant impacts of Moon to roughly Mars-mass planetary embryos formed around ⪆1.0 au. Finally, our simulations produce a steep radial mass distribution of planetesimals in the terrestrial region, which is qualitatively aligned with formation models suggesting that the asteroid belt was born low mass.

Keywords: Protoplanetary disks, Solar system terrestrial planets, Planetesimals
Local Active Galactic Nuclei with Large Broad-Hα Variability Reside in Red Galaxies. Inspired by our serendipitous discovery of six active galactic nuclei (AGNs) with varying broad-Hα fluxes over years from our search for intermediate-mass black holes (IMBHs), we conduct a systematic investigation of changing-look (CL) and large-variability AGNs. We collect all the CL AGNs at z &lt; 0.15 and the reverberation-mapped AGNs with strongly variable broad Hα and perform careful decomposition fittings to both their images and spectra. We find two observational facts: (1) The host galaxies of local CL and large-variability AGNs, mainly being Seyferts, are in the red (gas-poor) tail of the general Seyfert galaxy population. (2) In contrast, there is a significant trend that their more luminous counterparts, namely CL and extremely variable quasars (CLQs and EVQs), are different: CLQs are generally in blue galaxies; in terms of the diagram of star formation rate and M*, local CL Seyfert galaxies are located in the green valley, whereas CLQ hosts are in the star-forming main sequence. We propose explanations for those strongly variable Seyferts and quasars, respectively, under the assumption that accretion disks broadly depend on nuclear fueling modes. Local large-variability and CL Seyferts are in nuclear famine mode, where cold-gas clumps can be formed stochastically in the fueling flow, and their episodic infall produces sharp peaks in the accretion-rate curve. CLQs and EVQs are in feast fueling mode, which may account for both their preference for blue galaxies and their variability pattern (high-amplitude tail of the continuous distribution). Lastly, we propose a new thinking: to search for IMBHs by optical variability in red galaxies.

Keywords: AGN host galaxies, Accretion, Intermediate-mass black holes, Quasars, Active galactic nuclei
Low-frequency Waves Upstream of Quasi-parallel Shocks: Two-dimensional Hybrid Simulations. In this paper, we study low-frequency waves upstream of quasi-parallel shocks by using two-dimensional (2D) hybrid simulations. Simulation results show that reflected particles can backstream and form a superthermal particle component in plasmas in an area just before the shock front. The component interacts with the incident particles and can result in quasi-parallel and quasi-perpendicular fast magnetosonic waves with comparable wave amplitudes, and they have right-hand and linear polarization, respectively. Further upstream, after being scattered by these upstream waves, the backstreaming particles develop a shell-like velocity distribution so that similar waves can be driven by the free energy from this newly formed distribution, and in this area the quasi-perpendicular waves are dominant over the quasi-parallel ones. Linear theory confirms the generation of these two types of upstream waves.

Keywords: Shocks, Interplanetary shocks, Planetary bow shocks
Resolving the Emission Regions of the Crab Pulsar's Giant Pulses. The Crab pulsar has striking radio emission properties, with the two dominant pulse components-the main pulse and the interpulse-consisting entirely of giant pulses. The emission is scattered in both the Crab Nebula and the interstellar medium, causing multipath propagation and thus scintillation. We study the scintillation of the Crab's giant pulses using phased Westerbork Synthesis Radio Telescope data at 1668 MHz. We find that giant pulse spectra correlate at only ~2%, much lower than the one-third correlation expected from a randomized signal imparted with the same impulse response function. In addition, we find that the main pulse and the interpulse appear to scintillate differently; the 2D cross-correlation of scintillation between the interpulse and main pulse has a lower amplitude and is wider in time and frequency delay than the 2D autocorrelation of the main pulses. These lines of evidence suggest that the giant pulse emission regions are extended, and that the main pulse and interpulse arise in physically distinct regions that are resolved by the scattering screen. Assuming the scattering takes place in the nebular filaments, the emission regions are of order a light-cylinder radius, as projected on the sky. With further very long baseline interferometry and multifrequency data, it may be possible to measure the distance to the scattering screens, the size of giant pulse emission regions, and the physical separation between the pulse components.

Keywords: Interstellar scintillation, Radio pulsars
Global 21 cm Signal Extraction from Foreground and Instrumental Effects. IV. Accounting for Realistic Instrument Uncertainties and Their Overlap with Foreground and Signal Models. All 21 cm signal experiments rely on electronic receivers that affect the data via both multiplicative and additive biases through the receiver's gain and noise temperature. While experiments attempt to remove these biases, the residuals of their imperfect calibration techniques can still confuse signal extraction algorithms. In this paper, the fourth and final installment of our pipeline series, we present a technique for fitting out receiver effects as efficiently as possible. The fact that the gain and global signal, which are multiplied in the observation equation, must both be modeled implies that the model of the data is nonlinear in its parameters, making numerical sampling the only way to explore the parameter distribution rigorously. However, multi-spectra fits, which are necessary to extract the signal confidently as demonstrated in the third paper of the series, often require large numbers of foreground parameters, increasing the dimension of the posterior distribution that must be explored and therefore causing numerical sampling inefficiencies. Building upon techniques in the second paper of the series, we outline a method to explore the full parameter distribution by numerically sampling a small subset of the parameters and analytically marginalizing over the others. We test this method in simulation using a type I Chebyshev bandpass filter gain model and a fast signal model based on a spline between local extrema. The method works efficiently, converging quickly to the posterior signal parameter distribution. The final signal uncertainties are of the same order as the noise in the data.

Keywords: Cosmology, Reionization, Astronomy data analysis
Anisotropic Turbulence in Position-Position-Velocity Space: Probing Three-dimensional Magnetic Fields. Direct measurements of three-dimensional magnetic fields in the interstellar medium are not achievable. However, the anisotropic nature of magnetohydrodynamic (MHD) turbulence provides a novel way of tracing the magnetic fields. Guided by the advanced understanding of turbulence's anisotropy in the position-position-velocity (PPV) space, we extend the structure-function analysis to measure both the three-dimensional magnetic field orientation and Alfvén Mach number MA, which provides the information on magnetic field strength. Following the theoretical framework developed in Kandel et al., we find that the anisotropy in a given velocity channel is affected by the inclination angle between the three-dimensional magnetic field direction and the line of sight as well as media magnetization. We analyze the synthetic PPV cubes generated by incompressible and compressible MHD simulations. We confirm that the PPV channel's intensity fluctuations measured in various position angles reveal plane-of-the-sky magnetic field orientation. We show that by varying the channel width, the anisotropies of the intensity fluctuations in PPV space can be used to simultaneously estimate both magnetic field inclination angle and strength of total magnetic fields.

Keywords: Interstellar magnetic fields, Interstellar dynamics, Interstellar medium
Switchback Boundary Dissipation and Relative Age. We examine Parker Solar Probe (PSP) magnetic field and plasma observations during its first encounter with the Sun in early 2018 November. During this perihelion time, impulsive reversals in the magnetic field, called "switchbacks," were found in the data set characterized by a quick rotation in B along with a simultaneous increase in solar wind flow. In this work, we examine the structure and morphology of 920 switchback boundaries as PSP enters and exits the structures, specifically looking for evidence of boundary degradation, dissipation, and associated ultralow frequency (ULF) magnetic wave activity. We find that boundaries with the most abrupt, step-function-like change in Br and Vr also show little evidence of dissipation and ULF wave activity. In contrast, there is a set of boundaries that appears highly degraded with ULF magnetic activity in the vicinity of the boundary. We thus infer that the steep, step-like boundaries with little ULF activity are relatively young in comparison to the degraded boundaries. The distribution in relative ages suggests that the switchback boundary formation process is dynamic and evolving, even occurring near the PSP observation point inside of 40 Rs.

Keywords: Solar physics, Solar wind, Solar magnetic flux emergence, Solar magnetic fields