Sazuna/UAT_keywords huggingface dataset:
Two Episodes of a Filament Eruption from a Fan-spine Magnetic Configuration. In this paper, we present detailed observations of a filament eruption associated with a B6.0 flare, a jet-like coronal mass ejection (CME), and a type-III radio burst on 2013 March 2. The filament, which is located at the northwest edge of active region (AR) 11183, experienced a partial and then a full eruption. Each episode of the filament eruption produced a circular flare ribbon and a blowout jet, which is a mixture of hot and cool plasma that can be observed by the Solar Dynamics Observatory. Extrapolated coronal magnetic configuration using both the potential field source surface and the nonlinear force-free magnetic field models shows that the filament is embedded in a fan-spine magnetic topology. Considering the photospheric magnetic evolution, we suggest that the first episode of the filament eruption (partial eruption) is caused by the continuous photospheric magnetic flux cancellation below its western segment, while the eruption that follows results from the reduction of magnetic constraint above the filament in the aftermath of the first eruption episode and reconnection. Combining the observations with the extrapolated coronal magnetic configuration, we find that the event is an example that fits the null-point reconnection scenario. Our event is a result of null-point reconnection (interchange reconnection) between a closed filament magnetic field and the ambient open field at the edge of an AR, thus it has implications for the source of the slow speed solar wind and the source of the cold and dense plasma detected within.

Keywords: Solar activity, Solar magnetic fields, Solar filaments, Solar coronal mass ejections
The Timing Behavior of the Central Compact Object Pulsar 1E 1207.4-5209. We present 20 yr of timing observations for 1E 1207.4-5209, the central compact object in supernova remnant PKS 1209-51/52, to follow up on our detection of an unexpected timing glitch in its spin-down. Using new XMM-Newton and NICER observations of 1E 1207.4-5209, we now find that the phase ephemeris can be well modeled by either two small glitches, or extreme timing noise. The implied magnitudes of the frequency glitches are ${\rm{\Delta }}f/f=(9\pm 2)\times {10}^{-10}$ and ${\rm{\Delta }}f/f=(3.7\pm 0.7)\times {10}^{-10}$ , at epochs 2010.9 and 2014.4, respectively. The updated timing solutions also rule out our previous suggestion of a large glitch in the frequency derivative $\dot{f}$ . No other canonical pulsar with such a small spin-down rate ( $\dot{f}=-1.2\times {10}^{-16}$ Hz s-1) or surface dipole magnetic field strength ( ${B}_{s}=9.8\times {10}^{10}$ G) has been observed to glitch; the glitch activity parameter of 1E 1207.4-5209 is larger than that of more energetic pulsars. Alternative parameterizations that do not involve glitches can fit the data, but they have timing residuals or a second frequency derivative $\ddot{f}$ that are orders of magnitude larger than in pulsars with similar spin-down parameters. These timing properties of 1E 1207.4-5209 further motivate the leading theory of central compact objects, that an initial B-field of normal strength was buried in the neutron star crust by fallback of supernova ejecta, suppressing the surface dipole field. The slow reemergence of the buried field may be involved in triggering glitches or excess timing noise.

Keywords: Neutron stars, Pulsar timing method, Compact objects, Pulsars
H<SUB>0</SUB> Reconstruction with Type Ia Supernovae, Baryon Acoustic Oscillation and Gravitational Lensing Time Delay. There is a persistent H0-tension, now at more than ≳4σ level, between the local distance ladder value and the Planck cosmic microwave background measurement, in the context of flat Lambda-cold-dark-matter (ΛCDM) model. We reconstruct H(z) in a cosmological-model-independent way using three low-redshift distance probes including the latest data from baryon acoustic oscillation, supernova Ia (SN Ia) and gravitational lensing time-delay (GLTD) observations. We adopt general parametric models of H(z) and assume a Gaussian sound horizon at drag epoch, ${r}_{{\rm{s}}}$ , from Planck measurement. The reconstructed Hubble constant H0,rec using Pantheon SN Ia and Baryon Acoustic Oscillations (BAO) data are consistent with the Planck flat ΛCDM value. When including the GLTD data, H0,rec increases mildly, yet remains discrepant with the local measurement at ∼2.2σ level. With our reconstructions being blind to the dark sectors at low redshift, we reaffirm the earlier claims that the Hubble tension is not likely to be solved by modifying the energy budget of the low-redshift universe. We further forecast the constraining ability of future realistic mock BAO data from Dark Energy Spectroscopic Instrument and GLTD data from Large Synoptic Survey Telescope, combining which, we anticipate that the uncertainty of H0,rec would be improved by ∼27%, reaching ${\sigma }_{{H}_{0,\mathrm{rec}}}\approx 0.67$ uncertainty level.

Keywords: Strong gravitational lensing, Observational cosmology, Type Ia supernovae, Distance indicators
The Coronal Mass Ejection Visibility Function of Modern Coronagraphs. We analyze the detection capability of coronal mass ejections (CMEs) for all currently operating coronagraphs in space. We define as CMEs events that propagate beyond 10 solar radii with morphologies broadly consistent with a magnetic flux-rope presence. We take advantage of multi-viewpoint observations over five month-long intervals, corresponding to special orbital configurations of the coronagraphs aboard the Solar Terrestrial Relations Observatory (STEREO) and Solar and Heliospheric Observatory missions. This allows us to sort out CMEs from other outward-propagating features (e.g., waves or outflows), and thus to identify the total number of unique CMEs ejected during those periods. We determine the CME visibility functions (VFs) of the STEREO COR2-A/B and LASCO C2/C3 coronagraphs directly as the ratio of observed to unique CMEs. The VFs range from 0.71 to 0.92 for a 95% confidence interval. By comparing detections between coronagraphs on the same spacecraft and from multiple spacecraft, we assess the influence of field of view (FOV), instrument performance, and projection effects on the CME detection ability without resorting to proxies, such as flares or radio bursts. We find that no major CMEs are missed by any of the coronagraphs, that a few slow halo-like events may be missed in synoptic cadence movies, and that narrow FOV coronagraphs have difficulties discriminating between CMEs and other ejections, leading to "false" detection rates. We conclude that CME detection can only be validated with multi-viewpoint imaging—two coronagraphs in quadrature offer adequate detection capability. Finally, we apply the VFs to observed CME rates resulting in upward corrections of 40%.

Keywords: Active solar corona, Coronagraphic imaging, Solar coronal mass ejections, Sunspot number
13 yr of P Cygni Spectropolarimetry: Investigating Mass Loss through Hα, Periodicity, and Ellipticity. We report on over 13 yr of optical and near-ultraviolet spectropolarimetric observations of the famous luminous blue variable (LBV) P Cygni. In the lives of the most massive stars, LBVs are a critical transitional phase and achieve the largest mass-loss rates of any group of stars. Using spectropolarimetry, we are able to learn about the geometry of the near-circumstellar environment surrounding P Cygni and gain insights into LBV mass loss. Using data from the HPOL and WUPPE spectropolarimeters, we estimate the interstellar polarization contribution to P Cygni's spectropolarimetric signal, analyze the variability of the polarization across the Hα emission line, search for periodic signals in the data, and introduce a statistical method to search for preferred position angles in deviations from spherical symmetry that is novel to astronomy. Our data are consistent with previous findings, showing free electron scattering off of clumps uniformly distributed around the star. This is complicated, however, by structure in the percent polarization of the Hα line and a series of previously undetected periodicities.

Keywords: Spectropolarimetry, Stellar phenomena, Luminous blue variable stars, Circumstellar matter, Polarimetry, Time series analysis
Tracing the Intrinsic Shapes of Dwarf Galaxies Out to Four Effective Radii: Clues to Low-mass Stellar Halo Formation. Though smooth, extended spheroidal stellar outskirts have long been observed around nearby dwarf galaxies, it is unclear whether dwarfs generically host an extended stellar halo. We use imaging from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) to measure the shapes of dwarf galaxies out to four effective radii for a sample of 6758 dwarfs at 0.005 &lt; z &lt; 0.2 and 107.0 &lt; M⋆/M⊙ &lt; 109.6. We find that dwarfs are slightly triaxial, with $\langle B/A\rangle \gtrsim 0.75$ (where the ellipsoid is characterized by three principal semiaxes constrained by C ≤ B ≤ A). At M⋆ &gt; 108.5 M⊙, the galaxies grow from thick disk-like at one effective radius toward the spheroidal extreme at four effective radii. We also see that although blue dwarfs are, on average, characterized by thinner disks than red dwarfs, both blue and red dwarfs grow more spheroidal as a function of radius. This relation also holds true for a comparison between field and satellite dwarfs. This uniform trend toward relatively spheroidal shapes as a function of radius is consistent with an in situ formation mechanism for stellar outskirts around low-mass galaxies, in agreement with proposed models where star formation feedback produces round stellar outskirts around dwarfs.

Keywords: Galaxy stellar halos, Dwarf galaxies, Observational astronomy, Galaxy structure
Is Extended Hard X-Ray Emission Ubiquitous in Compton-thick AGN?. The recent Chandra discovery of extended ∼kiloparsec-scale hard (&gt;3 keV) X-ray emission in nearby Compton-thick (CT) active galactic nuclei (AGN) opens a new window to improving AGN torus modeling and investigating how the central supermassive black hole interacts with and impacts the host galaxy. Since there are only a handful of detections so far, we need to establish a statistical sample to determine the ubiquity of the extended hard X-ray emission in CT AGN and quantify the amount and extent of this component. In this paper, we present the spatial analysis results of a pilot Chandra imaging survey of seven nearby ( $0.006\lt z\lt 0.013$ ) CT AGN selected from the Swift-BAT spectroscopic AGN survey. We find that five out of the seven CT AGN show extended emission in the 3-7 keV band detected at &gt;3σ above the Chandra point-spread function (PSF), with ∼12%-22% of the total emission in the extended components. ESO 137-G034 and NGC 3281 display biconical ionization structures with extended hard X-ray emission reaching kiloparsec scales (∼1.9 and 3.5 kpc in diameter). The other three show extended hard X-ray emission above the PSF out to at least ∼360 pc in radius. We find a trend that a minimum 3-7 keV count rate of 0.01 counts s-1 and total excess fraction &gt;20% are required to detect a prominent extended hard X-ray component. Given that this extended hard X-ray component appears to be relatively common in this uniformly selected CT AGN sample, we further discuss the implications for torus modeling and AGN feedback.

Keywords: AGN host galaxies, Active galaxies, X-ray active galactic nuclei
Tracing the Assembly of the Milky Way's Disk through Abundance Clustering. A major goal in the field of galaxy formation is to understand the formation of the Milky Way's disk. The first step toward doing this is to empirically describe its present state. We use the new high-dimensional data set of 19 abundances from 27,135 red clump Apache Point Observatory Galactic Evolution Experiment stars to examine the distribution of clusters defined using abundances. We explore different dimension reduction techniques and implement a nonparametric agglomerate hierarchical clustering method. We see that groups defined using abundances are spatially separated, as a function of age. Furthermore, the abundance groups represent different distributions in the [Fe/H]-age plane. Ordering our clusters by age reveals patterns suggestive of the sequence of chemical enrichment in the disk over time. Our results indicate that a promising avenue to trace the details of the disk's assembly is via a full interpretation of the empirical connections we report.

Keywords: Red giant clump, Stellar abundances, Stellar populations, Astrostatistics techniques, Clustering, Milky Way Galaxy
Turbulence in the Very Local Interstellar Medium (VLISM). The Voyager 1 spacecraft has been observing interstellar magnetic turbulence since it crossed the heliopause in 2012. Burlaga et al. reported that the turbulence appears to be compressible close to the heliopause and becomes incompressible farther away. In this paper, we undertake a more detailed analysis of the magnetic fluctuations measured by Voyager 1 from 2013 to 2019. We apply the techniques of wavelet analysis and Hilbert spectral analysis. These methods reveal temporal or spatial variations of the fluctuations that are not easily apparent using standard Fourier techniques. Our results suggest that the compressible fluctuations are confined to a smaller region than previously thought.

Keywords: Interplanetary turbulence, Interstellar magnetic fields, Interstellar medium
Cross Sections of Coronal Loop Flux Tubes. Coronal loops reveal crucial information about the nature of both coronal magnetic fields and coronal heating. The shape of the corresponding flux tube cross section and how it varies with position are especially important properties. They are a direct indication of the expansion of the field and of the cross-field spatial distribution of the heating. We have studied 20 loops using high spatial resolution observations from the first flight of the Hi-C rocket experiment, measuring the intensity and width as a function of position along the loop axis. We find that intensity and width tend to either be uncorrelated or to have a direct dependence, such that they increase or decrease together. This implies that the flux tube cross sections are approximately circular under the assumptions that the tubes have nonnegligible twist and that the plasma emissivity is approximately uniform along the magnetic field. The shape need not be a perfect circle and the emissivity need not be uniform within the cross section, but subresolution patches of emission must be distributed quasi-uniformly within an envelope that has an aspect ratio of order unity. This raises questions about the suggestion that flux tubes expand with height, but primarily in the line-of-sight direction so that the corresponding (relatively noticeable) loops appear to have roughly uniform width, a long-standing puzzle. It also casts doubt on the idea that most loops correspond to simple warped sheets, although we leave open the possibility of more complex manifold structures.

Keywords: Solar coronal loops, Solar coronal heating, Solar magnetic fields, Solar extreme ultraviolet emission
Intriguing Drifting Subpulses in the Vela Pulsar. We report on the discovery of drifting subpulses from the Vela pulsar, observed using the Yunnan 40 m radio telescope at 6800 MHz observing frequency. The single pulses show the presence of two distinct drifting patterns, where the central component is modulated in longitude and amplitude simultaneously with a period of 9 pulses, and the trailing component remains phase stationary within the pulse window but periodically changes in intensity with a period of 29 pulses. The leading component emission remains constant in intensity and pulse phase. Such periodic modulation in the Vela pulsar is a separate phenomenon from periodic nulling and traditional subpulse drifting, which may lead to a greater understanding of the pulse emission mechanism.

Keywords: Pulsars
Dispersion Measures of Fast Radio Burst Host Galaxies Derived from IllustrisTNG Simulation. We calculate the dispersion measures (DMs) contributed by host galaxies of fast radio bursts (FRBs). Based on a few host galaxy observations, a large sample of galaxies with similar properties to observed ones has been selected from the IllustrisTNG simulation. They are used to compute the distributions of host galaxy DMs for repeating and nonrepeating FRBs. For repeating FRBs, we infer the DMhost for FRBs like FRB 121102 and FRB 180916 by assuming that the burst sites are tracing the star formation rates in host galaxies. The median DMshost are 35 (1 + z)1.08 and 96(1 + z)0.83 pc cm-3 for FRBs like FRB 121102 and FRB 180916, respectively. In another case, the median of DMhost is about 30-70 pc cm-3 for nonrepeating FRBs in the redshift range z = 0.1-1.5, assuming that the burst sites are the locations of binary neutron star mergers. In this case, the evolution of the median DMhost can be calculated by 33(1 + z)0.84 pc cm-3. The distributions of DMhost of repeating and nonrepeating FRBs can be well fitted with the log-normal function. Our results can be used to infer redshifts of nonlocalized FRBs.

Keywords: Radio bursts, Galaxies, Radio transient sources
Preferential Heating of Heavy Ions in Shocks. Observations show that postshock temperatures of heavy ions in supernovae collisionless shocks are approximately proportional to their masses. So far there is no convincing explanation of this dependence that would take into account the microphysics of the ion interaction with the electromagnetic fields inside the shock front. Here it is shown that perpendicular temperature increases due to the gyration of heavy ions starts inevitably upon crossing the shock front because of the global change of the magnetic field. An estimate for the downstream temperature as a function of the shock angle and magnetic compression is derived.

Keywords: Shocks
The Radio/X-Ray Burst from SGR 1935+2154: Radiation Mechanisms and the Possible QPOs. Recently, a fast radio burst (FRB)-like event was found to be associated with a Galactic magnetar, SGR 1935+2154, accompanied by an X-ray burst. We find this radio burst challenges the typical emission mechanisms involving magnetars, which includes coherent curvature radiation from charged bunches, fast magnetosonic (FMS) waves, synchrotron maser from shocks, and the pulsar-like mechanism for low-twist magnetars. More specifically, we find that (1) the X-rays are most likely to be produced inside the magnetosphere. (2) For the coherent curvature radiation from the decay of the Alfvén wave, it will generally predict a duration (≲0.1 ms) smaller than observations, because of the strong twists of magnetic field lines and the internal damping of Alfvén waves. (3) The FMS wave model predicts a very low emission frequency νp ∼ 0.03 MHz ≪ GHz, unless it is produced inside the magnetosphere. But the absorption effect of the magnetospheric FMS wave model remains to be studied. (4) The synchrotron maser model is challenged because observations show that the peaks in both X-ray and radio light curves are with the same temporal separation ΔtFRB = Δtγ ≈ 0.03 s, while it would predict ΔtFRB ≪ Δtγ. (5) It seems to be difficult to directly apply the low-twist pulsar-like mechanism to flaring magnetars, as magnetar activity can significantly deform the magnetosphere. (6) We suggested four possibilities to study the general properties of FRBs for future observations, especially the possibility of identifying quasi-periodic oscillations with period ∼1-10 ms in double/multiple-peaked FRBs.

Keywords: Magnetars, Soft gamma-ray repeaters, Magnetospheric radio emissions, Radio transient sources
Long-term Periodicities in Kepler Photometry of Open Cluster NGC 6811. Long-term photometric variability can sometimes be related to the emergence of starspots in the photosphere following a quasi-periodic magnetic activity cycle. In order to investigate the existence and properties of magnetic cycles in a narrow range of fundamental parameters, we focused on solar-type stars in the intermediate-age open cluster NGC 6811 (1 Gyr). The cluster membership was analyzed both in terms of stellar kinematics and Gaia photometry. Rotation periods and photometric variability were analyzed for 138 stars from Kepler light curves and we discuss the existing trends and relationships. We also searched a sample of 11 solar-type stars for cycle-like periodicities and in each case classified the variability as either cyclic, multicyclic, flat, or acyclic. The results suggest a significant scatter, possibly due to sensitive nonlinearities in the dynamo process. This raises theoretical questions on whether these periodicities can be associated to activity cycles and what determines the stellar cycle presence or its period. Also, the lack of solar-twin flat activity stars in NGC 6811 combined with other recent results, suggests that the presence of magnetic grand minima in the Sun is a relatively recent phenomenon.

Keywords: Open star clusters, Light curves, Solar analogs, Stellar activity
The Role of Infrared Radiation Pressure in Shaping Dusty Winds in AGNs. The detection of dusty winds dominating the infrared emission of active galactic nuclei (AGNs) on parsec scales has revealed the limitations of traditional radiative transfer models based on a toroidal distribution of dusty gas. A new, more complex, dynamical structure is emerging and the physical origin of such dusty winds has to be critically assessed. We present a semi-analytical model to test the hypothesis of radiatively accelerated dusty winds launched by the AGN and by the heated dust itself. The model consists of an AGN and an infrared radiating dusty disk, the latter being the primary mass reservoir for the outflow. We calculate the trajectories of dusty gas clumps in this environment, accounting for both gravity and the AGN radiation as well as the re-radiation by the hot, dusty gas clouds themselves. We find that the morphology consists of a disk of material that orbits with sub-Keplerian velocities and a hyperboloid polar wind launched at the inner edge of the dusty disk. This is consistent with high-angular resolution infrared and sub-mm observations of some local Seyfert AGN. The strength of the wind and its orientation depend on the Eddington ratio and the column density of the dusty clumps, which is in agreement with proposed radiation regulated obscuration models developed for the X-ray obscuring material around AGNs.

Keywords: Seyfert galaxies, Active galactic nuclei, Infrared galaxies
Gravitational-wave Capture in Spinning Black Hole Encounters. The orbits of two black holes (BHs) that are initially unbound can be transformed into bound orbits by emitting gravitational waves during close encounters in a star cluster, which is called gravitational-wave (GW) capture. The effects of spin of BHs on GW capture are investigated in the context of numerical relativity. The radiated energy during the encounter is dependent on the effective spin when the BHs have equal masses, as expected from post-Newtonian approximation. The strongest emission is produced when the spins of both BHs are anti-aligned to the orbital angular momentum in the case of fly-by encounters. But the opposite is true in the case of direct merging: the strongest emission comes from the BHs with aligned spins to the orbital angular momentum. The fraction of direct merging among the GW captures increases in proportion to v4/7, assuming the uniform distribution of pericenter distances in the encounters, where v is the velocity dispersion of the cluster, which means about 5% of GW capture leads to the direct merging for star clusters with v = 150 km s-1.

Keywords: Rotating black holes, General relativity, Two-body problem