Sazuna/UAT_keywords huggingface dataset:
Observations of Magnetospheric Solar Wind Charge Exchange. The study of solar wind charge exchange (SWCX) emission is vital to both the X-ray astrophysics and heliophysics communities. SWCX emission contaminates all astrophysical observations in X-rays regardless of the direction. Ignoring this contribution to X-ray spectra can lead to erroneous conclusions regarding the astrophysical plasmas along the line of sight owing to the similar spectral distributions of SWCX and several common types of more distant astrophysical plasmas. Since its discovery, the literature has distinguished between diffuse SWCX emission resulting from solar wind-neutral interactions within Earth's magnetosphere, called magnetospheric SWCX, and similar interactions occurring more generally throughout the heliosphere, called heliospheric SWCX. Here we build on previous work validating a modeling method for the heliospheric SWCX contribution in X-ray spectra obtained with a medium-resolution CubeSat instrument named HaloSat at low ecliptic latitudes. We now apply this model to a specially designed set of extended observations with the same instrument and successfully separate the spectral contributions of the astrophysical background and the heliospheric SWCX from the remaining contributions. Specifically, we find significant excess emission for four observations in the O VII emission line not explained by other sources, possibly indicative of magnetospheric SWCX. We discuss these results in comparison with simulation results publicly available through the Community Coordinated Modeling Center. We also report an absorbed high-temperature component in 2 of the 12 fields of view analyzed.

Keywords: Solar wind, Diffuse x-ray background
Andromeda's Parachute: Time Delays and Hubble Constant. The gravitational lens system PS J0147+4630 (Andromeda's Parachute) consists of four quasar images ABCD and a lensing galaxy. We obtained r-band light curves of ABCD in the 2017-2022 period from monitoring with two 2 m class telescopes. Applying state-of-the-art curve-shifting algorithms to these light curves led to measurements of time delays between images, and the three independent delays relative to image D are accurate enough to be used in cosmological studies (uncertainty of about 4%): ∆t AD = -170.5 ± 7.0, ∆t BD = -170.4 ± 6.0, and ∆t CD = -177.0 ± 6.5 days, where image D is trailing all the other images. Our finely sampled light curves and some additional fluxes in the years 2010-2013 also demonstrated the presence of significant microlensing variations. From the measured delays relative to image D and typical values of the external convergence, recent lens mass models yielded a Hubble constant that is in clear disagreement with currently accepted values around 70 km s-1 Mpc-1. We discuss how to account for a standard value of the Hubble constant without invoking the presence of an extraordinary high external convergence.

Keywords: Strong gravitational lensing, Quasars
Metal Abundances of Intermediate-redshift Active Galactic Nuclei: Evidence for a Population of Lower-metallicity Seyfert 2 Galaxies at z = 0.3-0.4. We derive oxygen abundances for two samples of Seyfert 2 (Sy2) active galactic nuclei (AGNs) selected from the KPNO International Spectroscopic Survey (KISS). The two samples from KISS include 17 intermediate-redshift (0.29 ≤ z ≤ 0.42) Sy2s detected via their [O III] lines, and 35 low-redshift (z ≤ 0.1), Hα-detected Sy2s. The primary goal of this work is to explore whether the metallicity distribution of these two samples changes with redshift. To determine the oxygen abundances of the KISS galaxies, we use CLOUDY to create a large number of photoionization model grids by varying the temperature of the accretion disk, the ratio of X-ray to UV continuum light, the ionization parameter, the hydrogen density, and the metallicity of the narrow-line region clouds. We link the results of these models to the observed [O III]/Hβ and [N II]/Hα emission-line ratios of the KISS sample on a Baldwin-Philips-Terlevich diagram, interpolating across the model grids to derive metallicity. The two redshift samples overlap substantially in terms of derived metal abundances, but we find that some of the intermediate-redshift Sy2s possess lower abundances than their local universe counterparts. Our analysis provides evidence for modest levels of chemical evolution (0.18 ± 0.06 dex) over 3-4 Gyr of look-back time. We compare our results to other AGN abundance derivation methods from the literature.

Keywords: Cosmological evolution, Galaxy chemical evolution, Chemical abundances, Emission line galaxies, Seyfert galaxies, Active galactic nuclei, Galaxy abundances, Galaxy evolution, Metallicity, Galaxies
FAST Observations of FRB 20220912A: Burst Properties and Polarization Characteristics. We report the observations of FRB 20220912A using the Five-hundred-meter Aperture Spherical radio Telescope. We conducted 17 observations totaling 8.67 hr and detected a total of 1076 bursts with an event rate up to 390 hr-1. The cumulative energy distribution can be well described using a broken power-law function with the lower- and higher-energy slopes of -0.38 ± 0.02 and -2.07 ± 0.07, respectively. We also report the L-band (1-1.5 GHz) spectral index of the synthetic spectrum of FRB 20220912A bursts, which is -2.6 ± 0.21. The average rotation measure value of the bursts from FRB 20220912A is -0.08 ± 5.39 rad m-2, close to 0 rad m-2 and was relatively stable over 2 months. Most bursts have nearly 100% linear polarization. About 45% of the bursts have circular polarization with Signal-to-Noise ratio &gt; 3, and the highest circular polarization degree can reach 70%. Our observations suggest that FRB 20220912A is located in a relatively clean local environment with complex circular polarization characteristics. These various behaviors imply that the mechanism of circular polarization of FRBs likely originates from an intrinsic radiation mechanism, such as coherent curvature radiation or inverse Compton scattering inside the magnetosphere of the FRB engine source (e.g., a magnetar).

Keywords: Radio transient sources
Photometry and Polarimetry of 2010 XC<SUB>15</SUB>: Observational Confirmation of E-type Near-Earth Asteroid Pair. Asteroid systems such as binaries and pairs are indicative of the physical properties and dynamical histories of small solar system bodies. Although numerous observational and theoretical studies have been carried out, the formation mechanism of asteroid pairs is still unclear, especially for near-Earth asteroid (NEA) pairs. We conducted a series of optical photometric and polarimetric observations of a small NEA 2010 XC15 in 2022 December to investigate its surface properties. The rotation period of 2010 XC15 is possibly a few to several dozen hours and the color indices of 2010 XC15 are derived as g - r = 0.435 ± 0.008, r - i = 0.158 ± 0.017, and r - z = 0.186 ± 0.009 in the Pan-STARRS system. The linear polarization degrees of 2010 XC15 are a few percent at the phase angle range of 58°-114°. We found that 2010 XC15 is a rare E-type NEA on the basis of its photometric and polarimetric properties. Taking the similarity of not only physical properties but also dynamical integrals and the rarity of E-type NEAs into account, we suppose that 2010 XC15 and 1998 WT24 are of common origin (i.e., an asteroid pair). These two NEAs are the sixth NEA pair and first E-type NEA pair ever confirmed, possibly formed by rotational fission. We conjecture that the parent body of 2010 XC15 and 1998 WT24 was transported from the main belt through the ν 6 resonance or Hungaria region.

Keywords: Near-Earth objects, Multi-color photometry, Asteroids, Light curves, Photometry, Polarimetry
Rapidly Evolving Transients in Archival ZTF Public Alerts. We search the archival Zwicky Transient Facility public survey for rapidly evolving transient (RET) candidates based on well-defined criteria between 2018 May and 2021 December. The search yielded 19 bona fide RET candidates, corresponding to a discovery rate of ~5.2 events per year. Even with a Galactic latitude cut of 20°, eight of the 19 events (~42%) are Galactic, including one with a light-curve shape closely resembling that of the GW170817 kilonova (KN). An additional event is a nova in M31. Four out of the 19 events (~21%) are confirmed extragalactic RETs (one confirmed here for the first time) and the origin of six additional events cannot be determined. We did not find any extragalactic events resembling the GW170817 KN, from which we obtain an upper limit on the volumetric rate of GW170817-like KNe of R ≤ 2400 Gpc-3 yr-1 (95% confidence). These results can be used for quantifying contaminants to RET searches in transient alert streams, specifically when searching for KNe independently of gravitational-wave and gamma-ray-burst triggers.

Keywords: Time domain astronomy, Transient sources, Supernovae, High energy astrophysics
Probing the Conditions for the H I-to-H<SUB>2</SUB> Transition in the Interstellar Medium. We investigate the conditions for the H I-to-H2 transition in the solar neighborhood by analyzing H I emission and absorption measurements toward 58 Galactic lines of sight (LOSs) along with 12CO(1-0) (CO) and dust data. Based on the accurate column densities of the cold and warm neutral medium (CNM and WNM), we first perform a decomposition of gas into atomic and molecular phases, and show that the observed LOSs are mostly H I-dominated. In addition, we find that the CO-dark H2, not the optically thick H I, is a major ingredient of the dark gas in the solar neighborhood. To examine the conditions for the formation of CO-bright molecular gas, we analyze the kinematic association between H I and CO, and find that the CNM is kinematically more closely associated with CO than the WNM. When CNM components within CO line widths are isolated, we find the following characteristics: spin temperature &lt; 200 K, peak optical depth &gt; 0.1, CNM fraction of ~0.6, and V-band dust extinction &gt; 0.5 mag. These results suggest that CO-bright molecular gas preferentially forms in environments with high column densities where the CNM becomes colder and more abundant. Finally, we confront the observed CNM properties with the steady-state H2 formation model of Sternberg et al. and infer that the CNM must be clumpy with a small volume filling factor. Another possibility would be that missing processes in the model, such as cosmic-rays and gas dynamics, play an important role in the H I-to-H2 transition.

Keywords: Interstellar molecules, Interstellar atomic gas, Molecular clouds, Interstellar dust extinction, Interstellar medium, Radio astronomy
Evolution of Elemental Abundances in Hot Active Region Cores from Chandrayaan-2 XSM Observations. The first ionization potential (FIP) bias, whereby elemental abundances for low-FIP elements in different coronal structures vary from their photospheric values and may also vary with time, has been widely studied. In order to study the temporal variation and understand the physical mechanisms giving rise to the FIP bias, we have investigated the hot cores of three active regions (ARs) using disk-integrated soft X-ray spectroscopic observations with the Solar X-ray Monitor on board Chandrayaan-2. Observations for periods when only one AR was present on the solar disk were used to ensure that the AR was the principal contributor to the total X-ray intensity. The average values of temperature and emission measure were ~3 MK and 3 × 1046 cm-3, respectively. Regardless of the AR's age or activity, the elemental abundances for the low-FIP elements Al, Mg, and Si with respect to the soft X-ray continuum were consistently higher than their photospheric values. The average FIP bias for Mg and Si was 2-2.5, whereas the FIP bias for the mid-FIP element, S, was almost unity. However, the FIP bias for the lowest-FIP element, Al, was observed to be a factor of 2 higher than Si, which, if real, suggests a dependence of the FIP bias of low-FIP elements on their FIP value. Another major result from our analysis is that the FIP bias of these elements is established within ~10 hr of emergence of the AR and remains almost constant throughout its lifetime.

Keywords: Solar abundances, Active solar corona, Solar active regions, Solar x-ray emission
On the Nature of the Energy-dependent Morphology of the Composite Multi-TeV Gamma-Ray Source J1702-420. HESS J1702-420 is a multi-TeV gamma-ray source with an unusual energy-dependent morphology. The recent H.E.S.S. observations suggest that the emission is well described by a combination of the point-like HESS J1702-420A (dominating at highest energies, ≳30 TeV) and diffuse (~0.°3) HESS J1702-420B (dominating below ≲5 TeV) sources with very hard (Γ ~ 1.5) and soft (Γ ~ 2.6) power-law spectra, respectively. Here, we propose a model that postulates that the proton accelerator is located at the position of HESS J1702-420A and is embedded into a dense molecular cloud that coincides with HESS J1702-420B. In the proposed model, the very-high-energy radiation of HESS J1702-420 is explained by pion-decay emission from the continuously injected relativistic protons propagating through a dense cloud. The energy-dependent morphology is defined by the diffusive nature of the low-energy proton propagation, transiting sharply to (quasi) ballistic propagation at higher energies. Adopting a strong energy dependence of the diffusion coefficient, D ∝ E  β  with β ≥ 1, we argue that HESS J1702-420 as a system of two gamma-ray sources is the result of the propagation effect. Protons injected by a single accelerator at a rate ${Q}_{0}\simeq {10}^{38}\,{({n}_{0}/100\,\,{\mathrm{cm}}^{-3})}^{-1}\,{(d/0.25\,\mathrm{kpc})}^{-1}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ can reasonably reproduce the morphology and fluxes of the two gamma-ray components.

Keywords: Gamma-ray sources, High energy astrophysics
Probabilistic Solar Flare Forecasting Using Historical Magnetogram Data. Solar flare forecasting research using machine learning (ML) has focused on high-resolution magnetogram data from the SDO/HMI era covering solar cycle 24 and the start of solar cycle 25, with some efforts looking back to SOHO/MDI for data from solar cycle 23. In this paper, we consider over four solar cycles of daily historical magnetogram data from multiple instruments. This is the first attempt to take advantage of this historical data for ML-based flare forecasting. We apply a convolutional neural network (CNN) to extract features from full-disk magnetograms together with a logistic regression model to incorporate scalar features based on magnetograms and flaring history. We use an ensemble approach to generate calibrated probabilistic forecasts of M-class or larger flares in the next 24 hr. Overall, we find that including historical data improves forecasting skill and reliability. We show that single-frame magnetograms do not contain significantly more relevant information than can be summarized in a small number of scalar features, and that flaring history has greater predictive power than our CNN-extracted features. This indicates the importance of including temporal information in flare forecasting models.

Keywords: Solar flares, Space weather, Convolutional neural networks, Solar magnetic fields, Solar activity
Measuring the Hubble Constant with Dark Neutron Star-Black Hole Mergers. Detection of gravitational waves (GWs) from neutron star-black hole (NSBH) standard sirens provides local measurements of the Hubble constant (H 0), regardless of the detection of an electromagnetic (EM) counterpart, given that matter effects can be exploited to break the redshift degeneracy of the GW waveforms. The distinctive merger morphology and the high-redshift detectability of tidally disrupted NSBH make them promising candidates for this method. Also, the detection prospects of an EM counterpart for these systems will be limited to z &lt; 0.8 in the optical, in the era of future GW detectors. Using recent constraints on the equation of state of NSs from multi-messenger observations of NICER and LIGO/Virgo/KAGRA, we show the prospects of measuring H 0 solely from GW observation of NSBH systems, achievable by the Einstein telescope (ET) and Cosmic Explorer (CE) detectors. We first analyze individual events to quantify the effect of high-frequency (≥500 Hz) tidal distortions on the inference of NS tidal deformability parameter (Λ) and hence on H 0. We find that disruptive mergers can constrain Λ up to ${ \mathcal O }(60 \% )$ more precisely than nondisruptive ones. However, this precision is not sufficient to place stringent constraints on the H 0 from individual events. By performing Bayesian analysis on simulated NSBH data (up to N = 100 events, corresponding to a day of observation) in the ET+CE detectors, we find that NSBH systems enable unbiased 4%-13% precision on the estimate of H 0 (68% credible interval). This is a similar measurement precision found in studies analyzing NSBH mergers with EM counterparts in the LVKC O5 era.

Keywords: Cosmology, Gravitational wave sources, Gravitational wave astronomy, General relativity, Gravitational waves
A Surprising Periodicity Detected during a Super-outburst of V844 Herculis by TESS. We identify a previously undetected periodicity at a frequency of 49.08 ± 0.01 days-1 (period of 29.34 ± 0.01 minutes) during a super-outburst of V844 Her observed by TESS. V844 Her is an SU UMa type cataclysmic variable with an orbital period of 78.69 minutes, near the period minimum. The frequency of this new signal is constant in contrast to the superhump oscillations commonly seen in SU UMa outbursts. We searched without success for oscillations during quiescence using MDM, TESS, and XMM-Newton data. The lack of a periodic signal in the XMM light curve and the relatively low X-ray luminosity of V844 Her suggest that it is not a typical IP. We consider the possibility that the 29-minute signal is the result of super-Nyquist sampling of a dwarf nova oscillation with a period near the 2-minute cadence of the TESS data. Our analysis of archival AAVSO photometry from a 2006 super-outburst supports the existence of a 29-minute oscillation, although a published study of an earlier super-outburst did not detect the signal. We compare the X-ray properties of V844 Her with short orbital period intermediate polars (IP), V1025 Cen and DW Cnc. We conclude that the new signal is a real photometric oscillation coming from the V844 Her system and that it is unlikely to be an aliased high-frequency oscillation. The steady frequency of the new signal suggests that its origin is related to an asynchronously rotating white dwarf in V844 Her, although the precise mechanism producing the flux variations remains unclear.

Keywords: Stellar oscillations, Cataclysmic variable stars, White dwarf stars, X-ray stars
Numerical Models of Planetary Nebulae with Different Episodes of Mass Ejection: The Particular Case of HuBi 1. We have studied the evolution of HuBi 1-like planetary nebulae, considering several stages of mass injection. We have carried out numerical ionization+1D hydrodynamics+atomic/ionic rate models with our code CORAL1D to reproduce planetary nebulae that present multiple shells produced by different ejection events around the ionizing source. We are interested in comparing numerical simulations with Hα and [N II] λ6584 emission structures and the position-velocity diagrams observed for HuBi 1. This object also has a phase where it has drastically decreased the injection of ionized photons ejected from the source. The result of these different stages of ejection is a nebula with intense [N II] line emission in the inner part of the planetary nebula and extended H II recombination line emission around the central zone. The model for HuBi 1 shows the capability of our code to explain the hydrodynamical and photoionization evolution in ionization nebulae. This is our first step with a 1D code to study these two physical phenomena at the same time.

Keywords: Hydrodynamical simulations, Emission nebulae, Planetary nebulae
The Eruption of a Magnetic Flux Rope Observed by Solar Orbiter and Parker Solar Probe. Magnetic flux ropes are a key component of coronal mass ejections, forming the core of these eruptive phenomena. However, determining whether a flux rope is present prior to eruption onset and, if so, the rope's handedness and the number of turns that any helical field lines make is difficult without magnetic field modeling or in situ detection of the flux rope. We present two distinct observations of plasma flows along a filament channel on 2022 September 4 and 5 made using the Solar Orbiter spacecraft. Each plasma flow exhibited helical motions in a right-handed sense as the plasma moved from the source active region across the solar disk to the quiet Sun, suggesting that the magnetic configuration of the filament channel contains a flux rope with positive chirality and at least one turn. The length and velocity of the plasma flow increased from the first to the second observation, suggesting evolution of the flux rope, with the flux rope subsequently erupting within ~5 hr of the second plasma flow. The erupting flux rope then passed over the Parker Solar Probe spacecraft during its encounter (13), enabling in situ diagnostics of the structure. Although complex and consistent with the flux rope erupting from underneath the heliospheric current sheet, the in situ measurements support the inference of a right-handed flux rope from remote-sensing observations. These observations provide a unique insight into the eruption and evolution of a magnetic flux rope near the Sun.

Keywords: Solar physics, Solar flares, Solar magnetic fields, Solar magnetic flux emergence
The Evolution of the Cold Gas Fraction in Nearby Clusters' Ram-pressure-stripped Galaxies. Cluster galaxies are affected by the surrounding environment, which influences, in particular, their gas, stellar content, and morphology. In particular, the ram pressure exerted by the intracluster medium promotes the formation of multiphase tails of stripped gas detectable both at optical wavelengths and in the submillimeter and radio regimes, tracing the cold molecular and atomic gas components, respectively. In this work we analyze a sample of 16 galaxies belonging to clusters at redshift ~0.05 showing evidence of an asymmetric H I morphology (based on MeerKAT observations) with and without a star-forming tail. To this sample we add three galaxies with evidence of a star-forming tail and no H I detection. Here we present the galaxies' H2 gas content from APEX observations of the CO (2-1) emission. We find that in most galaxies with a star-forming tail the H2 global content is enhanced with respect to undisturbed field galaxies with similar stellar masses, suggesting an evolutionary path driven by the ram pressure stripping. As galaxies enter into the clusters, their H I is displaced but also partially converted into H2, so that they are H2 enriched when they pass close to the pericenter, that is, when they also develop the star-forming tails that are well visible in UV or B broad bands and in Hα emission. An inspection of the phase-space diagram for our sample suggests an anticorrelation between the H I and H2 gas phases as galaxies fall into the cluster potential. This peculiar behavior is a key signature of the ram pressure stripping in action.

Keywords: Galaxy clusters, Late-type galaxies, Spiral galaxies, Disk galaxies, Galaxy environments, Galaxy tails, Galaxy evolution