Sazuna/UAT_keywords huggingface dataset:
Discovery of a 2.8 s Pulsar in a 2 Day Orbit High-mass X-Ray Binary Powering the Ultraluminous X-Ray Source ULX-7 in M51. We discovered 2.8 s pulsations in the X-ray emission of the ultraluminous X-ray source (ULX) M51 ULX-7 within the UNSEeN project, which was designed to hunt for new pulsating ULXs (PULXs) with XMM-Newton. The pulse shape is sinusoidal, and large variations of its amplitude were observed even within single exposures (pulsed fraction from less than 5% to 20%). Source M51 ULX-7 is variable, generally observed at an X-ray luminosity between 1039 and 1040 erg s-1, located in the outskirts of the spiral galaxy M51a at a distance of 8.6 Mpc. According to our analysis, the X-ray pulsar orbits in a 2 day binary with a projected semimajor axis ${a}_{{\rm{X}}}\sin I\,\simeq $ 28 lt-s. For a neutron star (NS) of 1.4 M☉, this implies a lower limit on the companion mass of 8 M☉, placing the system hosting M51 ULX-7 in the high-mass X-ray binary class. The barycentric pulse period decreased by ≃0.4 ms in the 31 days spanned by our 2018 May-June observations, corresponding to a spin-up rate $\dot{P}\simeq -1.5\times {10}^{-10}\,{\rm{s}}\ {{\rm{s}}}^{-1}$ . In an archival 2005 XMM-Newton exposure, we measured a spin period of ∼3.3 s, indicating a secular spin-up of ${\dot{P}}_{\sec }\simeq -{10}^{-9}\,{\rm{s}}\ {{\rm{s}}}^{-1}$ , a value in the range of other known PULXs. Our findings suggest that the system consists of a massive donor, possibly an OB giant or supergiant, and a moderately magnetic (dipole field component in the range 1012 G $\lesssim {B}_{\mathrm{dip}}\lesssim {10}^{13}$ G) accreting NS with weakly beamed emission ( $1/12\lesssim b\lesssim 1/4$ ).

Keywords: Neutron stars, X-ray binary stars, Stellar magnetic fields, Pulsars, X-ray sources, Stellar accretion
Modeling Bias in Supermassive Black Hole Spin Measurements. X-ray reflection spectroscopy (or iron line method) is a powerful tool to probe the strong gravity region of black holes, and currently is the only technique for measuring the spin of the supermassive ones. While all the available relativistic reflection models assume thin accretion disks, we know that several sources accrete near or above the Eddington limit and therefore must have thick accretion disks. In this work, we employ the Polish donut model for the description of thick disks. We thus estimate the systematic error on the spin measurement when a source with a thick accretion disk is fitted with a thin disk model. Our results clearly show that spin measurements can be significantly affected by the morphology of the accretion disk. Current spin measurements of sources with high-mass accretion rate are therefore not reliable.

Keywords: Active galactic nuclei, General relativity, Astrophysical black holes
Planetary Transits at Radio Wavelengths: Secondary Eclipses of Hot Jupiter Extended Atmospheres. When a planet transits in front of its host star, a fraction of its light is blocked, decreasing the observed flux from the star. The same is expected to occur when observing the stellar radio flux. However, at radio wavelengths, the planet also radiates, depending on its temperature, and thus modifies the transit depths. We explore this scenario simulating the radio lightcurves of transits of hot Jupiters, Kepler-17b, and WASP-12b, around solar-like stars. We calculated the bremsstrahlung radio emission at 17, 100, and 400 GHz originating from the star, considering a solar atmospheric model. The planetary radio emission was calculated modeling the planets in two scenarios: as a blackbody or with a dense and hot extended atmosphere. In both cases the planet radiates and contributes to the total radio flux. For a blackbody planet, the transit depth is in the order of 2%-4% and it is independent of the radio frequency. Hot Jupiters planets with atmospheres appear bigger and brighter in radio, thus having a larger contribution to the total flux of the system. Therefore, the transit depths are larger than in the case of blackbody planets, reaching up to 8% at 17 GHz. Also the transit depth is frequency-dependent. Moreover, the transit caused by the planet passing behind the star is deeper than when the planet transits in front of the star, being as large as 18% at 400 GHz. In all cases, the contribution of the planetary radio emission to the observed flux is evident when the planet transits behind the star.

Keywords: Radio continuum emission, Eclipses, Exoplanet atmospheres, Hot Jupiters
Superparticle Method for Simulating Collisions. For problems in astrophysics, planetary science, and beyond, numerical simulations are often limited to simulating fewer particles than in the real system. To model collisions, the simulated particles (a.k.a. superparticles) need to be inflated to represent a collectively large collisional cross section of real particles. Here we develop a superparticle-based method that replicates the kinetic energy loss during real-world collisions, implement it in an N-body code, and test it. The tests provide interesting insights into dynamics of self-gravitating collisional systems. They show how particle systems evolve over several freefall timescales to form central concentrations and equilibrated outer shells. The superparticle method can be extended to account for the accretional growth of objects during inelastic mergers.

Keywords: Gravitational collapse, Protoplanetary disks, Planetesimals, N-body simulations, Planet formation
Radio Linear Polarization of GRB Afterglows: Instrumental Systematics in ALMA Observations of GRB 171205A. Polarization measurements of gamma-ray burst (GRB) afterglows are a promising means of probing the structure, geometry, and magnetic composition of relativistic GRB jets. However, a precise treatment of instrumental calibration is vital for a robust physical interpretation of polarization data, requiring tests of and validations against potential instrumental systematics. We illustrate this with Atacama Large Millimeter/Sub-millimeter Array (ALMA) Band 3 (97.5 GHz) observations of GRB 171205A taken ≈5.19 days after the burst, where a detection of linear polarization was recently claimed. We describe a series of tests for evaluating the stability of polarization measurements with ALMA. Using these tests to reanalyze and evaluate the archival ALMA data, we uncover systematics in the polarization calibration at the ≈0.09% level. We derive a 3σ upper limit on the linearly polarized intensity of P &lt; 97.2 μJy, corresponding to an upper limit on the linear fractional polarization of ΠL &lt; 0.30%, in contrast to the previously claimed detection. Our upper limit improves upon existing constraints on the intrinsic polarization of GRB radio afterglows by a factor of 3. We discuss this measurement in the context of constraints on the jet magnetic field geometry. We present a compilation of polarization observations of GRB radio afterglows, and demonstrate that a significant improvement in sensitivity is desirable for eventually detecting signals polarized at the ≈0.1% level from typical radio afterglows.

Keywords: Millimeter astronomy, Radio astronomy, Gamma-ray bursts, Polarimetry
Estimation of Key Sunquake Parameters through Hydrodynamic Modeling and Cross-correlation Analysis. Sunquakes are one of the more distinct secondary phenomena related to solar flares, where energy deposition in the lower layers of the Sun's atmosphere excites acoustic waves easily visible in photospheric dopplergrams. We explore two possible excitation mechanisms of sunquakes in the context of the electron beam hypothesis: an instantaneous transfer of momentum and a gradual applied force due to flare eruption. We model the sunquake excitation and compare with five observed sunquake events using a cross-correlation analysis. We find that at least half the events studied are consistent with the electron beam hypothesis and estimate the energy required to excite the sunquakes to be within the range determined by previous studies.

Keywords: Helioseismology, Solar physics, Solar flares
Using the Modified Lognormal Power-law Distribution to Model the Mass Function of NGC 1711. A determination of the mass function (MF) of stellar clusters can be quite dependent on the range of measured masses, the fitting technique, and the analytic function that is being fit to the data. Here, we use Hubble Space Telescope/WFPC2 data of NGC 1711, a stellar cluster in the Large Magellanic Cloud, as a test case to explore a range of possible determinations of the MF from a single data set. We employ the analytic modified lognormal power-law (MLP) distribution, a hybrid function that has a peaked lognormal-like body and a power-law tail at intermediate and high masses. A fit with the MLP has the advantage that the resulting best-fit function can be either a hybrid function, a pure lognormal, or a pure power law, in different limits of the function. The completeness limit for the observations means that the data contains masses above ∼0.90 M⊙. In this case, the MLP fits yield essentially a pure power-law MF. We demonstrate that the nonlinear regression/least-squares approach is not justified since the underlying assumptions are not satisfied. By using maximum-likelihood estimation, which is independent of binning, we find a best-fit functional form ${dN}/d\mathrm{ln}m\propto {m}^{-\alpha }$ , where α = 1.72 ± 0.05 or 1.75 ± 0.05 for two different theoretical isochrone models, respectively. Furthermore, we explore the possibility of systematic errors in the determination of the power-law index due to the depth of the observations. When we combine the observational data with artificially generated data from the lognormal Chabrier initial MF for masses below 0.90M⊙, the best-fit MLP is a hybrid function but with a steeper asymptotic slope I.e., α = 2.04 ± 0.07. This illustrates the systematic uncertainties in commonly used MF parameters that can depend on the range of data that is fitted.

Keywords: Star clusters
Signatures of Untwisting Magnetic Field in a Small Emerging Bipole in the Solar Photosphere. We perform a study of fluid motions and its temporal evolution in and around a small bipolar emerging flux region using observations made by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. We employ local correlation tracking of the Doppler observations to follow horizontal fluid motions and line-of-sight magnetograms to follow the flux emergence. Changes in vertical vorticity and horizontal divergence are used to derive signatures of evolving twists in the magnetic field. Our analysis reveals that the two polarities of the magnetic flux swirl in opposite directions in the early stages of flux emergence indicating an unwinding of the pre-emergence twists in the magnetic field. We further find that during the emergence, there is an increase in swirly motions in the neighboring nonmagnetic regions. We estimate the magnetic and kinetic energies and find that magnetic energy is about a factor of 10 larger than the kinetic energy. During the evolution, when the magnetic energy decreases, an increase in the kinetic energy is observed indicating transfer of energy from the unwinding of the magnetic flux tube to the surrounding fluid motions. Our results thus demonstrate the presence of pre-emergence twists in an emerging magnetic field that is important in the context of the hemispheric helicity rule warranting a detailed statistical study in this context. Further, our observations point to a possible widespread generation of torsional waves in emerging flux regions due to the untwisting magnetic field with implications for upward energy transport to the corona.

Keywords: Solar magnetic flux emergence, Solar photosphere, Solar magnetic fields, Solar activity, Solar evolution
Solar Wind Reconnection Exhausts in the Inner Heliosphere Observed by Helios and Detected via Machine Learning. Reconnecting current sheets in the solar wind play an important role in the dynamics of the heliosphere and offer an opportunity to study magnetic reconnection exhausts under a wide variety of inflow and magnetic shear conditions. However, progress in understanding reconnection can be frustrated by the difficulty of finding events in long time-series data. Here we describe a new method to detect magnetic reconnection events in the solar wind based on machine learning, and apply it to Helios data in the inner heliosphere. The method searches for known solar wind reconnection exhaust features, and parameters in the algorithm are optimized to maximize the Matthews Correlation Coefficient using a training set of events and non-events. Applied to the whole Helios data set, the trained algorithm generated a candidate set of events that were subsequently verified by hand, resulting in a database of 88 events. This approach offers a significant reduction in construction time for event databases compared to purely manual approaches. The database contains events covering a range of heliospheric distances from ∼0.3 to ∼1 au, and a wide variety of magnetic shear angles, but is limited by the relatively coarse time resolution of the Helios data. Analysis of these events suggests that proton heating by reconnection in the inner heliosphere depends on the available magnetic energy in a manner consistent with observations in other regimes such as at the Earth's magnetopause, suggesting this may be a universal feature of reconnection.

Keywords: Space plasmas, Solar wind, Solar magnetic reconnection, Heliosphere
Milky Way Subsystems from Globular Cluster Kinematics Using Gaia DR2 and HST Data. We employ Gaia DR2 proper motions for 151 Milky Way globular clusters (GCs) from Vasiliev in tandem with distances and line-of-sight velocities to derive their kinematical properties. To assign clusters to the Milky Way thick disk, bulge, and halo, we follow the approach of Posti et al., who distinguished among different Galactic stellar components using stars' orbits. In particular, we use the ratio Lz/e, the Z projection of the angular momentum to the eccentricity, as a population tracer, which we complement with chemical abundances extracted from the literature and Monte Carlo simulations. We find that 20 GCs belong to the bar/bulge of the Milky Way, 35 exhibit disk properties, and 96 are members of the halo. Moreover, we find that halo GCs have close to zero rotational velocity with an average value $\langle {\rm{\Theta }}\rangle =1\pm 4$ km s-1. On the other hand, the sample of clusters that belong to the thick disk possess a significant rotation with average rotational velocity 179 ± 6 km s-1. The 20 GCs orbiting within the bar/bulge region of the Milky Way have an average rotational velocity of 49 ± 11 km s-1.

Keywords: Globular star clusters, Milky Way rotation, Milky Way dynamics, Milky Way Galaxy
Carbon-Oxygen Classical Novae Are Galactic <SUP>7</SUP>Li Producers as well as Potential Supernova Ia Progenitors. We report on studies of classical nova (CN) explosions where we follow the evolution of thermonuclear runaways (TNRs) on carbon-oxygen (CO) white dwarfs (WDs). We vary both the mass of the WD (from 0.6 M⊙ to 1.35 M⊙) and the composition of the accreted material. Our simulations are guided by the results of multidimensional studies of TNRs in WDs, which find that sufficient mixing with WD core material occurs after the TNR is well underway, and levels of enrichment are reached that agree with observations of CN ejecta abundances. We use NOVA (our one-dimensional hydrodynamic code) to accrete solar matter until the TNR is ongoing and then switch to a mixed composition (either 25% WD material and 75% solar or 50% WD material and 50% solar). Because the amount of accreted material is inversely proportional to the initial 12C abundance, by first accreting solar matter the amount of material taking part in the outburst is larger than in those simulations where we assume a mixed composition from the beginning. Our results show large enrichments of 7Be in the ejected gases, implying that CO CNe may be responsible for a significant fraction (∼100 M⊙) of the 7Li in the galaxy (∼1000 M⊙). Although the ejected gases are enriched in WD material, the WDs in these simulations eject less material than they accrete. We predict that the WD is growing in mass as a consequence of the accretion-outburst-accretion cycle, and CO CNe may be an important channel for SN Ia progenitors.

Keywords: White dwarf stars, Supernovae, Nucleosynthesis, Classical novae
Observing the Earliest Stages of Star Formation in Galaxies: 8 μm Cores in Three Edge-on Disks. To study the vertical distribution of the earliest stages of star formation in galaxies, three edge-on spirals, NGC 891, NGC 3628, and IC 5052, observed by the Spitzer Space Telescope InfraRed Array Camera (IRAC) were examined for compact 8 μm cores using an unsharp mask technique; 173, 267, and 60 cores were distinguished, respectively. Color-color distributions suggest a mixture of polycyclic aromatic hydrocarbons and highly extincted photospheric emission from young stars. The average V-band extinction is ∼20 mag, equally divided between foreground and core. IRAC magnitudes for the clumps are converted to stellar masses assuming an age of 1 Myr, which is about equal to the ratio of the total core mass to the star formation rate in each galaxy. The extinction and stellar mass suggest an intrinsic core radius of ∼18 pc for 5% star formation efficiency. The half-thickness of the disk of 8 μm cores is 105 pc for NGC 891 and 74 pc for IC 5052, varying with radius by a factor of ∼2. For NGC 3628, which is interacting, the half-thickness is 438 pc, but even with this interaction, the 8 μm disk is remarkably flat, suggesting vertical stability. Small-scale structures like shingles or spirals are seen in the core positions. Very few of the 8 μm cores have optical counterparts.

Keywords: Spiral galaxies, Disk galaxies, Star forming regions, Young star clusters, Interstellar emissions, Star formation
Coincident Sunyaev-Zel'dovich and Gamma-Ray Signals from Cluster Virial Shocks. Virial shocks around galaxy clusters are expected to show a cutoff in the thermal Sunyaev-Zel'dovich (SZ) signal, coincident with a leptonic ring. However, until now, leptonic virial signals have only been reported in Coma and in stacked Fermi Large Area Telescope (LAT) clusters, and an SZ virial shock signal reported only in A2319. We point out that a few clusters—presently Coma, A2319, and A2142—already show a significant ( $3.1\sigma -14\sigma $ ) sharp drop in the Planck y parameter near the virial radius, coincident with a (2.2σ-3.9σ) LAT γ-ray excess. These signatures are naturally interpreted as tracers of the virial shocks of these clusters, at joint medium to high confidence levels. The electron acceleration rates inferred from the γ-rays are consistent with previous measurements. The combined signal, along with galaxy count data, allows a separate measurement of the ∼0.5% (with a factor of ∼2 uncertainty) acceleration efficiency and of the accretion rate. Lower limits on order of a few are imposed on the shock Mach numbers.

Keywords: Galaxy clusters, Non-standard theories of gravity, Sunyaev-Zeldovich effect, Shocks, Gamma-rays
A Massive Molecular Torus inside a Gas-poor Circumnuclear Disk in the Radio Galaxy NGC 1052 Discovered with ALMA. We report ALMA observations of NGC 1052 to search for mass accretion in a gas-poor active galactic nucleus. We detected CO emission representing a rotating ring-like circumnuclear disk (CND) seen edge-on with a gas mass of 5.3 × 105 M⊙. The CND has smaller gas mass than that in typical Seyfert galaxies with circumnuclear star formation and is too gas-poor to drive mass accretion onto the central engine. The continuum emission casts molecular absorption features of CO, HCN, HCO+, SO, SO2, CS, CN, and H2O, with H13CN and HC15N and vibrationally excited (V2 = 1) HCN and HCO+. Broader absorption line widths than CND emission-line widths imply the presence of a geometrically thick molecular torus with a radius of 2.4 ± 1.3 pc and a thickness ratio of 0.7 ± 0.3. We obtain an H2 column density of (3.3 ± 0.7) × 1025 cm-2 using H12CN, H13CN, and HCO+ absorption features and adopting abundance ratios of 12C to 13C and HCO+ to H2, and we derived a torus gas mass of (1.3 ± 0.3) × 107 M⊙, which is ∼9% of the central black hole mass. The molecular gas in the torus is clumpy, with an estimated covering factor of ${0.17}_{-0.03}^{+0.06}$ . The gas density of the clumps inside the torus is inferred to be (6.4 ± 1.3) × 107 cm-3, which meets the excitation conditions for an H2O maser. The specific angular momentum in the torus exceeds the flat rotation curve extrapolated from that of the CND, indicating a Keplerian rotation inside a 14.4 pc sphere of influence.

Keywords: Molecular gas, Active galaxies, Molecular spectroscopy, Radio galaxies, Active galactic nuclei, Radio continuum emission, Radio interferometry, Radio astronomy
ALMA Observations of Quasar Host Galaxies at z ≃ 4.8. We present ALMA Band 7 data of the [C II] $\lambda 157.74\,\mu {\rm{m}}$ emission line and underlying far-IR (FIR) continuum for 12 luminous quasars at $z\simeq 4.8$ powered by fast-growing supermassive black holes (SMBHs). Our total sample consists of 18 quasars, 12 of which are presented here for the first time. The new sources consist of six Herschel/SPIRE-detected systems, which we define as "FIR-bright" sources, and six Herschel/SPIRE-undetected systems, which we define as "FIR-faint" sources. We determine dust masses for the quasars hosts of ${M}_{\mathrm{dust}}\leqslant 0.2\mbox{--}25.0\times {10}^{8}{M}_{\odot }$ , implying interstellar medium gas masses comparable to the dynamical masses derived from the [C II] kinematics. It is found that, on average, the Mg II line is blueshifted by $\sim 500\,\mathrm{km}\,{{\rm{s}}}^{-1}$ with respect to the [C II] emission line, which is also observed when complementing our observations with data from the literature. We find that all of our FIR-bright subsample and most of the FIR-faint objects lie above the main sequence of star-forming galaxies at $z\sim 5$ . We detect companion submillimeter galaxies for two sources, both FIR-faint, with a range of projected distances of $\sim 20\mbox{--}60$ kpc and typical velocity shifts of $\left|{\rm{\Delta }}V\right|\lesssim 200\,\mathrm{km}\,{{\rm{s}}}^{-1}$ from the quasar hosts. Of our total sample of 18 quasars, 5/18 are found to have dust-obscured star-forming companions.

Keywords: Quasars, Active galaxies, Galaxy interactions, Star formation, High-redshift galaxies
Magnetic Field Effects on the Vishniac Overstability in Scaled Radiative Blast Waves. We report experimental results on the stability of a magnetized laser-launched blast wave scaled to simulate a late-stage supernova remnant. We extend previous results to show the effect of a dynamically significant magnetic field on the spatial mode spectrum of the instability. We find that magnetic fields reduce instability growth, possibly influencing turbulent feedback to the interstellar medium.

Keywords: Supernova remnants, Laboratory astrophysics, Supernova dynamics