Sazuna/UAT_keywords huggingface dataset:
Multiwavelength Variability of Sagittarius A* in 2019 July. We report a timing analysis of near-infrared (NIR), X-ray, and submillimeter data during a 3 day coordinated campaign observing Sagittarius A*. Data were collected at 4.5 μm with the Spitzer Space Telescope, 2-8 keV with the Chandra X-ray Observatory, 3-70 keV with NuSTAR, 340 GHz with ALMA, and 2.2 μm with the GRAVITY instrument on the Very Large Telescope Interferometer. Two dates show moderate variability with no significant lags between the submillimeter and the infrared at 99% confidence. A moderately bright NIR flare (F K ~ 15 mJy) was captured on July 18 simultaneous with an X-ray flare (F 2-10 keV ~ 0.1 counts s-1) that most likely preceded bright submillimeter flux (F 340 GHz ~ 5.5 Jy) by about $+{34}_{-33}^{+14}$ minutes at 99% confidence. The uncertainty in this lag is dominated by the fact that we did not observe the peak of the submillimeter emission. A synchrotron source cooled through adiabatic expansion can describe a rise in the submillimeter once the synchrotron self-Compton NIR and X-ray peaks have faded. This model predicts high GHz and THz fluxes at the time of the NIR/X-ray peak and electron densities well above those implied from average accretion rates for Sgr A*. However, the higher electron density postulated in this scenario would be in agreement with the idea that 2019 was an extraordinary epoch with a heightened accretion rate. Since the NIR and X-ray peaks can also be fit by a nonthermal synchrotron source with lower electron densities, we cannot rule out an unrelated chance coincidence of this bright submillimeter flare with the NIR/X-ray emission.

Keywords: Accretion, Black hole physics, Supermassive black holes, Galactic center, Non-thermal radiation sources
Secular Dynamics around a Supermassive black hole via Multipole Expansion. In galactic nuclei, the gravitational potential is dominated by the central supermassive black hole, so stars follow quasi-Keplerian orbits. These orbits are distorted by gravitational forces from other stars, leading to long-term orbital relaxation. The direct numerical study of these processes is challenging because the fast orbital motion imposed by the central black hole requires very small timesteps. An alternative approach, pioneered by Gauß, is to use the secular approximation of smearing out N stars over their Keplerian orbits, using K nodes along each orbit. In this study, we propose three novel improvements to this method. First, we reformulate the discretization of the rates of change of the variables describing the orbital states to ensure that all conservation laws are exactly satisfied. Second, we replace the pairwise sum over nodes by a multipole expansion up to order ${{\ell }}_{\max }$ , reducing the overall computational cost from O(N 2 K 2) to $O({NK}{{\ell }}_{\max }^{2})$ . Finally, we show that the averaged dynamical system is equivalent to 2N interacting unit spin vectors and provide two time integrators: a second-order symplectic scheme, and a fourth-order Lie-group Runge-Kutta method, both of which are straightforward to generalize to higher order. These new simulations recover the diffusion coefficients of stellar eccentricities obtained through analytical calculations of the secular dynamics.

Keywords: Gravitation, Celestial mechanics, Galactic center, Galaxy nuclei
Systematic Investigation of Dust and Gaseous CO in 12 Nearby Molecular Clouds. We report on the first uniform and systematic study of dust and molecular gas in nearby molecular clouds. We use surveys of dust extinction and emission to determine the opacity and map the distribution of the dust within a dozen local clouds in order to derive a uniform set of basic cloud properties. We find (1) the average dust opacity &lt;κ  d,353&gt; = 0.8 cm2 g-1 with variations of a factor of ~2 between clouds, (2) cloud probability density functions are exquisitely described by steeply falling power laws with a narrow range of slope, and (3) a tight ${M}_{\mathrm{GMC}}\sim {R}_{\mathrm{GMC}}^{2}$ scaling relation for the cloud sample, indicative of a cloud population with an exactingly constant average surface density above a common fixed boundary. We compare these results to uniformly analyzed CO surveys. We measure the CO mass conversion factors and assess the efficacy of CO for tracing the physical properties of molecular clouds. We find &lt;α CO&gt; = 4.31 ± 0.67 M ⊙ (K km s-1 pc2)-1 (corresponding to X CO = 1.97 ×1020 cm-2(K km s-1)-1). We demonstrate that CO observations are a poor tracer of column density and structure on sub-cloud spatial scales. On cloud scales, CO observations can provide measurements consistent with those of the dust, provided data are analyzed in a similar, self-consistent fashion. Measurements of average giant molecular cloud surface density are sensitive to choice of cloud boundary. Care must be exercised to adopt common fixed boundaries when comparing surface densities for cloud populations within and between galaxies.

Keywords: Giant molecular clouds, Molecular gas, Interstellar dust extinction
Inflated Eccentric Migration of Evolving Gas Giants I - Accelerated Formation and Destruction of Hot and Warm Jupiters. Hot and warm Jupiters (HJs and WJs, correspondingly) are gas giants orbiting their host stars at very short orbital periods (P HJ &lt; 10 days; 10 &lt; P WJ &lt; 200 days). HJs and a significant fraction of WJs are thought to have migrated from initially farther-out birth locations. While such migration processes have been extensively studied, the thermal evolution of gas giants and its coupling with migration processes are usually overlooked. In particular, gas giants end their core accretion phase with large radii, then contract slowly to their final radii. Moreover, intensive heating can slow the contraction at various evolutionary stages. The initial large inflated radii lead to faster tidal migration, due to the strong dependence of tides on the radius. Here, we explore this accelerated migration channel, which we term inflated eccentric migration, using a semi-analytical, self-consistent model of the thermal-dynamical evolution of the migrating gas giants, later validated by our numerical model (see the companion paper, paper II). We demonstrate our model for specific examples and carry out a population synthesis study. Our results provide a general picture of the properties of the formed HJs and WJs via inflated migration, and their dependence on the initial parameters/distributions. We show that the tidal migration of gas giants could occur much more rapidly then previously thought, and could lead to the accelerated destruction and formation of HJs and an enhanced formation rate for WJs. Accounting for the coupled thermal-dynamical evolution is therefore critical to understanding the formation of HJs/WJs, and the evolution and final properties of the population, and it plays a key role in their migration processes.

Keywords: Exoplanet dynamics, Exoplanet migration, Exoplanets, Hot Jupiters, Exoplanet astronomy, Exoplanet evolution, Exoplanet tides, Extrasolar gaseous planets, Exoplanet structure, Exoplanet formation
Inflated Eccentric Migration of Evolving Gas Giants II - Numerical Methodology and Basic Concepts. Hot and warm Jupiters (HJs&amp;WJs) are gas-giant planets orbiting their host stars at short orbital periods, posing a challenge to their efficient in situ formation. Therefore, most HJs&amp;WJs are thought to have migrated from an initially farther-out birth location. Current migration models, i.e., disk migration (gas-dissipation driven) and eccentric migration (tidal evolution driven), fail to produce the occurrence rate and orbital properties of HJs&amp;WJs. Here we study the role of thermal evolution and its coupling to tidal evolution. We use AMUSE, a numerical environment, and MESA, planetary evolution modeling, to model in detail the coupled internal and orbital evolution of gas giants during their eccentric migration. In a companion paper, we use a simple semianalytic model, validated by our numerical model, and run a population-synthesis study. We consider the initially inflated radii of gas giants (expected following their formation), as well study the effects of the potentially slowed contraction and even reinflation of gas giants (due to tidal and radiative heating) on the eccentric migration. Tidal forces that drive eccentric migration are highly sensitive to the planetary structure and radius. Consequently, we find that this form of inflated eccentric migration operates on significantly (up to an order of magnitude) shorter timescales than previously studied eccentric-migration models. Therefore, inflated eccentric migration gives rise to the more rapid formation of HJs&amp;WJs, higher occurrence rates of WJs, and higher rates of tidal disruptions, compared with previous eccentric-migration models that consider constant ~Jupiter radii for HJ and WJ progenitors. Coupled thermal-dynamical evolution of eccentric gas giants can therefore play a key role in their evolution.

Keywords: Exoplanet migration, Exoplanet formation, Hot Jupiters, Exoplanet evolution
Toward Astrometric Constraints on a Supermassive Black Hole Binary in the Early-type Galaxy NGC 4472. The merger of two galaxies, each hosting a supermassive black hole (SMBH) of mass 106 M ⊙ or more, could yield a bound SMBH binary. For the early-type galaxy NGC 4472, we study how astrometry with a next-generation Very Large Array could be used to monitor the reflex motion of the primary SMBH of mass M pri, as it is tugged on by the secondary SMBH of mass ${M}_{\sec }$ . Casting the orbit of the putative SMBH binary in terms of its period P, semimajor axis a bin, and mass ratio $q={M}_{\sec }/{M}_{\mathrm{pri}}\leqslant 1$ , we find the following: (1) Orbits with fiducial periods of P = 4 yr and 40 yr could be spatially resolved and monitored. (2) For a 95% accuracy of 2 μas per monitoring epoch, subparsec values of a bin could be accessed over a range of mass ratios notionally encompassing major $\left(q\gt \tfrac{1}{4}\right)$ and minor $\left(q\lt \tfrac{1}{4}\right)$ galaxy mergers. (3) If no reflex motion is detected for M pri after 1 (10) yr of monitoring, an SMBH binary with period P = 4 (40) yr and mass ratio q &gt; 0.01 (0.003) could be excluded. This would suggest no present-day evidence for a past major merger like that recently simulated, where scouring by a q ~ 1 SMBH binary formed a stellar core with kinematic traits like those of NGC 4472. (4) Astrometric monitoring could independently check the upper limits on q from searches for continuous gravitational waves from NGC 4472.

Keywords: Supermassive black holes, Active galactic nuclei, Early-type galaxies, Interferometry
X-Ray Observation of the Roche-lobe-filling White Dwarf plus Hot Subdwarf System ZTF J213056.71+442046.5. ZTF J213056.71+442046.5 is the prototype of a small class of recently discovered compact binaries composed of a white dwarf and a hot subdwarf that fills its Roche lobe. Its orbital period of only 39 minutes is the shortest known for the objects in this class. Evidence for a high orbital inclination (i = 86°) and for the presence of an accretion disk has been inferred from a detailed modeling of its optical photometric and spectroscopic data. We report the results of an XMM-Newton observation carried out on 2021 January 7. ZTF J213056.71+442046.5 was clearly detected by the Optical Monitor, which showed a periodic variability in the UV band (200-400 nm), with a light curve similar to that seen at longer wavelengths. Despite accretion on the white dwarf at an estimated rate of the order of 10-9  M ☉ yr-1, no X-rays were detected with the EPIC instrument, with a limit of ~1030 erg s-1 on the 0.2-12 keV luminosity. We discuss possible explanations for the lack of a strong X-ray emission from this system.

Keywords: White dwarf stars, B subdwarf stars, Compact binary stars, Stellar accretion
How Well Can We Measure Galaxy Dust Attenuation Curves? The Impact of the Assumed Star-dust Geometry Model in Spectral Energy Distribution Fitting. One of the most common methods for inferring galaxy attenuation curves is via spectral energy distribution (SED) modeling, where the dust attenuation properties are modeled simultaneously with other galaxy physical properties. In this paper, we assess the ability of SED modeling to infer these dust attenuation curves from broadband photometry, and suggest a new flexible model that greatly improves the accuracy of attenuation curve derivations. To do this, we fit mock SEDs generated from the SIMBA cosmological simulation with the PROSPECTOR SED fitting code. We consider the impact of the commonly assumed uniform screen model and introduce a new nonuniform screen model parameterized by the fraction of unobscured stellar light. This nonuniform screen model allows for a nonzero fraction of stellar light to remain unattenuated, resulting in a more flexible attenuation curve shape by decoupling the shape of the UV attenuation curve from the optical attenuation curve. The ability to constrain the dust attenuation curve is significantly improved with the use of a nonuniform screen model, with the median offset in UV attenuation decreasing from -0.30 dex with a uniform screen model to -0.17 dex with the nonuniform screen model. With this increase in dust attenuation modeling accuracy, we also improve the star formation rates (SFRs) inferred with the nonuniform screen model, decreasing the SFR offset on average by 0.12 dex. We discuss the efficacy of this new model, focusing on caveats with modeling star-dust geometries and the constraining power of available SED observations.

Keywords: Hydrodynamical simulations, Radiative transfer simulations, Spectral energy distribution, Galactic and extragalactic astronomy
Supernova Shock Breakout/Emergence Detection Predictions for a Wide-field X-Ray Survey. There are currently many large-field surveys that are operational and are being planned including the powerful Vera C. Rubin Observatory Legacy Survey of Space and Time. These surveys will increase the number and diversity of transients dramatically. However, for some transients, like supernovae (SNe), we can gain more understanding by directed observations (e.g., shock breakout and γ-ray detections) than by simply increasing the sample size. For example, the initial emission from these transients can be a powerful probe of these explosions. Upcoming ground-based detectors are not ideally suited to observing the initial emission (shock emergence) of these transients. These observations require a large field-of-view X-ray mission with a UV follow-up within the first hour of shock breakout. The emission in the first 1 hr to even 1 day provides strong constraints on the stellar radius and asymmetries in the outer layers of stars, the properties of the circumstellar medium (e.g., inhomogeneities in the wind for core-collapse SNe and accreting companions in thermonuclear SNe), and the transition region between these two areas. This paper describes a simulation for the number of SNe that could be seen by a large field-of-view lobster-eye X-ray and UV observatory.

Keywords: Supernovae, Core-collapse supernovae, Astronomical simulations
Galaxy Zoo: Clump Scout: Surveying the Local Universe for Giant Star-forming Clumps. Massive, star-forming clumps are a common feature of high-redshift star-forming galaxies. How they formed, and why they are so rare at low redshift, remains unclear. In this paper we identify the largest sample yet of clumpy galaxies (7050) at low redshift using data from the citizen science project Galaxy Zoo: Clump Scout, in which volunteers classified 58,550 Sloan Digital Sky Survey (SDSS) galaxies spanning redshift 0.02 &lt; z &lt; 0.15. We apply a robust completeness correction by comparing with simulated clumps identified by the same method. Requiring that the ratio of clump to galaxy flux in the SDSS u band be greater than 8% (similar to clump definitions used by other works), we estimate the fraction of local star-forming galaxies hosting at least one clump (f clumpy) to be ${3.22}_{-0.34}^{+0.38} \% $ . We also compute the same fraction with a less stringent relative flux cut of 3% ( ${12.68}_{-0.88}^{+1.38} \% $ ), as the higher number count and lower statistical noise of this fraction permit finer comparison with future low-redshift clumpy galaxy studies. Our results reveal a sharp decline in f clumpy over 0 &lt; z &lt; 0.5. The minor merger rate remains roughly constant over the same span, so we suggest that minor mergers are unlikely to be the primary driver of clump formation. Instead, the rate of galaxy turbulence is a better tracer for f clumpy over 0 &lt; z &lt; 1.5 for galaxies of all masses, which supports the idea that clump formation is primarily driven by violent disk instability for all galaxy populations during this period.

Keywords: Starburst galaxies, Galaxy formation, Cosmological evolution, Galaxy structure, Galaxy evolution, Galaxies
The Redshift Evolution of the Binary Black Hole Merger Rate: A Weighty Matter. Gravitational-wave detectors are starting to reveal the redshift evolution of the binary black hole (BBH) merger rate, R BBH(z). We make predictions for R BBH(z) as a function of black hole mass for systems originating from isolated binaries. To this end, we investigate correlations between the delay time and black hole mass by means of the suite of binary population synthesis simulations, COMPAS. We distinguish two channels: the common envelope (CE), and the stable Roche-lobe overflow (RLOF) channel, characterized by whether the system has experienced a common envelope or not. We find that the CE channel preferentially produces BHs with masses below about 30 M ⊙ and short delay times (t delay ≲ 1 Gyr), while the stable RLOF channel primarily forms systems with BH masses above 30 M ⊙ and long delay times (t delay ≳ 1 Gyr). We provide a new fit for the metallicity-dependent specific star formation rate density based on the Illustris TNG simulations, and use this to convert the delay time distributions into a prediction of R BBH(z). This leads to a distinct redshift evolution of R BBH(z) for high and low primary BH masses. We furthermore find that, at high redshift, R BBH(z) is dominated by the CE channel, while at low redshift, it contains a large contribution (~40%) from the stable RLOF channel. Our results predict that, for increasing redshifts, BBHs with component masses above 30 M ⊙ will become increasingly scarce relative to less massive BBH systems. Evidence of this distinct evolution of R BBH(z) for different BH masses can be tested with future detectors.

Keywords: Close binary stars, Stellar mass black holes, Gravitational wave sources, Astrophysical black holes, Stellar evolution
Solar Cycle and Seasonal Variability of Martian Ionospheric Irregularities from Mars Atmosphere and Volatile Evolution Observations. Spacecraft observations around Mars show that ionospheric irregularities occur frequently in the Martian ionosphere. In this study, Mars Atmosphere and Volatile Evolution data (the region is below ~200 km) during 2015 January to 2021 March were used to revisit the statistical characteristics of ionospheric irregularities and the comparison of irregularities in Martian years with higher or lower solar activity phase of solar cycle. Results show that the characteristics of the irregularities with a larger length scale associated with the magnetic field and solar zenith angle are similar to the previous studies. Moreover, our results show that the occurrence rate of irregularities exhibits dawn and dusk asymmetry, and the occurrence rate at dusk is higher than that at dawn. In addition, results demonstrate that the occurrence rate of irregularities is higher in Martian years with higher solar activity than Martian years with lower solar activity, which means that the solar cycle might play an important role in the formation of irregularity events. Further studies show that the solar zenith angle (SZA) and altitude at the maximum occurrence rate depend on the level of solar activity. The SZA and altitude of the maximum occurrence rate are smaller in the Martian year with higher solar activity than the lower. We also found that the rate of events is lower during the day than the terminator in the ionospheric dynamo region. By contrast, in the regions where both electrons and ions are magnetized, events have a higher rate during the day than the terminator. Furthermore, the seasonal variation of the irregularity events was also presented in this study. Results show that the occurrence rate in the dynamo region with 80° &lt; SZA &lt; 150° in MY34 and MY35 show an incremental trend from spring to winter, but this trend is not obvious in MY33.

Keywords: Mars, Solar-planetary interactions, Plasma physics
Discovery of NES, an Extended Tidal Structure in the Northeast of the Large Magellanic Cloud. We report on the discovery of a new diffuse stellar substructure protruding for &gt;5° from the northeastern rim of the LMC disk. The structure, which we dub the northeast structure (NES), was identified by applying a Gaussian mixture model to a sample of strictly selected candidate members of the Magellanic System, extracted from the Gaia EDR3 catalog. The NES fills the gap between the outer LMC disk and other known structures in the same region of the LMC, namely the northern tidal arm and the eastern substructures. Particularly noteworthy is that the NES is placed in a region where N-body simulations foresee a bending of the LMC disk due to tidal stresses induced by the MW. The velocity field in the plane of the sky indicates that the complex of tidal structures in the northeastern part of the LMC, including NES, shows a complex pattern. Additional data, as well as extensive dynamical modeling, is required to shed light onto the origin of NES as well as on the relationships with the surrounding substructures.

Keywords: Parallax, Hertzsprung Russell diagram, Stellar kinematics, Gaussian mixture model, Galaxy interactions, Large Magellanic Cloud, Proper motions, Broad band photometry
Physical Properties of the Supernova Remnant Population in the Small Magellanic Cloud. The X-ray emission from a supernova remnant is a powerful diagnostic of the state of its shocked plasma. The temperature and the emission measure are related to the energy of the explosion, the age of the remnant, and the density of the surrounding medium. Here we present the results of a study of the remnant population of the Small Magellanic Cloud. Progress in X-ray observations of remnants has resulted in a sample of 20 remnants in the Small Magellanic Cloud with measured temperatures and emission measures. We apply spherically symmetric supernova remnant evolution models to this set of remnants to estimate ages, explosion energies, and circumstellar medium densities. The distribution of ages yields a remnant birth rate of ~1/1200 yr. The energies and densities are well fit with log-normal distributions, with means of 1.6 × 1051 erg and 0.14 cm-3, and 1σ dispersions of a factor of 1.87 in energy and 3.06 in density, respectively.

Keywords: Supernova remnants, Small Magellanic Cloud, Magellanic Clouds
Possible In Situ Formation of Uranus and Neptune via Pebble Accretion. The origin of Uranus and Neptune is still unknown. In particular, it has been challenging for planet formation models to form the planets in their current radial distances within the expected lifetime of the solar nebula. In this paper, we simulate the in situ formation of Uranus and Neptune via pebble accretion and show that both planets can form within ~3 Myr at their current locations, and have final compositions that are consistent with the heavy element to H-He ratios predicted by structure models. We find that Uranus and Neptune could have been formed at their current locations. In several cases a few earth masses (M ⊕ ) of heavy elements are missing, suggesting that Uranus and/or Neptune may have accreted ~1-3 M⊕ of heavy elements after their formation via planetesimal accretion and/or giant impacts.

Keywords: Extrasolar ice giants, Extrasolar gaseous planets, Exoplanet formation, Extrasolar gaseous giant planets, Planet formation