Sazuna/UAT_keywords huggingface dataset:
Physical Parameters of the Torus for the Type 2 Seyfert IC 5063 from Mid-IR and X-Ray Simultaneous Spectral Fitting. In order to understand the diversity of classes observed in active galactic nuclei (AGNs), a geometrically and optically thick torus of gas and dust is required to obscure the central engine depending on the line of sight to the observer. We perform a simultaneous fitting of X-ray and mid-infrared (mid-IR) spectra to investigate whether the same structure could produce both emissions and, if this the case, to obtain better constraints for the physical parameters of the torus. In this case we take advantage of the fact that both emissions show important signatures of obscuration. We used the nearby type 2 active nucleus IC 5063 as a test object. This object is ideal because of the wealth of archival data, including some high-resolution data. It also has a relatively high AGN luminosity that dominates at both X-ray and mid-IR frequencies. We use high spectral resolution NuSTAR and Spitzer/IRS spectra. The AGN dusty models used several physically motivated models. We found that the combination of the smooth torus models at mid-IR by Fritz et al. and at X-rays by Baloković et al., with the viewing and half-opening angles linked to the same value, is the best choice to fit the spectra at both wavelengths. This allows us to determine all the parameters of its torus. This result suggests that the structure producing the continuum emission at mid-IR and the reflection component at X-ray is the same. Therefore, we prove that this technique can be used to infer the physical properties of the torus, at least when AGN dust dominates the mid-IR emission and the reflection component is significant at X-rays.

Keywords: Infrared astronomy, Active galactic nuclei, X-ray astronomy
Stability of Nitrogen in Planetary Atmospheres in Contact with Liquid Water. Molecular nitrogen is the most commonly assumed background gas that supports habitability on rocky planets. Despite its chemical inertness, nitrogen molecules are broken by lightning, hot volcanic vents, and bolide impacts, and can be converted into soluble nitrogen compounds and then sequestered in the ocean. The very stability of nitrogen, and that of nitrogen-based habitability, is thus called into question. Here we determine the lifetime of molecular nitrogen vis-à-vis aqueous sequestration, by developing a novel model that couples atmospheric photochemistry and oceanic chemistry. We find that HNO, the dominant nitrogen compound produced in anoxic atmospheres, is converted to N2O in the ocean, rather than oxidized to nitrites or nitrates as previously assumed. This N2O is then released back into the atmosphere and quickly converted to N2. We also find that the deposition rate of NO is severely limited by the kinetics of the aqueous-phase reaction that converts NO to nitrites in the ocean. Putting these insights together, we conclude that the atmosphere must produce nitrogen species at least as oxidized as NO2 and HNO2 to enable aqueous sequestration. The lifetime of molecular nitrogen in anoxic atmospheres is determined to be &gt;1 billion years on temperate planets of both Sun-like and M dwarf stars. This result upholds the validity of molecular nitrogen as a universal background gas on rocky planets.

Keywords: Extrasolar rocky planets, Exoplanet atmospheric composition , Super Earths, Exoplanet evolution, Habitable planets
A Unified Binary Neutron Star Merger Magnetar Model for the Chandra X-Ray Transients CDF-S XT1 and XT2. Two bright X-ray transients were reported from the Chandra Deep Field South (CDF-S) archival data, namely CDF-S XT1 and XT2. Whereas the nature of the former is not identified, the latter was suggested as an excellent candidate for a rapidly spinning magnetar born from a binary neutron star (BNS) merger. Here we propose a unified model to interpret both transients within the framework of the BNS merger magnetar model. According to our picture, CDF-S XT2 is observed from the “free zone” where the magnetar spindown powered X-ray emission escapes freely, whereas CDF-S XT1 originates from the “trapped zone” where the X-ray emission is initially blocked by the dynamical ejecta and becomes transparent after the ejecta is pushed to a distance where Thomson optical depth drops below unity. We fit the magnetar model to the light curves of both transients and derived consistent parameters for the two events, with magnetic field, initial spin period, and X-ray emission efficiency being (B  p  = 1016 G, P  i  = 1.2 ms, η = 0.001) and (B  p  = 1015.8 G, P  i  = 4.4 ms, η = 0.001) for XT1 and XT2, respectively. The “isotropic equivalent” ejecta mass of XT1 is M ej ∼ 10-3 M ⊙, while it is not constrained for XT2. Our results suggest that more extreme magnetar parameters are required to have XT1 detected from the trapped zone. The model parameters for both events are generally consistent with those derived from short gamma-ray burst (SGRB) X-ray plateau observations. The host-galaxy properties of both transients are also consistent with those of SGRBs. The event rate densities of both XT1 and XT2 are consistent with that of BNS mergers.

Keywords: Neutron stars, Magnetars, X-ray transient sources, Gamma-ray bursts
Formation of Massive Protostellar Clusters—Observations of Massive 70 μm Dark Molecular Clouds. We present Submillimeter Array observations of seven massive molecular clumps that are dark in the far-infrared for wavelengths up to 70 μm. Our 1.3 mm continuum images reveal 44 dense cores, with gas masses ranging from 1.4 to 77.1 M ⊙. Twenty-nine dense cores have masses greater than 8 M ⊙ and the other 15 dense cores have masses between 1.4 and 7.5 M ⊙. Assuming the core density follows a power law in radius ρ ∝ r -b , the index b is found to be between 0.6 and 2.1, with a mean value of 1.3. The virial analysis reveals that the dense cores are not in virial equilibrium. CO outflow emission was detected toward six out of seven molecular clumps and associated with 17 dense cores. For five of these cores, CO emissions appear to have line wings at velocities of greater than 30 km s-1 with respect to the source systemic velocity, which indicates that most of the clumps harbor protostars and thus are not quiescent in star formation. The estimated outflow timescale increases with core mass, which likely indicates that massive cores have longer accretion timescales than less massive ones. The fragmentation analysis shows that the masses of low-mass and massive cores are roughly consistent with thermal and turbulent Jeans masses, respectively.

Keywords: Radio spectroscopy, Early-type stars, Submillimeter astronomy, Massive stars, Stellar jets, Stellar winds, Star formation, Dust continuum emission, Protostars
Waldmeier Effect in Stellar Cycles. One of the most robust features of the solar magnetic cycle is that the stronger cycles rise faster than the weaker ones. This is popularly known as the Waldmeier Effect, which has been known for more than 100 yr. This fundamental feature of the solar cycle has not only practical implications, e.g., in predicting the solar cycle, but also implications in understanding the solar dynamo. Here we ask whether the Waldmeier Effect exists in other Sun-like stars. To answer this question, we analyze the Ca II H and K S-index from Mount Wilson Observatory for 21 Sun-like G-K stars. We specifically check two aspects of Waldmeier Effect, namely, (1) WE1: the anticorrelation between the rise times and the peaks and (2) WE2: the positive correlation between rise rates and amplitudes. We show that, except for HD 16160, HD 81809, HD 155886, and HD 161239, all stars considered in the analysis show WE2, while WE1 is found to be present only in some of the stars studied. Furthermore, the WE1 correlation is weaker than the WE2. Both WE1 and WE2 exist in the solar S-index as well. Similar to the solar cycles, the magnetic cycles of many stars are asymmetric about their maxima. The existence of the Waldmeier Effect and asymmetric cycles in Sun-like stars suggests that the dynamo mechanism which operates in the Sun is also operating in other stars.

Keywords: Solar cycle, Solar dynamo, Stellar activity, Stellar types, Solar magnetic fields
Relating the Carriers of λ5797.1 Diffuse Interstellar Band and λ5800 Red Rectangle Band. The emission spectra of the λ5800 Red Rectangle Band (RRB) are simulated at all regions of the Red Rectangle Nebula, utilizing a polar carbon chain model previously developed for the λ5797.1 diffuse interstellar band (DIB) in absorption in the interstellar medium. If high radiative temperatures are assumed, radiative pumping of numerous rotational J levels of a polar (μ = 4 D) carbon chain whose rotational constant B = 1200 MHz decreases by 3% upon electronic excitation produces an emission spectrum with a sharp blue edge and an extended tail toward the red (ETR). This ETR broadens with increasing temperature, resembling the behavior of the λ5800 RRB. It is shown that subsequent self-absorption in the foreground of the nebula can saturate the lower-wavelength emission to redshift the peak wavelengths of the simulated emission profiles, reproducing the observed λ5800 RRB sequence structure. The requirement of high column densities of DIB absorbers in the nebula presents one difficulty with this model. If overcome, the simulations present empirical evidence that the λ5797.1 DIB and the λ5800 RRB can originate from identical carrier molecules.

Keywords: Interstellar molecules, Interstellar medium, Astrochemistry
Fast-pairwise Collective Neutrino Oscillations Associated with Asymmetric Neutrino Emissions in Core-collapse Supernovae. We present a linear stability analysis of the fast-pairwise neutrino flavor conversion based on a result of our latest axisymmetric core-collapse supernova (CCSN) simulation with full Boltzmann neutrino transport. In the CCSN simulation, coherent asymmetric neutrino emissions of electron-type neutrinos (ν e) and their antiparticles ({\bar{ν }}{{e}}), in which the asymmetries of ν e and {\bar{ν }}{{e}} are anticorrelated with each other, occur at almost the same time as the onset of aspherical shock expansion. We find that the asymmetric neutrino emissions play a crucial role on occurrences of fast flavor conversions. The linear analysis shows that unstable modes appear in both pre- and post-shock flows; for the latter, they appear only in the hemisphere of higher {\bar{ν }}{{e}} emissions (the same hemisphere with stronger shock expansion). We analyze the characteristics of electron-lepton number (ELN) crossing in depth by closely inspecting the angular distributions of neutrinos in momentum space. The ELN crossing happens in various ways, and the property depends on the radius: in the vicinity of neutron star, {\bar{ν }}{{e}} (ν e) dominates over ν e ({\bar{ν }}{{e}}) in the forward (backward) direction; at the larger radius, the ELN crossing occurs in the opposite way. We also find that the non-radial ELN crossing occurs at the boundary between no ELN crossing and the radial one, which is an effect of genuine multi-dimensional transport. Our findings indicate that the collective neutrino oscillation may occur more commonly in CCSNe and suggest that the CCSN community needs to accommodate these oscillations self-consistently in the modeling of CCSNe.

Keywords: Neutron stars, Supernova neutrinos, Neutrino oscillations, Nuclear astrophysics, Radiative transfer simulations, Supernova dynamics
Identifying Candidate Atmospheres on Rocky M Dwarf Planets via Eclipse Photometry. Most rocky planets in the galaxy orbit a cool host star, and there is large uncertainty among theoretical models whether these planets can retain an atmosphere. The James Webb Space Telescope (JWST) might be able to settle this question empirically, but most proposals for doing so require large observational effort because they are based on spectroscopy. Here we show that infrared photometry of secondary eclipses could quickly identify “candidate” atmospheres, by searching for rocky planets with atmospheres thick enough that atmospheric heat transport noticeably reduces their dayside thermal emission compared to that of a bare rock. For a planet amenable to atmospheric follow-up, we find that JWST should be able to confidently detect the heat redistribution signal of an { \mathcal O }(1) bar atmosphere with one to two eclipses. One to two eclipses is generally much less than the effort needed to infer an atmosphere via transmission or emission spectroscopy. Candidate atmospheres can be further validated via follow-up spectroscopy or phase curves. In addition, because this technique is fast it could enable a first atmospheric survey of rocky exoplanets with JWST. We estimate that the TESS mission will find ∼100 planets that are too hot to be habitable but that can be quickly probed via eclipse photometry. Knowing whether hot, rocky planets around M dwarfs have atmospheres is important not only for understanding the evolution of uninhabitable worlds: if atmospheres are common on hot planets, then cooler, potentially habitable planets around M dwarfs are also likely to have atmospheres.

Keywords: Atmospheric circulation, Infrared photometry, Super Earths, Planetary atmospheres, Exoplanet surface characteristics, Exoplanet atmospheres
Analyzing Atmospheric Temperature Profiles and Spectra of M Dwarf Rocky Planets. The James Webb Space Telescope (JWST) will make it possible to comprehensively measure the thermal emission spectra of rocky exoplanets orbiting M dwarfs and thus characterize their atmospheres. In preparation for this opportunity, we present model atmospheres for three M-dwarf planets particularly amenable to secondary eclipse spectroscopy—TRAPPIST-1b, GJ 1132b, and LHS 3844b. Using three limiting cases of candidate atmospheric compositions (pure H2O, pure CO2, and solar abundances) we calculate temperature-pressure profiles and emission spectra in radiative-convective equilibrium, including the effects of a solid surface. We find that the atmospheric radiative transfer is significantly influenced by the cool M-star irradiation; H2O and CO2 absorption bands in the near-infrared are strong enough to absorb a sizeable fraction of the incoming stellar light at low pressures, which leads to temperature inversions in the upper atmosphere. The non-gray band structure of gaseous opacities in the infrared is hereby an important factor. Opacity windows are muted at higher atmospheric temperatures, so we expect temperature inversions to be common only for sufficiently cool planets. We also find that pure CO2 atmospheres exhibit lower overall temperatures and stronger reflection spectra compared to models of the other compositions. We estimate that for GJ 1132b and LHS 3844b we should be able to distinguish between different atmospheric compositions with JWST. The emission lines from the predicted temperature inversions are currently hard to measure, but high-resolution spectroscopy with future extremely large telescopes may be able to detect them.

Keywords: Extrasolar rocky planets, Radiative transfer, Exoplanet atmospheres
Comparison of the Scaling Properties of EUV Intensity Fluctuations in Coronal Hole and Quiet-Sun Regions. Using detrended fluctuation analysis and rescaled range analysis, we investigate the scaling properties of extreme ultraviolet (EUV) intensity fluctuations of low-latitude coronal holes (CHs) and neighboring quiet-Sun (QS) regions in signals obtained with the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly instrument. Contemporaneous line-of-sight SDO/Helioseismic and Magnetic Imager magnetic fields provide a context for the physical environment. We find that the intensity fluctuations in the time series of EUV images present at each spatial point a scaling symmetry over the range ∼20 minute to ∼1 hr. Thus we are able to calculate a generalized Hurst exponent and produce image maps, not of physical quantities like intensity or temperature, but of a single dynamical parameter that sums up the statistical nature of the intensity fluctuations at each pixel. In QS regions and in CHs with magnetic bipoles, the scaling exponent (1.0 &lt; α ≤ 1.5) corresponds to anticorrelated turbulent-like processes. In CHs, and in QS regions primarily associated with (open) magnetic field of dominant polarity, the generalized exponent (0.5 &lt; α &lt; 1) corresponds to positively correlated (persistent) processes. We identify a tendency for α ∼ 1 near CH boundaries and in other regions in which open and closed magnetic fields are in proximity. This is a signature of an underlying 1/f type process that is characteristic for self-organized criticality and shot-noise models.

Keywords: Solar extreme ultraviolet emission, Solar coronal loops, Quiet sun, Quiet solar corona, Solar magnetic fields, Solar coronal holes
ACR Proton Acceleration Associated with Reconnection Processes beyond the Heliospheric Termination Shock. One of the curious observations from the Voyagers is that the intensity of anomalous cosmic rays (ACRs) did not peak at the heliospheric termination shock (HTS) but instead a short distance (within ∼1 au) downstream of the HTS. One possible explanation is that the interaction of the wavy heliospheric current sheet with the HTS enhances magnetic reconnection and generates numerous small-scale magnetic flux ropes in the heliosheath immediately downstream of the HTS. Charged particles are accelerated in this region due to Fermi acceleration and the reconnection electric field. In this work, we provide observational evidence of the presence of magnetic flux ropes in the heliosheath region just downstream of the HTS using a wavelet analysis of the reduced magnetic helicity and Grad-Shafranov reconstruction techniques. The Zank et al. kinetic transport theory for particles propagating through the magnetic islands region is employed to fit the observed energetic proton intensities in the post-HTS region. Our modeling results agree reasonably well with the observations, which suggests that stochastic acceleration via reconnection processes can explain the ACR proton peak beyond the HTS.

Keywords: Termination shock, Interplanetary particle acceleration, Solar wind, Solar magnetic reconnection
The Nature of the Broadband X-Ray Variability in the Dwarf Seyfert Galaxy NGC 4395. We present a flux-resolved X-ray analysis of the dwarf Seyfert 1.8 galaxy NGC 4395, based on three archival XMM-Newton and one archival NuSTAR observations. The source is known to harbor a low-mass black hole (∼ {10}4{--}{{a}} {few} × {10}5 {M}☉ ) and shows strong variability in the full X-ray range during these observations. We model the flux-resolved spectra of the source assuming three absorbing layers: neutral, mildly ionized, and highly ionized ({N}{{H}}∼ 1.6× {10}22{--}3.4× {10}23 {cm}}-2, ∼ 0.8{--}7.8× {10}22 {cm}}-2, and 3.8 × 1022 cm-2, respectively). The source also shows intrinsic variability by a factor of ∼3 on short timescales, which is due to changes in the nuclear flux, assumed to be a power law (Γ = 1.6-1.67). Our results show a positive correlation between the intrinsic flux and the absorbers’ ionization parameter. The covering fraction of the neutral absorber varies during the first XMM-Newton observation, which could explain the pronounced soft X-ray variability. However, the source remains fully covered by this layer during the other two observations, largely suppressing the soft X-ray variability. This suggests an inhomogeneous and layered structure in the broad-line region. We also find a difference in the characteristic timescale of the power spectra between different energy ranges and observations. We finally show simulated spectra with XRISM, eXTP, and Athena, which will allow us to characterize the different absorbers, study their dynamics, and will help us identify their locations and sizes.

Keywords: X-ray astronomy, Intermediate-mass black holes, Supermassive black holes, High energy astrophysics, Seyfert galaxies, X-ray active galactic nuclei, Active galactic nuclei, Low-luminosity active galactic nuclei, Astrophysical black holes
Detectability of Modulated X-Rays from LISA’s Supermassive Black Hole Mergers. One of the central goals of the Laser Interferometer Space Antenna (LISA) is the detection of gravitational waves from the merger of supermassive black holes. Contrary to stellar-mass black hole mergers, such events are expected to be rich X-ray sources due to the accretion of material from the circumbinary disks onto the black holes. The orbital dynamics before merger is also expected to modulate the resulting X-ray emission via Doppler boosting in a quasiperiodic way and in a simple phase relation with the gravitational wave from the inspiral of the black holes. Detecting the X-ray source would enable a precise and early localization of the binary, thus allowing many telescopes to observe the very moment of the merger. Although identifying the correct X-ray source in the relatively large LISA sky localization will be challenging due to the presence of many confounding point sources, the quasiperiodic modulation may aid in the identification. We explore the practical feasibility of such idea. We simulate populations of merging supermassive black holes, their detection with LISA, and their X-ray light curves using a simple model. Taking the parameters of the X-ray telescope on the proposed NASA Transient Astrophysics Probe, we then design and simulate an observation campaign that searches for the modulated X-ray source while LISA is still observing the inspiral of the black holes. Assuming a fiducial LISA detection rate of 10 mergers per year at redshift closer than 3.5, we expect a few detections of modulated X-ray counterparts over the nominal duration of the LISA mission.

Keywords: Accretion, Supermassive black holes, X-ray astronomy, Relativistic binary stars, Astronomy data analysis, Gravitational wave astronomy, Astronomical simulations, Relativistic disks
The Matter Beyond the Ring: The Recent Evolution of SN 1987A Observed by the Hubble Space Telescope. The nearby SN 1987A offers a spatially resolved view of the evolution of a young supernova (SN) remnant. Here we present recent Hubble Space Telescope imaging observations of SN 1987A, which we use to study the evolution of the ejecta, the circumstellar equatorial ring (ER), and the increasing emission from material outside the ER. We find that the inner ejecta have been brightening at a gradually slower rate and that the western side has been brighter than the eastern side since ∼7000 days. This is expected given that the X-rays from the ER are most likely powering the ejecta emission. At the same time, the optical emission from the ER continues to fade linearly with time. The ER is expanding at 680 ± 50 km s-1, which reflects the typical velocity of transmitted shocks in the dense hot spots. A dozen spots and a rim of diffuse Hα emission have appeared outside the ER since 9500 days. The new spots are more than an order of magnitude fainter than the spots in the ER and also fade faster. We show that the spots and diffuse emission outside the ER may be explained by fast ejecta interacting with high-latitude material that extends from the ER toward the outer rings. Further observations of this emission will make it possible to determine the detailed geometry of the high-latitude material and provide insight into the formation of the rings and the mass-loss history of the progenitor.

Keywords: Ejecta, Core-collapse supernovae, Supernova remnants, Circumstellar matter, Shocks