Sazuna/UAT_keywords huggingface dataset:
Probing the Dipole of the Diffuse Gamma-Ray Background. We measured the dipole of the diffuse γ-ray background (DGB), identifying a highly significant time-independent signal coincidental with that of the Pierre Auger UHECR. The DGB dipole is determined from flux maps in narrow energy bands constructed from 13 yr of observations by the Large Area Telescope (LAT) of the Fermi satellite. The γ-ray maps were clipped iteratively of sources and foregrounds similar to that done for the cosmic infrared background. The clipped narrow energy band maps were then assembled into one broad energy map out to the given energy starting at E = 2.74 GeV, where the LAT beam falls below the sky's pixel resolution. Next we consider cuts in Galactic latitude and longitude to probe residual foreground contaminations from the Galactic plane and center. In the broad energy range 2.74 &lt; E ≤ 115.5 GeV, the measured dipoles are stable with respect to the various Galactic cuts, consistent with an extragalactic origin. The γ-ray sky's dipole/monopole ratio is much greater than that expected from the DGB clustering component and the Compton-Getting effect origin with reasonable velocities. At ≃(6.5-7)% it is similar to the Pierre Auger UHECRs with E UHECR ≥ 8 EeV, pointing to a common origin of the two dipoles. However, the DGB flux associated with the found DGB dipole reaches parity with that of the UHECR around E UHECR ≤ 1 EeV, perhaps arguing for a non-cascading mechanism if the DGB dipole were to come from the higher-energy UHECRs. The signal-to-noise ratio of the DGB dipole is largest in the 5-30 GeV range, possibly suggesting the γ-photons at these energies are the ones related to cosmic rays.

Keywords: Ultra-high-energy cosmic radiation, High-energy cosmic radiation
The Peak of the Fallback Rate from Tidal Disruption Events: Dependence on Stellar Type. A star completely destroyed in a tidal disruption event (TDE) ignites a luminous flare that is powered by the fallback of tidally stripped debris to a supermassive black hole (SMBH) of mass M •. We analyze two estimates for the peak fallback rate in a TDE, one being the "frozen-in" model, which predicts a strong dependence of the time to peak fallback rate, t peak, on both stellar mass and age, with 15 days ≲ t peak ≲ 10 yr for main sequence stars with masses 0.2 ≤ M ⋆/M ⊙ ≤ 5 and M • = 106 M ⊙. The second estimate, which postulates that the star is completely destroyed when tides dominate the maximum stellar self-gravity, predicts that t peak is very weakly dependent on stellar type, with ${t}_{\mathrm{peak}}=\left(23.2\pm 4.0\,{\rm{days}}\right){\left({M}_{\bullet }/{10}^{6}{M}_{\odot }\right)}^{1/2}$ for 0.2 ≤ M ⋆/M ⊙ ≤ 5, while ${t}_{\mathrm{peak}}\,=\left(29.8\pm 3.6\,{\rm{days}}\right){\left({M}_{\bullet }/{10}^{6}{M}_{\odot }\right)}^{1/2}$ for a Kroupa initial mass function truncated at 1.5M ⊙. This second estimate also agrees closely with hydrodynamical simulations, while the frozen-in model is discrepant by orders of magnitude. We conclude that (1) the time to peak luminosity in complete TDEs is almost exclusively determined by SMBH mass, and (2) massive-star TDEs power the largest accretion luminosities. Consequently, (a) decades-long extra-galactic outbursts cannot be powered by complete TDEs, including massive-star disruptions, and (b) the most highly super-Eddington TDEs are powered by the complete disruption of massive stars, which-if responsible for producing jetted TDEs-would explain the rarity of jetted TDEs and their preference for young and star-forming host galaxies.

Keywords: Black hole physics, Supermassive black holes, Hydrodynamics, Tidal disruption, Astrophysical black holes
A Near-half-century Simulation of the Solar Corona. We present an overview of results from a magnetofrictional model of the entire solar corona over a period of 47 yr. The simulation self-consistently reproduces decades of solar phenomena, varying in duration between rapid eruptions and the long-term solar cycles, from an input of observed active regions emerging at the photosphere. We have developed a geometric approach to use magnetic helicity to identify and localize the frequent eruptions that occur in the simulation. This method allows us to match our results to extreme-ultraviolet observations of transient events. We have analyzed the evolving magnetic topology by computing the squashing factor and segmenting the corona into discrete magnetic domains bounded by the Separatrix-Web. The simulations show a more dynamic structure to the Separatrix-Web than is predicted by potential field models, which may explain solar wind observations.

Keywords: Solar cycle, Solar prominences, Solar physics, Solar coronal mass ejections, Solar corona
An Inward-moving and Asymmetric Velocity Wave Detected in LAMOST-Gaia. The phase space, as coded by kinematic parameters and chemical abundances, is crucial for understanding the formation of the Galactic disk. Using red giant stars from the Galactic thin disk with [Fe/H] &gt; - 0.8 and low-α ratios identified in LAMOST-Gaia, we detect numerous ridges and undulations in the R-V  ϕ  diagram coded by median V  R . Strikingly, the slope of these features changes from -22 km s-1 kpc-1 to -8 km s-1 kpc-1 at R ~ 11.5 kpc. Accordingly, the R g-V  ϕ  plane, also coded by median V  R , reveals wave-like structures that propagate outwards in the inner disk but reverse direction and move inwards beyond R g = 11.5 kpc. The most prominent feature is the G1 group, distinguished by its wider spread and negative median V  R  at R g ~ 15 kpc, contrasting with the narrower G0 group that exhibits positive median V  R  at R g &lt; 11.5 kpc. Furthermore, the [C/N] versus [Fe/H] relationship for the G1 group mirrors the opposite trend compared to the G0 group. Since [C/N] serves as a proxy for age, this contrasting behavior suggests an inverse age-metallicity relation for the G1 group. Comparison with the Sagittarius dwarf galaxy reveals that the G1 group possesses distinct [Mg/Fe] and [Al/Fe] ratios, yet its [C/N] versus [Fe/H] pattern is similar to that of the Sgr dwarf galaxy. Based on these observations, we proposed that the inward-moving and asymmetric velocity wave G1 might be linked to the minor merge of the Sagittarius galaxy.

Keywords: Stellar kinematics, Milky Way disk, Milky Way dynamics, Milky Way evolution
Tilted Circumbinary Planetary Systems as Efficient Progenitors of Free-floating Planets. The dominant mechanism for generating free-floating planets has so far remained elusive. One suggested mechanism is that planets are ejected from planetary systems due to planet-planet interactions. Instability around a single star requires a very compactly spaced planetary system. We find that around binary star systems instability can occur even with widely separated planets that are on tilted orbits relative to the binary orbit due to combined effects of planet-binary and planet-planet interactions, especially if the binary is on an eccentric orbit. We investigate the orbital stability of planetary systems with various planet masses and architectures. We find that the stability of the system depends upon the mass of the highest-mass planet. The order of the planets in the system does not significantly affect stability, but, generally, the most massive planet remains stable and the lower-mass planets are ejected. The minimum planet mass required to trigger the instability is about that of Neptune for a circular orbit binary and a super-Earth of about 10 Earth masses for highly eccentric binaries. Hence, we suggest that planet formation around inclined binaries can be an efficient formation mechanism for free-floating planets. While most observed free-floating planets are giant planets, we predict that there should be more low-mass free-floating planets that are as of yet unobserved than higher-mass planets.

Keywords: Exoplanet dynamics, Computational astronomy, Binary stars, Exoplanet systems, Three-body problem, N-body simulations
Early TeV Photons of GRB 221009A Were Absorbed by the Prompt MeV Photons. GRB 221009A produced the highest flux of gigaelectronvolt-teraelectronvolt (GeV-TeV) photons ever observed, allowing the construction of a detailed TeV light curve. We focus on explaining the noticeable dip in the light curve around 2-5 s after the onset of TeV emission. We propose that megaelectronvolt (MeV) photons from the prompt emission annihilate with TeV photons from the afterglow, producing an optical depth that obscures the TeV emission during this period. We develop a two-zone model accounting for the angles of MeV photons that can successfully reproduce the time delay between MeV and TeV photons, the peak optical depth over 3, and the rapid decline in optical depth. Our model supports MeV-TeV annihilation as the cause of the dip and provides reasonable constraints on the emission region parameters.

Keywords: Gamma-ray bursts, Relativistic jets, High energy astrophysics
Subphotospheric Emission from Short Gamma-Ray Bursts: Protons Mold the Multimessenger Signals. The origin of the observed Band-like photon spectrum in short gamma-ray bursts (sGRBs) is a long-standing mystery. We carry out the first general relativistic magnetohydrodynamic simulation of an sGRB jet with initial magnetization σ 0 = 150 in dynamical ejecta from a binary merger. From this simulation, we identify regions along the jet of efficient energy dissipation due to magnetic reconnection and collisionless subshocks. Taking into account electron and proton acceleration processes, we solve for the first time the coupled transport equations for photons, electrons, protons, neutrinos, and intermediate particle species up to close to the photosphere (i.e., up to 1 × 1012 cm), accounting for all relevant radiative and cooling processes. We find that the subphotospheric multimessenger signals carry strong signatures of the hadronic interactions and their resulting particle cascades. Importantly, the spectral energy distribution of photons is significantly distorted with respect to the Wien one, commonly assumed below the photosphere. Our findings suggest that the bulk of the nonthermal photon spectrum observed in sGRBs can stem from hadronic processes occurring below the photosphere and previously neglected, with an accompanying energy flux of neutrinos peaking in the GeV energy range.

Keywords: Gamma-ray bursts, Transient sources, Particle astrophysics
X-Ray Polarized View of the Accretion Geometry in the X-Ray Binary Circinus X-1. Cir X-1 is a neutron star X-ray binary characterized by strong variations in flux during its eccentric ~16.6 day orbit. There are also strong variations in the spectral state, and it has historically shown both atoll and Z state properties. We observed the source with the Imaging X-ray Polarimetry Explorer during two orbital segments, 6 days apart, for a total of 263 ks. We find an X-ray polarization degree in these segments of 1.6% ± 0.3% and 1.4% ± 0.3% at polarization angles of 37° ± 5° and -12° ± 7°, respectively. Thus, we observed a rotation of the polarization angle by 49° ± 8° along the orbit. Because variations of accretion flow, and then of the hardness ratio, are expected during the orbit, we also studied the polarization binned in hardness ratio and found the polarization angle differing by 67° ± 11° between the lowest and highest values of the hardness ratio. We discuss possible interpretations of this result that could indicate a possible misalignment between the symmetry axes of the accretion disk and the Comptonizing region caused by the misalignment of the neutron star's angular momentum with respect to the orbital one.

Keywords: X-ray astronomy, X-ray binary stars, Polarimetry, X-ray sources
Probing Shocked Ejecta in SN 1987A: A Novel Diagnostic Approach Using XRISM-Resolve. Supernova (SN) 1987A is one of the best candidates to exploit the capabilities of the freshly launched XRISM satellite. This celestial object offers the unique opportunity to study the evolution of an SN into a young supernova remnant. To date, the X-ray emission has been dominated by the shocked circumstellar medium, with no shocked ejecta firmly detected. However, recent studies provide compelling evidence that in the forthcoming years, the X-ray emission from SN 1987A will increasingly stem from the ejecta. Our aim is to assess the proficiency of the XRISM-Resolve high-resolution spectrometer in pinpointing signatures of the shocked ejecta in SN 1987A. Taking advantage of a self-consistent state-of-the-art magneto-hydrodynamic simulation that describes the evolution from SN 1987A to its remnant, we synthesized the XRISM-Resolve spectrum of SN 1987A, as it would be collected in the allocated observation during the performance verification phase, which is foreseen for 2024. Our predictions clearly show the leading role of shocked ejecta in shaping the profile of the emission lines. The Doppler broadening associated with the bulk motion along the line of sight of the rapidly expanding ejecta is shown to increase the line widths well above the values observed so far. The quantitative comparison between our synthetic spectra and the XRISM spectra will enable us to establish a strong connection between the broadened line emission and the freshly shocked ejecta. This, in turn, will allow us to retrieve the ejecta dynamics and chemical composition from the X-ray emission.

Keywords: Supernova remnants, High energy astrophysics, Interstellar medium, Plasma astrophysics
Baryon-induced Collapse of Dark Matter Cores into Supermassive Black Holes. Nonlinear structure formation for fermionic dark matter particles leads to dark matter density profiles with a degenerate compact core surrounded by a diluted halo. For a given fermion mass, the core has a critical mass that collapses into a supermassive black hole (SMBH). Galactic dynamics constraints suggest a ~100 keV/c 2 fermion, which leads to ~107 M ⊙ critical core mass. Here, we show that baryonic (ordinary) matter accretion drives an initially stable dark matter core to SMBH formation and determines the accreted mass threshold that induces it. Baryonic gas density ρ  b  and velocity v  b  inferred from cosmological hydrosimulations and observations produce sub-Eddington accretion rates triggering the baryon-induced collapse in less than 1 Gyr. This process produces active galactic nuclei in galaxy mergers and the high-redshift Universe. For TXS 2116-077, merging with a nearby galaxy, the observed 3 × 107 M ⊙ SMBH, for ${Q}_{b}={\rho }_{b}/{v}_{b}^{3}=0.125{M}_{\odot }/{(100\,\mathrm{km}\,{{\rm{s}}}^{-1}\,\mathrm{pc})}^{3}$ , forms in ≈0.6 Gyr, consistent with the 0.5-2 Gyr merger timescale and younger jet. For the farthest central SMBH detected by the Chandra X-ray satellite in the z = 10.3 UHZ1 galaxy observed by the James Webb Space Telescope (JWST), the mechanism leads to a 4 × 107 M ⊙ SMBH in 87-187 Myr, starting the accretion at z = 12-15. The baryon-induced collapse can also explain the ≈107-108 M ⊙ SMBHs revealed by JWST at z ≈ 4-6. After its formation, the SMBH can grow to a few 109 M ⊙ in timescales shorter than 1 Gyr via sub-Eddington baryonic mass accretion.

Keywords: Supermassive black holes, Galaxy dark matter halos, Active galactic nuclei, Gravitational collapse, High-redshift galaxies, Dark matter
Discovery of a Large-scale H I Plume in the NGC 7194 Group. We present the discovery of a new H I structure in the NGC 7194 group from the observations using the Karl G. Jansky Very Large Array. NGC 7194 group is a nearby (z ~ 0.027) small galaxy group with five quiescent members. The observations reveal a 200 kpc long H I plume that spans the entire group with a total mass of M H I = 3.4 × 1010 M ⊙. The line-of-sight velocity of the H I gas gradually increases from south (7200 km s-1) to north (8200 km s-1), and the local velocity dispersion is up to 70 km s-1. The structure is not spatially coincident with any member galaxies but it shows close associations with a number of blue star-forming knots. Intragroup H I gas is not rare, but this particular structure is still one of the unusual cases in the sense that it does not show any clear connection with sizable galaxies in the group. We discuss the potential origins of this large-scale H I gas in the NGC 7194 group and its relation with the intergalactic star-forming knots. We propose that this H I feature could have originated from tidal interactions among group members or the infall of a late-type galaxy into the group. Alternatively, it might be leftover gas from flyby intruders.

Keywords: Star forming regions, Neutral hydrogen clouds, Galaxy groups
X-Ray Polarization of the Eastern Lobe of SS 433. How astrophysical systems translate the kinetic energy of bulk motion into the acceleration of particles to very high energies is a pressing question. SS 433 is a microquasar that emits TeV γ-rays indicating the presence of high-energy particles. A region of hard X-ray emission in the eastern lobe of SS 433 was recently identified as an acceleration site. We observed this region with the Imaging X-ray Polarimetry Explorer and measured a polarization degree in the range 38%-77%. The high polarization degree indicates the magnetic field has a well-ordered component if the X-rays are due to synchrotron emission. The polarization angle is in the range -12° to +10° (east of north), which indicates that the magnetic field is parallel to the jet. Magnetic fields parallel to the bulk flow have also been found in supernova remnants and the jets of powerful radio galaxies. This may be caused by interaction of the flow with the ambient medium.

Keywords: Jets, High energy astrophysics, High mass x-ray binary stars, Supernova remnants, Astrophysical black holes
On the Source Contribution to the Galactic Diffuse Gamma Rays above 398 TeV Detected by the Tibet ASγ Experiment. Potential contribution from gamma-ray sources to the Galactic diffuse gamma rays observed above 100 TeV (sub-PeV energy range) by the Tibet ASγ experiment is an important key to interpreting recent multimessenger observations. This paper reveals a surprising fact: none of the 23 Tibet ASγ diffuse gamma-ray events above 398 TeV within the Galactic latitudinal range of ∣b∣ &lt; 10° come from the 43 sub-PeV gamma-ray sources reported in the 1LHAASO catalog, which proves that these sources are not the origins of the Tibet ASγ diffuse gamma-ray events. No positional overlap between the Tibet ASγ diffuse gamma-ray events and the sub-PeV LHAASO sources currently supports the diffusive nature of the Tibet ASγ diffuse gamma-ray events, although their potential origin in the gamma-ray sources yet unresolved in the sub-PeV energy range cannot be ruled out.

Keywords: Galactic cosmic rays, Gamma-ray astronomy
TeV Neutrinos and Hard X-Rays from Relativistic Reconnection in the Corona of NGC 1068. The recent discovery of astrophysical neutrinos from the Seyfert galaxy NGC 1068 suggests the presence of nonthermal protons within a compact "coronal" region close to the central black hole. The acceleration mechanism of these nonthermal protons remains elusive. We show that a large-scale magnetic reconnection layer, of the order of a few gravitational radii, may provide such a mechanism. In such a scenario, rough energy equipartition between magnetic fields, X-ray photons, and nonthermal protons is established in the reconnection region. Motivated by recent 3D particle-in-cell simulations of relativistic reconnection, we assume that the spectrum of accelerated protons is a broken power law, with the break energy being constrained by energy conservation (i.e., the energy density of accelerated protons is at most comparable to the magnetic energy density). The proton spectrum is ${{dn}}_{p}/{{dE}}_{p}\propto {E}_{p}^{-1}$ below the break and ${{dn}}_{p}/{{dE}}_{p}\propto {E}_{p}^{-s}$ above the break, with IceCube neutrino observations suggesting s ≃ 3. Protons above the break lose most of their energy within the reconnection layer via photohadronic collisions with the coronal X-rays, producing a neutrino signal in good agreement with the recent observations. Gamma rays injected in photohadronic collisions are cascaded to lower energies, sustaining the population of electron-positron pairs that makes the corona moderately Compton thick.

Keywords: High energy astrophysics, Neutrino astronomy, Plasma astrophysics, Non-thermal radiation sources, Active galactic nuclei
Snapshots of an Evolving Solar Nebula Recorded in Nucleosynthetic Sr and Ba Signatures of Early Condensates. The discovery of extreme strontium isotope anomalies (μ 84Sr) in refractory leachates from Allende fine-grained calcium-aluminum-rich inclusions (CAIs) is at odds with long-standing predictions regarding the homogenization of presolar components in the CAI-forming region. Elucidating the stellar source(s) of these phases and the mechanisms for their preservation holds potential significance in understanding the dynamics and evolution of the protoplanetary disk. Here we present barium isotope data for the same set of leachates previously analyzed for μ 84Sr. Our results show fairly homogeneous Ba isotope anomalies across leachates (~100-200 ppm variability), in contrast to the observed μ 84Sr variations (up to ~8%). Secondary phases extracted in earlier leaching steps (L1 and L3) reveal trends in μ 137Ba and μ 138Ba akin to that of mainstream SiC and a second nucleosynthetic component. We show that SiC X grains from Type II supernovae are good end-member candidates for explaining the intra-leachate spread in L1 and L3 μ 13x Ba. Notably, neither s-variability nor X-variability appears to contribute to trends in the barium isotope anomalies of the most refractory components (L4 and L5). We propose that the contrast in isotope anomaly systematics between the labile and refractory leachates could reflect a shift in the nucleosynthetic signatures of reservoirs sampled by these components. These observations are consistent with extreme 84Sr p-excesses manifesting only in L4 and L5 leachates. Finally, the decoupled Sr and Ba isotope anomalies point to a nucleosynthetic source that significantly overproduces strontium relative to barium, such as electron-capture supernovae or the collapse of rotating massive stars.

Keywords: Meteorites, Cosmochemistry, Chondrites, Solar system evolution
Diurnal Ejection of Boulder Clusters on Comet 67P Lasting beyond 3 au. Ejection of large boulder-like debris is a vigorous form of cometary activity that is unlikely induced by water ice out-gassing alone but rather associated with the sublimation of super-volatile ices. Though perceived on several comets, the actual pattern and mechanism of such activity are still unclear. Here we report on a specialized observation of ejections of decimeter- to meter-sized boulders on comet 67P/Churyumov-Gerasimenko outbound between 2.5 and 3.3 au from the Sun. With a common source region, these events recurred in local morning. The boulders of elongated shapes were ejected in clusters at low inclinations comparable to the solar elevation below 40° at the time. We show that these chunks could be propelled by the surrounding asymmetric gas field that produced a distinct lateral acceleration. Possibly both water and carbon dioxide have contributed to their mobilization, while the season and local topography are among deciding factors. The mechanisms for sustaining regular activity of comets at large heliocentric distances are likely more diverse and intricate than previously thought.

Keywords: Comet surfaces, Comets, Comet volatiles , Coma dust