Sazuna/UAT_keywords huggingface dataset:
Resolving Decades of Periodic Spirals from the Wolf-Rayet Dust Factory WR 112. WR 112 is a dust-forming carbon-rich Wolf-Rayet (WC) binary with a dusty circumstellar nebula that exhibits a complex asymmetric morphology, which traces the orbital motion and dust formation in the colliding winds of the central binary. Unraveling the complicated circumstellar dust emission around WR 112 therefore provides an opportunity to understand the dust formation process in colliding-wind WC binaries. In this work, we present a multi-epoch analysis of the circumstellar dust around WR 112 using seven high spatial resolution (FWHM ∼ 0"3-0"4) N-band (λ ∼ 12 μm) imaging observations spanning almost 20 yr and that includes images obtained from Subaru/COMICS in 2019 October. In contrast to previous interpretations of a face-on spiral morphology, we observe clear evidence of proper motion of the circumstellar dust around WR 112 consistent with a nearly edge-on spiral with a θs = 55° half-opening angle and a ∼20 yr period. The revised near edge-on geometry of WR 112 reconciles previous observations of highly variable nonthermal radio emission that was inconsistent with a face-on geometry. We estimate a revised distance to WR 112 of $d={3.39}_{-0.84}^{+0.89}$ kpc based on the observed dust expansion rate and a spectroscopically derived WC terminal wind velocity of ${v}_{\infty }=1230\pm 260$ km s-1. With the newly derived WR 112 parameters, we fit optically thin dust spectral energy distribution models and determine a dust production rate of ${\dot{M}}_{{\rm{d}}}={2.7}_{-1.3}^{+1.0}\times {10}^{-6}$ M☉ yr-1, which demonstrates that WR 112 is one of the most prolific dust-making WC systems known.

Keywords: WC stars, Dust nebulae, Binary stars, Dust shells, Circumstellar dust
Cosmic Distributions of Stellar Tidal Disruptions by Massive Black Holes at Galactic Centers. Stars can be consumed (either tidally disrupted or swallowed whole) by massive black holes (MBHs) at galactic centers when they move into the vicinity of the MBHs. In this study, we investigate the rates of stellar consumption by central MBHs and their cosmic distributions, including the effects of triaxial galaxy shapes in enhancing the reservoir of low-angular-momentum stars and incorporating realistic galaxy distributions. We find that the enhancement in the stellar consumption rates due to triaxial galaxy shapes can be significant, by a factor of ∼3 for MBH mass ${M}_{\mathrm{BH}}\sim {10}^{5}$ - ${10}^{6}\,{M}_{\odot }$ and up to more than one order of magnitude for ${M}_{\mathrm{BH}}\gtrsim {10}^{8}\,{M}_{\odot }$ . Only for ${M}_{\mathrm{BH}}\lesssim {10}^{7}\,{M}_{\odot }$ are the stellar consumption rates significantly higher in galaxies with steeper inner surface brightness profiles. The average (per galaxy) stellar consumption rates correlate with central MBH masses positively for ${M}_{\mathrm{BH}}\gtrsim {10}^{7}\,{M}_{\odot }$ and negatively for ${M}_{\mathrm{BH}}\lesssim {10}^{7}\,{M}_{\odot }$ . The volumetric stellar tidal disruption rates are $\sim 3\times {10}^{-5}\,{\mathrm{yr}}^{-1}\,{\mathrm{Mpc}}^{-3}$ for MBHs in the mass range 105- ${10}^{8}\,{M}_{\odot }$ at z = 0; and the volumetric stellar consumption rates by MBHs with higher masses are $\sim {10}^{-6}\,{\mathrm{yr}}^{-1}\,{\mathrm{Mpc}}^{-3}$ , which can be the stellar tidal disruption rate if the high-mass BHs are extremely spinning Kerr BHs or the rate of being swallowed if those BHs are Schwarzschild ones. The volumetric stellar consumption rates decrease with increasing redshift, and the decrease is relatively mild for ${M}_{\mathrm{BH}}\sim {10}^{5}$ - ${10}^{7}\,{M}_{\odot }$ and stronger for higher ${M}_{\mathrm{BH}}$ . Most of the stellar tidal disruption events (TDEs) at z = 0 occur in galaxies with mass ${M}_{\mathrm{gal}}\lesssim {10}^{11}\,{M}_{\odot }$ , and about 1%-2% of the TDEs can occur in high-mass galaxies with ${M}_{\mathrm{gal}}\gtrsim {10}^{11}\,{M}_{\odot }$ .

Keywords: Astrodynamics, Supermassive black holes, High energy astrophysics, Tidal disruption, Galaxy dynamics, Transient sources, Gravitational wave astronomy, Time domain astronomy
Dynamics of Late-stage Reconnection in the 2017 September 10 Solar Flare. In this multi-instrument paper, we search for evidence of sustained magnetic reconnection far beyond the impulsive phase of the X8.2-class solar flare on 2017 September 10. Using Hinode/EIS, CoMP, SDO/AIA, K-Cor, Hinode/XRT, RHESSI, and IRIS, we study the late-stage evolution of the flare dynamics and topology, comparing signatures of reconnection with those expected from the standard solar flare model. Examining previously unpublished EIS data, we present the evolution of nonthermal velocity and temperature within the famous plasma sheet structure, for the first four hours of the flare's duration. On even longer timescales, we use differential emission measures and polarization data to study the longevity of the flare's plasma sheet and cusp structure, discovering that the plasma sheet is still visible in observations of CoMP linear polarization on 2017 September 11, long after its last appearance in EUV. We deduce that magnetic reconnection of some form is still ongoing at this time—27 hr after flare onset.

Keywords: Spectropolarimetry, Solar flares, Solar magnetic reconnection, Solar flare spectra, Spectroscopy
How Dense of a Circumstellar Medium Is Sufficient to Choke a Jet?. The progenitor stars of stripped-envelope high-velocity supernovae (Ic-BL SNe) can explode inside a dense circumstellar medium (CSM) that extends out to many times the progenitor radius. This complicates the question of whether all Ic-BL SNe harbor a jet, which can tunnel through the star and be viewed on-axis as a long-duration gamma-ray burst (GRB). More specifically, a sufficiently dense CSM might "choke" the jet, redistributing its energy quasi-spherically. In this study, we numerically calculate the CSM density necessary for jet choking. For typical GRBs, we determine the jet is not choked in the CSM unless $\rho {r}^{2}\gt 4\times {10}^{19}\,{\rm{g}}\,{\mathrm{cm}}^{-1};$ this requires several solar masses of CSM to be situated within 1013 cm of the progenitor, a much higher density than any CSM observed. We conclude that typical GRB jets are not choked in the CSM. However, in many cases the CSM has sufficient mass to decelerate the jet to a modest Lorentz factor (Γ ∼ 10), which should lead to a long coasting phase for the jet, observable as a long plateau (potentially up to a few days) in the afterglow light curve. For extreme cases of low-energy GRBs in a high-mass CSM, the jet will decelerate to nonrelativistic velocities, causing it to spread modestly to a larger opening angle (θj ≈ 20°) before breaking out of the CSM. Even in these extreme examples, the jet does not have time to redistribute its energy quasi-spherically in the CSM before breakout.

Keywords: Gamma-ray bursts, Relativistic jets, Relativistic fluid dynamics, Circumstellar matter, Supernovae
Study of Eclipses for Redback Pulsar J1227-4853. We present a multifrequency study of eclipse properties of a transitional redback millisecond pulsar J1227-4853 discovered in 2014 with the GMRT. Emission from this pulsar is eclipsed at 607 MHz for about 37% of its orbit around the superior conjunction. We observe eclipse ingress and egress transitions that last for 12% and 15% of its orbit, respectively, resulting in only 36% of the orbit being unaffected by eclipsing material. We report an excess dispersion measure (DM) at eclipse boundaries of 0.079(3) pc cm-3, and the corresponding electron column density (Ne) is 24.4(8) × 1016 cm-2. Simultaneous timing and imaging studies suggest that the eclipses in J1227-4853 are not caused by temporal smearing due to excess dispersion and scattering but could be caused by removal of pulsar flux due to cyclotron absorption of the pulsed signal by intra-binary material constraining the companion's magnetic field. Additionally, near the inferior conjunction at orbital phases 0.71 and 0.82 the pulsed emission is significantly delayed, which is associated with a fading of the pulsed and continuum flux densities. At orbital phase ∼0.82, we measure a change in DM of 0.035(3) pc cm-3 and Ne of 10.8(8) × 1016 cm-2 associated with a dimming of up to ∼30% of the peak flux density. Such flux fading around a fixed orbital phase is not reported for other eclipsing binaries. Moreover, this event around the inferior conjunction could be caused by absorption of the pulsed signal by fragmented blobs of plasma generated from mass loss through the L2 Lagrangian point.

Keywords: Accretion, Eclipses, Binary pulsars, Millisecond pulsars
A Binary Star in the Superbubble N160 in the Large Magellanic Cloud. We have made a spectroscopic investigation of the nature of 053949.17-693747.4, a blue star with mid-infrared excess, projected within a superbubble in the H II complex N160 in the Large Magellanic Cloud (LMC). Analyses of photometric and spectrophotometric data of this star indicate that it is an O7 ± 1 V in the LMC. The radial velocity of this star from a 2010 spectrum shows an offset of ∼150 km s-1 from that of the background interstellar medium (ISM), while the spectra taken in 2020 show stellar velocity similar to the ISM velocity. The velocity variations indicate that 053949.17-693747.4 must be a binary system. The lack of spectroscopic features from a stellar companion and the large radial velocity variations of the primary O7 star imply that the companion is most likely an early-type B star. Hubble Space Telescope Hα and [O III] images of 053949.17-693747.4 show a small nebula around the star with the southern rim resembling a blow-shock-like structure. While the physical nature as a bow shock cannot be robustly established, this small nebula is likely the cause of 053949.17-693747.4's mid-infrared excess. Spectroscopic monitoring over an entire binary period is needed to establish the period and systemic velocity to determine the properties of the binary companion and whether this binary system is a runaway.

Keywords: Interstellar medium, Massive stars, Large Magellanic Cloud
Observations of a Radial Density Gradient in the Very Local Interstellar Medium by Voyager 2. Beginning on 2020 June 19, at a heliocentric distance of 124.2 au, the Voyager 2 Plasma Wave Science instrument began to observe radio emissions followed by electron plasma oscillations in its 3.11 kHz spectrum analyzer channel. Plasma oscillations at this frequency imply an electron density in the range of 0.12 cm-3 ± 15%, although some response in the 1.78 kHz channel near the peak of the plasma oscillations suggest a density of 0.087 cm-3 ± 8%. Shortly after Voyager 2 crossed the heliopause, in late 2019 January, the Voyager 2 Plasma Wave Science instrument detected plasma oscillations in its 1.78 kHz channel giving an electron density of 0.039 cm-3 ± 15%. While the Voyager spectrum analyzer affords relatively poor spectral resolution, the recent observation of plasma oscillations in the 3.11 kHz channel provides definitive evidence of a radial density gradient in the very local interstellar medium (VLISM), just beyond the heliopause with a magnitude similar to that observed by Voyager 1 obtained with higher spectral resolution measurements. Plasma oscillations observed by Voyager 1 range from frequencies as low as 2.1 kHz increasing to about 3.2 kHz, giving an electron density profile that increases from about 0.055 to about 0.13 cm-3 over a distance spanning some 20 au. Given the 67° difference in heliographic latitude and 43° difference in longitude between the two Voyagers, the new Voyager 2 observations imply that the density gradient is a large-scale feature of the VLISM in the general direction of the heliospheric nose.

Keywords: Interstellar medium, Interstellar plasma
Salt, Hot Water, and Silicon Compounds Tracing Massive Twin Disks. We report results of $0\buildrel{\prime\prime}\over{.} 05$-resolution observations toward the O-type proto-binary system IRAS 16547-4247 with the Atacama Large Millimeter/submillimeter Array. We present dynamical and chemical structures of the circumbinary disk, circumstellar disks, outflows, and jets, illustrated by multi-wavelength continuum and various molecular lines. In particular, we detect sodium chloride, silicon compounds, and vibrationally excited water lines as probes of the individual protostellar disks at a scale of 100 au. These are complementary to typical hot-core molecules tracing the circumbinary structures on a 1000 au scale. The H2O line tracing inner disks has an upper-state energy of ${E}_{u}/k\gt 3000\,{\rm{K}}$, indicating a high temperature of the disks. On the other hand, despite the detected transitions of NaCl, SiO, and SiS not necessarily having high upper-state energies, they are enhanced only in the vicinity of the protostars. We posit that these molecules are the products of dust destruction, which only happens in the inner disks. This is the second detection of alkali metal halide in protostellar systems after the case of the disk of Orion Source I, and also one of few massive protostellar disks associated with high-energy transition water and silicon compounds. These new results suggest that these "hot-disk" lines may be common in innermost disks around massive protostars, and have great potential for future research of massive star formation. We also tentatively find that the twin disks are counter-rotating, which might give a hint of the origin of the massive proto-binary system IRAS 16547-4247.

Keywords: Binary stars, Radio jets, Massive stars, Stellar jets, Astrochemistry, Young stellar objects, Star formation, Circumstellar disks, Protostars
A Radio Pinwheel Emanating from WR 147. Wolf-Rayet (WR) stars are evolved massive stars, presumably on their way to becoming supernovae. They are characterized by high luminosities and fast and dense stellar winds. We have detected signs of a radio continuum pinwheel associated with WR 147, a nitrogen-rich WR star with spectral subtype WN8. These structures are known to exist around a handful of late-type carbon-rich WR stars with massive companions where dust has formed in the zone where the two winds collide and produced a plume of dense gas and dust that is carried out with the WR wind. As the binary system rotates, an Archimedean spiral detectable in the infrared is formed. The resulting pinwheel contains information on wind speeds, wind-momentum ratio, and orbital parameters. However, WR 147 is a WN star and the formation of dust is unlikely, so a different emission mechanism must be at work. Our analysis of the data suggests that in this case the emission is dominantly of a nonthermal nature (synchrotron), although we cannot exclude the possibility that some clumps could be brighter in free-free emission. It is possible that the pinwheels associated with WN stars will be detectable only as nonthermal emitters at radio wavelengths. From the characteristics of the pinwheel we estimate a period of 1.7 yr for the binary system (the WN8 star and a companion yet undetected directly) that is responsible for the pinwheel.

Keywords: Wolf-Rayet stars, Stellar winds, Binary stars
Different Fates of Young Star Clusters after Gas Expulsion. We identify structures of the young star cluster NGC 2232 in the solar neighborhood (323.0 pc) and a newly discovered star cluster, LP 2439 (289.1 pc). Member candidates are identified using the Gaia DR2 sky position, parallax, and proper-motion data by an unsupervised machine-learning method, STARGO. Member contamination from the Galactic disk is further removed using the color-magnitude diagram. The four identified groups (NGC 2232, LP 2439, and two filamentary structures) of stars are coeval with an age of 25 Myr and were likely formed in the same giant molecular cloud. We correct the distance asymmetry from the parallax error with a Bayesian method. The 3D morphology shows the two spherical distributions of clusters NGC 2232 and LP 2439. Two filamentary structures are spatially and kinematically connected to NGC 2232. Both NGC 2232 and LP 2439 are expanding. The expansion is more significant in LP 2439, generating a loose spatial distribution with shallow volume number and mass density profiles. The expansion is suggested to be mainly driven by gas expulsion. With 73% of the cluster mass bound, NGC 2232 is currently experiencing a process of revirialization, However, LP 2439, with 52% of the cluster mass unbound, may fully dissolve in the near future. The different survivability traces the different dynamical states of NGC 2232 and LP 2439 prior to the onset of gas expulsion. While NGC 2232 may have been substructured and subvirial, LP 2439 may have either been virial/supervirial or experienced a much faster rate of gas removal.

Keywords: Open star clusters, Star clusters
Shock-Cloud Interaction in the Southwestern Rim of RX J1713.7-3946 Evidenced by Chandra X-Ray Observations. We report on results of Chandra X-ray observations of the southwestern part of the supernova remnant (SNR) RX J1713.7-3946. We measure proper motions of two X-ray bright blobs, named Blobs A and B, in regions presumably corresponding to the forward shock of the SNR. The measured velocities are 3800 ± 100 km s-1 and 2300 ± 200 km s-1 for Blobs A and B, respectively. Since a dense molecular clump is located close to Blob B, its slower velocity is attributed to shock deceleration as a result of a shock-cloud interaction. This result provides solid evidence that the forward shock of RX J1713.7-3946 is indeed colliding with dense gas discovered through radio observations reported in the literature. The locations and velocity differences of the two blobs lead to an estimate that the shock encountered with the dense gas ∼100 yr ago. The shock velocities, together with cutoff energies of the synchrotron X-ray spectra of the blobs, indicate that particle acceleration in these regions is close to the Bohm limit. Blob B, in particular, is almost at the limit, accelerating particles at the fastest possible rate. We discuss possible influence of the shock-cloud interaction on the efficiency of particle acceleration.

Keywords: Molecular clouds, Supernova remnants, Galactic cosmic rays, Cosmic ray sources, X-ray sources, Interstellar medium
Magnetosheath Jets and Plasmoids: Characteristics and Formation Mechanisms from Hybrid Simulations. Magnetosheath jets and plasmoids are very common phenomena downstream of Earth's quasi-parallel bow shock. As the increase of the dynamic pressure is one of the principal characteristics of magnetosheath jets, the embedded paramagnetic plasmoids have been considered as an special case of the former. Although the properties of both types of structures have been widely studied during the last 20 years, their formation mechanisms have not been examined thoroughly. In this work we perform a 2D local hybrid simulation (kinetic ions - fluid electrons) of a quasi-parallel (θBn = 15°), supercritical (MA = 7) collisionless shock in order to study these mechanisms. Specifically, we analyze the formation of one jet and one plasmoid, showing for the first time that they can be produced by different mechanisms related to the same shock. In our simulation, the magnetosheath jet is formed according to the mechanism proposed by Hietala, where at the shock ripples the upstream solar wind suffers locally less deceleration and the flow is focused in the downstream side, producing a compressed and high-velocity region that leads to an increase of dynamic pressure downstream of the shock. The formation of the plasmoid, however, follows a completely new scenario being generated by magnetic reconnection between two plasma layers with opposite B-field orientation in the region just behind the shock.

Keywords: Interplanetary medium, Space plasmas, Interplanetary shocks, Heliosphere, Plasma physics, Space weather, Planetary bow shocks, Plasma astrophysics, Shocks
Discovery of State Transition Behaviors in PSR J1124-5916. With the 12 year long observations by Fermi-LAT, we discover two pairs of spin-down state transitions of PSR J1124-5916, making it the second young pulsar detected to have such behaviors. PSR J1124-5916 shows mainly two states according to its spin-down rate evolution, the normal spin-down state and the low spin-down state. In about 80% of the observation time, the pulsar is in the normal spin-down state, in which the spin-down rate decreases linearly and gives a braking index of 1.98 ± 0.04. The two transitions to the low spin-down state are in MJD 55183-55803 and MJD 56114-56398, respectively, with fractional amplitudes both ∼0.4%. No significant difference between the γ-ray profiles of the two spin-down states is detected, which is similar to PSR B0540-69, the other young pulsar with state transition detected.

Keywords: Rotation powered pulsars, Radio pulsars
Detectability of Ultra-compact X-Ray Binaries as LISA Sources. Ultra-compact X-ray binaries (UCXBs) are low-mass X-ray binaries with ultra-short orbital periods (usually less than 1 hr) and hydrogen-poor donor stars, which are proposed to be potential Laser Interferometer Space Antenna (LISA) sources. In this work, we first employ the Modules for Experiments in Stellar Astrophysics code to examine the parameter space of the progenitors of UCXBs that LISA will detect. Our simulations indicate that the initial binaries with a neutron star and a $0.4\mbox{--}3.5\,{M}_{\odot }$ companion star, in an orbit of initial orbital period smaller than the bifurcation period, could evolve into UCXBs, some of which will emit gravitational wave signals that can be detectable by LISA. However, the initial orbital periods of the binaries that will evolve into UCXB-LISA sources in a distance of 10 kpc are located in a very narrow range, i.e., the formation of these LISA source requires an extreme fine-tuning of initial parameter. According to the characteristic strains and the derived maximum detectable distances, four sources among eight UCXBs with the observed distances are expected to be detected by LISA. Based on the parameter space given by the detailed binary evolution models and the rapid binary star evolution code, the birthrate of UCXBs appearing as LISA sources in the Galaxy is estimated to be $(2\mbox{--}2.6)\times {10}^{-6}\,{\mathrm{yr}}^{-1}$. Considering the contribution of UCXBs in globular clusters, the number of UCXB-LISA sources can reach 240-320. Although the formation condition is severe, the detectability of UCXBs by LISA is still significant because it provides an opportunity to pursue full multi-messenger investigations.

Keywords: X-ray binary stars, Compact binary stars, Gravitational wave sources, Gravitational waves, Stellar evolution
Detection of Interstellar HC<SUB>4</SUB>NC and an Investigation of Isocyanopolyyne Chemistry under TMC-1 Conditions. We report an astronomical detection of HC4NC for the first time in the interstellar medium with the Green Bank Telescope toward the TMC-1 molecular cloud with a minimum significance of 10.5σ. The total column density and excitation temperature of HC4NC are determined to be ${3.29}_{-1.20}^{+8.60}\times {10}^{11}$ cm-2 and ${6.7}_{-0.3}^{+0.3}\ {\rm{K}}$ , respectively, using Markov chain Monte Carlo analysis. In addition to HC4NC, HCCNC is distinctly detected whereas no clear detection of HC6NC is made. We propose that the dissociative recombination of the protonated cyanopolyyne, HC5NH+, and the protonated isocyanopolyyne, HC4NCH+, are the main formation mechanisms for HC4NC while its destruction is dominated by reactions with simple ions and atomic carbon. With the proposed chemical networks, the observed abundances of HC4NC and HCCNC are reproduced satisfactorily.

Keywords: Interstellar molecules, Chemical abundances, Dense interstellar clouds, Astrochemistry, Dark interstellar clouds, Interstellar medium