adsabs/SciX_UAT_keywords huggingface dataset:
VOLKS2: A Transient Search and Localization Pipeline for VLBI Observations

We present VOLKS2, the second release of "VLBI Observation for transient Localization Keen Searcher." The pipeline aims at transient search in regular VLBI observations as well as detection of single pulses from known sources in dedicated VLBI observations. The underlying method takes the idea of geodetic VLBI data processing, including fringe fitting to maximize the signal power and geodetic VLBI solving for localization. By filtering the candidate signals with multiple windows within a baseline and by cross matching with multiple baselines, RFIs are eliminated effectively. Unlike the station autospectrum-based method, RFI flagging is not required in the VOLKS2 pipeline. EVN observation (EL060) is carried out, so as to verify the pipelines detection efficiency and localization accuracy in the whole FoV. The pipeline is parallelized with MPI and further accelerated with GPU, so as to exploit the hardware resources of modern GPU clusters. We can prove that, with proper optimization, VOLKS2 could achieve comparable performance as autospectrum-based pipelines. All the code and documents are publicly available, in the hope that our pipeline is useful for radio transient studies.

Keywords: very long baseline interferometry; publicly available software; transient detection; distributed computing; gpu computing; pulsars
NICER Detection of Thermal X-Ray Pulsations from the Massive Millisecond Pulsars PSR J0740+6620 and PSR J1614-2230

We report the detection of X-ray pulsations from the rotation-powered millisecond-period pulsars PSR J0740+6620 and PSR J1614-2230, two of the most massive neutron stars known, using observations with the Neutron Star Interior Composition Explorer (NICER). We also analyze X-ray Multi-Mirror Mission (XMM-Newton) data for both pulsars to obtain their time-averaged fluxes and study their respective X-ray fields. PSR J0740+6620 exhibits a broad double-peaked profile with a separation of ~0.4 in phase. PSR J1614-2230, on the other hand, has a broad single-peak profile. We show the NICER detections of X-ray pulsations for both pulsars and also discuss the phase relationship to their radio pulsations. The XMM-Newton X-ray spectra of both pulsars shows they are thermally dominated but in the case of PSR J1614-2230 a weak nonthermal high energy tail appears to be present in the spectrum. The thermally dominated spectra along with broad modulations for both pulsars are indicative of thermal radiation from one or more small regions of the stellar surface. For PSR J0740+6620, this paper documents the data reduction performed to obtain the pulsation detection and prepare for pulse light curve modeling analysis.

Keywords: millisecond pulsars; neutron stars; rotation powered pulsars; x-ray binary stars
Anatomy of Pulsar XTE J1829-098: Ultramassive SXFT with a Dominant Nondipolar Magnetic Field, or the Third Canonical HMXB Caught at the Bottom of the Corbet Gap?

The X-ray binary pulsar XTE J1829-098 has been observed at extremely low luminosities for its spin period of 7.8448 s. Although its distance is uncertain by a factor of 4, the lowest observed X-ray fluxes may not correspond to its minimal-accretion propeller state or to nonaccreting states occurring at even lower X-ray luminosities, in which case the source has been caught at the bottom of the Corbet gap. We analyze all proposed distances D to the binary and the lowest X-ray fluxes, and we find only two physically acceptable solutions: (a) For D = 4.5 kpc (if the companion is a main-sequence B0 star), the neutron star is canonical with mass 1.41 M ⊙, radius 10.1 km, and a purely dipolar magnetic field as indicated by a cyclotron absorption line detected at 15 keV. In this case, the source has been observed at the bottom of the Corbet gap, the third high-mass X-ray binary pulsar to be caught in this state after the "twins" 4U 0115+63 and V 0332+53 found by Tsygankov et al. (b) For D = 18 kpc (if the companion is a B0.5Ib supergiant), the neutron star is ultramassive with mass 2.62 M ⊙, radius 18.7 km, and a dominant nondipolar magnetic field B mul = 1.26 TG (versus a dipolar component of only B dip = 0.43 TG). In this case, the source has been observed in its propeller state.

Keywords: magnetic fields; stellar accretion disks; x-ray binary stars
A Model-independent Method to Determine H 0 Using Time-delay Lensing, Quasars, and Type Ia Supernovae

Absolute distances from strong lensing can anchor Type Ia Supernovae (SNe Ia) at cosmological distances giving a model-independent inference of the Hubble constant (H 0). Future observations could provide strong lensing time-delay distances with source redshifts up to z ≃ 4, which are much higher than the maximum redshift of SNe Ia observed so far. In order to make full use of time-delay distances measured at higher redshifts, we use quasars as a complementary cosmic probe to measure cosmological distances at redshifts beyond those of SNe Ia and provide a model-independent method to determine H 0. In this work, we demonstrate a model-independent, joint constraint of SNe Ia, quasars, and time-delay distances from strong lensed quasars. We first generate mock data sets of SNe Ia, quasar, and time-delay distances based on a fiducial cosmological model. Then, we calibrate the quasar parameters model independently using Gaussian process (GP) regression with mock SNe Ia data. Finally, we determine the value of H 0 model-independently using GP regression from mock quasars and time-delay distances from strong lensing systems. As a comparison, we also show the H 0 results obtained from mock SNe Ia in combination with time-delay lensing systems whose redshifts overlap with SNe Ia. Our results show that quasars at higher redshifts show great potential to extend the redshift coverage of SNe Ia and thus enable the full use of strong lens time-delay distance measurements from ongoing cosmic surveys and improve the accuracy of the estimation of H 0 from 2.1% to 1.3% when the uncertainties of the time-delay distances are 5% of the distance values.

Keywords: hubble constant; observational cosmology; strong gravitational lensing; hubble diagram
Evidence for Dense Gas Heated by the Explosion in Orion KL

We mapped the kinetic temperature structure of Orion KL in a ∼20″ (∼8000 au) sized region with para-H2CS 707 - 606, 726 - 625, and 725 - 624 making use of Atacama Large Millimeter/submillimeter Array Band 6 Science Verification data. The kinetic temperatures obtained with a resolution of 1"65 × 1"14 (∼550 au) are deduced by modeling the measured averaged velocity-integrated intensity ratios of para-H2CS 726 - 625/707 - 606 and 725 - 624/707 - 606 with a RADEX non-LTE model. The kinetic temperatures of the dense gas, derived from the para-H2CS line ratios at a spatial density of 107 cm-3, are high, ranging from 43 to >500 K with an unweighted average of ∼170 K. There is no evidence for internal sources playing an important role in the heating of the various structures identified in previous work, namely the elongated ridge, the northwestern clump, and the eastern region of the compact ridge, while the high temperatures in the western region of the compact ridge may be dominated by internal massive star formation. Significant gradients of kinetic temperature along molecular filaments traced by H2CS indicate that the dense gas is heated by the shocks induced by the enigmatic explosive event which occurred several hundred years ago and greatly affected the energetics of the Orion KL region. Thus, with the notable exception of the western region of the compact ridge, the high temperatures of the dense gas in Orion KL are probably caused by shocks from the explosive event, leading to a dominant component of externally heated dense gas.

Keywords: interstellar medium; interstellar clouds
Three-dimensional Modeling of the Magnetothermal Evolution of Neutron Stars: Method and Test Cases

Neutron stars harbor extremely strong magnetic fields within their solid outer crust. The topology of this field strongly influences the surface temperature distribution and, hence, the star's observational properties. In this work, we present the first realistic simulations of the coupled crustal magnetothermal evolution of isolated neutron stars in three dimensions accounting for neutrino emission, obtained with the pseudo-spectral code PARODY. We investigate both the secular evolution, especially in connection with the onset of instabilities during the Hall phase, and the short-term evolution following episodes of localized energy injection. Simulations show that a resistive tearing instability develops in about a Hall time if the initial toroidal field exceeds $\approx {10}^{15}$ G. This leads to crustal failures because of the huge magnetic stresses coupled with the local temperature enhancement produced by dissipation. Localized heat deposition in the crust results in the appearance of hot spots on the star surface, which can exhibit a variety of patterns. Because the transport properties are strongly influenced by the magnetic field, the hot regions tend to drift away and get deformed following the magnetic field lines while cooling. The shapes obtained with our simulations are reminiscent of those recently derived from NICER X-ray observations of the millisecond pulsar PSR J0030+0451.

Keywords: magnetars; neutron stars; magnetohydrodynamical simulations; pulsars; stellar magnetic fields
Diffuse Lyα Halos around 300 Spectroscopically Confirmed Lyα Emitters at z ∼ 5.7

We report the detection of diffuse Lyα halos (LAHs) around star-forming galaxies at z ∼ 5.7 by stacking 310 spectroscopically confirmed Lyα emitters (LAEs). The majority of the LAEs are identified from our spectroscopic survey of galaxies at z > 5.5. They are all located in well-studied fields with deep narrowband and broadband imaging data. We combine the LAE sample and its subsamples in the narrowband NB816 (I.e., the Lyα band) and z band (I.e., the continuum band). By comparing the stacked objects with their corresponding point-spread functions, we clearly detect extended LAHs around these LAEs. We perform sophisticated simulations and analyses on statistical and systematic errors, and confirm that the detected halos are not caused by errors. The scale lengths of the LAHs, when described by a double-component model, range from 1.2 to 5.3 kpc with a typical value of ∼2 kpc. The LAH sizes from our sample are in agreement with those of individual LAEs at the similar redshift measured by Very Large Telescope/MUSE but are relatively smaller than those of photometrically selected LAEs in previous studies. We also find that LAEs with higher Lyα luminosities, higher UV-continuum luminosities, or smaller Lyα equivalent widths tend to have larger LAH sizes. Our results are consistent with a scenario that LAHs originate from the scattered light of the central galaxies by H I gas in the circumgalactic medium.

Keywords: high-redshift galaxies; lyman-alpha galaxies; galaxy properties; circumgalactic medium
Scaling and Anisotropy of Solar Wind Turbulence at Kinetic Scales during the MMS Turbulence Campaign

We employ data from the 2019 Magnetospheric Multiscale (MMS) Solar Wind Turbulence Campaign to evaluate scaling and anisotropy of second-order magnetic field structure functions and scale-dependent kurtosis from a single data interval. Prior results have been based either on the Taylor approximation, which conflates time and space dependence, or on averaging many data sets, which introduces sample-to-sample variation of plasma parameters. The present results overcome these systematic effects. We find that for length scales between 57 and 201 km the fluctuations are anisotropic with a preferred orientation of 60°-70° to the magnetic field direction. The peak kurtosis also lies in this angular range. This confirms anisotropy of the spectrum and suggests that coherent structures such as current sheets are oriented nearly perpendicular to the magnetic field direction. Both the anisotropy and the kurtosis decrease approaching the ion inertial length, here ≈91 km.

Keywords: interplanetary magnetic fields; interplanetary turbulence; space plasmas; plasma astrophysics
Mid-IR Observations of IRAS, AKARI, WISE/NEOWISE, and Subaru for Large Icy Asteroid (704) Interamnia: A New Perspective of Regolith Properties and Water Ice Fraction

(704) Interamnia is one of the largest asteroids located in the outer main-belt region, which may contain a large amount of water ice underneath its surface. We observe this asteroid using 8.2 m Subaru telescope at mid-infrared wave bands and utilize a thermophysical model for realistic surface layers to analyze mid-infrared data from Subaru along with those of IRAS, AKARI, and Wide-field Infrared Survey Explorer (WISE)/NEOWISE. We optimize the method to convert the WISE magnitude to thermal infrared flux with temperature-dependent color corrections, which can provide significant references for main-belt asteroids at a large heliocentric distance with low surface temperature. We derive best-fitting thermal parameters of Interamnia-a mean regolith grain size of ${190}_{-180}^{+460}$ μm, with a roughness of ${0.30}_{-0.17}^{+0.35}$ and rms slope of ${27}_{-9}^{+13}$ deg, thereby producing thermal inertia ranging from 9 to 92 Jm-2 s-1/2 K-1 due to seasonal temperature variation. The geometric albedo and effective diameter are evaluated to be ${0.0472}_{-0.0031}^{+0.0033}$ and ${339}_{-11}^{+12}\,\mathrm{km}$ , respectively, being indicative of a bulk density of 1.86 ± 0.63 g cm-3. The low thermal inertia is consistent with typical B/C-type asteroids with D ≥ 100 km. The tiny regolith grain size suggests the presence of a fine regolith on the surface of Interamnia. Moreover, the seasonal and diurnal temperature distribution indicates that thermal features between the southern and northern hemispheres appear to be very different. Finally, we present an estimation of volume fraction of water ice of 9%-66% from the published grain density and porosity of carbonaceous chondrites.

Keywords: main belt asteroids; asteroids; small solar system bodies
Confinedness of an X3.1-class Solar Flare Occurred in NOAA 12192: Analysis from Multi-instrument Observations

The nonassociation of coronal mass ejections with high energetic flares is sparse. For this reason, the magnetic conditions required for the confinedness of major flares is a topic of active research. Using multi-instrument observations, we investigated the evolution and effects of confinedness in an X3.1 flare, which occurred in active region (AR) 12192. The decrease of net fluxes in the brightening regions near the footpoints of the multisigmoidal AR in the photosphere and chromosphere, indicative of flux cancellation favoring tether-cutting reconnection (TCR), is observed using the magnetic field observations of HMI/SDO and SOT/Hinode, respectively. The analysis of spectropolarimetric data obtained by the Interferometric Bidimensional Spectrometer over the brightening regions suggests untwisting of field lines, which further supports TCR. Filaments near the polarity inversion line region, resulting from TCR of low-lying sheared loops, undergo merging and form an elongated filament. The temperature and density differences between the footpoints of the merged filament, revealed by DEM analysis, cause streaming and counterstreaming of the plasma flow along the filament and unload at its footpoints with an average velocity of ≈40 km s-1. This results in a decrease of the mass of the filament (density decreased by >50%), leading to its rise and expansion outward. However, due to strong strapping flux, the filament separates itself instead of erupting. Further, the evolution of nonpotential parameters describes the characteristics of confinedness of the flare. Our study suggests that the sigmoid-filament system exhibits upward catastrophe due to mass unloading but gets suppressed by strong confinement of the external poloidal field.

Keywords: solar active regions; solar active region magnetic fields; solar activity; solar active region filaments; solar flares
Evidence of the Alfvén Transition Layer and Particle Precipitation in the Cusp Region: 3D Global PIC Simulation of the Solar Wind-Earth Magnetosphere Interaction

A transition layer, named the Alfvénic transition layer (or ATL), has been clearly evidenced near the outer boundary of the cusp by experimental observations from the Cluster mission. This layer characterized by a local value of Log M A ~ 1, where M A is the Alfvén Mach number, allows the bulk flow to transit from super-Alfvénic to sub-Alfvénic from the exterior to the interior side of the outer cusp. The ATL has been observed during northward interplanetary magnetic field orientation, and mainly within the meridian plane. Currently, 3D Particle In Cell (PIC) global simulations of the solar wind-magnetosphere interaction are being performed in order to analyze the cusp region and this layer in detail. Present results stress the following points: (i) the ATL has a 3D structure; (ii) within the meridian plane, the ATL appears as a sublayer within a much more extended slow-mode pattern, and it is almost adjacent and located above the upper edge of the stagnant exterior cusp (SEC); and (iii) the plasma deceleration through the ATL is not uniform in the region located above the cusp. In addition, present preliminary results stress that (a) the spiraled streamlines of ion/electron fluxes converge when approaching the cusp, and their intensity strongly increases; and (b) ion and electron energetic fluxes penetrating the cusp region strongly differ in terms of their penetration depths and are issued from different regions of the magnetosphere/magnetosheath. Our results illustrate the importance of 3D effects used with a PIC simulation approach allowing the analysis of each population simultaneously.

Keywords: planetary magnetospheres
Multiple Stellar Populations of Globular Clusters from Homogeneous Ca-CN-CH-NH Photometry. VI. M3 (NGC 5272) Is Not a Prototypical Normal Globular Cluster

We present Ca-CN-CH-NH photometry for the well-known globular cluster (GC) M3 (NGC 5272). We show new evidence for two M3 populations with distinctly different carbon and nitrogen abundances, seen in a sharp division between CN-weak and CN-strong red-giant branches (RGBs) in M3. The CN-strong population shows a C-N anticorrelation that is a natural consequence of the CN cycle, while the CN-weak population shows at most a very weak C-N anticorrelation. Additionally, the CN-weak population exhibits an elongated spatial distribution that is likely linked to its fast rotation. Our derived metallicities reveal bimodal distributions in both populations, with ⟨[Fe/H]⟩ ≈ -1.60 and -1.45, which appear to be responsible for the discrete double RGB bumps in the CN-weak population and the large ${W}_{{\rm{F}}275{\rm{W}}-{\rm{F}}814{\rm{W}}}^{1G}$ <!-- --> range. From this discovery, we propose that M3 consists of two GCs, namely C1 (23%, ⟨[Fe/H]⟩ ≈ -1.60) and C2 (77%, ⟨[Fe/H]⟩ ≈ -1.45), each of which has its own C-N anticorrelation and structural and kinematical properties, which are strong indications of independent systems in M3. The fractions of the CN-weak population for both C1 and C2 are high compared to Galactic GCs but they are in good agreement with GCs in the Magellanic Clouds. We suggest that M3 is a merger remnant of two GCs, most likely in a dwarf galaxy environment, and accreted to our Galaxy later in time. This is consistent with recent proposals of an ex situ origin for M3. * Based on observations made with the Kitt Peak National Observatory (KPNO) 0.9 m telescope, which is operated by WIYN Inc. on behalf of a consortium of partner universities and organizations. † This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

Keywords: hertzsprung russell diagram; globular star clusters; stellar abundances; stellar evolution
An in-beam Source-frequency Phase Referencing VLBI Positioning Method for China's First Martian Rover

Very long baseline interferometry (VLBI) plays a crucial role in geodesy and astrometry, and it is also being successfully used in spacecraft tracking. Phase referencing VLBI is a technique that uses phase information rather than the traditional VLBI group time delay to achieve higher measurement accuracy. The newly developed source-frequency phase referencing (SFPR) VLBI has been proven to be a powerful method to eliminate errors, but for positioning purposes, only "core shifts" are left in SFPR. Therefore, in this paper, an in-beam SFPR (IB-SFPR) VLBI method based on SFPR is proposed to overcome the positioning deficiency in SFPR, and to achieve high positioning accuracy. The proposed IB-SFPR method is further researched in more detail and shown to have the ability to achieve high positioning accuracy. For the first Martian rover of China, the IB-SFPR is first applied in its positioning. The positioning results of the rover have shown that the 1σ formal position error is hundreds of meters, with a formal error of post-fitted phase time delay of about 1.3 ps. However, the position discrepancies among the results of IB-SFPR, the guidance, navigation and control system, and the visual localization are at kilometer level, which are mainly affected by the orbit error of the orbiter. Therefore, considering the external reference's (the obiter) orbit error, the final positioning accuracy of the Martian rover is at the kilometer level.

Keywords: astronomical methods; deep space probes; rovers; very long baseline interferometry; aperture synthesis
Tidal Spin-up of Black Hole Progenitor Stars

Gravitational wave observations indicate the existence of merging black holes (BHs) with high spin (a ≳ 0.3), whose formation pathways are still an open question. A possible way to form those binaries is through the tidal spin-up of a Wolf-Rayet (WR) star by its BH companion. In this work, we investigate this scenario by directly calculating the tidal excitation of oscillation modes in WR star models, determining the tidal spin-up rate, and integrating the coupled spin-orbit evolution for WR-BH binaries. We find that, for short-period orbits and massive WR stars, the tidal interaction is mostly contributed by standing gravity modes, in contrast to Zahn's model of traveling waves, which is frequently assumed in the literature. The standing modes are less efficiently damped than traveling waves, meaning that prior estimates of tidal spin-up may be overestimated. We show that tidal synchronization is rarely reached in WR-BH binaries, and the resulting BH spins have a ≲ 0.4 for all but the shortest-period (P orb ≲ 0.5 day) binaries. Tidal spin-up in lower-mass systems is more efficient, providing an anticorrelation between the mass and spin of the BHs, which could be tested in future gravitational wave data. Nonlinear damping processes are poorly understood but may allow for more efficient tidal spin-up. We also discuss a new class of gravito-thermal modes that appear in our calculations.

Keywords: wolf-rayet stars; stellar oscillations; stellar evolution; tidal interaction; astrophysical black holes