Sazuna/UAT_keywords huggingface dataset:
Exploring the Individual Pulse Behavior of Pulsar J1701-3726 with Parkes. We have carried out a detailed study of polarimetric individual pulse emission from the pulsar J1701-3726 (B1658-37), observed at 1369 MHz using the Parkes 64 m radio telescope. The single-pulse sequences reveal the presence of the three major emission phenomena of pulse nulling, mode changing, and subpulse drifting. Trimodal distribution of the pulse energy is present, implying one population of nulls and two others of emission in the phase window. The mean flux density of the normal mode is almost two times that of the abnormal mode. Our data show that, for PSR J1701-3726, 64% of the time was spent in the normal mode and 12% was in the abnormal mode. The single pulses show the presence of two distinct periodic modulations using a fluctuation spectral analysis. About 24% of the nulls are found to create alternating bunches of nulls and bursts in a quasiperiodic manner with a longer periodicity of 48 ± 4 rotational periods. Additionally, the pulsar presents a steady even-odd modulated feature with a stationary longitude within the pulse window. The ramifications for constraining the viewing geometry and understanding the radio emission mechanisms are discussed.

Keywords: Radio pulsars
Spectroscopic Analysis of Milky Way Outer Halo Satellites: Aquarius II and Boötes II. In this paper, we present a chemical and kinematic analysis of two ultrafaint dwarf galaxies (UFDs), Aquarius II (Aqu II) and Boötes II (Boo II), using Magellan/IMACS spectroscopy. We present the largest sample of member stars for Boo II (12), and the largest sample of red giant branch members with metallicity measurements for Aqu II (eight). In both UFDs, over 80% of targets selected based on Gaia proper motions turned out to be spectroscopic members. In order to maximize the accuracy of stellar kinematic measurements, we remove the identified binary stars and RR Lyrae variables. For Aqu II, we measure a systemic velocity of -65.3 ± 1.8 km s-1 and a metallicity of [Fe/H] = $-{2.57}_{-0.17}^{+0.17}$ . When compared with previous measurements, these values display a ~6 km s-1 difference in radial velocity and a decrease of 0.27 dex in metallicity. Similarly for Boo II, we measure a systemic velocity of $-{130.4}_{-1.1}^{+1.4}$ km s-1, more than 10 km s-1 different from the literature, a metallicity almost 1 dex smaller at [Fe/H] = $-{2.71}_{-0.10}^{+0.11}$ , and a velocity dispersion 3 times smaller at ${\sigma }_{{v}_{\mathrm{hel}}}={2.9}_{-1.2}^{+1.6}$ km s-1. Additionally, we derive systemic proper-motion parameters and model the orbits of both UFDs. Finally, we highlight the extremely dark-matter-dominated nature of Aqu II and compute the J-factor for both galaxies to aid searches of dark matter annihilation. Despite the small size and close proximity of Boo II, it is an intermediate target for the indirect detection of dark matter annihilation due to its low-velocity dispersion and corresponding low dark matter density.

Keywords: Binary stars, Stellar kinematics, Dwarf galaxies, Spectroscopy, Dark matter, Milky Way Galaxy
The Nonorthogonal X-line in a Small Guide-field Reconnection Event in the Magnetotail. Magnetic reconnection is a fundamental plasma process that has been studied with analytical theory, numerical simulations, in situ observations, and laboratory experiments for decades. The models that have been established to describe magnetic reconnection often assume a reconnection plane normal to the current sheet in which an antiparallel magnetic field annihilates. The annihilation points, also known as the X-points, form an x-line, which is believed to be perpendicular to the reconnection plane. Recently, a new study using Magnetospheric Multiscale mission observations has challenged our understanding of magnetic reconnection by providing evidence that the x-line is not necessarily orthogonal to the reconnection plane. In this study we report a second nonorthogonal x-line event with similar features as that in the previous case study, supporting that the sheared x-line phenomenon is not an aberrant event. We employ a detailed directional derivative analysis to identify the x-line direction and show that the in-plane reconnection characteristics are well maintained even with a nonorthogonal x-line. In addition, we find the x-line tends to follow the magnetic field on one side of the current sheet, which suggests an asymmetry across the current sheet. We discuss the possibility that the nonorthogonal x-line arises from an interplay between the two aspects of reconnection: the macroscopic magnetic field topology and microscopic particle kinetics.

Keywords: Space plasmas, Plasma physics
Effective Resistivity in Relativistic Collisionless Reconnection. Magnetic reconnection can power spectacular high-energy astrophysical phenomena by producing nonthermal energy distributions in highly magnetized regions around compact objects. By means of two-dimensional fully kinetic particle-in-cell (PIC) simulations, we investigate relativistic collisionless plasmoid-mediated reconnection in magnetically dominated pair plasmas with and without a guide field. In X-points, where diverging flows result in a nondiagonal thermal pressure tensor, a finite residence time for particles gives rise to a localized collisionless effective resistivity. Here, for the first time for relativistic reconnection in a fully developed plasmoid chain, we identify the mechanisms driving the nonideal electric field using a full Ohm law by means of a statistical analysis based on our PIC simulations. We show that the nonideal electric field is predominantly driven by gradients of nongyrotropic thermal pressures. We propose a kinetic physics motivated nonuniform effective resistivity model that is negligible on global scales and becomes significant only locally in X-points. It captures the properties of collisionless reconnection with the aim of mimicking its essentials in nonideal magnetohydrodynamic descriptions. This effective resistivity model provides a viable opportunity to design physically grounded global models for reconnection-powered high-energy emission.

Keywords: Magnetohydrodynamics, High energy astrophysics, Relativity, Plasma astrophysics, Compact objects, Magnetic fields
A NICER Viewing Angle on the Accretion Stream of Vela X-1. Vela X-1 is the archetypal eclipsing high-mass X-ray binary, composed of a neutron star (NS) accreting the B-star wind. It was observed by nearly all X-ray observatories, often multiple times, featuring a rich spectrum of variable emission lines. However, the precise origin of these lines in the binary system remains uncertain. We perform a systematic, orbital-phase-dependent analysis of the reflected Fe Kα fluorescence line at 6.4 keV using over 100 NS Interior Composition Explorer observations. We resolve the line variability into 500 s time bins and find that it is predominantly due to variation in the ionizing flux, with a moderate underlying phase dependence over the 9-day orbital period. Our analysis reveals a significant reflection component that cannot originate from the companion B star alone. We also find that an appreciable portion of the B-star surface is obscured opposite the eclipse, and this obscuration is not symmetric around the midpoint (phase = 0.5). We argue that an accretion stream, from the B star to the NS and distorted by the orbital motion, is responsible both for the additional fluorescence emission component and for obscuring the B star.

Keywords: X-ray astronomy, High mass x-ray binary stars
Spatial and Temporal Analysis of Quiescent Coronal Rain over an Active Region. The solar corona produces coronal rain, hundreds of times colder and denser material than the surroundings. Coronal rain is known to be deeply linked to coronal heating, but its origin, dynamics, and morphology are still not well understood. The leading theory for its origin is thermal instability (TI) occurring in coronal loops in a state of thermal nonequilibrium (TNE), the TNE-TI scenario. Under steady heating conditions, TNE-TI repeats in cycles, leading to long-period EUV intensity pulsations and periodic coronal rain. In this study, we investigate coronal rain on the large spatial scales of an active region (AR) and over the long temporal scales of EUV intensity pulsations to elucidate its distribution at such scales. We conduct a statistical study of coronal rain observed over an AR off limb with Interface Region Imaging Spectrograph and Solar Dynamics Observatory imaging data, spanning chromospheric to transition region (TR) temperatures. The rain is widespread across the AR, irrespective of the loop inclination, and with minimal variation over the 5.45 hr duration of the observation. Most rain has a downward (87.5%) trajectory; however, upward motions (12.5%) are also ubiquitous. The rain dynamics are similar over the observed temperature range, suggesting that the TR emission and chromospheric emission are colocated on average. The average clump widths and lengths are similar in the SJI channels and wider in the AIA 304 Å channel. We find ubiquitous long-period EUV intensity pulsations in the AR. Short-term periodicity is found (16 minutes) linked to the rain appearance, which constitutes a challenge to explain under the TNE-TI scenario.

Keywords: Solar prominences, Solar coronal heating, Solar transition region, Active solar corona, Solar chromosphere
The Effect of the Ambient Solar Wind Medium on a CME-driven Shock and the Associated Gradual Solar Energetic Particle Event. We present simulation results of a gradual solar energetic particle (SEP) event detected on 2021 October 9 by multiple spacecraft, including BepiColombo (Bepi) and near-Earth spacecraft such as the Advanced Composition Explorer (ACE). A peculiarity of this event is that the presence of a high-speed stream (HSS) affected the low-energy ion component (≲5 MeV) of the gradual SEP event at both Bepi and ACE, despite the HSS having only a modest solar wind speed increase. Using the EUHFORIA (European Heliospheric FORecasting Information Asset) magnetohydrodynamic model, we replicate the solar wind during the event and the coronal mass ejection (CME) that generated it. We then combine these results with the energetic particle transport model PARADISE (PArticle Radiation Asset Directed at Interplanetary Space Exploration). We find that the structure of the CME-driven shock was affected by the nonuniform solar wind, especially near the HSS, resulting in a shock wave front with strong variations in its properties such as its compression ratio and obliquity. By scaling the emission of energetic particles from the shock to the solar wind compression at the shock, an excellent match between the PARADISE simulation and in situ measurements of ≲5 MeV ions is obtained. Our modeling shows that the intricate intensity variations observed at both ACE and Bepi were influenced by the nonuniform emission of energetic particles from the deformed shock wave and demonstrates the influence of even modest background solar wind structures on the development of SEP events.

Keywords: Solar energetic particles, Solar wind, Solar coronal mass ejections, Interplanetary shocks
The Detection of Possible Transient Quasiperiodic Oscillations in the γ-Ray Light Curve of PKS 0244-470 and 4C+38.41. The continuous monitoring capability of Fermi-LAT has enabled the exploration of quasiperiodic oscillations (QPOs) in the γ-ray light curve of blazars that has given a new perspective to probe these sources over a wide range of timescales. We report the presence of transient QPOs in the long-term γ-ray light curve of blazars PKS 0244-470 and 4C +38.41. We first identified different flux states using the Bayesian block algorithm and then explored the possible transient QPOs in the segments of each flux phase where the flux level changes over fairly regular intervals. Combining this with the source's intrinsic variance, we identified two flux phases for PKS 0244-470: one activity (AP-1) and one quiescent phase (QP-1). For 4C+38.41, we similarly identified four activity (AP-1, AP-2, AP-3, and AP-4) and two quiescent (QP-1 and QP-2) phases. The AP-1 phase of PKS 0244-470 shows QPO of ~225 days persisting for eight cycles (~4.1σ). In 4C+38.41, AP-1 and AP-2 phases show QPO-like behavior of ~110 days and ~60 days, respectively, persisting for five cycles. In AP-3, we identified three subphases, and all show a ~7 day scale possible recurrent rise with five complete cycles, while in QP-1, we could identify two subphases (Q1 and Q2). The Q1 phase shows a period of ~104 days with six complete cycles. The Q2 phase also shows QPO but with only ~3.7 cycles. We discuss the possible origin and argue that the current-driven kink instability and curved jet model seem to be the most likely causes for shorter and longer QPOs.

Keywords: Blazars, Active galaxies, Gamma-rays
A QPO in Mkn 421 from Archival RXTE Data. We report a 325(-7, +8) day quasi-periodic oscillation (QPO) in the X-ray emission of the blazar Mkn 421 based on data obtained with the Rossi X-ray Timing Explorer satellite. The QPO is seen prominently in the ASM data (at least 15 cycles) due to the fact that it has had near-continuous sampling for more than a decade. The PCA data, where the sampling is not uniform and shows many large gaps, provide supporting evidence at lower significance. The QPOs are an important observable in accretion disks, can be modulated by various orbital timescales, and may be generated by a number of mechanisms. They have been studied extensively in X-ray binaries and should be present in active galactic nuclei (AGN) if they are governed by a common set of physical principles. In jetted sources, QPOs can probe jet-disk interactions or helical oscillations. This QPO has previously been claimed intermittently in X-ray, radio, and gamma-ray data, but the continuous, 15 yr extent (1996-2011) of the ASM observations (in which Mkn 421 is the brightest AGN observed) provides a unique window. The QPO appears to be present for nearly the entire extent of the ASM observations. We explore various physical origins and modulating mechanisms, particularly interpretations of the QPO as a result of disk-jet interactions, due to either an accretion disk limit cycle, jet instabilities, or helical motions. Limit cycle oscillations would not interact with either Keplerian or Lense-Thirring modulated oscillations; however, those associated with jet instabilities or helical motions in the jet would likely be modulated by Lense-Thirring precession.

Keywords: X-ray astronomy, BL Lacertae objects, Blazars, Galaxy accretion disks, Active galactic nuclei
Deep Synoptic Array Science: A Massive Elliptical Host Among Two Galaxy-cluster Fast Radio Bursts. The stellar population environments that are associated with fast radio burst (FRB) sources provide important insights for developing their progenitor theories. We expand the diversity of known FRB host environments by reporting two FRBs in massive galaxy clusters that were discovered by the Deep Synoptic Array (DSA-110) during its commissioning observations. FRB 20220914A has been localized to a star-forming, late-type galaxy at a redshift of 0.1139 with multiple starbursts at lookback times less than ~3.5 Gyr in the A2310 galaxy cluster. Although the host galaxy of FRB 20220914A is similar to typical FRB hosts, the FRB 20220509G host stands out as a quiescent, early-type galaxy at a redshift of 0.0894 in the A2311 galaxy cluster. The discovery of FRBs in both late- and early-type galaxies adds to the body of evidence that the FRB sources have multiple formation channels. Therefore, even though FRB hosts are typically star-forming, there must exist formation channels that are consistent with old stellar population in galaxies. The varied star formation histories of the two FRB hosts that we report here indicate a wide delay-time distribution of FRB progenitors. Future work in constraining the FRB delay-time distribution, using the methods that we develop herein, will prove crucial in determining the evolutionary histories of FRB sources.

Keywords: Galaxy clusters, Elliptical galaxies, Star formation, Radio transient sources
Tidal Dissipation in Stratified and Semi-convective Regions of Giant Planets. We study how stably stratified or semi-convective layers alter the tidal dissipation rates associated with the generation of internal waves in planetary interiors. We consider if these layers could contribute to the high rates of tidal dissipation observed for Jupiter and Saturn in our solar system. We use an idealized global spherical Boussinesq model to study the influence of stable stratification and semi-convective layers on tidal dissipation rates. We carry out analytical and numerical calculations considering realistic tidal forcing and measure how the viscous and thermal dissipation rates depend on the parameters relating to the internal stratification profile. We find that the strongly frequency-dependent tidal dissipation rate is highly dependent on the parameters relating to the stable stratification, with strong resonant peaks that align with the internal modes of the system. The locations and sizes of these resonances depend on the form and parameters of the stratification, which we explore both analytically and numerically. Our results suggest that stable stratification can significantly enhance the tidal dissipation in particular frequency ranges. Analytical calculations in the low-frequency regime give us scaling laws for the key parameters, including the tidal quality factor $Q^{\prime} $ due to internal gravity waves. Stably stratified layers can significantly contribute to tidal dissipation in solar and extrasolar giant planets, and we estimate substantial tidal evolution for hot Neptunes. Further investigation is needed to robustly quantify the significance of the contribution in realistic interior models, and to consider the contribution of inertial waves.

Keywords: Internal waves, Solar system gas giant planets, Exoplanet tides, Tides, Astrophysical fluid dynamics, Extrasolar gaseous giant planets
A NuSTAR and Chandra Investigation of the Misaligned Outflow of PSR J1101-6101 and the Lighthouse Pulsar Wind Nebula. PSR J1101-6101 is an energetic young pulsar that powers the remarkable Lighthouse pulsar wind nebula (PWN). The pulsar belongs to the rare type of radio- and gamma-ray-quiet pulsars that are bright in hard X-rays. Moreover, the Lighthouse PWN is remarkable for its misaligned outflow (which gave rise to the PWN's nickname). Also known as "pulsar filaments," these collimated parsec-scale X-ray structures have been recently discovered in the vicinity of a handful of fast-moving pulsars, and they appear unaffected by the ram pressure that confines pulsar tails. We report on NuSTAR observations of PSR J1101-6101 and its misaligned outflow-the first observation of such a structure above ~10 keV. We detect the outflow up to 25 keV, spatially resolve its spectral evolution with distance from the pulsar, find unambiguous evidence of spectral cooling with distance from the pulsar, and infer physical properties of the particles and magnetic field in the outflow. We also reanalzye archival Chandra data and discuss the outflow's small-scale structure. We detect pulsations from PSR J1101-6101 up to 20 keV, present the X-ray pulse profile, confirm its period derivative, and perform phase-resolved spectroscopy. Finally, we discuss the X-ray source 2CXO J110158.4-605649 = 2XMM J110158.5-605651 (a serendipitously observed blazar) and suggest it may be the X-ray counterpart to the GeV source 4FGL J1102.0-6054.

Keywords: X-ray astronomy, Magnetohydrodynamics, Pulsars, Interstellar magnetic fields, Interstellar medium, Pulsar wind nebulae, Relativistic fluid dynamics
Distinguishing Dark Matter Cusps from Cores Using Globular Clusters. Globular clusters (GCs) provide valuable insight into the properties of their host galaxies' dark matter halos. Using N-body simulations incorporating semianalytic dynamical friction and GC-GC merger prescriptions, we study the evolution of GC radial distributions and mass functions in cuspy and cored dark matter halos. Modeling the dynamics of the GC-rich system in the dwarf galaxy UGC 7369, we find that friction-induced inspiral and subsequent mergers of massive GCs can naturally and robustly explain the mass segregation of the GCs and the existence of a nuclear star cluster (NSC). However, the multiple mergers required to form the NSC only take place when the dark matter halo is cuspy. In a cored halo, stalling of the dynamical friction within the core halts the inspiral of the GCs, and so the GC merger rate falls significantly, precluding the formation of an NSC. We therefore argue that the presence of an NSC requires a cusp in UGC 7369. More generally, we propose that the presence of an NSC and the corresponding alteration of the GC mass function due to mergers may be used as an indicator of a cuspy halo for galaxies in which we expect NSC formation to be merger dominated. These observables represent a simple, powerful complement to other inner halo density profile constraint techniques and should allow for straightforward extension to larger samples.

Keywords: Globular star clusters, Galaxy dark matter halos, Dwarf galaxies, Dynamical friction
Investigating the M <SUB>GCS</SUB>-M <SUB> h </SUB> Relation in the Most Massive Galaxies. The relation between the total mass contained in the globular clusters of a galaxy and the mass of its dark-matter halo has been found observationally to be nearly linear over five decades of mass. However, the high-mass end of this relation is not well determined from previous data and shows large scatter. We analyze the globular cluster systems (GCSs) of a homogeneous sample of 11 brightest cluster galaxies (BCGs) through DOLPHOT photometry of their deep Hubble Space Telescope images in the F814W filter. We standardize the definition of M GCS, the total GCS mass, by using the GC total population within a limiting radius of 0.1R virial, while the dark-matter halo mass M h is determined from the weak-lensing calibration of M h versus M bary. When these 11 BCGs are added to the previously studied homogeneous catalog of Virgo member galaxies, a total value for η = M GCS/M h is found to be (3.0 ± 1.8internal) × 10-5, slightly higher than previous estimates but with much reduced uncertainty. Perhaps more importantly, the results suggest that the relation continues to have a near-linear shape at the highest galaxy masses, strongly reinforcing the conclusion that accreted GCs make a major contribution to the GC populations at high galaxy mass.

Keywords: Globular star clusters, Brightest cluster galaxies, Galaxy dark matter halos, Elliptical galaxies