adsabs/SciX_UAT_keywords huggingface dataset:
The Impact of Pickup Ion Thermal Spread on Pickup Ion Ring-beam-driven Instabilities and Scattering in the Outer Heliosheath

The present study investigates the unstable waves driven by the pickup ions of ring-beam distributions with various pickup angles and pickup ion temperatures in the outer heliosheath, using both linear instability analysis and hybrid simulations. While previous papers have generally assumed specific pickup ion temperatures, this study takes a more comprehensive approach by examining a wide range of pickup ion temperatures that may occur in the outer heliosheath. Our one-dimensional simulations demonstrate that regardless of the initial pickup ion temperature, the pitch-angle scattering of the pickup ions at small pickup angles saturates before the pickup ions can reach the hemisphere of negative parallel velocities with respect to the background magnetic field in velocity space, while at a 90° pickup angle, the pickup ions of ring distributions attain a significant level of isotropy. In contrast, the two-dimensional simulation results show that at all pickup angles, increasing the pickup ion temperature only slightly reduces the pickup ion scattering rate, but does not prevent the pickup ions from reaching the hemisphere of negative parallel velocities. Overall, the results do not align with the requirements of the earlier proposed scenarios for the secondary energetic neutral atom (ENA) mechanism of the Interstellar Boundary Explorer ENA ribbon, which demand either weak pickup ion scattering in the outer heliosheath or at least incomplete pickup ion scattering in the off-ribbon directions.

Keywords: pickup ions
The Common Origin of High-energy Protons in Solar Energetic Particle Events and Sustained Gamma-Ray Emission from the Sun

We report that the number of >500 MeV protons (Ng) inferred from sustained gamma-ray emission (SGRE) from the Sun is significantly correlated with that of protons propagating into space (NSEP) as solar energetic particles (SEPs). Under the shock paradigm for SGRE, shocks driven by coronal mass ejections (CMEs) accelerate high-energy protons sending them toward the Sun to produce SGRE by interacting with the atmospheric particles. Particles also escape into the space away from the Sun to be detected as SEP events. Therefore, the significant NSEP-Ng correlation (correlation coefficient 0.77) is consistent with the common shock origin for the two proton populations. Furthermore, the underlying CMEs have properties akin to those involved in ground level enhancement events indicating the presence of high-energy (up to ~GeV) particles required for SGRE. We show that the observed gamma-ray flux is an underestimate in limb events (central meridian distance >60°) because SGRE sources are partially occulted when the emission is spatially extended. With the assumption that the SEP spectrum at the shock nose is hard and that the 100 MeV particles are accelerated throughout the shock surface (half width in the range 60°-120°) we find that the latitudinal widths of SEP distributions are energy dependent with the smallest width at the highest energies. Not using the energy-dependent width results in an underestimate of NSEP in SGRE events occurring at relatively higher latitudes. Taking these two effects into account removes the apparent lack of NSEP-Ng correlation reported in previous studies.

Keywords: solar gamma-ray emission; solar energetic particles; solar coronal mass ejection shocks; solar coronal mass ejections; solar flares
The Magellan M2FS Spectroscopic Survey of High-redshift Galaxies: The Brightest Lyman-break Galaxies at z ∼ 6

We present a study of a sample of 45 spectroscopically confirmed, UV luminous galaxies at z ∼ 6. They were selected as bright Lyman-break galaxies (LBGs) using deep multiband optical images in more than 2 deg2 of the sky, and subsequently identified via their strong Lyα emission. The majority of these LBGs span an absolute UV magnitude range from ‑22.0 to ‑20.5 mag with Lyα equivalent width (EW) between ∼10 and ∼200 Å, representing the most luminous galaxies at z ∼ 6 in terms of both UV continuum emission and Lyα line emission. We model the spectral energy distributions of 10 LBGs that have deep infrared observations from Hubble Space Telescope, JWST, and/or Spitzer, and find that they have a wide range of stellar masses and ages. They also have high star formation rates ranging from a few tens to a few hundreds of solar mass per year. Five of the LBGs have JWST or HST images, and four of them show compact morphology in these images, including one that is roughly consistent with a point source, suggesting that UV luminous galaxies at this redshift are generally compact. The fraction of our photometrically selected LBGs with strong Lyα emission (EW > 25 Å) is about 0.2, which is consistent with previous results and supports a moderate evolution of the intergalactic medium opacity at the end of cosmic reionization. Using deep X-ray images, we do not find evidence of strong active galactic nucleus (AGN) activity in these galaxies, but our constraint is loose, and we are not able to rule out the possibility of any weak AGN activity.

Keywords: high-redshift galaxies; lyman-break galaxies; lyman-alpha galaxies; galaxy properties; reionization
Fallback Rates in Partial Tidal Disruptions of White Dwarfs by Intermediate-mass Black Holes

The fallback rate of debris after the partial tidal disruption of a star by an intermediate-mass black hole (IMBH) might provide important signatures of such black holes rather than supermassive ones. Here using smoothed particle hydrodynamics methods, we provide a comprehensive numerical analysis of this phenomenon. We perform numerical simulations of single partial tidal disruptions of solar-mass white dwarfs in parabolic orbits, with a nonspinning 103 M ⊙ IMBH for various values of the impact parameter, and determine the core mass fractions and fallback rates of debris into the IMBH. For supermassive black holes, in full disruption processes, it is known that the late-time fallback rate follows a power law t ‑5/3, whereas for partial disruptions, such a rate has recently been conjectured to saturate at a steeper power law t ‑9/4, independent of the mass of the remnant core. We show here that for IMBHs, partial disruptions significantly alter this conclusion. That is, the fallback rate at late times does not asymptote to a t ‑9/4 power law, and this rate is also a strong function of the core mass. We derive a robust formula for the late-time fallback rate as a function of the core mass fraction, which is independent of the mass of the white dwarf, as we verify numerically by varying it.

Keywords: tidal disruption
BASS. XXI. The Data Release 2 Overview

The BAT AGN Spectroscopic Survey (BASS) is designed to provide a highly complete census of the key physical parameters of the supermassive black holes (SMBHs) that power local active galactic nuclei (AGNs) (z ≲ 0.3), including their bolometric luminosity (L bol), black hole (BH) mass (M BH), accretion rates (L bol/L Edd), line-of-sight gas obscuration (N H), and the distinctive properties of their host galaxies (e.g., star formation rates, masses, and gas fractions). We present an overview of the second data release of BASS (DR2), an unprecedented spectroscopic AGN survey in spectral range, resolution, and sensitivity, including 1449 optical (∼3200 Å–1 μm) and 233 near-IR (1–2.5 μm) spectra for the brightest 858 ultrahard X-ray (14–195 keV) selected AGNs across the entire sky and essentially all levels of obscuration. This release provides a highly complete set of key measurements (emission-line measurements and central velocity dispersions), with 99.9% measured redshifts and 98% BH masses estimated (for unbeamed AGNs outside the Galactic plane). The BASS DR2 AGN sample represents a unique census of nearby powerful AGNs, spanning over 5 orders of magnitude in AGN bolometric luminosity (L bol ∼ 1040–1047 erg s‑1), BH mass (M BH ∼ 105–1010 M ⊙), Eddington ratio (L bol/L Edd ≳ 10‑5), and obscuration (N H ∼ 1020–1025 cm‑2). The public BASS DR2 sample and measurements can thus be used to answer fundamental questions about SMBH growth and its links to host galaxy evolution and feedback in the local universe, as well as open questions concerning SMBH physics. Here we provide a brief overview of the survey strategy, the key BASS DR2 measurements, data sets and catalogs, and scientific highlights from a series of DR2-based works pursued by the BASS team.

Keywords: active galactic nuclei; agn host galaxies; x-ray active galactic nuclei; x-ray surveys; sky surveys; supermassive black holes
Multiple Measurements of Quasars Acting as Standard Probes: Exploring the Cosmic Distance Duality Relation at Higher Redshift

General relativity reproduces main current cosmological observations, assuming the validity of the cosmic distance duality relation (CDDR) at all scales and epochs. However, CDDR is poorly tested in the redshift interval between the farthest observed Type Ia supernovae and that of the cosmic microwave background. We present a new idea of testing the validity of CDDR, through the multiple measurements of high-redshift quasars. Luminosity distances are derived from the relation between the UV and X-ray luminosities of quasars, while angular diameter distances are obtained from the compact structure in radio quasars. This will create a valuable opportunity where two different cosmological distances from the same kind of objects at high redshifts are compared. Our constraints are more stringent than other currently available results based on different observational data and show no evidence for the deviation from CDDR at z ∼ 3. Such an accurate model-independent test of fundamental cosmological principles can become a milestone in precision cosmology.

Keywords: radio loud quasars; x-ray quasars; cosmological parameters; quasars
The First Polarimetric View on Quasiperiodic Oscillations in a Black Hole X-Ray Binary

We present the first polarimetric analysis of quasiperiodic oscillations (QPOs) in a black hole binary utilizing IXPE data. Our study focuses on Swift J1727.8–1613, which experienced a massive outburst that was observed by various telescopes across different wavelengths. The IXPE observation we studied was conducted during the hard-intermediate state. The polarization degree (PD) and polarization angle (PA) were measured at 4.28% ± 0.20% and 1.°9 ± 1.°4, respectively. Remarkably, significant QPO signals were detected during this observation, with a QPO frequency of approximately 1.34 Hz and a fractional rms amplitude of about 12.3%. Furthermore, we conducted a phase-resolved analysis of the QPO using the Hilbert–Huang transform technique. The photon index showed a strong modulation with respect to the QPO phase. In contrast, the PD and PA exhibit no modulations in relation to the QPO phase, which is inconsistent with the expectation of the Lense–Thirring precession of the inner flow. Further theoretical studies are needed to conform with the observational results.

Keywords: low-mass x-ray binary stars; accretion; polarimetry
Hidden Companions to Nearby Intermediate-mass Stars. II. Discovery of a 0.80 M ⊙, 10.5 au Companion to the λ Boötis Star HIP 83650

HIP 83650 is a nearby intermediate mass star that shows the rare λ Boötis phenomenon of still uncertain origin. Here we report the discovery of a companion to this star with a K band flux ratio of 5.9% based on an archival VLTI/GRAVITY observation. This 0.80M ⊙ companion at a projected separation 149.8 mas ↔ 10.5au confirms that the system is rather old as there is no detected X-ray emission from it. We therefore argue that the λ Boötis character of this star is not caused by a circumstellar debris disk (for which there is also no evidence in the near-infrared interferometry) but potentially by accretion from the ablated wind of a hot Jupiter. This can be tested with AO-assisted spectroscopy of the newly discovered companion.

Keywords: multiple stars; chemically peculiar stars; a stars; optical interferometry
Decomposition of Benzene during Impacts in N2-dominated Atmospheres

Benzene is a simple neutral aromatic compound found in molecular clouds, comets, and planetary atmospheres. It has been confirmed on Jupiter, Saturn, Titan, and is expected on exoplanets. In this paper, the decomposition of benzene in a simulated asteroid or comet impact into an N2-dominated atmosphere was investigated. The impact plasma was simulated with laser-induced dielectric breakdown and the gas phase decomposition products were observed using high-resolution Fourier transform infrared spectroscopy. The gas phase decomposition products involve mainly HCN, C2H2, and smaller amounts of CH4 with yields of 3.1%-24.0%, 0-11.7%, and 0.5%-3.3%, respectively. Furthermore, in presence of water, benzene also produces CO and CO2 with yields of 2.4%-35.1% and 0.01%-4.8%, respectively. The oxidation state of the product mixture is proportional to the water content. Apart from that, a black-brownish solid phase is formed during the experiments, which makes up about 60% of the original carbon content. Our results therefore show that in anoxic N2-dominated planetary atmospheres, impacts might lead to the depletion of benzene and the formation of HCN, C2H2, and CH4 and, in the presence of water, to the formation of CO and CO2.

Keywords: laboratory astrophysics; infrared spectroscopy; exoplanet atmospheric evolution; titan; exoplanet atmospheres
Dust Enrichment and Grain Growth in a Smooth Disk around the DG Tau Protostar Revealed by ALMA Triple Bands Frequency Observations

Characterizing the physical properties of dust grains in a protoplanetary disk is critical to comprehending the planet formation process. Our study presents Atacama Large Millimeter/submillimeter Array (ALMA) high-resolution observations of the young protoplanetary disk around DG Tau at a 1.3 mm dust continuum. The observations, with a spatial resolution of ≈0.″04, or ≈5 au, revealed a geometrically thin and smooth disk without substantial substructures, suggesting that the disk retains the initial conditions of the planet formation. To further analyze the distributions of dust surface density, temperature, and grain size, we conducted a multiband analysis with several dust models, incorporating ALMA archival data of the 0.87 and 3.1 mm dust polarization. The results showed that the Toomre Q parameter is ≲2 at a 20 au radius, assuming a dust-to-gas mass ratio of 0.01. This implies that a higher dust-to-gas mass ratio is necessary to stabilize the disk. The grain sizes depend on the dust models, and for the DSHARP compact dust, they were found to be smaller than ~400 μm in the inner region (r ≲ 20 au) while exceeding larger than 3 mm in the outer part. Radiative transfer calculations show that the dust scale height is lower than at least one-third of the gas scale height. These distributions of dust enrichment, grain sizes, and weak turbulence strength may have significant implications for the formation of planetesimals through mechanisms such as streaming instability. We also discuss the CO snowline effect and collisional fragmentation in dust coagulation for the origin of the dust size distribution.

Keywords: protoplanetary disks; planet formation; protostars; circumstellar disks; young stellar objects; dust continuum emission; star formation
Total Solar Irradiance during the Last Five Centuries

The total solar irradiance (TSI) varies on timescales of minutes to centuries. On short timescales it varies due to the superposition of intensity fluctuations produced by turbulent convection and acoustic oscillations. On longer timescales, it changes due to photospheric magnetic activity, mainly because of the facular brightenings and dimmings caused by sunspots. While modern TSI variations have been monitored from space since the 1970s, TSI variations over much longer periods can only be estimated either using historical observations of magnetic features, possibly supported by flux transport models, or from the measurements of the cosmogenic isotope (e.g., 14C or 10Be) concentrations in tree rings and ice cores. The reconstruction of the TSI in the last few centuries, particularly in the 17th/18th centuries during the Maunder minimum, is of primary importance for studying climatic effects. To separate the temporal components of the irradiance variations, specifically the magnetic cycle from secular variability, we decomposed the signals associated with historical observations of magnetic features and the solar modulation potential Φ by applying an empirical mode decomposition algorithm. Thus, the reconstruction is empirical and does not require any feature contrast or field transport model. The assessed difference between the mean value during the Maunder minimum and the present value is ≃2.5 W m-2. Moreover it shows, in the first half of the last century, a growth of ≃1.5 W m-2, which stops around the middle of the century to remain constant for the next 50 years, apart from the modulation due to the solar cycle.

Keywords: solar activity; solar cycle; solar photosphere; solar faculae; solar-terrestrial interactions; active solar chromosphere
Discovery of γ-Ray Pulsations from PSR J1835-3259B in the Globular Cluster NGC 6652

Motivated by the recent discovery of the pulsar J1835-3259B with a spin period 1.83 ms in the globular cluster (GC) NGC 6652, we analyze the γ-ray data obtained with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope (Fermi) for the GC and detect the pulsations of this millisecond pulsar (MSP) at a 5.4σ confidence level (the weighted H-test value is ~41). From timing analysis of the data, a pulse profile that is similar to the radio one is established. We thus consider that we have detected the γ-ray emission of the MSP, and discuss the implications. Based on the results of our analysis and different studies of the sources in the GC, the observed γ-ray emission from the GC could mainly arise from this MSP, like the previous two cases in the GCs NGC 6624 and NGC 6626. Assuming this is the case, the pulsar, at the GC's distance of 9.46 kpc and having a spin-down luminosity of ≤4.3 × 1035 erg s-1, would have a γ-ray luminosity of ≃(5.04 ± 0.44) × 1034 erg s-1 and a γ-ray efficiency of ≳0.12.

Keywords: gamma-rays; globular star clusters; pulsars
XMM–NuSTAR Observation and Multiwavelength Spectral Energy Distribution Modeling of Blazar 4FGL J1520.8–0348

Active galactic nuclei (AGNs) can power relativistic jets, which are called blazars when pointed close to our line of sight. Depending on the presence or absence of emission lines in their optical spectra, blazars are categorized into flat spectrum radio quasars (FSRQs) or BL Lacertae (BL Lac) objects. According to the "blazar sequence," as synchrotron peak frequency ( ${\nu }_{\mathrm{pk}}^{\mathrm{sy}}$ ) shifts to higher energies, the synchrotron peak luminosity decreases. This means that BL Lac objects as luminous as FSRQs, and with synchrotron peak frequencies ${\nu }_{\mathrm{pk}}^{\mathrm{sy}}\gt {10}^{15}$ Hz, should not exist. Detected as a high-synchrotron peak (HSP; ${\nu }_{\mathrm{pk}}^{\mathrm{sy}}\gt {10}^{15}$ Hz) BL Lac object, 4FGL J1520.8-0348 shows high γ-ray luminosity (L γ > 1046 erg s‑1), being at a high redshift of z = 1.46. Since it is an outlier in the "blazar sequence," the process of its jet acceleration and power may be different from bona fide BL Lac objects. In this work, we constrain its spectral energy distribution (SED) by modeling the multiwavelength data from infrared to γ-ray regime. Simultaneous X-ray data were obtained from X-ray Multi-Mirror Mission and Nuclear Spectroscopic Telescope Array to constrain the synchrotron emission and underlying electron distribution. On undertaking the SED modeling of the source, including the effect of extragalactic background light, we conclude that the source is more likely to be a "blue FSRQ" or "masquerading BL Lac" where the BL Lac object is actually an FSRQ in disguise.

Keywords: blazars; active galactic nuclei; bl lacertae objects; high-redshift galaxies; astronomy data modeling; active galaxies
New Dynamical State and Habitability of the HD 45364 Planetary System

Planetary systems with multiple giant planets provide important opportunities to study planetary formation and evolution. The HD 45364 system hosts two giant planets that reside within the habitable zone (HZ) of their host star and was the first system discovered with a 3:2 mean motion resonance (MMR). Several competing migration theories with different predictions have previously provided explanations regarding the observed resonance through dynamical simulations that utilized limited data. Here, over ten years since the original discovery, we revisit the system with a substantially increased radial velocity (RV) sample from High Accuracy Radial Velocity Planet Searcher spectrograph and High Resolution Echelle Spectrometer that significantly extends the observational baseline. We present the revised orbital solutions for the two planets using both Keplerian and dynamical models. Our RV models suggest orbits that are more circular and separated than those previously reported. As a result, the predicted strong planet-planet interactions were not detected. The system dynamics were reanalyzed, and the planet pair was found to exhibit apsidal behavior of both libration and circulation, indicating a quasi-resonance state rather than being truly in MMR. The new orbital solution and dynamical state of the system confirm migration models that predicted near-circular orbits as the preferred scenario. We also study the habitability prospects of this system and found that an additional Earth-mass planet and exomoons in the HZ are possible. This work showcases the importance of continued RV observations and its impact on our knowledge of the system's dynamical history. HD 45364 continues to be an interesting target for both planetary formation and habitability studies.

Keywords: exoplanet dynamics; exoplanets; radial velocity; astrobiology; natural satellites (extrasolar); exoplanet systems
The First Flare Observation with a New Solar Microwave Spectrometer Working in 35-40 GHz

The microwave spectrum contains valuable information about solar flares. Yet, the present spectral coverage is far from complete and broad data gaps exist above 20 GHz. Here we report the first flare (the X2.2 flare on 2022 April 20) observation of the newly built Chashan Broadband Solar millimeter spectrometer (CBS) working from 35 to 40 GHz. We use the CBS data of the new Moon to calibrate, and the simultaneous NoRP data at 35 GHz to cross-calibrate. The impulsive stage has three local peaks with the middle one being the strongest and the maximum flux density reaches ~9300 solar flux unit at 35-40 GHz. The spectral index of the CBS data (α C) for the major peak is mostly positive, indicating the gyrosynchrotron turnover frequency (ν t ) goes beyond 35-40 GHz. The frequency ν t is smaller yet still larger than 20 GHz for most of the other two peaks according to the spectral fittings with NoRP-CBS data. The CBS index manifests the general rapid-hardening-then-softening trend for each peak and gradual hardening during the decay stage, agreeing with the fitted optically thin spectral index (α tn) for ν t < 35 GHz. In addition, the obtained turnover frequency (ν t ) during the whole impulsive stage correlates well with the corresponding intensity (I t ) according to a power-law dependence ( ${I}_{t}\propto {\nu }_{t}^{4.8}$ ) with a correlation coefficient of 0.82. This agrees with earlier studies on flares with low turnover frequency (≤17 GHz), yet it is being reported for the first time for events with a high turnover frequency (≥20 GHz).

Keywords: radio bursts; solar flares; spectrometers; spectral index