adsabs/SciX_UAT_keywords huggingface dataset:
Measures of Scale-dependent Alfvénicity in the First PSP Solar Encounter

The solar wind shows periods of highly Alfvénic activity, where velocity fluctuations and magnetic fluctuations are aligned or antialigned with each other. It is generally agreed that solar wind plasma velocity and magnetic field fluctuations observed by the Parker Solar Probe (PSP) during the first encounter are mostly highly Alfvénic. However, quantitative measures of Alfvénicity are needed to understand how the characterization of these fluctuations compares with standard measures from prior missions in the inner and outer heliosphere, in fast wind and slow wind, and at high and low latitudes. To investigate this issue, we employ several measures to quantify the extent of Alfvénicity—the Alfvén ratio rA, the normalized cross helicity σc, the normalized residual energy σr, and the cosine of angle between velocity and magnetic fluctuations $\cos {\theta }_{{vb}}$ . We show that despite the overall impression that the Alfvénicity is large in the solar wind sampled by PSP during the first encounter, during some intervals the cross helicity starts decreasing at very large scales. These length scales (often >1000dI) are well inside inertial range, and therefore, the suppression of cross helicity at these scales cannot be attributed to kinetic physics. This drop at large scales could potentially be explained by large scale shears present in the inner heliosphere sampled by PSP. In some cases, despite the cross helicity being constant down to the noise floor, the residual energy decreases with scale in the inertial range. These results suggest that it is important to consider all these measures to quantify Alfvénicity.

Keywords: heliosphere; solar wind; space plasmas
On the X-Ray, Optical, and Radio Afterglows of the BdHN I GRB 180720B Generated by Synchrotron Emission

Gamma-ray bursts (GRBs) are systems of unprecedented complexity across all the electromagnetic spectrum, including the radio, optical, X-rays, gamma rays in the MeV and GeV regimes, as well as ultrahigh-energy cosmic rays, each manifested in seven specific physical processes with widely different characteristic evolution timescales ranging from 10-14 s to 107 s or longer. We here study the long GRB 180720B originating from a binary system composed of a massive carbon-oxygen (CO) star of about 10M ⊙ and a companion neutron star (NS). The gravitational collapse of the CO star gives rise to a spinning newborn NS (νNS), with an initial period of P 0 = 1 ms that powers the synchrotron radiation in the radio, optical, and X-ray wavelengths. We here investigate solely the GRB 180720B afterglows and present a detailed treatment of its origin based on the synchrotron radiation released by the interaction of the νNS and the SN ejecta. We show that in parallel to the X-ray afterglow, the spinning νNS also powers the optical and radio afterglows and allows to infer the νNS and ejecta parameters that fit the observational data.

Keywords: gamma-ray bursts
An X-Ray Census of Fast Radio Burst Host Galaxies: Constraints on Active Galactic Nuclei and X-Ray Counterparts

We present the first X-ray census of fast radio burst (FRB) host galaxies to conduct the deepest search for active galactic nuclei (AGN) and X-ray counterparts to date. Our sample includes seven well-localized FRBs with unambiguous host associations and existing deep Chandra observations, including two events for which we present new observations. We find evidence for AGN in two FRB host galaxies based on the presence of X-ray emission coincident with their centers, including the detection of a luminous (L X ≈ 5 × 1042 erg s-1) X-ray source at the nucleus of FRB 20190608B's host, for which we infer an SMBH mass of M BH ~ 108 M ⊙ and an Eddington ratio L bol/L Edd ≈ 0.02, characteristic of geometrically thin disks in Seyfert galaxies. We also report nebular emission-line fluxes for 24 highly secure FRB hosts (including 10 hosts for the first time), and assess their placement on a BPT diagram, finding that FRB hosts trace the underlying galaxy population. We further find that the hosts of repeating FRBs are not confined to the star-forming locus, contrary to previous findings. Finally, we place constraints on associated X-ray counterparts to FRBs in the context of ultraluminous X-ray sources (ULXs), and find that existing X-ray limits for FRBs rule out ULXs brighter than L X ≳ 1040 erg s-1. Leveraging the CHIME/FRB catalog and existing ULX catalogs, we search for spatially coincident ULX-FRB pairs. We identify a total of 28 ULXs spatially coincident with the localization regions for 17 FRBs, but find that the DM-inferred redshifts for the FRBs are inconsistent with the ULX redshifts, disfavoring an association between these specific ULX-FRB pairs.

Keywords: radio transient sources; active galactic nuclei; ultraluminous x-ray sources; agn host galaxies
Longitudinal Variation of H2O Ice Absorption on Miranda

Many tidally locked icy satellites in the outer solar system show leading/trailing hemispherical asymmetries in the strength of near-infrared (NIR) H2O ice absorption bands, in which the absorption bands are stronger on the leading hemisphere. This is often attributed to a combination of magnetospheric irradiation effects and impact gardening, which can modify grain size, expose fresh ice, and produce dark contaminating compounds that reduce the strength of absorption features. Previous research identified this leading/trailing asymmetry on the four largest classical Uranian satellites but did not find a clear leading/trailing asymmetry on Miranda, the smallest and innermost classical moon. We undertook an extensive observational campaign to investigate variations of the NIR spectral signature of H2O ice with longitude on Miranda's northern hemisphere. We acquired 22 new spectra with the TripleSpec spectrograph on the ARC 3.5 m telescope and four new spectra with GNIRS on Gemini North. Our analysis also includes three unpublished and seven previously published spectra taken with SpeX on the 3 m IRTF. We confirm that Miranda has no substantial leading/trailing hemispherical asymmetry in the strength of its H2O ice absorption features. We additionally find evidence for an anti-Uranus/sub-Uranus asymmetry in the strength of the 1.5 μm H2O ice band that is not seen on the other Uranian satellites, suggesting that additional endogenic or exogenic processes influence the longitudinal distribution of H2O ice band strengths on Miranda.

Keywords: uranian satellites; planetary surfaces; surface composition; surface ices; surface processes
Detection of the Occultation of 55 Cancri e with TESS

55 Cancri e is an ultra-short period transiting Super-Earth observed by TESS in Sector 21. Using this photometry, we measure the occultation depth in the TESS bandpass, leveraging the precise transit light curve and comparing multiple detrending methods. We measure the occultation depth to be (15.0 ± 4.8) ppm—a staggeringly small change in brightness, yet one detected by TESS in just a single sector of data. This implies a brightness temperature of ${2800}_{-160}^{+130}$ K, which is around 1.5σ greater than expected given the mean depth measured with Spitzer. This is not a formally significant difference, and may be accounted for by the known variability, or by an albedo of ∼0.5. In any case, future TESS observations of this system will provide an exciting opportunity to further study this diminutive world's atmosphere.

Keywords: exoplanet astronomy; exoplanet atmospheres
Detecting New Visual Binaries in Gaia DR3 with Gaia and Two Micron All Sky Survey (2MASS) Photometry. II. Speckle Observations of 16 Low-separation Systems

Here we present speckle observations of 16 low-separation (s < 30 au) high-probability candidate binaries from the catalog by Medan et al., where secondaries typically lack astrometric solutions in Gaia. From these speckle observations, we find a second component is always detected within the field of view. To determine if the detection is consistent with a physical companion or a chance alignment with a background source, we utilize a statistic from Tokovinin & Kiyaeva that compares the apparent motion of the systems to the expected orbital motion ( $\mu ^{\prime} $ ). Using simulated binary orbits, we construct likelihood distributions of $\mu ^{\prime} $ assuming various total errors on the measurements. With the hypothesis that the system is a true binary, we show that large measurement errors can result in $\mu ^{\prime} $ values higher than expected for bound systems. Using simulated chance alignments, we also create similar likelihoods to test this alternative hypothesis. By combining likelihoods of both true binaries and chance alignments, we find that 15 of the 16 candidates are physical systems regardless of the level of measurement error. Our findings also accommodate all 16 as physical systems if the average, relative measurement error on the binary separations and position angles is ∼4.3%, which is consistent with our knowledge of the Gaia and Gemini speckle pipelines. Importantly, beyond assessing the likelihood of a true binary versus chance alignment, this quantitative assessment of the true average measurement error will allow more robust error estimates of mass determinations from short separation binaries with Gaia and/or Gemini speckle data.

Keywords: close binary stars; catalogs; visual binary stars
6 cm OH Masers in Northern Star Formation Regions

We have used the Shanghai Tianma Radio Telescope to search for three OH transitions at 4.7 GHz toward 155 northern star formation regions. We detect 4.7 GHz OH masers in 18 star formation regions, 8 of which are reported here for the first time. From these 18 sources, we detect 6 4660 MHz masers, 13 4765 MHz masers, and no 4750 MHz masers. A further 1 source (Sgr B2N) has been re-detected with broad quasi-thermal emission in all three OH lines. W49SW was re-detected with broad quasi-thermal emission at both 4660 and 4750 MHz. One source (W31, G010.626-0.387) was re-detected with quasi-thermal emission at both 4750 and 4765 MHz. One source (G005.885-0.392) was first detected with quasi-thermal emission at 4660 MHz. We have investigated the associations between the detected 4.7 GHz OH masers with ground-state OH masers near 1.7 GHz, 6.7 GHz methanol masers and 22 GHz water masers reported in the literature. We find that the presence of 1665 MHz OH masers is a better indicator of the presence of 4.7 GHz OH masers than 1720 MHz OH masers. The majority of the 4.7 GHz OH masers are associated with 6.7 GHz methanol and/or 22 GHz water masers. We have compared the characteristics of our detections with those reported previously in the literature and found that only five sources are fairly stable.

Keywords: interstellar medium
Connection between Galaxies and H I in Circumgalactic and Intergalactic Media: Variation according to Galaxy Stellar Mass and Star Formation Activity

This paper systematically investigates the comoving megaparsec-scale intergalactic medium (IGM) environment around galaxies traced by the Lyα forest. Using our cosmological hydrodynamic simulations, we investigate the IGM-galaxy connection at z = 2 by two methods: (i) cross-correlation analysis between galaxies and the fluctuation of Lyα forest transmission (δF) and (ii) comparison of the overdensity of neutral hydrogen (H I) and galaxies. Our simulations reproduce observed cross-correlation functions (CCFs) between Lyα forest and Lyman-break galaxies. We further investigate the variation of the CCF using subsamples divided by dark matter halo mass (MDH), galaxy stellar mass (M⋆), and star formation rate (SFR) and find that the CCF signal becomes stronger with increasing MDH, M⋆, and SFR. The CCFs between galaxies and gas density fluctuation are also found to have similar trends. Therefore, the variation of δF-CCF depending on MDH, M⋆, and SFR is due to varying gas densities around galaxies. We find that the correlation between galaxies and the IGM H I distribution strongly depends on MDH as expected from linear theory. Our results support the ΛCDM paradigm, confirming a spatial correlation between galaxies and IGM H I, with more massive galaxies being clustered in higher-density regions.

Keywords: galaxy evolution; galaxy formation; intergalactic medium; lyman alpha forest; hydrodynamical simulations; large-scale structure of the universe; circumgalactic medium
The ESO-VLT MIKiS Survey Reloaded: Velocity Dispersion Profile and Rotation Curve of NGC 1904

We present an investigation of the internal kinematic properties of M79 (NGC 1904). Our study is based on radial velocity measurements obtained from the ESO-VLT Multi-Instrument Kinematic Survey (MIKiS) of Galactic globular clusters for more than 1700 individual stars distributed between ~0.″3 and 770″ (~14 three-dimensional half-mass radii) from the center. Our analysis reveals the presence of ordered line-of-sight rotation with a rotation axis almost aligned along the east-west direction and a velocity peak of 1.5 km s-1 at ~70″ from the rotation axis. The velocity dispersion profile is well described by the same King model that best fits the projected density distribution, with a constant central plateau at σ 0 ~ 6 km s-1. To investigate the cluster rotation in the plane of the sky, we have analyzed the proper motions provided by the Gaia EDR3, finding a signature of rotation with a maximum amplitude of ~2.0 km s-1 at ~80″ from the cluster center. Analyzing the three-dimensional velocity distribution for a subsample of 130 stars, we confirm the presence of systemic rotation and find a rotation axis inclination angle of 37° with respect to the line of sight. As a final result, the comparison of the observed rotation curves with the results of a representative N-body simulation of a rotating star cluster shows that the present-day kinematic properties of NGC 1904 are consistent with those of a dynamically old system that has lost a significant fraction of its initial angular momentum. *Based on observations collected at the European Southern Observatory, Cerro Paranal (Chile), under proposal 193.D-0232 (PI: Ferraro) and 0104.D-0636 (PI: Ferraro).

Keywords: globular star clusters; stellar kinematics; spectroscopy
Nonlinear Fast Magnetosonic Waves in Solar Prominence Pillars

We investigate the properties of nonlinear fast magnetosonic (NFM) waves in a solar prominence, motivated by recent high-resolution and high-cadence Hinode/Solar Optical Telescope (SOT) observations of small-scale oscillations in a prominence pillar. As an example, we analyze the details of the 2012 February 14 Hinode/SOT observations of quasi-periodic propagating features consistent with NFM waves, imaged in emission in Ca II and in the far blue wing of Hα. We perform wavelet analysis and find oscillations in the 1-3 minutes period range. Guided by these observations, we model the NFM waves with a three-dimensional magnetohydrodynamics (3D MHD) model, extending previous 2.5D MHD studies. The new model includes the structure of the high-density, low-temperature material of the prominence pillar embedded in the hot corona, in both potential and non-force-free sheared magnetic field configurations. The nonlinear model demonstrates the effects of mode coupling and the propagating density compressions associated with linear and NFM waves. The guided fast magnetosonic waves, together with density compressions and currents, are reproduced in the 3D pillar structure. We demonstrate for the first time the dynamic effects of the Lorentz force due to the magnetic shear in the non-force-free field on the pillar structure and on the propagation of the waves. The insights gained from the 3D MHD modeling are useful for improving the coronal seismology of prominence structures that exhibit fast MHD wave activity.

Keywords: active solar corona; solar prominences; solar filaments; magnetohydrodynamical simulations
The White Dwarf Opportunity: Robust Detections of Molecules in Earth-like Exoplanet Atmospheres with the James Webb Space Telescope

The near-term search for life beyond the solar system currently focuses on transiting planets orbiting small M dwarfs, and the challenges of detecting signs of life in their atmospheres. However, planets orbiting white dwarfs (WDs) would provide a unique opportunity to characterize rocky worlds. The discovery of the first transiting giant planet orbiting a WD, WD 1856+534, showed that planetary-mass objects can survive close-in orbits around WDs. The large radius ratio between WD planets and their host renders them exceptional targets for transmission spectroscopy. Here, we explore the molecular detectability and atmospheric characterization potential for a notional Earth-like planet, evolving in the habitable zone of WD 1856+534, with the James Webb Space Telescope (JWST). We establish that the atmospheric composition of such Earth-like planets orbiting WDs can be precisely retrieved with JWST. We demonstrate that robust >5σ detections of H2O and CO2 can be achieved in a five-transit reconnaissance program, while the biosignatures O3 + CH4 and CH4 + N2O can be detected to >4σ in as few as 25 transits. N2 and O2 can be detected to >5σ within 100 transits. Given the short transit duration of WD habitable zone planets (∼2 minutes for WD 1856+534), conclusive molecular detections can be achieved in a small or medium JWST transmission spectroscopy program. Rocky planets in the WD habitable zone therefore represent a promising opportunity to characterize terrestrial planet atmospheres and explore the possibility of a second genesis on these worlds.

Keywords: exoplanet atmospheres; extrasolar rocky planets; habitable planets; exoplanet atmospheric composition; transmission spectroscopy; molecular spectroscopy; bayesian statistics; white dwarf stars
A Gaia View on the Star Formation in the Monoceros OB1 and R1 Associations

Stellar kinematics provides the key to understanding the star formation process. In this respect, we present a kinematic study of the Monoceros OB1 (Mon OB1) and R1 (Mon R1) associations using the recent Gaia data and radial velocities of stars derived from high-resolution spectroscopy and the literature. A total of 728 members are selected using the criteria based on the intrinsic properties of young stars, parallaxes, and proper motions. The spatial distribution and kinematic properties of members show that these associations have distinct substructures. In Mon OB1, we find one northern group and two southern groups. Mon R1 is composed of three small stellar groups that are spatially and kinematically distinct. Some stars are found in a halo around these two associations. We detect patterns of expansion for most stellar groups in the associations. In addition, two stellar groups in Mon OB1 show the signature of rotation, which provides an important constraint on cluster formation. The star formation history of Mon OB1 is slightly revised. Star formation first occurred in the southern region and subsequently in the northern region. Recent star-forming events ignited deeper into the southern region, while some stars are escaping from Mon OB1, forming a halo. Mon R1 might have formed at the same epoch as the formation of the northern group in Mon OB1. Given that star formation is taking place on different scales along a large arc-like structure, Mon OB1 and Mon R1 may be the results of hierarchical star formation.

Keywords: star formation; stellar kinematics; stellar associations; stellar dynamics; open star clusters
Using the Mark Weighted Correlation Functions to Improve the Constraints on Cosmological Parameters

We used the mark weighted correlation functions (MCFs), W(s), to study the large-scale structure of the universe. We studied five types of MCFs with the weighting scheme ρα, where ρ is the local density, and α is taken as -1, -0.5, 0, 0.5, and 1. We found that different MCFs have very different amplitudes and scale dependence. Some of the MCFs exhibit distinctive peaks and valleys that do not exist in the standard correlation functions. Their locations are robust against the redshifts and the background geometry; however, it is unlikely that they can be used as "standard rulers" to probe the cosmic expansion history. Nonetheless, we find that these features may be used to probe parameters related with the structure formation history, such as the values of σ8 and the galaxy bias. Finally, after conducting a comprehensive analysis using the full shapes of the W(s)s and WΔs(μ)s, we found that combining different types of MCFs can significantly improve the cosmological parameter constraints. Compared with using only the standard correlation function, the combinations of MCFs with α = 0, 0.5, 1 and α = 0, -1, -0.5, 0.5, 1 can improve the constraints on Ωm and w by ≈30% and 50%, respectively. We find highly significant evidence that MCFs can improve cosmological parameter constraints.

Keywords: large-scale structure of the universe; cosmological parameters from large-scale structure
Resolved Near-infrared Stellar Photometry from the Magellan Telescope for 13 Nearby Galaxies: J-region Asymptotic Giant Branch Method Distances

We present near-infrared JHK photometry for the resolved stellar populations in 13 nearby galaxies: NGC 6822, IC 1613, NGC 3109, Sextans B, Sextans A, NGC 300, NGC 55, NGC 7793, NGC 247, NGC 5253, Cen A, NGC 1313, and M83, acquired from the 6.5 m Baade–Magellan telescope. We measure distances to each galaxy using the J-region asymptotic giant branch (JAGB) method, a new standard candle that leverages the constant luminosities of color-selected, carbon-rich AGB stars. While only single-epoch, random-phase photometry is necessary to derive JAGB distances, our photometry is time-averaged over multiple epochs, thereby decreasing the contribution of the JAGB stars' intrinsic variability to the measured dispersions in their observed luminosity functions. To cross-validate these distances, we also measure near-infrared tip of the red giant branch (TRGB) distances to these galaxies. The residuals obtained from subtracting the distance moduli from the two methods yield an rms scatter of σ JAGB‑TRGB = ±0.07 mag. Therefore, all systematics in the JAGB method and TRGB method (e.g., crowding, differential reddening, star formation histories) must be contained within these ±0.07 mag bounds for this sample of galaxies because the JAGB and TRGB distance indicators are drawn from entirely distinct stellar populations and are thus affected by these systematics independently. Finally, the composite JAGB star luminosity function formed from this diverse sample of galaxies is well described by a Gaussian function with a modal value of M J = –6.20 ± 0.003 mag (stat), indicating that the underlying JAGB star luminosity function of a well-sampled full star formation history is highly symmetric and Gaussian based on over 6700 JAGB stars in the composite sample.

Keywords: observational astronomy; near infrared astronomy; distance indicators; asymptotic giant branch stars; carbon stars; galaxy distances; red giant branch