adsabs/SciX_UAT_keywords huggingface dataset:
Vacuum Ultraviolet Fourier-transform Spectroscopy of 16O and 18O

A spectroscopic study of atomic oxygen (O I) is performed using the Fourier-transform vacuum ultraviolet (VUV) spectrometer at the Dichroïsme Et Spectroscopie par Interaction avec le Rayonnement Synchrotron beamline of the SOLEIL synchrotron. Transition frequencies of O I lines in the range between 76,000 and 151,000 cm-1, corresponding to wavelengths between 665 and 1306 Å, are presented. In the wavelength window a data set of 208 lines is obtained for which line centers were determined at an accuracy of ≤0.035 cm-1, verified through a comparison with previous VUV-laser spectroscopy at an accuracy of 0.008 cm-1. Transitions to upper states belonging to several ns and nd Rydberg series that converge to the 4S3/2, 2D, and 2P ionization limits are presented. Besides studies on the main 16O isotope, measurements of the 18O isotope are also performed, for which an enriched sample of 18O2 gas is used. A least-squares optimization analysis is performed after merging the present new data set with some relevant accurate literature data to extract a list of level energies at high accuracy. When comparing with the database of the National Institute of Standards and Technology, good agreement is found for levels with low principal quantum numbers n ≤ 7 or below excitation energies of 108,000 cm-1; however, significant deviations were found for levels with n > 7. The main result of the present study is the realization of an improved data set of transition frequencies and level energies for O I, with its usefulness demonstrated in a comparison with high-resolution astronomical spectra showing absorption in the line of sight to distant quasars.

Keywords: atomic spectroscopy
A Characterization of the ALMA Phasing System at 345 GHz

The development of the Atacama Large Millimeter/submillimeter Array (ALMA) phasing system (APS) has allowed ALMA to function as an extraordinarily sensitive station for very long baseline interferometry (VLBI) at frequencies of up to 230 GHz (λ ≈ 1.3 mm). Efforts are now underway to extend the use of the APS to 345 GHz (λ ≈ 0.87 mm). Here we report a characterization of APS performance at 345 GHz based on a series of tests carried out between 2015 and 2021, including a successful global VLBI test campaign conducted in 2018 October in collaboration with the Event Horizon Telescope.

Keywords: astronomical instrumentation; astronomical techniques; astronomy data acquisition; astronomy software; millimeter astronomy; radio astronomy; radio interferometers; very long baseline interferometry
Superrotation of Titan's Stratosphere Driven by the Radiative Heating of the Haze Layer

Titan's stratosphere has been observed in a superrotation state, where the atmosphere rotates many times faster than the surface does. Another characteristic of Titan's atmosphere is the presence of a thick haze layer. In this paper, we performed numerical experiments using a general circulation model to explore the effects of the haze layer on the stratospheric superrotation. We employed a semigray radiation model of Titan's atmosphere following McKay et al., which takes account of sunlight absorption by the haze particles. The phase change of methane or seasonal changes were not taken into account. Our model with radiation parameters tuned for Titan yielded a global eastward wind around the equator with larger velocities at higher altitudes, except at around 70 km, after 105 Earth days. Although the atmosphere is not in an equilibrium state, the zonal wind profiles are approximately consistent with the observed one. By changing the parameters of the radiation model, we found that the intensity and the location of the maximum zonal wind velocity highly depended on the optical thickness and the altitude of the haze layer, respectively. Analysis of our experiments suggests that the quasi-stationary stratospheric superrotation is maintained by the balance between the meridional circulation decoupled from the surface and the eddies that transport angular momentum equatorward. This is different from, but similar to, the so-called Gierasch mechanism, in which momentum is supplied from the surface. This structure may explain the no-wind region at about 80 km in altitude.

Keywords: titan; planetary atmospheres; atmospheric circulation
The Behavior of HgMn Stars in the Far UV-Paper 22: HD 37752

The analysis of three spectra of the He-weak Hg star HD 37752 recorded by the SWP camera on board the International Ultraviolet Explorer does not reveal variations of the far-ultraviolet flux of this star over one set of observations on 1982 September 19th. The IUE spectra cover only a very small fraction (10%) of the rotational period derived from the TESS lightcurve which precludes any conclusion on the far-ultraviolet variability of HD 37752.

Keywords: chemically peculiar stars; helium-weak stars
Contribution of Magnetic Reconnection Events to Energy Dissipation in Space Plasma Turbulence

By analyzing the magnetosheath measurements from the Magnetospheric Multiscale Spacecraft, we obtain statistical results for the contribution of magnetic reconnection (MR) events at electron scales to the energy dissipation of coherent structures in shocked turbulent plasmas. The partial variance of increments (PVI) method is employed to find coherent structures in the magnetic field data. We consider criteria to further identify MR events, such as reversal of magnetic field components, significant energy dissipation, and evident electron outflow velocity. Statistically, for most MR events, their PVI values are larger than those of other types of coherent structures, and their energy dissipations are also stronger. However, due to the relatively small number of MR events, their contribution to coherent structures' energy dissipation is relatively trivial. If the dissipation of non-coherent structures is taken into account, MR's contribution to energy dissipation would be even less. Hence, we suggest that MR events, though having strong dissipation locally, are not the major contributor to energy dissipation in the turbulent magnetosheath. After analyzing the features of non-MR current sheets, we propose that these are mainly coherent structures inherent to kinetic Alfvén fluctuations.

Keywords: space plasmas; interplanetary turbulence; alfven waves; planetary magnetospheres
The Long-term Spin-down Trend of Ultraluminous X-Ray Pulsar M82 X-2

The discovery in 2014 of the pulsation from the ultraluminous X-ray source (ULX) M82 X-2 has changed our view of ULXs. Because of the relatively short baseline over which pulsations have been detected so far, M82 X-2's spin state had been assumed to be in an equilibrium state. Using Chandra and XMM-Newton archive data, we are able to investigate the pulsation of M82 X-2 back to 2005 and 2001. The newly determined spin frequencies clearly show a long-term spin-down trend. If this trend is caused by magnetic threading, we infer a dipolar magnetic field of ∼1.2 × 1013 G and that a mild beaming factor (∼4) is needed to match the braking torque with the mass accretion torque. On the other hand, there are NuSTAR observations showing instantaneous spin-down behaviors, which might favor a variable prograde/retrograde flow scenario for M82 X-2.

Keywords: accretion; x-ray binary stars; ultraluminous x-ray sources
The Dark Energy Survey Supernova Program: Cosmological Biases from Host Galaxy Mismatch of Type Ia Supernovae

Redshift measurements, primarily obtained from host galaxies, are essential for inferring cosmological parameters from type Ia supernovae (SNe Ia). Matching SNe to host galaxies using images is nontrivial, resulting in a subset of SNe with mismatched hosts and thus incorrect redshifts. We evaluate the host galaxy mismatch rate and resulting biases on cosmological parameters from simulations modeled after the Dark Energy Survey 5 Yr (DES-SN5YR) photometric sample. For both DES-SN5YR data and simulations, we employ the directional light radius method for host galaxy matching. In our SN Ia simulations, we find that 1.7% of SNe are matched to the wrong host galaxy, with redshift differences between the true and matched hosts of up to 0.6. Using our analysis pipeline, we determine the shift in the dark energy equation of state parameter (Δw) due to including SNe with incorrect host galaxy matches. For SN Ia–only simulations, we find Δw = 0.0013 ± 0.0026 with constraints from the cosmic microwave background. Including core-collapse SNe and peculiar SNe Ia in the simulation, we find that Δw ranges from 0.0009 to 0.0032, depending on the photometric classifier used. This bias is an order of magnitude smaller than the expected total uncertainty on w from the DES-SN5YR sample of ∼0.03. We conclude that the bias on w from host galaxy mismatch is much smaller than the uncertainties expected from the DES-SN5YR sample, but we encourage further studies to reduce this bias through better host-matching algorithms or selection cuts.

Keywords: cosmology; type ia supernovae; dark energy
Beyond Ultra-diffuse Galaxies. II. Environmental Quenching of Mass-Size Outliers among the Satellites of Milky Way Analogs

Recent observations have reignited interest in a population of dwarf galaxies that are large and diffuse for their mass, often called ultra-diffuse galaxies (UDGs). However, the origin and evolution of these mass-size outliers and the role of the environment are still unclear. Using the exquisitely deep and wide Hyper Suprime-Cam Strategic Survey images, we search for ultra-puffy galaxies (UPGs), defined as being 1.5σ larger than the average size for their mass, around Milky Way-like galaxies. We present the sizes and radial distributions of mass-size outliers and derive their quenched fraction to explore the impact of the environment. Surprisingly, despite being outliers in size, the UPGs have a similar quenched fraction as normal-sized satellites of Milky Way analogs in both observations and simulations, suggesting that quenching is not tied to being a mass-size outlier. The quenched fraction is higher for the UPGs associated with redder hosts, as well as those that are closer to the host in projection. In contrast, the UDGs are overall redder and more quiescent compared with normal satellites. We show that the classic definition of UDGs is heavily weighted toward quenched galaxies and thus cannot be used for a study of quenching of mass-size outliers.

Keywords: low surface brightness galaxies; galaxy properties; dwarf galaxies; galaxy quenching; galaxy evolution
Observable Signature of Merging Stellar-mass Black Holes in Active Galactic Nuclei

The origin of stellar-mass black hole mergers discovered through gravitational waves is being widely debated. Mergers in the disks of active galactic nuclei (AGNs) represent a promising source of origin, with possible observational clues in the gravitational-wave data. Beyond gravitational waves, a unique signature of AGN-assisted mergers is electromagnetic emission from the accreting black holes. Here we show that jets launched by accreting black holes merging in an AGN disk can be detected as peculiar transients by infrared, optical, and X-ray observatories. We further show that this emission mechanism can explain the possible associations between gravitational-wave events and the optical transient ZTF 19abanrhr and the proposed gamma-ray counterparts GW150914-GBM and LVT151012-GBM. We demonstrate how these associations, if genuine, can be used to reconstruct the properties of these events' environments. Searching for infrared and X-ray counterparts to similar electromagnetic transients in the future, once host galaxies are localized by optical observations, could provide a smoking-gun signature of the mergers' AGN origin.

Keywords: gravitational wave sources; high energy astrophysics; black hole physics; active galactic nuclei; jets; transient sources; time domain astronomy
S-PLUS: Photometric Recalibration with the Stellar Color Regression Method and an Improved Gaia XP Synthetic Photometry Method

We present a comprehensive recalibration of narrowband/medium-band and broadband photometry from the Southern Photometric Local Universe Survey (S-PLUS) by leveraging two approaches: an improved Gaia XP synthetic photometry (XPSP) method with corrected Gaia XP spectra, and the stellar color regression (SCR) method with corrected Gaia Early Data Release 3 photometric data and spectroscopic data from LAMOST Data Release 7. Through the use of millions of stars as standards per band, we demonstrate the existence of position-dependent systematic errors, up to 23 mmag for the main survey region, in the S-PLUS iDR4 photometric data. A comparison between the XPSP and SCR methods reveals minor differences in zero-point offsets, typically within the range of 1–6 mmag, indicating the accuracy of the recalibration, and a twofold to threefold improvement in the zero-point precision. During this process, we also verify and correct for systematic errors related to CCD position. The corrected S-PLUS iDR4 photometric data will provide a solid data foundation for conducting scientific research that relies on high-precision calibration. Our results underscore the power of the XPSP method in combination with the SCR method, showcasing their effectiveness in enhancing calibration precision for wide-field surveys when combined with Gaia photometry and XP spectra, to be applied for other S-PLUS subsurveys.

Keywords: stellar photometry; astronomy data analysis; calibration
New Post-DART Collision Period for the Didymos System: Evidence for Anomalous Orbital Decay

On 2022 September 26, NASA's DART spacecraft impacted Dimorphos, the secondary asteroid in the (65803) Didymos system, so that the efficiency with which a satellite could divert an asteroid could be measured from the change in the systems period. We present new data from the Thacher Observatory and measure a change in period, ΔP = - 34.2 ± 0.1 minutes, which deviates from previous measurements by 3.5σ. This suggests that the system period may have decreased by ~1 minute in the 20-30 days between previous measurements and our measurements. We find that no mechanism previously presented for this system can account for this large of a period change, and drag from impact ejecta is an unlikely explanation. Further observations of the (65803) Didymos system are needed to both confirm our result and to further understand this system post impact.

Keywords: near-earth objects; asteroid satellites; ccd photometry; light curves
Improved Models of R Coronae Borealis Stars

We present an improved numerical method to model subsolar He+CO-WD merger progenitors of R Corona Borealis stars that builds on our previous work. These improvements include a smooth entropy transition from the core to the envelope of the post-merger, inclusion of single-zone nucleosynthesis to mimic the effects of burning during the merger event, and post-processing the models with a larger nuclear network for analysis of s-process nucleosynthesis. We perform a parameter study to understand the effects of the entropy transition, peak temperature, and overshooting on our models. The models that best agree with observations of R Corona Borealis stars are processed with a much larger nuclear network to investigate s-process nucleosynthesis and the dredge-up of s-process products into the outer envelope in detail. We present a model with a significant enhancement in s-process elements, which also agrees with observed surface abundances and isotopic ratios of 16O/16O and C/O between 1 and 10. Finally, we find that the neutron exposure and initial neutron densities this model requires to obtain such an enhancement are much more consistent with i-process nucleosynthesis.

Keywords: stellar mergers; close binary stars; stellar abundances; stellar evolution; white dwarf stars; nucleosynthesis
The First TESS Self-lensing Pulses: Revisiting KIC 12254688

We report the observations of two self-lensing pulses from KIC 12254688 in Transiting Exoplanet Survey Satellite (TESS) light curves. This system, containing an F2V star and white-dwarf companion, was among the first self-lensing binary systems discovered by the Kepler Space Telescope over the past decade. Each observed pulse occurs when the white dwarf transits in front of its companion star, gravitationally lensing the star's surface, thus making it appear brighter to a distant observer. These two pulses are the very first self-lensing events discovered in TESS observations. We describe the methods by which the data were acquired and detrended, as well as the best-fit binary parameters deduced from our self-lensing+radial velocity model. We highlight the difficulties of finding new self-lensing systems with TESS, and we discuss the types of self-lensing systems that TESS may be more likely to discover in the future.

Keywords: compact binary stars; gravitational microlensing; white dwarf stars
Dynamical Hotness, Star Formation Quenching, and Growth of Supermassive Black Holes

A stellar system is dynamically hot when its kinetic energy is dominated by random motion represented by the velocity dispersion σ hot. We use MaNGA data to obtain the inner and outer dispersion of a galaxy, σ in and σ out, to characterize its dynamical status and study its connection with star formation quenching and the growth of its supermassive black hole (SMBH). We divide galaxies into fully quenched (FQGs), partially quenched (PQGs), and fully star-forming (FSGs) populations, and identify quenched central cores (QCCs) in PQGs. The galaxy distribution in (σ in/σ hot)-(σ out/σ hot) diagram is L-shaped, consisting of a horizontal sequence (σ out/σ hot ~ 0) and a vertical sequence (σ in/σ hot ~ 1). FQGs and QCCs are located at the top of the vertical sequence, σ out/σ hot ~ 1, and are thus dynamically hot over their entire bodies. PQGs reside along the vertical sequence, so they have hot centers but cold outskirts. FSGs are diverse and can be found in both sequences. Galaxy structural properties, star formation, and AGN activities make a transition along the horizontal sequence at σ in/σ hot ~ 0.5, and along the vertical sequence at σ out/σ hot ~ 0.5. The fractions of optical AGNs and barred galaxies increase rapidly in the first transition and decline rapidly in the second; radio galaxies are located at the top of the vertical sequence. Our results demonstrate that star formation quenching and SMBH growth are effective only in dynamically hot systems. A simple model along this line can reproduce the observed SMBH scaling relations. We discuss how secular processes and strong interactions can make a system dynamically hot, and lead to the SMBH growth and star formation quenching.

Keywords: galaxy formation; galaxy evolution; galaxy classification systems; galaxy quenching; galaxy dynamics; active galactic nuclei; supermassive black holes; scaling relations; star formation
Random Walk and Trapping of Interplanetary Magnetic Field Lines: Global Simulation, Magnetic Connectivity, and Implications for Solar Energetic Particles

The random walk of magnetic field lines is an important ingredient in understanding how the connectivity of the magnetic field affects the spatial transport and diffusion of charged particles. As solar energetic particles propagate away from near-solar sources, they interact with the fluctuating magnetic field, which modifies their distributions. We develop a formalism in which the differential equation describing the field line random walk contains both effects due to localized magnetic displacements and a non-stochastic contribution from the large-scale expansion. We use this formalism together with a global magnetohydrodynamic simulation of the inner-heliospheric solar wind, which includes a turbulence transport model, to estimate the diffusive spreading of magnetic field lines that originate in different regions of the solar atmosphere. We first use this model to quantify field line spreading at 1 au, starting from a localized solar source region, and find rms angular spreads of about 20°-60°. In the second instance, we use the model to estimate the size of the source regions from which field lines observed at 1 au may have originated, thus quantifying the uncertainty in calculations of magnetic connectivity; the angular uncertainty is estimated to be about 20°. Finally, we estimate the filamentation distance, i.e., the heliocentric distance up to which field lines originating in magnetic islands can remain strongly trapped in filamentary structures. We emphasize the key role of slab-like fluctuations in the transition from filamentary to more diffusive transport at greater heliocentric distances.

Keywords: solar energetic particles; interplanetary turbulence; interplanetary magnetic fields; solar wind
Low-lying Dipole Resonances in FeCN-: A Viable Formation Pathway for FeCN- in Space

A low-lying resonance in FeCN- anion was identified through abrupt changes in the spectral dependence of the photoelectron angular distribution. Non-Franck-Condon transitions from the resonance to the neutral FeCN (4Δ), and the corresponding photoelectron angular distributions revealed that the resonance is a dipole scattering state. Significant thermionic electron emission was observed in the resonant photoelectron spectra, indicating a strong coupling of the resonance with the ground state of this triatomic anion and its competition over autodetachment. This low-lying resonance is identified to be an efficient pathway for the formation of FeCN- anion in the outer envelope of IRC+10216. The results in general reveal formation pathways in space for anions with low-lying resonances and large permanent dipole moment.

Keywords: interstellar molecules; molecular physics; photoelectron spectroscopy
Constraints on Solar Wind Density and Velocity Based on Coronal Tomography and Parker Solar Probe Measurements

Previous work has established an empirical relationship between densities gained from coronal rotational tomography near the ecliptic plane with solar wind outflow speeds at heliocentric distance r 0 = 8R ⊙. This work aims to include solar wind acceleration, and thus velocity profiles out to 1 au. Inner boundary velocities are given as a function of normalized tomographic densities, ρ N , as ${V}_{0}=\left(75\ast {e}^{-\left[5.2* {\rho }_{N}\right]}+108\right)$ , and typically range from 100 to 180 km s-1. The subsequent acceleration is defined as $V(r)={V}_{0}\left(1+{\alpha }_{\mathrm{IP}}\left[1-{e}^{\left(-\left[r-{r}_{0}\right]/{r}_{{\rm{H}}}\right)}\right]\right)$ , with α IP ranging between 1.75 and 2.7, and r H between 50 and 35 R ⊙ dependent on V 0. These acceleration profiles approximate the distribution of in situ measurements by Parker Solar Probe (PSP) and other measurements at 1 au. Between 2018 November and 2021 September these constraints are applied using the HUXt model and give good agreement with in situ observations at PSP, with a ~6% improvement compared with using a simpler constant acceleration model previously considered. Given the known tomographical densities at 8 R ⊙, we extrapolate density to 1 au using the model velocities and assuming mass flux conservation. Extrapolated densities agree well with OMNI measurements. Thus coronagraph-based estimates of densities define the ambient solar wind outflow speed, acceleration, and density from 8 R ⊙ to at least 1 au. This sets a constraint on more advanced models, and a framework for forecasting that provides a valid alternative to the use of velocities derived from magnetic field extrapolations.

Keywords: solar wind; solar coronal mass ejections; space weather; solar corona; heliosphere