adsabs/SciX_UAT_keywords huggingface dataset:
The Sun's Magnetic Power Spectra over Two Solar Cycles. I. Calibration between SDO/HMI and SOHO/MDI Magnetograms

The Sun's magnetic field is strongly structured over a broad range of scales. Magnetic spatial power spectral analysis provides a powerful tool for understanding the various scales of magnetic fields and their interactions with plasma motions. We aim to investigate the power spectra using spherical harmonic decomposition of high-resolution Solar and Heliospheric Observatory (SOHO)/Michelson Doppler Imager (MDI) and Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager (HMI) synoptic magnetograms covering three consecutive solar cycle minima, in a series of papers. As the first of the series, we calibrate and analyze the power spectra based on cotemporal SDO/HMI and SOHO/MDI data in this paper. For the first time, we find that the calibration factor r between SOHO/MDI and SDO/HMI varies with the spatial scale l of the magnetic field, where l is the degree of the spherical harmonic. The calibration factor satisfies $r(l)=\sqrt{-0.021{l}^{0.64}+2}\quad (5\lt {\rm{l}}\leqslant 539)$ . With the calibration function, most contemporaneous SOHO/MDI and SDO/HMI magnetograms show consistent power spectra from about 8 Mm to the global scales over about three orders of magnitude. Moreover, magnetic power spectra from SOHO/MDI and SDO/HMI maps show peaks/knees at l ≈ 120, corresponding to the typical supergranular scale (about 35 Mm) constrained from direct velocimetric measurements. This study paves the way for investigating the solar cycle dependence of supergranulation and magnetic power spectra in subsequent studies.

Keywords: supergranulation; solar photosphere; calibration; solar magnetic fields
APOGEE-2S Discovery of Light- and Heavy-element Abundance Correlations in the Bulge Globular Cluster NGC 6380

We derive abundance ratios for nine stars in the relatively high-metallicity bulge globular cluster NGC 6380. We find a mean cluster metallicity between [Fe/H] = -0.80 and -0.73, with no clear evidence for a variation in iron abundances beyond the observational errors. Stars with strongly enhanced [N/Fe] abundance ratios populate the cluster and are anticorrelated with [C/Fe], trends that are considered a signal of the multiple-population phenomenon in this cluster. We detect an apparent intrinsic star-to-star spread (≳0.27 dex) in the slow neutron-capture process element (s-element) Ce II. Moreover, the [Ce/Fe] abundance ratio exhibits a likely correlation with [N/Fe], and a somewhat weaker correlation with [Al/Fe]. If confirmed, NGC 6380 could be the first high-metallicity globular cluster where a N-Ce correlation is detected. Furthermore, this correlation suggests that Ce may also be an element involved in the multiple-population phenomenon. Currently, a consensus interpretation for the origin of the this apparent N-Ce correlation in high-metallicity clusters is lacking. We tentatively suggest that it could be reproduced by different channels-low-mass asymptotic giant branch stars in the high-metallicity regime or fast-rotating massive stars ("spinstars"), due to the rotational mixing. It may also be the cumulative effect of several pollution events including the occurrence of peculiar stars. Our findings should guide stellar nucleosynthesis models, in order to understand the reasons for its apparent exclusivity in relatively high-metallicity globular clusters.

Keywords: globular star clusters; stellar abundances
Self-consistent Semianalytic Modeling of Feedback during Primordial Star Formation and Reionization

We present a new semianalytic model of the formation of the first stars. Our method takes dark matter halo merger trees (including three-dimensional spatial information) from cosmological N-body simulations as input and applies analytic prescriptions to compute both the Population III and metal-enriched star formation histories. We have developed a novel method to accurately compute the major feedback processes affecting Population III star formation: H2 photodissociation from Lyman-Werner (LW) radiation, suppression of star formation due to inhomogeneous reionization, and metal enrichment via supernova winds. Our method utilizes a grid-based approach relying on fast Fourier transforms to rapidly track the LW intensity, ionization fraction, and metallicity in three dimensions throughout the simulation box. We present simulations for a wide range of astrophysical model parameters from z ≈ 30 to 6. Initially long-range LW feedback and local metal enrichment and reionization feedback dominate. However, for z ≲ 15 we find that the star formation rate density (SFRD) of Population III stars is impacted by the combination of external metal enrichment (metals from one halo polluting other pristine halos) and inhomogeneous reionization. We find that the interplay of these processes is particularly important for the Population III SFRD at z ≲ 10. Reionization feedback delays star formation long enough for metal bubbles to reach halos that would otherwise form Population III stars. Including these effects can lead to more than an order-of-magnitude decrease in the Population III SFRD at z = 6 compared to LW feedback alone.

Keywords: high-redshift galaxies; population iii stars; cosmology
Tracking a Beam of Electrons from the Low Solar Corona into Interplanetary Space with the Low Frequency Array, Parker Solar Probe, and 1 au Spacecraft

Type III radio bursts are the result of plasma emission from mildly relativistic electron beams propagating from the low solar corona into the heliosphere where they can eventually be detected in situ if they align with the location of a heliospheric spacecraft. Here we observe a type III radio burst from 0.1 to 16 MHz using the Parker Solar Probe (PSP) FIELDS Radio Frequency Spectrometer (RFS) and from 20 to 80 MHz using the Low Frequency Array (LOFAR). This event was not associated with any detectable flare activity but was part of an ongoing type III and noise storm that occurred during PSP encounter 2. A deprojection of the LOFAR radio sources into 3D space shows that the type III radio burst sources were located on open magnetic field from 1.6 to 3 R ⊙ and originated from a near-equatorial active region around longitude E48°. Combining PSP/RFS observations with WIND/WAVES and Solar Terrestrial Relations Observatory (STEREO) WAVES, we reconstruct the type III radio source trajectory in the heliosphere interior to PSP's position, assuming ecliptic confinement. An energetic electron enhancement is subsequently detected in situ at the STEREO A spacecraft at compatible times, although the onset and duration suggests the individual burst contributes a subset of the enhancement. This work shows relatively small-scale flux emergence in the corona can cause the injection of electron beams from the low corona into the heliosphere, without needing a strong solar flare. The complementary nature of combined ground and space-based radio observations, especially in the era of PSP, is also clearly highlighted by this study.

Keywords: solar coronal radio emission; active solar corona; solar corona; heliosphere; solar energetic particles
Nondetection of CHIME/Fast Radio Burst Sources with the Arecibo Observatory

In this work, we present follow-up observations of two known repeating fast radio bursts (FRBs) and seven nonrepeating FRBs with complex morphology discovered with the CHIME/FRB project. These observations were conducted with the Arecibo Observatory 327 MHz receiver. We detected no additional bursts from these sources, nor did CHIME/FRB detect any additional bursts from these sources during our follow-up program. Based on these nondetections, we provide constraints on the repetition rate for all nine sources. We calculate repetition rates above 1 Jy using both a Poisson distribution of repetition and the Weibull distribution of repetition presented by Oppermann et al. For both distributions we find repetition upper limits of the order λ = 10-2-10-1 hr-1 for all sources. These rates are much lower than those published for notable repeating FRBs like FRB 20121102A and FRB 20201124A, suggesting the possibility of a low-repetition subpopulation.

Keywords: radio transient sources; compact objects
Model-independent Approach of the JUNO 8B Solar Neutrino Program

The physics potential of detecting 8B solar neutrinos will be exploited at the Jiangmen Underground Neutrino Observatory (JUNO), in a model-independent manner by using three distinct channels of the charged current (CC), neutral current (NC), and elastic scattering (ES) interactions. Due to the largest-ever mass of 13C nuclei in the liquid scintillator detectors and the expected low background level, 8B solar neutrinos are observable in the CC and NC interactions on 13C for the first time. By virtue of optimized event selections and muon veto strategies, backgrounds from the accidental coincidence, muon-induced isotopes, and external backgrounds can be greatly suppressed. Excellent signal-to-background ratios can be achieved in the CC, NC, and ES channels to guarantee the observation of the 8B solar neutrinos. From the sensitivity studies performed in this work, we show that JUNO, with 10 yr of data, can reach the 1σ precision levels of 5%, 8%, and 20% for the 8B neutrino flux, ${\sin }^{2}{\theta }_{12}$ , and ${\rm{\Delta }}{m}_{21}^{2}$ , respectively. Probing the details of both solar physics and neutrino physics would be unique and helpful. In addition, when combined with the Sudbury Neutrino Observatory measurement, the world's best precision of 3% is expected for the measurement of the 8B neutrino flux.

Keywords: solar neutrinos
25 au Angular Resolution Observations of HH 211 with ALMA: Jet Properties and Shock Structures in SiO, CO, and SO

HH 211 is a highly collimated jet with a chain of knots and a wiggle structure on both sides of a young Class 0 protostar. We used two epochs of Atacama Large Millimeter/submillimeter Array (ALMA) data to study its inner jet in the CO(J = 3-2), SiO(J = 8-7), and SO(NJ = 89-78) lines at ∼25 au resolution. With these ALMA and previous 2008 Submillimeter Array data, the proper motion of 8 knots within ∼250 au of the central source is found to be ∼0"068 per year (∼102 km s-1), consistent with previous measurements in the outer jet. At about four times higher resolution, the reflection-symmetric wiggle can be still fitted by a previously proposed orbiting jet source model. Previously detected continuous structures in the inner jet are now resolved, containing at least 5 subknots. These subknots are interpreted in terms of a variation in the ejection velocity of the jet with a period of ∼4.5 yr, shorter than that of the outer knots. In addition, backward and forward shocks are resolved in a fully formed knot, BK3, and signatures of internal working surface and sideways ejection are identified in position-velocity diagrams. In this knot, low-density SO and CO layers are surrounded by a high-density SiO layer.

Keywords: shocks; stellar winds; stellar jets; star formation
The Spectrum and Orbit of a Fireball Producing Mesospheric Irregularity and Implications for Meteor Mass Deposition

The physical properties of meteoroids producing meteor plasma non-field-aligned irregularities (NFAI) in the Earth's atmosphere are poorly known. Here we report a complete picture of a fireball and mesospheric NFAI that it produced for the first time. Simultaneous radar and optical observations were made by the recently completed facility, Meteor and ionospheric Irregularity Observation System. The observations show that the mesospheric NFAI were clustered into three patches where the optical meteor flares took place, instead of being generated continuously along the whole meteor path. It is very likely that nanometer-or-larger-sized dust particles could be directly generated via meteoroid fragmentation at the flaring points and thus promote the generation of NFAI patches. The properties of the parent meteoroid show a chondrite type and a Jupiter family comet orbit, with Na/Mg and Fe/Mg intensity ratios of 1.5 and 1, respectively, photometric mass of about 4 g, and fragmentation strengths of around 10-74 kPa. The results suggest that the direct generation of dust particles, which was previously observed in the atmospheric disintegration of a kiloton-scale meteoroid, could be extended to the much smaller gram-scale meteoroids. Since meteoroids having such characteristics or more fragile material are not unusual, further studies leading to a better understanding of meteor mass deposition in the upper atmosphere, which consider the dust particles directly generated via gram-scale meteoroid fragmentation, are extremely important.

Keywords: meteoroids; fireballs; earth atmosphere; impact phenomena
CMZoom. IV. Incipient High-mass Star Formation throughout the Central Molecular Zone

In this work, we constrain the star-forming properties of all possible sites of incipient high-mass star formation in the Milky Way's Galactic Center. We identify dense structures using the CMZoom 1.3 mm dust continuum catalog of objects with typical radii of ∼0.1 pc, and measure their association with tracers of high-mass star formation. We incorporate compact emission at 8, 21, 24, 25, and 70 μm from the Midcourse Space Experiment, Spitzer, Herschel, and SOFIA, cataloged young stellar objects, and water and methanol masers to characterize each source. We find an incipient star formation rate (SFR) for the Central Molecular Zone (CMZ) of ∼0.08 M ⊙ yr‑1 over the next few 105 yr. We calculate upper and lower limits on the CMZ's incipient SFR of ∼0.45 and ∼0.05 M ⊙ yr‑1,respectively, spanning roughly equal to and several times greater than other estimates of CMZ's recent SFR. Despite substantial uncertainties, our results suggest the incipient SFR in the CMZ may be higher than previously estimated. We find that the prevalence of star formation tracers does not correlate with source volume density, but instead ≳75% of high-mass star formation is found in regions above a column density ratio (N SMA/N Herschel) of ∼1.5. Finally, we highlight the detection of atoll sources, a reoccurring morphology of cold dust encircling evolved infrared sources, possibly representing H II regions in the process of destroying their envelopes.

Keywords: star formation; galactic center; milky way galaxy; young stellar objects; protostars
Probing the Innermost Regions of AGN Jets and Their Magnetic Fields with RadioAstron. V. Space and Ground Millimeter-VLBI Imaging of OJ 287

We present the first polarimetric space very long baseline interferometry (VLBI) observations of OJ 287, observed with RadioAstron at 22 GHz during a perigee session on 2014 April 4 and five near-in-time snapshots, together with contemporaneous ground VLBI observations at 15, 43, and 86 GHz. Ground-space fringes were obtained up to a projected baseline of 3.9 Earth diameters during the perigee session, and at a record 15.1 Earth diameters during the snapshot sessions, allowing us to image the innermost jet at an angular resolution of ~50μ as, the highest ever achieved at 22 GHz for OJ 287. Comparison with ground-based VLBI observations reveals a progressive jet bending with increasing angular resolution that agrees with predictions from a supermassive binary black hole model, although other models cannot be ruled out. Spectral analyses suggest that the VLBI core is dominated by the internal energy of the emitting particles during the onset of a multiwavelength flare, while the parsec-scale jet is consistent with being in equipartition between the particles and magnetic field. Estimated minimum brightness temperatures from the visibility amplitudes show a continued rising trend with projected baseline length up to 1013 K, reconciled with the inverse-Compton limit through Doppler boosting for a jet closely oriented to the line of sight. The observed electric vector position angle suggests that the innermost jet has a predominantly toroidal magnetic field, which, together with marginal evidence of a gradient in rotation measure across the jet width, indicates that the VLBI core is threaded by a helical magnetic field, in agreement with jet formation models.

Keywords: active galactic nuclei; extragalactic magnetic fields; relativistic jets; polarimetry; blazars; magnetic fields; quasars; radio astronomy; very long baseline interferometry; space telescopes; plasma jets; radio cores
Using Giant Pulses to Measure the Impulse Response of the Interstellar Medium

Giant pulses emitted by PSR B1937+21 are bright, intrinsically impulsive bursts. Thus, the observed signal from a giant pulse is a noisy but direct measurement of the impulse response from the ionized interstellar medium. We use this fact to detect 13,025 giant pulses directly in the baseband data of two observations of PSR B1937+21. Using the giant pulse signals, we model the time-varying impulse response with a sparse approximation method, in which the time dependence at each delay is decomposed in Fourier components, thus constructing a wavefield as a function of delay and differential Doppler shift. We find that the resulting wavefield has the expected parabolic shape with several diffuse structures within it, suggesting the presence of multiple scattering locations along the line of sight. We also detect an echo at a delay of about 2.4 ms, over 1.5 times the rotation period of the pulsar, which moves along the trajectory expected from geometry between the two observations. The structures in the wavefield are insufficiently sparse to produce a complete model of the system; hence, the model is not predictive across gaps larger than about the scintillation time. Nevertheless, within its range, it reproduces about 75% of the power of the impulse response, a fraction limited mostly by the signal-to-noise ratio of the observations. Furthermore, we show that by deconvolution, using the model impulse response, we can successfully recover the intrinsic pulsar emission from the observed signal.

Keywords: pulsars; radio bursts; interstellar scintillation; deconvolution
Generally Applicable Formalism for Modeling the Observable Signatures of Inflows, Outflows, and Moving Coronal Plasma Close to Kerr Black Holes

We present a generally applicable formalism for modeling the emission, absorption, reflection, and reprocessing of radiation by moving plasma streams close to a Kerr black hole. The formalism can be used to investigate the observational signatures of a wide range of phenomena, including (i) the reflection of coronal X-ray radiation off plasma plunging from the inner edge of a black hole accretion disk toward the black hole, (ii) the reflection of coronal X-ray emission off the upper layers of a geometrically thick accretion flow, (iii) the illumination of the accretion disk by a corona moving with relativistic velocities toward or away from the accretion disk, and (iv) the emission from a jet forming close to the black hole. After introducing the general relativistic treatment, we show the results for a fast wind forming close to a Kerr black hole. The approach presented here can be used to model X-ray spectral, timing, reverberation, and polarization data.

Keywords: quasars; black hole physics; kerr black holes
Detection Feasibility of H2 in Ultra-hot Jupiter Atmospheres

Ultra-hot Jupiters (UHJs) have recently been the focus of several atmospheric studies due to their extreme properties. While molecular hydrogen (H2) plays a key role in UHJ atmospheres, it has not been directly detected on an exoplanet. To determine the feasibility of H2 detection via transmission spectroscopy of the Lyman and Werner bands, we modeled UHJ atmospheres with H2 rotational temperatures varying from 2000 to 4000 K orbiting A-type stars ranging from T eff = 8500 K to T eff = 10,300 K. We present simulated transmission spectra for each planet-star temperature combination while adding Poisson noise varying in magnitude from 0.5% to 2.0%. Finally, we cross-correlated the spectra with expected atmospheric H2 absorption templates for each temperature combination. Our results suggest that H2 detection with current facilities, namely the Hubble Space Telescope, is not possible. However, direct atmospheric transmission spectroscopy of H2 may be viable with future UV-capable flagship missions.

Keywords: exoplanet atmospheres; transmission spectroscopy
Spectroscopic Orbits of Subsystems in Multiple Stars. X (Summary)

Results of a large program of spectroscopic monitoring of nearby solar-type stellar hierarchical systems using the CHIRON echelle spectrograph at the 1.5 m telescope are summarized. Ten papers of this series contain 102 spectroscopic orbits and substantially contribute to the knowledge of periods and eccentricties, providing input for the study of their formation and early evolution. Radial velocities of an additional 91 targets without CHIRON orbits (members of wide physical pairs) are published here. Our results are compared to the recent Gaia nonsingle star (NSS) catalog, revealing its strengths and weaknesses. The NSS provides orbital periods for 31 objects of the CHIRON sample (about one third). Of the 22 spectroscopic NSS orbits in common, 14 are in good agreement with CHIRON, the rest have reduced velocity amplitudes or other problems. Hence ground-based monitoring gives, so far, a more accurate and complete picture of nearby hierarchies than Gaia. The distribution of inner periods in hierarchical systems is nonmonotonic, showing a shallow minimum in the 30-100 days bin and a strong excess at shorter periods, compared to the smooth distribution of simple binaries in the field. The period-eccentricity diagram of inner subsystems updated by this survey, recent literature, and Gaia, displays an interesting structure.

Keywords: spectroscopic binary stars; multiple stars; visual binary stars; radial velocity
CARMA-NRO Orion Survey: Unbiased Survey of Dense Cores and Core Mass Functions in Orion A

The mass distribution of dense cores is a potential key to understanding the process of star formation. Applying dendrogram analysis to the CARMA-NRO Orion C18O (J = 1-0) data, we identify 2342 dense cores, about 22% of which have virial ratios smaller than 2 and can be classified as gravitationally bound cores. The derived core mass function (CMF) for bound starless cores that are not associate with protostars has a slope similar to Salpeter's initial mass function (IMF) for the mass range above 1 M ⊙, with a peak at ~0.1 M ⊙. We divide the cloud into four parts based on decl., OMC-1/2/3, OMC-4/5, L1641N/V380 Ori, and L1641C, and derive the CMFs in these regions. We find that starless cores with masses greater than 10 M ⊙ exist only in OMC-1/2/3, whereas the CMFs in OMC-4/5, L1641N, and L1641C are truncated at around 5-10 M ⊙. From the number ratio of bound starless cores and Class II objects in each subregion, the lifetime of bound starless cores is estimated to be 5-30 freefall times, consistent with previous studies for other regions. In addition, we discuss core growth by mass accretion from the surrounding cloud material to explain the coincidence of peak masses between IMFs and CMFs. The mass accretion rate required for doubling the core mass within a core lifetime is larger than that of Bondi-Hoyle accretion by a factor of order 2. This implies that more dynamical accretion processes are required to grow cores.

Keywords: star formation; interstellar medium; molecular clouds; protostars