adsabs/SciX_UAT_keywords huggingface dataset:
An Aluminum-coated sCMOS Sensor for X-Ray Astronomy

In recent years, tremendous progress has been made on scientific Complementary Metal Oxide Semiconductor (sCMOS) sensors, making them a promising device for future space X-ray missions. We have customized a large-format sCMOS sensor, G1516BI, dedicated for X-ray applications. In this work, a 200 nm thick aluminum layer is successfully sputtered on the surface of this sensor. This Al-coated sensor, named EP4K, shows consistent performance with the uncoated version. The readout noise of the EP4K sensor is around 2.5 e- and the dark current is less than 0.01 e- pixel-1 s-1 at -30°C. The maximum frame rate is 20 Hz in the current design. The ratio of single pixel events of the sensor is 45.0%. The energy resolution can reach 153.2 eV at 4.51 keV and 174.2 eV at 5.90 keV at -30°C. The optical transmittance of the aluminum layer is approximately 10-8 to 10-10 for optical lights from 365 to 880 nm, corresponding to an effective aluminum thickness of around 140 to 160 nm. The good X-ray performance and low optical transmittance of this Al-coated sCMOS sensor make it a good choice for space X-ray missions. The Lobster Eye Imager for Astronomy, which has been working in orbit for about one year, is equipped with four EP4K sensors. Furthermore, 48 EP4K sensors are used on the Wide-field X-ray Telescope on the Einstein Probe satellite, which will be launched at the end of 2023.

Keywords: x-ray detectors; astronomical instrumentation; astronomical detectors
Comparing Observed with Simulated Solar-disk-center Scattering Polarization in the Sr I 4607 Å Line

Solar magnetic fields alter scattering polarization in spectral lines like Sr I at 4607 Å via the Hanle effect, making it a potential diagnostic for small-scale, mixed-polarity photospheric magnetic fields. Recently, observational evidence for scattering polarization in the Sr I 4607 Å line at the solar disk center was found. Here, we investigate the reliability of the reconstruction method that made possible this detection. To this end, we apply it to linear polarization profiles of the Sr I 4607 Å line radiation emerging at the disk center obtained from a detailed 3D radiative transfer calculation in a magneto-hydrodynamic (MHD) simulation snapshot with a small-scale dynamo contribution. The reconstruction method systematically reduces the scattering amplitudes by up to a factor of 2, depending on the noise level. We demonstrate that the decrease can be attributed to two systematic errors: first, the physical constraint that underlies our assumptions regarding the dependence of scattering polarization on the quadrupolar moment of the radiation field; and second, the limitations of our method in accurately determining the sign of the radiation field tensor from the observed intensity image. However, by consistently applying the reconstruction process and after taking into account image-degradation effects due to the temporally variable image quality, such as imposed by seeing, the observed and synthesized polarization signals show remarkable agreement. We thus conclude that the observed scattering polarization at the solar disk center is consistent with that emerging from a MHD model of the solar photosphere with an average magnetic field of 170 G at the visible surface.

Keywords: quiet sun; solar magnetic fields; radiative transfer simulations; spectropolarimetry; solar photosphere
Cosmic-Ray Anisotropies in Right Ascension Measured by the Pierre Auger Observatory

We present measurements of the large-scale cosmic-ray (CR) anisotropies in R.A., using data collected by the surface detector array of the Pierre Auger Observatory over more than 14 yr. We determine the equatorial dipole component, d\perp, through a Fourier analysis in R.A. that includes weights for each event so as to account for the main detector-induced systematic effects. For the energies at which the trigger efficiency of the array is small, the "east-west" method is employed. Besides using the data from the array with detectors separated by 1500 m, we also include data from the smaller but denser subarray of detectors with 750 m separation, which allows us to extend the analysis down to ∼0.03 EeV. The most significant equatorial dipole amplitude obtained is that in the cumulative bin above 8 EeV, d\perp={6.0}-0.9+1.0 %, which is inconsistent with isotropy at the 6σ level. In the bins below 8 EeV, we obtain 99% CL upper bounds on d⊥ at the level of 1%-3%. At energies below 1 EeV, even though the amplitudes are not significant, the phases determined in most of the bins are not far from the R.A. of the Galactic center, at αGC = -94°, suggesting a predominantly Galactic origin for anisotropies at these energies. The reconstructed dipole phases in the energy bins above 4 EeV point instead to R.A. that are almost opposite to the Galactic center one, indicative of an extragalactic CR origin.

Keywords: cosmic rays; cosmic ray sources; cosmic ray astronomy
Partial Eruption of Solar Filaments. I. Configuration and Formation of Double-decker Filaments

Partial eruptions of solar filaments are the typical representatives of solar eruptive behavior diversity. Here we investigate a typical filament partial eruption event and present integrated evidence for the configuration of the pre-eruption filament and its formation. The Chinese Hα Solar Explorer Hα observations reveal a structured Doppler velocity distribution within the pre-eruption filament, where distinct redshift only appeared in the eastern narrow part of the southern filament region and then disappeared after the partial eruption, while the northern part dominated by blueshift remained. Combining the Solar Dynamics Observatory and Advanced Space-based Solar Observatory observations, together with nonlinear-force-free-field modeling results, we verify that there were two independent material flow systems within the preflare filament, whose magnetic topology is a special double-decker configuration consisting of two magnetic flux ropes (MFRs) with opposite magnetic twist. During the formation of this filament system, continuous magnetic flux cancellation and footpoint motion were observed around its northern end. Therefore, we propose a new double-decker formation scenario: that the two MFRs composing such a double-decker configuration originated from two magnetic systems with different initial connections and opposite magnetic twist. Subsequent magnetic reconnection with the surrounding newly emerging fields resulted in the motion of the footpoint of the upper MFR to the region around the footpoint of the lower MFR, thus leading to the eventual formation of the double-decker configuration consisting of two MFRs with similar footpoints but opposite signs of magnetic twist. These results provide a potential way to determine unambiguously the progenitor configuration of a partially eruptive filament and reveal a special type of double-decker MFR configuration and a new double-decker formation scenario.

Keywords: solar activity; solar atmosphere; solar filaments; solar flares; solar magnetic fields
Circumgalactic Medium at High Halo Masses-Signatures of Cold Gas Depletion in Luminous Red Galaxies

We study ultraviolet H I and metal-line transitions in the circumgalactic medium (CGM) of 15 massive, quenched luminous red galaxies (LRGs) at redshift z ~ 0.5 and with impact parameters up to 400 kpc. We selected eight LRG-CGM systems to study general properties of the CGM around LRGs, while the other seven are already known to contain cool CGM gas from Mg II optical studies (Mg II-LRGs). In the general LRG population, we detect H I in four of eight LRGs, in all cases with N H I < 1016.7cm-2. In contrast, all Mg II-LRGs show H I; for four LRGs, the H I column density is N H I ≳ 1018cm-2. The CGM of LRGs also shows low and intermediate ionized lines (such as C III, C II, Si III, and Si II) and highly ionized lines of O VI (we detect O VI around five of seven Mg II-LRGs and one of eight in the random sample). Next, we combine our sample with literature LRGs and ≲L * galaxies, and we find that while for ≲L * galaxies CGM H I Lyα absorption is stronger as galaxies are more massive, the cool CGM traced by H I Lyα is suppressed above stellar masses of M* ~ 1011.5 M ⊙. While most LRG-CGM systems show weak or nondetectable O VI (equivalent width < 0.2 Å), a few LRG-CGM systems show strong O VI 1031, which in most cases likely originates from groups containing both an LRG and a blue star-forming neighboring galaxy.

Keywords: circumgalactic medium; galaxy environments; quasar absorption line spectroscopy; quenched galaxies; galaxy quenching
The Broadband Counterpart of the Short GRB 200522A at z = 0.5536: A Luminous Kilonova or a Collimated Outflow with a Reverse Shock?

We present the discovery of the radio afterglow and near-infrared (NIR) counterpart of the Swift short gamma-ray burst (GRB) GRB 200522A, located at a small projected offset of ≈1 kpc from the center of a young, star-forming host galaxy at z = 0.5536. The radio and X-ray luminosities of the afterglow are consistent with those of on-axis cosmological short GRBs. The NIR counterpart, revealed by our Hubble Space Telescope observations at a rest-frame time of ≈2.3 days, has a luminosity of ≈(1.3-1.7) × 1042 erg s-1. This is substantially lower than on-axis short GRB afterglow detections but is a factor of ≈8-17 more luminous than the kilonova of GW170817 and significantly more luminous than any kilonova candidate for which comparable observations exist. The combination of the counterpart's color (i - y = -0.08 ± 0.21; rest frame) and luminosity cannot be explained by standard radioactive heating alone. We present two scenarios to interpret the broadband behavior of GRB 200522A: a synchrotron forward shock with a luminous kilonova (potentially boosted by magnetar energy deposition), or forward and reverse shocks from a ≈14°, relativistic (Γ0 ≳ 10) jet. Models that include a combination of enhanced radioactive heating rates, low-lanthanide mass fractions, or additional sources of heating from late-time central engine activity may provide viable alternate explanations. If a stable magnetar was indeed produced in GRB 200522A, we predict that late-time radio emission will be detectable starting ≈0.3-6 yr after the burst for a deposited energy of ≈1053 erg. Counterparts of similar luminosity to GRB 200522A associated with gravitational wave events will be detectable with current optical searches to ≈250 Mpc.

Keywords: gamma-ray bursts; magnetars; r-process
The Prominence Driven Forced Reconnection in the Solar Corona and Associated Plasma Dynamics

Using the multitemperature observations from SDO/AIA on 2019 December 30, we provide a signature of prominence driven forced magnetic reconnection in the corona and associated plasma dynamics from 09:20 UT to 10:38 UT. A hot prominence segment erupts with a speed of ≈21 km s-1 and destabilizes the entire prominence system. Thereafter, it rises upward in the north from 09:28 UT to 09:48 UT with a speed of 24 km s-1 . The eruptive prominence stretches overlying field lines upward with the speed of 27-28 km s-1, which further undergo the forced reconnection. The coronal plasma also flows southward with a speed of 7 km s-1, and both of these inflows trigger the reconnection at ≈09:48 UT. Thereafter, the eastward and westward magnetic channels are developed and separated. The east-west reorganization of the magnetic fields starts creating bidirectional plasma outflows toward the limb with their respective speeds of 28 and 37 km s-1. Their upper ends are diffused in the overlying corona, transporting another set of upflows with the speeds of ≈22 km and 19 km s-1. The multitemperature plasma (log Te = 6.0-7.2 K) evolves and elongates to a length of ≈105 km on the reorganized fields. The hot plasma and remaining prominence threads move from the reconnection region toward another segment of a prominence in the eastward direction. The prominence-prominence/loop interaction and associated reconnection generate jet-like eruptions with a speed of 178-183 km s-1. After the formation of the jet, the overlying magnetic channel disappears in the corona.

Keywords: solar corona; solar coronal loops; solar magnetic reconnection; magnetic fields
The Solar Probe ANalyzers—Electrons on the Parker Solar Probe

Electrostatic analyzers of different designs have been used since the earliest days of the space age, beginning with the very earliest solar-wind measurements made by Mariner 2 en route to Venus in 1962. The Parker Solar Probe (PSP) mission, NASA’s first dedicated mission to study the innermost reaches of the heliosphere, makes its thermal plasma measurements using a suite of instruments called the Solar Wind Electrons, Alphas, and Protons (SWEAP) investigation. SWEAP’s electron PSP Analyzer (Solar Probe ANalyzer-Electron (SPAN-E)) instruments are a pair of top-hat electrostatic analyzers on PSP that are capable of measuring the electron distribution function in the solar wind from 2 eV to 30 keV. For the first time, in situ measurements of thermal electrons provided by SPAN-E will help reveal the heating and acceleration mechanisms driving the evolution of the solar wind at the points of acceleration and heating, closer than ever before to the Sun. This paper details the design of the SPAN-E sensors and their operation, data formats, and measurement caveats from PSP’s first two close encounters with the Sun.

Keywords: solar wind; solar instruments; solar coronal heating; space plasmas
Quantifying the Agyrotropy of Proton and Electron Heating in Turbulent Plasmas

An important aspect of energy dissipation in weakly collisional plasmas is that of energy partitioning between different species (e.g., protons and electrons) and between different energy channels. Here we analyse pressure-strain interaction to quantify the fractions of isotropic compressive, gyrotropic, and nongyrotropic heating for each species. An analysis of kinetic turbulence simulations is compared and contrasted with corresponding observational results from Magnetospheric Multiscale Mission data in the magnetosheath. In assessing how protons and electrons respond to different ingredients of the pressure-strain interaction, we find that compressive heating is stronger than incompressive heating in the magnetosheath for both electrons and protons, while incompressive heating is stronger in kinetic plasma turbulence simulations. Concerning incompressive heating, the gyrotropic contribution for electrons is dominant over the nongyrotropic contribution, while for protons nongyrotropic heating is enhanced in both simulations and observations. Variations with plasma β are also discussed, and protons tend to gain more heating with increasing β.

Keywords: space plasmas; plasma physics; interplanetary turbulence; interplanetary physics; planetary magnetospheres
The Infrared Medium-deep Survey. IX. Discovery of Two New z 6 Quasars and Space Density Down to M 1450 -23.5 mag

We present the result of the Infrared Medium-deep Survey (IMS) z ~ 6 quasar survey, using the combination of the IMS near-infrared images and the Canada-France-Hawaii Telescope Legacy Survey optical images. The traditional color selection method results in 25 quasar candidates over 86 deg2. We introduce the corrected Akaike information criterion (AICc) with the high-redshift quasar and late-type star models to prioritize the candidates efficiently. Among the color-selected candidates, seven plausible candidates finally passed the AICc selection, of which three are known quasars at z ~ 6. The follow-up spectroscopic observations for the remaining four candidates were carried out, and we confirmed that two out of four are z ~ 6 quasars. With this complete sample, we revisited the quasar space density at z ~ 6 down to M 1450 ~ -23.5 mag. Our result supports the low quasar space density at the luminosity where the quasar's ultraviolet ionizing emissivity peaks, favoring a minor contribution of quasars to the cosmic reionization.

Keywords: quasars; active galactic nuclei; reionization; early universe; sky surveys; observational astronomy
Weak Solar Radio Bursts from the Solar Wind Acceleration Region Observed by the Parker Solar Probe and Its Probable Emission Mechanism

The Parker Solar Probe (PSP) provides us with an unprecedentedly close approach to the observation of the Sun and hence the possibility of directly understanding the elementary process that occurs on the kinetic scale of particles' collective interaction in solar coronal plasmas. We report a type of weak solar radio burst (SRB) that was detected by PSP when it passed a low-density magnetic channel during its second encounter phase. These weak SRBs have a low starting frequency of ~20 MHz and a narrow frequency range from a few tens of MHz to a few hundred kHz. Their dynamic spectra display a strongly evolving feature of the intermediate relative drift rate decreasing rapidly from above 0.01 s-1 to below 0.01 s-1. Analyses based on common empirical models of solar coronal plasmas indicate that these weak SRBs originate from a heliocentric distance of ~1.1-6.1 R S (the solar radius), a typical solar wind acceleration region with a low-β plasma, and that their sources have a typical motion velocity of ~v A (Alfvén velocity) obviously lower than that of the fast electrons required to effectively excite SRBs. We propose that solitary kinetic Alfvén waves with kinetic scales could be responsible for the generation of these small-scale weak SRBs, called solitary wave radiation.

Keywords: solar coronal radio emission; interplanetary physics
Application of Orbital Stability and Tidal Migration Constraints for Exomoon Candidates

Satellites of extrasolar planets, or exomoons, are on the frontier of detectability using current technologies and theoretical constraints should be considered in their search. In this Letter, we apply theoretical constraints of orbital stability and tidal migration to the six candidate Kepler Object of Interest (KOI) systems proposed by Fox & Wiegert to identify whether these systems can potentially host exomoons. The host planets orbit close to their respective stars and the orbital stability extent of exomoons is limited to only ∼40% of the host planet's Hill radius (∼20 Rp). Using plausible tidal parameters from the solar system, we find that four out of six systems would either tidally disrupt their exomoons or lose them to outward migration within the system lifetimes. The remaining two systems (KOI 268.01 and KOI 1888.01) could host exomoons that are within 25 Rp and less than ∼3% of the host planet's mass. However, a recent independent transit timing analysis by Kipping found that these systems fail rigorous statistical tests to validate them as candidates. Overall, we find the presence of exomoons in these systems that are large enough for transit timing variation signatures to be unlikely given the combined constraints of observational modeling, tidal migration, and orbital stability. Software to reproduce our results is available in the GitHub repository: Multiversario/satcand.

Keywords: exoplanet dynamics; exoplanet tides; natural satellites (extrasolar); exoplanet systems
Finding Candidate TeV Halos among Very-high-energy Sources

We search for possible pulsar TeV halos among the very-high-energy (VHE) sources reported in different VHE surveys, among which in particular we use the results from the first Large High Altitude Air Shower Observatory catalog of γ-ray sources. Six candidates are found. They share similar properties of containing a middle-aged, γ-ray–bright pulsar in their positional error circles (the respective pulsars are J0248+6021, J0359+5414, J0622+3749, J0633+0632, J2006+3102, and J2238+5903), being in a rather clean field without any common Galactic VHE-emitting supernova remnants or (bright) pulsar wind nebulae (PWNe), and showing an absence of any γ-ray emissions in 0.1–500 GeV after removing the pulsars' emissions. Combining these candidates with several reported (candidate) TeV halos, we obtain relationships between their luminosity at 50 TeV (L 50TeV) and the corresponding pulsars' spin-down energy ( ), which are and , respectively. The relationships are nearly identical to previously reported ones. We probe possible connections between the extent/sizes of the VHE sources and the pulsars' ages, and find a weak older-and-smaller trend. By comparing to the VHE detection results for PWNe, it is clear that the (candidate) TeV halos have hard emissions by either having power-law indices smaller than 2 in 1–25 TeV or by only being detected in 25–100 TeV. In addition, we also consider seven other VHE sources as possible TeV halos based on the results from different studies of them, but they do not fit cleanly with the properties listed above, indicating their potentially complex nature.

Keywords: gamma-rays; pulsars
The First Gamma-Ray Emitting BL Lacertae Object at the Cosmic Dawn

One of the major challenges in studying the cosmic evolution of relativistic jets is the identification of the high-redshift (z > 3) BL Lacertae objects (BL Lacs), a class of jetted active galactic nuclei characterized by their quasi-featureless optical spectra. Here we report the identification of the first γ-ray emitting BL Lac, 4FGL J1219.0+3653 (J1219), beyond z = 3, i.e., within the first two billion years of the age of the universe. The optical and near-infrared spectra of J1219 taken from 10.4 m Gran Telescopio Canarias exhibit no emission lines down to an equivalent width of ∼3.5 Šsupporting its BL Lac nature. The detection of a strong Lyα break at ∼5570 Å, on the other hand, confirms that J2119 is indeed a high-redshift (z ∼ 3.59) quasar. Based on the prediction of a recent BL Lac evolution model, J1219 is one of the only two such objects expected to be present within the comoving volume at z = 3.5. Future identifications of more z > 3 γ-ray emitting BL Lac sources, therefore, will be crucial to verify the theories of their cosmic evolution.

Keywords: bl lacertae objects; high-redshift galaxies; spectroscopy; relativistic jets; gamma-ray sources
Small-scale Dynamo in Stably Stratified Turbulence

We present numerical investigations into three principal properties of a small-scale dynamo in stably stratified turbulence: the onset criterion, the growth rate, and the nature of the magnetic field anisotropy in the kinematic regime. The results suggest that all three dynamo properties are controlled by the scale separation between the Ozmidov scale and the viscous or resistive scale. In addition to the critical magnetic Reynolds number, this allows for the definition of critical buoyancy and magnetic buoyancy Reynolds numbers for stratified small-scale dynamo onset in the high and low magnetic Prandtl number regimes, respectively. The presence of a small-scale dynamo in stellar radiative zones could affect dynamics through the resulting Maxwell stresses or its influence on large-scale dynamo mechanisms in regions of differential rotation. Taking the solar radiative zone as a representative example and applying the onset criterion, we find that the stratification is strong enough to make the small-scale dynamo marginally active in the stably stratified turbulence of the solar tachocline.

Keywords: solar dynamo; stellar interiors; solar interior; magnetic fields; solar magnetic fields; stellar magnetic fields