adsabs/SciX_UAT_keywords huggingface dataset:
A Data-driven Approach for Mitigating Dark Current Noise and Bad Pixels in Complementary Metal Oxide Semiconductor Cameras for Space-based Telescopes

In recent years, there has been a gradual increase in the performance of complementary metal oxide semiconductor (CMOS) cameras. These cameras have gained popularity as a viable alternative to charge-coupled device cameras in a wide range of applications. One particular application is the CMOS camera installed in small space telescopes. However, the limited power and spatial resources available on satellites present challenges in maintaining ideal observation conditions, including temperature and radiation environment. Consequently, images captured by CMOS cameras are susceptible to issues such as dark current noise and defective pixels. In this paper, we introduce a data-driven framework for mitigating dark current noise and bad pixels for CMOS cameras. Our approach involves two key steps: pixel clustering and function fitting. During the pixel clustering step, we identify and group pixels exhibiting similar dark current noise properties. Subsequently, in the function fitting step, we formulate functions that capture the relationship between dark current and temperature, as dictated by the Arrhenius law. Our framework leverages ground-based test data to establish distinct temperature–dark current relations for pixels within different clusters. The cluster results could then be utilized to estimate the dark current noise level and detect bad pixels from real observational data. To assess the effectiveness of our approach, we have conducted tests using real observation data obtained from the Yangwang-1 satellite, equipped with a near-ultraviolet telescope and an optical telescope. The results show a considerable improvement in the detection efficiency of space-based telescopes.

Keywords: near ultraviolet astronomy; gaussian mixture model; clustering; observational astronomy
Radio and γ-ray Evidence for the Supernova Origin of High-velocity Cloud Complex M

Using λ21 cm galactic neutral hydrogen data from the HI4PI survey and 0.75-30 MeV γ-ray emission from the Imaging Compton Telescope, we have searched for the origin event that accelerated high-velocity cloud Complex M. Radio plots of l - b, l - v, and b - v show a cavity centered at (l, b) ~ (150°, 50.°) and extending about ±33°. The best view of the cavity is at a velocity of -25 km s-1, which shows a circular cross section on the back (receding) face. Complex M, at -85 km s-1, is on the front (approaching) face. The γ-ray emission reveals several minima, the largest centered at (l, b) ~(150°, 50.°) and coincident with the position and extent of the cavity seen in the radio data. Using the known distance to Complex M and assuming that the cavity is spherical, we can bootstrap the distance to the original, explosive source of the cavity D = 307 pc, calculate the radius of the cavity R = 166 pc, and approximate the expansion velocity V E ≈ 40 km s-1 of the cavity. The total energy of the expanding cavity is 3.0 ± 1.0 × 1050 erg, well within the range of a single supernova. These results indicate that this explosion took place about four million years ago. As the blast wave from this supernova propagated outwards, it began to sweep up interstellar gas and carved out the Local Chimney, a low-density extension of the Local Bubble that reaches into the galactic halo.

Keywords: radio astronomy; gamma-ray astronomy
The Aligned Orbit of the Eccentric Proto Hot Jupiter TOI-3362b

High-eccentricity tidal migration predicts the existence of highly eccentric proto hot Jupiters on the "tidal circularization track," meaning that they might eventually become hot Jupiters, but that their migratory journey remains incomplete. Having experienced moderate amounts of tidal evolution of their orbital elements, proto hot Jupiter systems can be powerful test beds for the underlying mechanisms of eccentricity growth. Notably, they may be used for discriminating between variants of high-eccentricity migration, each predicting a distinct evolution of misalignment between the star and the planet's orbit. We constrain the spin-orbit misalignment of the proto hot Jupiter TOI-3362b with high-precision radial-velocity observations using ESPRESSO at Very Large Telescope. The observations reveal a sky-projected obliquity $\lambda ={1.2}_{-2.7}^{+2.8}$ ° and constrain the orbital eccentricity to e = 0.720 ± 0.016, making it one of the most eccentric gas giants for which the obliquity has been measured. Although the large eccentricity and the striking orbit alignment of the planet are puzzling, we suggest that ongoing coplanar high-eccentricity migration driven by a distant companion is a possible explanation for the system's architecture. This distant companion would need to reside beyond 5 au at 95% confidence to be compatible with the available radial-velocity observations. *Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under program ID 110.23Y8.004.

Keywords: exoplanets; hot jupiters; exoplanet dynamics; planetary alignment; exoplanet migration
Fast Radio Bursts from Reconnection in a Magnetar Magnetosphere

The nearly 100% linear polarization has been reported for a few fast radio bursts (FRBs). This finding places severe limits on the emission mechanism. I argue that the completely polarized radiation could be generated in the course of relativistic magnetic reconnection in the outer magnetosphere of the magnetar. At the onset of the magnetar flare, a large-scale magnetic perturbation forms a magnetic pulse, which propagates from the flare cite outward. The pulse strongly compresses magnetospheric plasma and pushes it away. The high-frequency MHD waves are generated when the magnetic pulse reaches the current sheet separating, just beyond the light cylinder, the oppositely directed magnetic fields. Coalescence of magnetic islands in the reconnecting current sheet produces magnetosonic waves, which propagate away on the top of the magnetic pulse and escape in the far zone of the wind as radio waves polarized along the rotational axis of the magnetar. I estimate parameters of the outgoing radiation and show that they are compatible with the observed properties of FRBs.

Keywords: non-thermal radiation sources; plasma astrophysics; magnetohydrodynamics
The Pan-STARRS1 z > 5.6 Quasar Survey. II. Discovery of 55 Quasars at 5.6 < z < 6.5

The identification of bright quasars at z ≳ 6 enables detailed studies of supermassive black holes, massive galaxies, structure formation, and the state of the intergalactic medium within the first billion years after the Big Bang. We present the spectroscopic confirmation of 55 quasars at redshifts 5.6 < z < 6.5 and UV magnitudes -24.5 < M 1450 < -28.5 identified in the optical Pan-STARRS1 and near-IR VIKING surveys (48 and 7, respectively). Five of these quasars have independently been discovered in other studies. The quasar sample shows an extensive range of physical properties, including 17 objects with weak emission lines, 10 broad absorption line quasars, and 5 objects with strong radio emission (radio-loud quasars). There are also a few notable sources in the sample, including a blazar candidate at z = 6.23, a likely gravitationally lensed quasar at z = 6.41, and a z = 5.84 quasar in the outskirts of the nearby (D ~ 3 Mpc) spiral galaxy M81. The blazar candidate remains undetected in NOEMA observations of the [C II] and underlying emission, implying a star formation rate <30-70 M ⊙ yr-1. A significant fraction of the quasars presented here lies at the foundation of the first measurement of the z ~ 6 quasar luminosity function from Pan-STARRS1 (introduced in a companion paper). These quasars will enable further studies of the high-redshift quasar population with current and future facilities.

Keywords: quasars; active galactic nuclei
The Criterion for Chaos in Three-planet Systems

We establish the criterion for chaos in three-planet systems, for systems similar to those discovered by the Kepler spacecraft. Our main results are as follows: (i) The simplest criterion, which is based on overlapping mean motion resonances (MMRs), only agrees with numerical simulations at a very crude level. (ii) Much greater accuracy is attained by considering neighboring MMRs that do not overlap. We work out the widths of the chaotic zones around each of the neighbors, and also provide simple approximate expressions for the widths. (iii) Even greater accuracy is provided by the overlap of three-body resonances (3BRs), which accounts for the fine-grained structure seen in maps from N-body simulations, and also predicts Lyapunov times. From previous studies, it is unclear whether interplanetary chaos should be attributed to the overlap of MMRs or of 3BRs. We show that the two apparently contradictory viewpoints are in fact consistent: both predict the same criterion for chaos. (iv) We compare the predicted criterion with high-resolution maps of chaos from N-body simulations, and show that they agree at a high level of detail.

Keywords: celestial mechanics; orbits; orbital resonances; exoplanet dynamics
Testing the Kerr Black Hole Hypothesis Using X-Ray Reflection Spectroscopy and a Thin Disk Model with Finite Thickness

X-ray reflection spectroscopy is a powerful tool for probing the strong gravity region of black holes and can be used for testing general relativity in the strong field regime. Simplifications of the available relativistic reflection models limit the capability of performing accurate measurements of the properties of black holes. In this paper, we present an extension of the model RELXILL_NK in which the accretion disk has a finite thickness rather than being infinitesimally thin. We employ the accretion disk geometry proposed by Taylor & Reynolds and we construct relativistic reflection models for different values of the mass accretion rate of the black hole. We apply the new model to high-quality Suzaku data of the X-ray binary GRS 1915+105 to explore the impact of the thickness of the disk on tests of the Kerr metric.

Keywords: kerr metric; astrophysical black holes; x-ray astronomy
GeV γ-Ray Emission from M33 and Arp 299

Star-forming galaxies are huge reservoirs of cosmic rays (CRs) and these CRs convert a significant fraction of their energy into γ-rays by colliding with the interstellar medium (ISM). Several nearby star-forming galaxies have been detected in GeV-TeV γ-rays. It is also found that the γ-ray luminosities in 0.1-100 GeV correlate well with indicators of the star-formation rates of the galaxies, such as the total infrared (IR) luminosity. In this paper, we report a systematic search for possible γ-ray emission from galaxies in the IRAS Revised Bright Galaxies Sample, using 11.4 yr of γ-ray data taken by the Fermi Large Area Telescope. Two new galaxies, M33 and Arp 299, are detected significantly. The two galaxies are consistent with the empirical correlation between the γ-ray luminosity and IR luminosity, suggesting that their γ-ray emissions should mainly originate from CRs interacting with ISM. Nevertheless, there is tentative evidence that the flux of the γ-ray emission from Arp 299 is variable. If the variability is true, part of the emission from Arp 299 should originate from the obscured active galactic nucleus in this interacting galaxy system. In addition, we find that the γ-ray excess from M33 is located at the northeast region of the galaxy, where a supergiant H ii region, NGC 604, resides. This indicates that some bright star-forming regions in spiral galaxies could play a dominant role in the galaxy in producing γ-ray emission.

Keywords: gamma-ray sources; starburst galaxies
Evolution of High-redshift Quasar Hosts and Promotion of Massive Black Hole Seed Formation

High-redshift luminous quasars powered by accreting supermassive black holes (SMBHs) with mass ≳109 M⊙ constrain their formation pathways. We investigate the formation of heavy seeds of SMBHs through gas collapse in the quasar host progenitors, using merger trees to trace the halo growth in highly biased, overdense regions of the universe. The progenitor halos are likely irradiated by intense H2-photodissociating radiation from nearby star-forming galaxies and heat the interior gas by successive mergers. The kinetic energy of the gas originating from mergers, as well as the baryonic streaming motion, prevents gas collapse and delays prior star formation. With a streaming velocity higher than the rms value, gas clouds in nearly all 104 realizations of merger trees enter the atomic-cooling stage and begin to collapse isothermally with T ≃ 8000 K via Lyα cooling. The fraction of trees that host isothermal gas collapse is 14% and increases with streaming velocity, while the rest form H2-cooled cores after short isothermal phases. If the collapsing gas is enriched to Zcrit ~ 2 × 10-3 Z⊙, requiring efficient metal mixing, this fraction could be reduced by additional cooling via metal fine-structure lines. In the massive collapsing gas, the accretion rate onto a newly born protostar ranges between 3 × 10-3 M⊙ yr-1 and 5 M⊙ yr-1, among which a large fraction exceeds the critical rate suppressing stellar radiative feedback. As a result, we expect a distribution of stellar mass (presumably BH mass) ranging from several hundred to above 105 M⊙, potentially forming massive BH binary mergers and yielding gravitational-wave events.

Keywords: supermassive black holes; quasars; high-redshift galaxies
The Modulation of Anomalous and Galactic Cosmic-Ray Oxygen over Successive Solar Cycle Minima

Both the recent 2009 and 2020 solar minima were classified as unusually quiet and characterized with unusually high galactic cosmic-ray (GCR) levels. However, unlike the trends from previous decades, in which anomalous cosmic-ray (ACR) and GCR levels strongly agreed, the ACR intensities did not reach such high, record-setting levels. This discrepancy between the behavior of GCRs and ACRs is investigated in this work by simulating the acceleration and transport of GCR and ACR oxygen under different transport conditions. After using recent observations to constrain any remaining free parameters present in the model, we show that less turbulent conditions are characterized by higher GCR fluxes and lower ACR fluxes, due to less efficient ACR acceleration at the solar wind termination shock. We offer this as an explanation for the ACR/GCR discrepancy observed during 2009 and 2020, when compared to previous solar cycles.

Keywords: galactic cosmic rays; heliosphere; termination shock; interplanetary particle acceleration
On the Spatial Distribution of 13CO Structures within 12CO Molecular Clouds

We look into the 2851 12CO molecular clouds harboring 13CO structures to reveal the distribution of the projected angular separations and radial velocity separations between their internal 13CO structures. The projected angular separations are determined using the minimal spanning tree algorithm. We find that ~50% of the angular separations fall in a narrow range of ~3'-7' with a median of ~5', and the corresponding radial velocity separations mainly range from ~0.3 to 2.5 km s-1. The mean and standard deviation of the angular separations of the internal 13CO structures within 12CO clouds appear to be universal, independent of the 12CO cloud angular areas and the counts of their internal 13CO structures. We also reveal a scaling relation between the 12CO cloud angular area and its harbored 13CO structure count. These results suggest there is a preferred angular separation between 13CO structures in these 12CO clouds, considering the distance effects. According to that, we propose an alternative picture for the assembly and destruction of molecular clouds: there is a fundamental separation for the internal structures of molecular clouds, the build-up and destruction of molecular clouds proceeds under this fundamental unit.

Keywords: interstellar medium; interstellar molecules; molecular clouds
Emergence of Microphysical Bulk Viscosity in Binary Neutron Star Postmerger Dynamics

In nuclear matter in isolated neutron stars, the flavor content (e.g., proton fraction) is subject to weak interactions, establishing flavor (β-)equilibrium. However, there can be deviations from this equilibrium during the merger of two neutron stars. We study the resulting out-of-equilibrium dynamics during the collision by incorporating direct and modified Urca processes (in the neutrino-transparent regime) into general-relativistic hydrodynamics simulations with a simplified neutrino transport scheme. We demonstrate how weak-interaction-driven bulk viscosity in postmerger simulations can emerge and assess the bulk viscous dynamics of the resulting flow. We further place limits on the impact of the postmerger gravitational-wave strain. Our results show that weak-interaction-driven bulk viscosity can potentially lead to a phase shift of the postmerger gravitational-wave spectrum, although the effect is currently on the same level as the numerical errors of our simulation.

Keywords: neutron stars; nuclear astrophysics; nuclear physics; gravitational waves
Study of Transverse Oscillations in Coronal Loops Excited by Flares and Eruptions

We present measurements of periodicity for transverse loop oscillations during the periods of activity of two remote and separated (both temporally and spatially) flares. The oscillations are observed in the same location more than 100 Mm away from the visible footpoints of the loops. Evidence for several possible excitation sources is presented. After close examination, we find that the eruptions during the flaring activities play an important role in triggering the oscillations. We investigate periodicities using time-distance, fast Fourier transform, and wavelet techniques. Despite different excitation sources in the vicinity of the loops and the changing nature of amplitudes, the periodicity of multiple oscillations is found to be 4-6 min.

Keywords: solar coronal loops; solar flares
Linking Small-scale Solar Wind Properties with Large-scale Coronal Source Regions through Joint Parker Solar Probe-Metis/Solar Orbiter Observations

The solar wind measured in situ by Parker Solar Probe in the very inner heliosphere is studied in combination with the remote-sensing observation of the coronal source region provided by the METIS coronagraph aboard Solar Orbiter. The coronal outflows observed near the ecliptic by Metis on 2021 January 17 at 16:30 UT, between 3.5 and 6.3 R ⊙ above the eastern solar limb, can be associated with the streams sampled by PSP at 0.11 and 0.26 au from the Sun, in two time intervals almost 5 days apart. The two plasma flows come from two distinct source regions, characterized by different magnetic field polarity and intensity at the coronal base. It follows that both the global and local properties of the two streams are different. Specifically, the solar wind emanating from the stronger magnetic field region has a lower bulk flux density, as expected, and is in a state of well-developed Alfvénic turbulence, with low intermittency. This is interpreted in terms of slab turbulence in the context of nearly incompressible magnetohydrodynamics. Conversely, the highly intermittent and poorly developed turbulent behavior of the solar wind from the weaker magnetic field region is presumably due to large magnetic deflections most likely attributed to the presence of switchbacks of interchange reconnection origin.

Keywords: h ii regions; alfven waves; space plasmas; interplanetary turbulence; solar corona; heliosphere; solar wind
Fermi Constraints on the Ejecta Speed and Prompt Emission Region of the Distant GRB 220101A

At redshift z = 4.618, GRB 220101A is the most distant gamma-ray burst (GRB) detected by Fermi/LAT to date. It is also a very energetic event, with an equivalent isotropic energy of 3.6 × 1054 erg. We jointly analyzed the Fermi/GBM and LAT observations of GRB 220101A with two independent approaches and found a significant spectral break at sub-100 MeV energies during the prompt emission. The fast variability of the emission suggests that this spectral attenuation is caused by internal opacity to pair creation. Regardless of the nature of the emission processes assumed in the spectral analysis, we infer a moderate value for the jet Lorentz factor, Γ ~ 110, and find that all of the high-energy emission was produced above and near the photosphere, at a distance of ~1014 cm from the central engine. We compare these results with the four other LAT-detected GRBs with similar properties.

Keywords: gamma-ray bursts; high energy astrophysics
Quasar Main Sequence in the UV Plane

Active galaxies form a clear pattern in the optical plane showing the correlation between the FWHM of the Hβ line and the ratio of the equivalent width (EW) of the optical Fe II emission and the broad EW(Hβ). This pattern is frequently referred to as the quasar main sequence. In this paper, we study the UV plane showing the FWHM of Mg II line against the ratio of the EW of UV Fe II emission to the broad EW(Mg II). We show that the UV plane trends are different, with the underlying strong correlation between the FWHM(Mg II) and the EW(Mg II). This correlation is entirely driven by the choice of the continuum used to measure the EW(Mg II). If instead of the observationally determined continuum, we use a theoretically motivated power law extrapolated from the wide wavelength range, the behavior of the FWHM versus EW for Mg II becomes similar to the behavior for Hβ. Such a similarity is expected since both the lines belong to the low-ionization group of emission lines and come from a similar region. We discuss the behavior of the lines in the context of the broad line region model based on the presence of dust in the accretion disk atmosphere.

Keywords: catalogs; surveys
X-Ray Observations of 1ES 1959+650 in Its High-activity State in 2016-2017 with AstroSat and Swift

We present a comprehensive multifrequency study of the high-frequency-peaked BL Lac object 1ES 1959+650 using data from various facilities during the period 2016-2017, including X-ray data from AstroSat and Swift during the historically high X-ray flux state of the source observed until 2021 February. The unprecedented quality of X-ray data from high-cadence monitoring with AstroSat during 2016-2017 enables us to establish a detailed description of X-ray flares in 1ES 1959+650. The synchrotron peak shifts significantly between different flux states, in a manner consistent with a geometric (changing Doppler factor) interpretation. A time-dependent leptonic diffusive shock acceleration and radiation transfer model is used to reproduce the spectral energy distributions and X-ray light curves, to provide insight into the particle acceleration during the major activity periods observed in 2016 and 2017. The extensive data of Swift-XRT from 2015 December to 2021 February (exp. = 411.3 ks) reveals a positive correlation between flux and peak position.

Keywords: blazars; active galactic nuclei; black hole physics; jets; high energy astrophysics