adsabs/SciX_UAT_keywords huggingface dataset:
The First Data Release of CNIa0.02-A Complete Nearby (Redshift <0.02) Sample of Type Ia Supernova Light Curves

The CNIa0.02 project aims to collect a complete, nearby sample of Type Ia supernovae (SNe Ia) light curves, and the SNe are volume-limited with host-galaxy redshifts z host < 0.02. The main scientific goal is to infer the distributions of key properties (e.g., the luminosity function) of local SNe Ia in a complete and unbiased fashion in order to study SN explosion physics. We spectroscopically classify any SN candidate detected by the All-Sky Automated Survey for Supernovae (ASAS-SN) that reaches a peak brightness <16.5 mag. Since ASAS-SN scans the full sky and does not target specific galaxies, our target selection is effectively unbiased by host-galaxy properties. We perform multiband photometric observations starting from the time of discovery. In the first data release (DR1), we present the optical light curves obtained for 247 SNe from our project (including 148 SNe in the complete sample), and we derive parameters such as the peak fluxes, Δm 15, and s BV . * This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: type ia supernovae
Verification of Radiative Transfer Schemes for the EHT

The Event Horizon Telescope (EHT) Collaboration has recently produced the first resolved images of the central supermassive black hole in the giant elliptical galaxy M87. Here we report on tests of the consistency and accuracy of the general relativistic radiative transfer codes used within the collaboration to model M87* and Sgr A*. We compare and evaluate (1) deflection angles for equatorial null geodesics in a Kerr spacetime; (2) images calculated from a series of simple, parameterized matter distributions in the Kerr metric using simplified emissivities and absorptivities; (3) for a subset of codes, images calculated from general relativistic magnetohydrodynamics simulations using different realistic synchrotron emissivities and absorptivities; (4) observables for the 2017 configuration of EHT, including visibility amplitudes and closure phases. The error in total flux is of order 1% when the codes are run with production numerical parameters. The dominant source of discrepancies for small camera distances is the location and detailed setup of the software "camera" that each code uses to produce synthetic images. We find that when numerical parameters are suitably chosen and the camera is sufficiently far away the images converge and that for given transfer coefficients, numerical uncertainties are unlikely to limit parameter estimation for the current generation of EHT observations. The purpose of this paper is to describe a verification and comparison of EHT radiative transfer codes. It is not to verify EHT models more generally.

Keywords: general relativity; high energy astrophysics; event horizons; relativity; relativistic disks; radio astronomy; black hole physics; radiative transfer; very long baseline interferometry
Plasmoid Ejection by Alfvén Waves and the Fast Radio Bursts from SGR 1935+2154

Using numerical simulations we show that low-amplitude Alfvén waves from a magnetar quake propagate to the outer magnetosphere and convert to "plasmoids" (closed magnetic loops) that accelerate from the star, driving blast waves into the magnetar wind. Quickly after its formation, the plasmoid becomes a thin relativistic pancake. It pushes out the magnetospheric field lines, and they gradually reconnect behind the pancake, generating a variable wind far stronger than the normal spindown wind of the magnetar. Repeating ejections drive blast waves in the amplified wind. We suggest that these ejections generate the simultaneous X-ray and radio bursts detected from SGR 1935+2154. A modest energy budget of the magnetospheric perturbation ∼1040 erg is sufficient to produce the observed bursts. Our simulation predicts a narrow (a few milliseconds) X-ray spike from the magnetosphere, arriving almost simultaneously with the radio burst emitted far outside the magnetosphere. This timing is caused by the extreme relativistic motion of the ejecta.

Keywords: magnetars; neutron stars; non-thermal radiation sources; radio transient sources; shocks; radio bursts
Translational Tomography with the Wide-field Imager for Parker Solar Probe (WISPR). I. Theoretical Basis and Initial Modeling

In the first of a planned sequence of articles, we present a simple method for reconstructing radial density structures of the solar corona in the vicinity of the Parker Solar Probe (PSP) near and during perihelion passes. We describe how we model the apparent kinematics of stationary K-corona striae from the PSP Wide-field Imager for Parker Solar Probe (WISPR) viewpoint using a simple two-parameter model, form a partial basis of the data space that is a WISPR image sequence, and change the basis from image coordinates to "tomographic coordinates" in order to determine the parameters of such features. We apply the method to a simple three-dimensional model of a WISPR coronal flythrough, demonstrate the ways that it succeeds and fails, and discuss possible improvements to the sensitivity and applicability of the method for real WISPR data.

Keywords: solar corona; solar wind
The First Fast Radio Burst Detected with VLITE-Fast

The VLITE-Fast experiment combines the wide-field-of-view of single dish antennas operating at low frequency with the high angular resolution furnished by the 3-30 km baselines of the VLA, making it ideal for the detection and precise localization of radio transients. We describe the VLITE-Fast experiment, its capabilities, and operational status, and we briefly overview its main science case, the detection of fast radio bursts (FRBs) and determination of their host galaxies. We report on commissioning observations in an incoherent mode prohibiting precise localization. These include discovery of FRB 20200405A, detected during early science operations at dispersion measure (DM) = 212.3 pc cm-3, strongly in excess of the Galactic DM along the line of sight.

Keywords: radio transient sources
On the Metamorphosis of the Bailey Diagram for RR Lyrae Stars

We collected over 6000 high-resolution spectra of four dozen field RR Lyrae (RRL) variables pulsating either in the fundamental (39 RRab) or in the first overtone (9 RRc) mode. We measured radial velocities (RVs) of four strong metallic and four Balmer lines along the entire pulsational cycle and derived RV amplitudes with accuracies better than 1-2 km s-1. The new amplitudes were combined with literature data for 23 RRab and 3 RRc stars (total sample of 74 RRLs), which allowed us to investigate the variation of the Bailey diagram (photometric amplitude versus period) when moving from optical to mid-infrared bands and to recast the Bailey diagram in terms of RV amplitudes. We found that RV amplitudes for RRab are minimally affected by nonlinear phenomena (shocks) and multiperiodicity (Blazhko effect). The RV slope (logP-A(Vr)) when compared with the visual slope (logP-A(V)) is shallower, and the dispersion, at fixed period, decreases by a factor of two. We constructed homogeneous sets of horizontal branch evolutionary models and nonlinear, convective pulsation models of RRLs to constrain the impact of evolutionary effects on their pulsation properties. Evolution causes, on the Bailey diagram based on RV amplitudes, a modest variation in pulsation period and a large dispersion in amplitude. The broad dispersion in period of the Bailey diagram is mainly caused by variation in RRL intrinsic parameters (stellar mass, chemical composition). Empirical evidence indicates that RV amplitudes are an optimal diagnostic for tracing the mean effective temperature across the RRab instability strip.

Keywords: horizontal branch stars; stellar oscillations; rr lyrae variable stars; radial velocity
Observations of Electron Secondary Reconnection in Magnetic Reconnection Front

Magnetic reconnection, a fundamental plasma process transforming magnetic field energy into particle energy, is ubiquitous in space and responsible for many explosive phenomena, such as solar flares and gamma-ray bursts. Recent numerical theories have predicted that reconnection fronts far from the primary reconnection region can host secondary reconnection in three-dimensional scenarios, different from the conventional two-dimensional diagram where only one X-line stands to sustain reconnection. In this study, we provide direct observational evidence for ongoing secondary reconnection in the reconnection front via the unprecedentedly high-cadence data from NASA's MMS mission. The secondary reconnection is identified by the presence of an X-line, a super-Alfvénic electron jet, and nonideal energy dissipation. Different from the primary ion-electron reconnection, the secondary reconnection is electron-only, with its X-line quasi-perpendicular to the primary X-line. Hence reconnection, when evolving from local to global scales, becomes essentially three-dimensional with different patterns developed. These results provide crucial insights into understanding cross-scale energy transport driven by reconnection in space plasmas.

Keywords: space plasmas
On the Local Structure of Stochastic Parker Spirals in the Solar Wind

We present a Langevin model describing the local structure of the interplanetary magnetic field lines. It is established on the basis of the analysis of the Lagrangian properties of strong Alfvénic turbulence, which provides a new perspective on the critical balance condition. The model is consistent with the ${k}_{\parallel }^{-2}$ spectrum of magnetic fluctuations derived from in situ measurements. We show that the magnetic field line diffusivity at the spacecraft position can be inferred from the wavelet analysis of one-point measurements of the fluctuating magnetic fields in the solar wind independently of the three-dimensional nature of the anisotropy.

Keywords: magnetohydrodynamics; interplanetary turbulence
Low Mass Stars as Tracers of Star and Cluster Formation

We review the use of young low mass stars and protostars, or young stellar objects (YSOs), as tracers of star formation. Observations of molecular clouds at visible, infrared, radio and X-ray wavelengths can identify and characterize the YSOs populating these clouds, with the ability to detect deeply embedded objects at all evolutionary stages. Surveys with the Spitzer, Herschel, XMM-Newton and Chandra space telescopes have measured the spatial distribution of YSOs within a number of nearby (<2.5 kpc) molecular clouds, showing surface densities varying by more than three orders of magnitude. These surveys have been used to measure the spatially varying star formation rates and efficiencies within clouds, and when combined with maps of the molecular gas, have led to the discovery of star-forming relations within clouds. YSO surveys can also characterize the structures, ages, and star formation histories of embedded clusters, and they illuminate the relationship of the clusters to the networks of filaments, hubs and ridges in the molecular clouds from which they form. Measurements of the proper motions and radial velocities of YSOs trace the evolving kinematics of clusters from the deeply embedded phases through gas dispersal, providing insights into the factors that shape the formation of bound clusters. On 100 pc scales that encompass entire star-forming complexes, Gaia is mapping the young associations of stars that have dispersed their natal gas and exist alongside molecular clouds. These surveys reveal the complex structures and motions in associations, and show evidence for supernova driven expansions. Remnants of these associations have now been identified by Gaia, showing that traces of star-forming structures can persist for a few hundred million years.

Keywords: protostars; pre-main sequence stars; star formation; star forming regions; star clusters; stellar associations; molecular clouds; low mass stars
The CAMELS Project: Expanding the Galaxy Formation Model Space with New ASTRID and 28-parameter TNG and SIMBA Suites

We present CAMELS-ASTRID, the third suite of hydrodynamical simulations in the Cosmology and Astrophysics with MachinE Learning (CAMELS) project, along with new simulation sets that extend the model parameter space based on the previous frameworks of CAMELS-TNG and CAMELS-SIMBA, to provide broader training sets and testing grounds for machine-learning algorithms designed for cosmological studies. CAMELS-ASTRID employs the galaxy formation model following the ASTRID simulation and contains 2124 hydrodynamic simulation runs that vary three cosmological parameters (Ω m , σ 8, Ω b ) and four parameters controlling stellar and active galactic nucleus (AGN) feedback. Compared to the existing TNG and SIMBA simulation suites in CAMELS, the fiducial model of ASTRID features the mildest AGN feedback and predicts the least baryonic effect on the matter power spectrum. The training set of ASTRID covers a broader variation in the galaxy populations and the baryonic impact on the matter power spectrum compared to its TNG and SIMBA counterparts, which can make machine-learning models trained on the ASTRID suite exhibit better extrapolation performance when tested on other hydrodynamic simulation sets. We also introduce extension simulation sets in CAMELS that widely explore 28 parameters in the TNG and SIMBA models, demonstrating the enormity of the overall galaxy formation model parameter space and the complex nonlinear interplay between cosmology and astrophysical processes. With the new simulation suites, we show that building robust machine-learning models favors training and testing on the largest possible diversity of galaxy formation models. We also demonstrate that it is possible to train accurate neural networks to infer cosmological parameters using the high-dimensional TNG-SB28 simulation set.

Keywords: large-scale structure of the universe; hydrodynamical simulations
Grain Growth in Newly Discovered Young Eruptive Stars

FU Orionis-type stars are young stellar objects showing large outbursts due to highly enhanced accretion from the circumstellar disk onto the protostar. FU Orionis-type object (FUor) outbursts happen in a wide variety of sources from the very embedded ones to those with almost no sign of extended emission beyond the disk. The subsequent eruptions might gradually clear up the obscuring envelope material and drive the protostar on its way to become a disk-only T Tauri star. We used the Very Large Telescope (VLT)/VLT spectrometer and imager for the mid-infrared (VISIR) to obtain the first spectra that cover the 8-13 μm mid-infrared wavelength range in low resolution of five recently discovered FUors. Four objects from our sample show the 10 μm silicate feature in emission. We study the shape and strength of the silicate feature in these objects and find that they mostly contain large amorphous grains, suggesting that large grains are typically not settled to the midplane in FUor disks. This is a general characteristic of FUors, as opposed to regular T Tauri-type stars whose disks display anything from pristine small grains to significant grain growth. We classify our targets by determining whether the silicate feature is in emission or in absorption, and confront them with the evolutionary scenarios on the dispersal of the envelopes around young stars. In our sample, all Class II objects exhibit silicate emission, while for Class I objects, the appearance of the feature in emission or absorption depends on the viewing angle with respect to the outflow cavity. This highlights the importance of geometric effects when interpreting the silicate feature. * Based on observations collected at the European Southern Observatory under ESO programs 097.C-0292, 098.C-0529, and 0102.C-0310.

Keywords: protoplanetary disks; pre-main sequence stars; circumstellar matter
Mapping the Multiphase Structure of H I in the Low-latitude Intermediate-velocity Arch 1

We have analyzed the thermal and turbulent properties of the low-latitude intermediate-velocity Arch 1 (LLIV1). This was accomplished using archival H I emission and absorption data from two 21 cm line surveys: GHIGLS at 9.'4 resolution and DHIGLS at $1^{\prime} $ resolution. The spectral decomposition code ROHSA was used to model the column density of different thermal phases and also to analyze an absorption measurement against the radio source 4C +66.09. From the latter, we found spin temperature T s ~ 75 K, cold gas mass fraction f ~ 0.5, and turbulent sonic Mach number M t ~ 3.4. Similar to the absorption line modeling against 4C +66.09, our best emission line decomposition model has no unstable gas across the whole field of view, suggesting that the thermal condensation and phase transition are not ongoing but rather have reached an equilibrium state. The cold phase of LLIV1 appears as a collection of elongated filaments that forms a closed structure within the field decomposed. These substructures follow the orientation of the overall large-scale cloud, along the diagonal of the GHIGLS field from northwest to southeast (in Galactic coordinates). The angular power spectrum of the cold phase is slightly shallower than that of the warm phase, quantifying that the cold phases have relatively more structure on small scales. Our spatially resolved map of the cold gas mass fraction in LLIV1 from DHIGLS reveals significant variations spanning the possible range of f, with a mean and standard deviation of 0.33 and 0.19, respectively.

Keywords: interstellar medium; interstellar atomic gas; interstellar phases; interstellar emissions; interstellar filaments; interstellar clouds; galaxy processes; milky way galaxy fountains; galaxy infall; galaxy structure; observational astronomy; astronomical methods
JWST MIRI MRS Observations of T Cha: Discovery of a Spatially Resolved Disk Wind

Understanding when and how circumstellar disks disperse is crucial to constrain planet formation and migration. Thermal winds powered by high-energy stellar photons have long been theorized to drive disk dispersal. However, evidence for these winds is currently based only on small (∼3–6 km s‑1) blueshifts in [Ne II] 12.81 μm lines, which does not exclude MHD winds. We report JWST MIRI MRS spectro-imaging of T Cha, a disk with a large dust gap (∼30 au in radius) and blueshifted [Ne II] emission. We detect four forbidden noble gas lines, [Ar II], [Ar III], [Ne II], and [Ne III], of which [Ar III] is the first detection in any protoplanetary disk. We use line flux ratios to constrain the energy of the ionizing photons and find that argon is ionized by extreme ultraviolet, whereas neon is most likely ionized by X-rays. After performing continuum and point-spread function subtraction on the integral field unit cube, we discover a spatial extension in the [Ne II] emission off the disk continuum emission. This is the first spatially resolved [Ne II] disk wind emission. The mostly ionic spectrum of T Cha, in combination with the extended [Ne II] emission, points to an evolved stage for any inner MHD wind and is consistent with the existence of an outer thermal wind ionized and driven by high-energy stellar photons. This work acts as a pathfinder for future observations aiming at investigating disk dispersal using JWST.

Keywords: planet formation; protoplanetary disks; t tauri stars; infrared spectroscopy
Observations and Analysis of CH+ Vibrational Emissions from the Young, Carbon-rich Planetary Nebula NGC 7027: A Textbook Example of Chemical Pumping

We discuss the detection of 14 rovibrational lines of CH+, obtained toward the planetary nebula NGC 7027 with the iSHELL spectrograph on NASA's Infrared Telescope Facility (IRTF) on Maunakea. Our observations in the 3.49-4.13 μm spectral region, obtained with a 0"375 slit width that provided a spectral resolving power λ/Δλ ~ 80,000, have resulted in the unequivocal detection of the R(0)-R(3) and P(1)-P(10) transitions within the v = 1-0 band of CH+. The R-branch transitions are anomalously weak relative to the P-branch transitions, a behavior that is explained accurately by rovibronic calculations of the transition dipole moment reported in a companion paper. Nine infrared transitions of H2 were also detected in these observations, comprising the S(8), S(9), S(13), and S(15) pure rotational lines; the v = 1-0 O(4)-O(7) lines; and the v = 2-1 O(5) line. We present a photodissociation model, constrained by the CH+ and H2 line fluxes that we measured, that includes a detailed treatment of the excitation of CH+ by inelastic collisions, optical pumping, and chemical ("formation") pumping. The latter process is found to dominate the excitation of the observed rovibrational lines of CH+, and the model is remarkably successful in explaining both the absolute and relative strengths of the CH+ and H2 lines.

Keywords: planetary nebulae; interstellar molecules; near infrared astronomy; interstellar line emission; molecular spectroscopy
The Role of O+ and He+ in the Propagation of Kinetic Alfvén Waves in the Earth's Inner Magnetosphere

Interactions between plasma particles and electromagnetic waves play a crucial role in the dynamics and regulation of the state of space environments. From plasma physics theory, the characteristics of the waves and their interactions with the plasma strongly depend on the composition of the plasma, among other factors. In the case of the Earth's magnetosphere, the plasma is usually composed of electrons, protons, O+ ions, and He+ ions, all with their particular properties and characteristics. Here, using plasma parameters relevant for the inner magnetosphere, we study the dispersion properties of kinetic Alfvén waves (KAWs) in a plasma composed of electrons, protons, He+ ions, and O+ ions. We show that heavy ions induce significant changes to the dispersion properties of KAWs, such as polarization, compressibility, and the electric-to-magnetic amplitude ratio, and therefore the propagation of KAWs is highly determined by the relative abundance of He+ and O+ in the plasma. These results, when discussed in the context of observations in the Earth's magnetosphere, suggest that for many types of studies based on theory and numerical simulations, the inclusion of heavy ions should be customary for the realistic modeling of plasma phenomena in the inner magnetosphere or other space environments in which heavy ions can contribute a substantial portion of the plasma, such as planetary magnetospheres and comet plasma tails.

Keywords: alfven waves; space plasmas; planetary magnetospheres
On the Fast Propagating Ultra-hot Disturbance Captured by SDO/AIA: An In-depth Insight into the Coronal Nonlinear Dynamics

The impulsive heating events and their corresponding nonlinear dynamics remain one of the most obscure physical processes in solar atmospheric physics. The complicacy of these processes together with limited observations have greatly hampered our understanding of them. Here, we present, for the first time, an unambiguous example of a nonlinear acoustic wave in a closed coronal loop or loop segment, which appeared as a fast propagating ultra-hot disturbance cohesively in an indistinguishable corona loop with a highly evolving emission intensity profile. Based on the theory of propagating nonlinear waves, we argue that this type of observation can provide further information for the disturbance during its propagation. With this information, we conclude that the propagating nonlinear disturbance can quickly heat the corona through the rarefaction wave, and the disturbance-induced magnetic reconnection should not happen in our observation. Besides, a convenient criterion has also been deduced for the existence of the disturbance-induced reconnection mechanism. All of this provides us with a new insight into the accompanying nonlinear dynamics of solar impulsive heating events, which can not only shed light on problems including coronal heating and the fast formation of hot coronal loops, but also show us a very novel and prospective seismology scheme for the diagnosis of coronal plasma properties.

Keywords: active solar corona; solar coronal waves; solar coronal loops; solar coronal heating