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Abstract We investigate the local proton energization at magnetic discontinuities/intermittent structures and the corresponding kinetic signatures in velocity phase space in Alfvénic (high cross helicity) and non-Alfvénic (low cross helicity) wind streams observed by Parker Solar Probe. By means of the partial variance of increments method, we find that the hottest proton populations are localized around compressible, coherent magnetic structures in both types of wind. Analysis of parallel and perpendicular temperature distributions suggest that the Alfvénic wind undergoes preferential enhancements ofT_∥at such structures, whereas the non-Alfvénic wind experiences preferentialT_⊥enhancements. Although proton beams are present in both types of wind, the proton velocity distribution function displays distinct features. Hot beams, i.e., beams with beam-to-core perpendicular temperatureT_⊥,b/T_⊥,cup to three times larger than the total distribution anisotropy, are found in the non-Alfvénic wind, whereas colder beams are in the Alfvénic wind. Our data analysis is complemented by 2.5D hybrid simulations in different geometrical setups, which support the idea that proton beams in Alfvénic and non-Alfvénic wind have different kinetic properties and different origins. The development of a perpendicular nonlinear cascade, favored in balanced turbulence, allows a preferential relative enhancement of the perpendicular plasma temperature and the formation of hot beams. Cold field-aligned beams are instead favored by Alfvén wave steepening. Non-Maxwellian distribution functions are found near discontinuities and intermittent structures, pointing to the fact that the nonlinear formation of small-scale structures is intrinsically related to the development of highly nonthermal features in collisionless plasmas. Our results contribute to understanding the role of different coherent structures in proton energization and their implication in collisionless energy dissipation processes in space plasmas. 

Context. Understanding the formation of substructures in protoplanetary disks is vital for gaining insights into dust growth and the process of planet formation. Studying these substructures in highly embedded Class 0 objects using the Atacama Large Millimeter-submillimeter Array (ALMA), however, poses significant challenges. Nonetheless, it is imperative to do so to unravel the mechanisms and timing behind the formation of these substructures. Aims. In this study, we present high-resolution ALMA data at Bands 6 and 4 of the NGC 1333 IRAS4A Class 0 protobinary system. This system consists of two components, A1 and A2, which are separated by 1.8″ and located in the Perseus molecular cloud at a distance of ~293 pc. Methods. To gain a comprehensive understanding of the dust properties and formation of substructures in the early stages, we conducted a multiwavelength analysis of IRAS4A1. Additionally, we sought to address whether the lack of observed substructures in very young disks could be attributed to factors such as high degrees of disk flaring and large scale heights. To explore this phenomenon, we employed radiative transfer models using RADMC-3D. We employed different approaches and compared the model outcomes with our observational data. This comparison allowed us to gain insights into the challenges in detecting substructures in nascent disks and shed light on the potential influence of the dust scale height on observations of protoplanetary disks. Results. The continuum data revealed the presence of two disks-envelopes around A1 and A2, along with structure connecting the two sources. Furthermore, spectral index measurements indicate lower optical depth within the A2 disk compared to the A1 disk. Our multiwavelength analysis of A1 discovered characteristics such as high dust surface density, substantial dust mass within the disk, and elevated dust temperatures. These findings suggest the presence of large dust grains compared to the ones in the interstellar medium (ISM), greater than 100 microns in size within the region. By employing RADMC-3D, we confirmed that increasing the scale height creates the appearance of an asymmetry in protoplanetary disks. Our findings indicate that a scale height of at least 0.3 (H/R) is necessary to produce this observed asymmetry. Furthermore, while there’s no direct detection of any substructure, our models indicate that some substructure, such as a small gap, must be present. However, reproducing the intensity profile along the major and minor axes necessitates considering other processes that may be occurring within the IRAS4A1 disk. Conclusions. The result implies that disk substructures may be masked or obscured by a large scale height in combination with a high degree of flaring in Class 0 disks. 

In this study we analyze 70 radio continuum sources associated with dust clumps and considered to be candidates for the earliest stages of high-mass star formation. The detection of these sources was reported by Rosero et al. (2016), who found most of them to show weak ( < 1 mJy) and compact ( < 0.6") radio emission. Herein, we used the observed parameters of these sources to investigate the origin of the radio continuum emission. We found that at least ∼ 30% of these radio detections are most likely ionized jets associated with high-mass protostars, but for the most compact sources we cannot discard the scenario that they represent pressure-confined HII regions. This result is highly relevant for recent theoretical models based on core accretion that predict the first stages of ionization from high-mass stars to be in the form of jets. Additionally, we found that properties such as the radio luminosity as a function of the bolometric luminosity of ionized jets from low and high-mass stars are extremely well-correlated. Our data improve upon previous studies by providing further evidence of a common origin for jets independently of luminosity. 

We present multiwavelength observations of two gap transients that were followed by the Carnegie Supernova Project-II. The observations are supplemented with data obtained by a number of different programs. Here in the first of two papers, we focus on the intermediate-luminosity red transient (ILRT) designated SNhunt120, while in a companion paper we examine the luminous red novae AT 2014ej. Our data set for SNhunt120 consists of an early optical discovery, estimated to be within three days after outburst, the subsequent optical and near-infrared broadband followup extending over a period of about two months, two visual and two near-infrared wavelength spectra, and Spitzer Space Telescope observations extending from early (+28 d) to late (+1155 d) phases. SNhunt120 resembles other ILRTs such as NGC 300-2008-OT and SN 2008S, and like these other ILRTs, SNhunt120 exhibits prevalent mid-infrared emission at both early and late phases. From the comparison of SNhunt120 and other ILRTs to electron-capture supernova simulations, we find that the current models underestimate the explosion kinetic energy and thereby produce synthetic light curves that overestimate the luminosity. Finally, examination of pre-outburst Hubble Space Telescope images yields no progenitor detection. 

We present optical and near-infrared broadband photometry and optical spectra of AT 2014ej from the Carnegie Supernova Project-II. These observations are complemented with data from the CHilean Automatic Supernova sEarch, the Public ESO Spectroscopic Survey of Transient Objects, and from the Backyard Observatory Supernova Search. Observational signatures of AT 2014ej reveal that it is similar to other members of the gap-transient subclass known as luminous red novae (LRNe), including the ubiquitous double-hump light curve and spectral properties similar to that of LRN SN 2017jfs. A medium-dispersion visual-wavelength spectrum of AT 2014ej taken with the Magellan Clay telescope exhibits a P Cygni H α feature characterized by a blue velocity at zero intensity of ≈110 km s −1 and a P Cygni minimum velocity of ≈70 km s −1 . We attribute this to emission from a circumstellar wind. Inspection of pre-outbust Hubble Space Telescope images yields no conclusive progenitor detection. In comparison with a sample of LRNe from the literature, AT 2014ej lies at the brighter end of the luminosity distribution. Comparison of the ultra-violet, optical, infrared light curves of well-observed LRNe to common-envelope evolution models from the literature indicates that the models underpredict the luminosity of the comparison sample at all phases and also produce inconsistent timescales of the secondary peak. Future efforts to model LRNe should expand upon the current parameter space we explore here and therefore may consider more massive systems and a wider range of dynamical timescales.