We present the kinematic and chemical profiles of red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE)-2 survey in the direction of the Jhelum stellar stream, a Milky Way substructure located in the inner halo of the Milky Way at a distance from the Sun of ≍13 kpc. From the six APOGEE-2 Jhelum pointings

We present an infrared (IR) characterization of the born-again planetary nebulae (PNe) A 30 and A 78 using IR images and spectra. We demonstrate that the carbon-rich dust in A 30 and A 78 is spatially coincident with the H-poor ejecta and coexists with hot X-ray-emitting gas up to distances of 50 arcsec from the central stars of PNe (CSPNe). Dust

We analyse a wealth of optical spectroscopic and photometric observations of the bright (V = 11.9) cataclysmic variable BG Tri. The Gaia DR2 parallax gives a distance d = 334(8) pc to the source, making the object one of the intrinsically brightest nova-like variables seen under a low orbital inclination angle. Time-resolved spectroscopic

We explore unsupervised machine learning for galaxy morphology analyses using a combination of feature extraction with a vector-quantized variational autoencoder (VQ-VAE) and hierarchical clustering (HC). We propose a new methodology that includes: (1) consideration of the clustering performance simultaneously when learning features from images; (2

Context. More than 10% of barred galaxies with a direct measurement of the bar pattern speed host an ultrafast bar. These bars extend well beyond the corotation radius and challenge our understanding of the orbital structure of barred galaxies. Most of the bars are found in spiral galaxies, rather than in lenticular galaxies. Aims: We analyse the

Planetesimals—the initial stage of the planetary formation process—are considered to be initially very porous aggregates of dusts 1,2, and subsequent thermal and compaction processes reduce their porosity 3. The Hayabusa2 spacecraft found that boulders on the surface of asteroid (162173) Ryugu have an average porosity of 30-50% (refs. 4-6), higher