Aims. We examined the velocity, density, and temperature structure of Taurus molecular cloud-1 (TMC-1), a filamentary cloud in a nearby quiescent star forming area, to understand its morphology and evolution. Methods. We observed high signal-to-noise (S/N), high velocity resolution NH 3 (1,1), and (2, 2) emission on an extended map. By fitting multiple hyperfine-split line profiles to the NH 3 (1, 1) spectra, we derived the velocity distribution of the line components and calculated gas parameters on several positions. Herschel SPIRE far-infrared continuum observations were reduced and used to calculate the physical parameters of the Planck Galactic Cold Clumps (PGCCs) in the region, including the two in TMC-1. The morphology of TMC-1 was investigated with several types of clustering methods in the parameter space consisting of position, velocity, and column density. Results. Our Herschel-based column density map shows a main ridge with two local maxima and a separated peak to the south-west. The H 2 column densities and dust colour temperatures are in the range of 0.5−3.3 × 10 22 cm −2 and 10.5−12 K, respectively. The NH 3 column densities and H 2 volume densities are in the range of 2.8−14.2 × 10 14 cm −2 and 0.4−2.8 × 10 4 cm −3 . Kinetic temperatures are typically very low with a minimum of 9 K at the maximum NH 3 and H 2 column density region. The kinetic temperature maximum was found at the protostar IRAS 04381+2540 with a value of 13.7 K. The kinetic temperatures vary similarly to the colour temperatures in spite of the fact that densities are lower than the critical density for coupling between the gas and dust phase. The k-means clustering method separated four sub-filaments in TMC-1 with masses of 32.5, 19.6, 28.9, and 45.9 M and low turbulent velocity dispersion in the range of 0.13−0.2 km s −1 . Conclusions. The main ridge of TMC-1 is composed of four sub-filaments that are close to gravitational equilibrium. We label these TMC-1F1 through F4. The sub-filaments TMC-1F1, TMC-1F2, and TMC-1F4 are very elongated, dense, and cold. TMC-1F3 is a little less elongated and somewhat warmer, and probably heated by the Class I protostar, IRAS 04381+2540, which is embedded in it. TMC-1F3 is approximately 0.1 pc behind TMC1-F1. Because of its structure, TMC-1 is a good target to test filament evolution scenarios.

GRB 170817A, associated with the LIGO-Virgo GW170817 neutron-star merger event, lacks the short duration and hard spectrum of a Short gammaray burst (GRB) expected from long-standing classification models. Correctly identifying the class to which this burst belongs requires comparison with other GRBs detected by the Fermi GBM. The aim of our analysis is to classify Fermi GRBs and to test whether or not GRB 170817A belongs -as suggested -to the Short GRB class. The Fermi GBM catalog provides a large database with many measured variables that can be used to explore gamma-ray burst classification. We use statistical techniques to look for clustering in a sample of 1298 gamma-ray bursts described by duration and spectral hardness. Classification of the detected bursts shows that GRB 170817A most likely belongs to the Intermediate, rather than the Short GRB class. We discuss this result in light of theoretical neutron-star merger models and existing GRB classification schemes. It appears that GRB classification schemes may not yet be linked to appropriate theoretical models, and that theoretical models may not yet adequately account for known GRB class properties. We conclude that GRB 170817A may not fit into a simple phenomenological classification scheme. I. Horváth B.G. Tóth J. Hakkila

The Hercules–Corona Borealis Great Wall is a statistically significant clustering of gamma-ray bursts around redshift 2. Motivated by recent theoretical results indicating that a maximal Universal structure size may indeed coincide with its estimated size (2−3 Gpc), we reexamine the question of this Great Wall’s existence from both observational and theoretical perspectives. Our statistical analyses confirm the clustering’s presence in the most reliable data set currently available, and we present a video showing what this data set looks like in 3D. Cosmological explanations (i.e. having to do with the distribution of gravitating matter) and astrophysical explanations (i.e. having to do with the rate of star formation over cosmic time and space) regarding the origin of such a structure are presented and briefly discussed, but the role of observational bias is also noted to be possibly serious. This, together with the scientific importance of using gamma-ray bursts as unique cosmological probes, emphasises the need for future missions such as the THESEUS satellite which will provide us with unprecedentedly homogeneous data of gamma-ray bursts with measured redshifts. We conclude from all this that the Hercules–Corona Borealis Great Wall may indeed be the largest structure in the Universe – but to be able to decide conclusively whether it actually exists, we need THESEUS.

The Fermi GBM catalog provides a large database with many measured variables that can be used to explore and verify gamma-ray burst classification results. We have used Principal Component Analysis and statistical clustering techniques to look for clustering in a sample of 801 gamma-ray bursts described by sixteen classification variables. The analysis recovers what appears to be the Short class and two longduration classes that differ from one another via peak flux, with negligible variations in fluence, duration and spectral hardness. Neither class has properties entirely consistent with the Intermediate GRB class. Spectral hardness has been a critical Intermediate class property. Rather than providing spectral hardness, Fermi GBM provides a range of fitting variables for four different spectral models; it is not intuitive how these variables can be used to support or disprove previous GRB classification results.

A significant number of the parameters of a gamma-ray burst (GRB) and its host galaxy are calculated from the afterglow. There are various methods obtaining extinction values for the necessary correction for galactic foreground. These are: galaxy counts, from HI 21 cm surveys, from spectroscopic measurements and colors of nearby Galactic stars, or using extinction maps calculated from infrared surveys towards the GRB. We demonstrate that AKARI Far-Infrared Surveyor sky surface brightness maps are useful uncovering the fine structure of the galactic foreground of GRBs. Galactic cirrus structures of a number of GRBs are calculated with a 2 arcminute resolution, and the results are compared to that of other methods.