We present detailed submillimeter-through centimeter-wave observations of the extraordinary extragalactic transient AT2018cow. The apparent characteristicsthe high radio luminosity, the rise and long-lived emission plateau at millimeter bands, and the sub-relativistic velocity -have no precedent. A basic interpretation of the data suggests E k 4 × 10 48 erg coupled to a fast but sub-relativistic (v ≈ 0.13c) shock in a dense (n e ≈ 3 × 10 5 cm −3 ) medium. We find that the X-ray emission is not naturally explained by an extension of the radio-submm synchrotron spectrum, nor by inverse Compton scattering of the dominant blackbody UVOIR photons by energetic electrons within the forward shock. By ∆t ≈ 20 days, the X-ray emission shows spectral softening and erratic inter-day variability. Taken together, we are led to invoke an additional source of X-ray emission: the central engine of the event. Regardless of the nature of this central engine, this source heralds a new class of

The Very Large Array Sky Survey (VLASS) is a synoptic, all-sky radio sky survey with a unique combination of high angular resolution (≈2 5), sensitivity (a 1σ goal of 70 μJy/beam in the coadded data), full linear Stokes polarimetry, time domain coverage, and wide bandwidth (2-4 GHz). The first observations began in 2017 September, and observing for the survey will finish in 2024. VLASS will use approximately 5500 hr of time on the Karl G. Jansky Very Large Array (VLA) to cover the whole sky visible to the VLA (decl. >−40°), a total of 33 885deg 2. The data will be taken in three epochs to allow the discovery of variable and transient radio sources. The survey is designed to engage radio astronomy experts, multi-wavelength astronomers, and citizen scientists alike. By utilizing an "on the fly" interferometry mode, the observing overheads are much reduced compared to a conventional pointed survey. In this paper, we present the science case and observational strategy for the survey, and also results from early survey observations.

We have carried out N-body simulations for rotating star clusters with equal mass and compared the results with Fokker-Planck models. These two different approaches are found to produce fairly similar results, although there are some differences with regard to the detailed aspects. We confirmed the acceleration of the core collapse of a cluster due to an initial non-zero angular momentum and found a similar evolutionary trend in the central density and velocity dispersion in both simulations. The degree of acceleration depends on the initial angular momentum. Angular momentum is being lost from the cluster due to the evaporation of stars with a large angular momentum on a relaxation time-scale.

We analyze Chandra X-ray observatory data for a sample of 63 luminous infrared galaxies (LIRGs), sampling the lower-infrared luminosity range of the Great Observatories All-Sky LIRG survey (GOALS), which includes the most luminous infrared selected galaxies in the local Universe. X-rays are detected for 84 individual galaxies within the 63 systems, for which arcsecond resolution X-ray images, fluxes, infrared and X-ray luminosities, spectra and radial profiles are presented. Using X-ray and mid-infrared (MIR) selection criteria, we find AGN in (31 ± 5)% of the galaxy sample, compared to the (38 ± 6)% previously found for GOALS galaxies with higher infrared luminosities (C-GOALS I). Using MIR data, we find that (59 ± 9)% of the X-ray selected AGN in the full C-GOALS sample do not contribute significantly to the bolometric luminosity of the host galaxy. Dual AGN are detected in two systems, implying a dual AGN fraction in systems that contain at least one AGN of (29 ± 14)%, compared to the (11 ± 10)% found for the C-GOALS I sample. Through analysis of radial profiles, we derive that most sources, and almost all AGN, in the sample are compact, with half of the soft X-ray emission generated within the inner ∼1 kpc. For most galaxies, the soft X-ray sizes of the sources are comparable to those of the MIR emission. We also find that the hard X-ray faintness previously reported for the bright C-GOALS I sources is also observed in the brightest LIRGs within the sample, with LFIR > 8 × 1010 L⊙.