We have detected CH + and CH molecular absorption lines from the youngcompact planetary nebula IC 4997 from high resolution optical spectra. A high-resolution infra-red (H and K bands) spectrum provides detection of H 2 emission lines among many other lines. The H 2 lines provide an excitation temperature of 2100 K which may result from UV

We present the analysis of a very high-magnification (A ∼ 900) microlensing event KMT-2019-BLG-1953. A single-lens single-source (1L1S) model appears to approximately delineate the observed light curve, but the residuals from the model exhibit small but obvious deviations in the peak region. A binary-lens (2L1S) model with a mass ratio of q ∼ 2 ×

The Milky Way underwent its last significant merger ten billion years ago, when the Gaia-Enceladus-Sausage (GES) was accreted. Accreted GES stars and progenitor stars born prior to the merger make up the bulk of the inner halo. Even though these two main populations of halo stars have similar durations of star formation prior to their merger, they

The emission from the relativistic jets in blazars usually outshines their host galaxies, challenging the determination of their distances and the characterization of the stellar population. The situation becomes more favourable in the case of the extreme blazars (EHBLs), for which the bulk of the emission of the relativistic jets is emitted at

In this work, we present the results of an observational study of 2I/Borisov carried out with the 10.4-m Gran Telescopio Canarias (GTC) and the 3.6-m Telescopio Nazionale Galileo (TNG), both telescopes located at the Roque de Los Muchachos Observatory, in the island of La Palma (Spain). The study includes images in the visible and near-infrared, as

The green valley (GV) represents an important transitional state from actively star-forming galaxies to passively evolving systems. Its traditional definition, based on colour, rests on a number of assumptions that can be subjected to non-trivial systematics. In Angthopo, Ferreras & Silk (2019), we proposed a new definition of the GV based on the