Search Publications
ALMA reveals a pseudo-disc in a proto-brown dwarf
Riaz, B.; Stamatellos, D.; Machida, M. N.
We present the observational evidence of a pseudo-disc around the proto-brown dwarf Mayrit 1701117, the driving source of the large-scale HH 1165 jet. Our analysis is based on Atacama Large Millimeter/submillimeter Array 12CO (2-1) line and 1.37 mm continuum observations at an angular resolution of ∼0.4 arcsec. The pseudo-disc is a brig…
Imprints of the first billion years: Lyman limit systems at z ∼ 5
Worseck, Gábor; Prochaska, J. Xavier; Murphy, Michael T. +3 more
Lyman limit systems (LLSs) trace the low-density circumgalactic medium and the most dense regions of the intergalactic medium, so their number density and evolution at high-redshift, just after reionization, are important to constrain. We present a survey for LLSs at high redshifts, zLLS = 3.5-5.4, in the homogeneous data set of 153 opt…
The GALAH survey: co-orbiting stars and chemical tagging
Lewis, Geraint F.; Ting, Yuan-Sen; Casey, Andrew R. +24 more
We present a study using the second data release of the GALAH survey of stellar parameters and elemental abundances of 15 pairs of stars identified by Oh et al. They identified these pairs as potentially co-moving pairs using proper motions and parallaxes from Gaia DR1. We find that 11 very wide (>1 pc) pairs of stars do in fact have similar Ga…
Fundamental parameters and evolutionary status of the magnetic chemically peculiar stars HD 188041 (V1291 Aquilae), HD 111133 (EP Virginis), and HD 204411: spectroscopy versus interferometry
Shulyak, D.; Ryabchikova, T.; Perraut, K. +4 more
The determination of fundamental parameters of stars is one of the main tasks of astrophysics. For magnetic chemically peculiar stars, this problem is complicated by the anomalous chemical composition of their atmospheres, which requires special analysis methods. We present the results of the effective temperature, surface gravity, abundance, and …
From ridges in the velocity distribution to wiggles in the rotation curve
Martinez-Medina, Luis; Pichardo, Barbara; Peimbert, Antonio +1 more
Recently, the Gaiadata release 2 (DR2) showed us the richness in the kinematics of the Milky Way disc. Of particular interest is the presence of ridges covering the stellar velocity distribution, Vϕ-R; as shown by others, it is likely that these ridges are the signature of phase mixing, transient spirals, or the bar. Here, with a Galact…
Progenitor constraints on the Type Ia supernova SN 2014J from Hubble Space Telescope H β and [O III] observations
Graur, Or; Woods, Tyrone E.
Type Ia supernovae are understood to arise from the thermonuclear explosion of a carbon-oxygen white dwarf, yet the evolutionary mechanisms leading to such events remain unknown. Many proposed channels, including the classical single-degenerate scenario, invoke a hot, luminous evolutionary phase for the progenitor, in which it is a prodigious sour…
An efficient approach to extract parameters from star cluster CMDs: fitCMD
Bonatto, Charles
This work presents an approach (fitCMD) designed to obtain a comprehensive set of astrophysical parameters from colour-magnitude diagrams (CMDs) of star clusters. Based on initial mass function (IMF) properties taken from isochrones, fitCMD searches for the values of total (or cluster) stellar mass, age, global metallicity, foreground reddening, d…
On the iron ionization balance of cool stars
Adibekyan, V.; Sousa, S. G.; Santos, N. C. +3 more
High-resolution spectroscopic studies of solar-type stars have revealed higher iron abundances derived from singly ionized species compared to neutral, violating the ionization equilibrium under the assumption of local thermodynamic equilibrium. In this work, we investigate the overabundances of Fe II lines reported in our previous work for a samp…
Chemical abundances in the metal-intermediate GC NGC 6723
Bono, Giuseppe; Alonso-García, Javier; Crestani, Juliana +2 more
We have performed a detailed spectral analysis of the inner halo Galactic globular cluster (GC) NGC 6723 using high-resolution (R{≈ } 22 000-48 000) spectra for for 11 red giant branch stars collected with MIKE (Magellan) and FEROS (MPG/ESO). This globular is located at the minimum of the bimodal metallicity distribution of GCs, which suggests tha…
Puzzling blue dips in the black hole candidate Swift J1357.2 - 0933, from ULTRACAM, SALT, ATCA, Swift, and NuSTAR
Altamirano, D.; Dhillon, V. S.; Charles, P. A. +13 more
We present rapid, multiwavelength photometry of the low-mass X-ray binary Swift J1357.2-0933 during its 2017 outburst. Using several sets of quasi-simultaneous ULTRACAM/NTT (optical), NuSTAR (X-ray), XRT/Swift (X-ray), SALT (optical), and ATCA (radio) observations taken during outburst decline, we confirm the frequent optical dipping that has prev…