Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Assuming that gas and dust separate in the interstellar medium (ISM) so that high-density regions, where stars can form, are almost devoid of dust, the amount of metals being removed from the ISM can be significantly reduced (minimized astration). Here, it is shown by simple analytical models that this may increase the total metal budget of a galaxy considerably. It is suggested that these extra metals may increase the mass of dust such that the “dust budget crisis”, i.e., the fact that there seems to be more dust at high redshifts than can be accounted for, can be ameliorated. Reducing the amount of astration, the metal budget can be more than doubled, in particular for systems that evolve under continuous gas accretion.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Astronomical observations of neutral atomic hydrogen (H <jats:sc>i</jats:sc>) are an important tracer of several key processes of galaxy evolution, but face significant difficulties with terrestrial telescopes. Among these is source confusion, or the inability to distinguish between emission from multiple nearby sources separated by distances smaller than the telescope’s spatial resolution. Confusion can compromise the data for the primary target if the flux from the secondary galaxy is sufficient. This paper presents an assessment of the confusion-flagging methods of the H <jats:sc>i</jats:sc>-MaNGA survey, using higher-resolution H <jats:sc>i</jats:sc> data from the Westorbork Synthesis Radio Telescope-Apertif survey. We find that removing potentially confused observations using a confusion probability metric—calculated from the relationship between galaxy color, surface brightness, and H <jats:sc>i</jats:sc> content—successfully eliminates all significantly confused observations in our sample, although roughly half of the eliminated observations are not significantly confused.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The abundances of elements lighter than scandium in the atmosphere of the A0 III giant, <jats:italic>α</jats:italic> Sex, are derived using archival ultraviolet and optical spectra. Most of the strongest lines present in the far-ultraviolet spectrum of <jats:italic>α</jats:italic> Sex can be attributed to chemical elements lighter than calcium. The synthesis of selected lines in the optical and ultraviolet yields new abundances, in particular for elements which have few lines in the optical range. Helium, oxygen, silicon and sulfur are found to have solar abundances, most other elements are underabundant. Aluminium may be marginally overabundant. The lines of chlorine are probably present in the FUV but they are too blended to derive the abundance of chlorine.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Dozens of exotic materials are found only in meteorites. These “meteorite minerals” are formed in the solar system's cold, long-lived, proto-planetary disk, in the slowly cooling cores of planetesimals, and in high-speed collisions. To the best of our knowledge no recent published work has aggregated information about minerals only found in meteorites in a comprehensive and machine readable manner. Thus, we have compiled a preliminary catalog of 81 known meteorite minerals from the literature to serve as a stepping stone for a future, more extensive effort. We also explore the distribution of these meteorite minerals by meteorite type.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A30 belongs to a class of planetary nebulae identified as “born-again”, containing dense, hydrogen-poor ejecta with extreme abundance discrepancy factors (ADFs), likely associated with a central binary system. We present intermediate-dispersion spectroscopy of one such feature—the J4 equatorial knot. We confirm the apparent physical and chemical segregation of the polar and equatorial knots observed in previous studies, and place an upper limit on the ADF for O<jats:sup>2+</jats:sup> of 35, significantly lower than that of the polar knots. These findings further reinforce the theory that the equatorial and polar knots originate from different events.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report a historic <jats:italic>K</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub>-band light curve spanning over three decades of the FUor PGIR20dci recently discovered by Hillenbrand et al. We find some minor variability of the object prior to the FUor outburst, an initial rather slow rise in brightness, followed in 2019 by a much steeper rise to the maximum.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Disks around young stellar objects (YSOs) consist of material that thermally emits the energy provided by a combination of passive heating from the central star, and active, viscous heating due to mass accretion. FU Ori stars are YSOs with substantially enhanced accretion rates in their inner disk regions. As a disk transitions from standard low-state, to FU Ori-like high-state accretion, the outburst manifests through photometric brightening over a broad range of wavelengths. We present results for the expected amplitudes of the brightening between ∼4000 Å and 8 <jats:italic>μ</jats:italic>m—the wavelength range where FU Ori type outburst events are most commonly detected. Our model consists of an optically thick passive + active steady-state accretion disk with low and high accretion states.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>NGC 628 is one of many spiral galaxies that has been observed and analyzed to determine the chemical composition. Since there have been improvements in the methods of analysis recently, this paper finds new values for the electron temperatures within this galaxy. Additionally, it brings up a previously unnoticed iron line contamination problem that has affected the [O <jats:sc>iii</jats:sc>] temperatures and fluxes. Temperature results are compared against, the most recent chemical analysis of the same galaxy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The majority of stars have one or more stellar companions. As exoplanets continue to be discovered, it is crucial to examine planetary systems to identify their stellar companions. By observing a change in proper motion, companions can be detected by the acceleration they induce on their host stars. We selected 701 stars from the Hipparcos–Gaia Catalog of Accelerations (HGCA) that have existing adaptive optics imaging data gathered with Gemini/Near InfraRed Imager (NIRI). Of these, we examined 21 stars known to host planet candidates and reduced their archival NIRI data with Gemini’s DRAGONS software. We assessed these systems for companions using the NIRI images as well as Renormalized Unit Weight Error values in Gaia and accelerations in the HGCA. We detected three known visible companions and found two more systems with no visible companions but astrometric measurements indicating likely unresolved companions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Cobalt and nickel abundances are rarely available for normal and Chemically Peculiar A stars because the strongest transitions of Co <jats:sc>ii</jats:sc> and Ni <jats:sc>ii</jats:sc> fall in the mid-UV. The abundances of cobalt and nickel are derived for 78 Vir using a mean mid-ultraviolet spectrum constructed by coadding 10 spectra collected with the Long Wave Prime and Long wavelength Redundant cameras over the 18 yr of the IUE mission. The strong transitions of Co <jats:sc>ii</jats:sc> at 2286.16 Å, 2307.86 Å, 2324.32 Å and 2580.33 Å and that of Ni <jats:sc>ii</jats:sc> et 2287.09 Å are present and more or less affected by blends. The least blended, <jats:italic>λ</jats:italic> 2286.16 Å, yields a mean overabundance of cobalt of 5 times the solar abundance, the Ni <jats:sc>ii</jats:sc> line at 2287.09 Å yields a 3 times solar overabundance. There is no convincing evidence that these lines varied in the spectra analyzed. The rotational period of 78 Vir estimated from its recent TESS lightcurve is 3.723 ± 0.055 days.</jats:p>