Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The Jupiter Trojan asteroid 128383 (2004 JW<jats:sub>52</jats:sub>) was recently reported to have optical colors that are incongruous with its dynamical class. New and archival observations show that this is not the case. This is a reminder that we must always rule out the possibility that the Point-Spread Function of a minor planet is blended with that of a background sidereal source in survey images before its colors in the associated survey catalog can be considered reliable.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We summarize the first exploratory investigation into whether Machine Learning techniques can augment science strategic planning. We find that an approach based on Latent Dirichlet Allocation using abstracts drawn from high-impact astronomy journals may provide a leading indicator of future interest in a research topic. We show two topic metrics that correlate well with the high-priority research areas identified by the 2010 National Academies’ Astronomy and Astrophysics Decadal Survey. One metric is based on a sum of the fractional contribution to each topic by all scientific papers (“counts”) while the other is the Compound Annual Growth Rate of counts. These same metrics also show the same degree of correlation with the whitepapers submitted to the same Decadal Survey. Our results suggest that the Decadal Survey may under-emphasize fast growing research. A preliminary version of our work was presented by Thronson et al.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>VY Canis Majoris (VY CMa) is one of the largest, most luminous red supergiant (RSG) stars in the Galaxy. This huge oxygen-rich RSG may be on the verge of becoming a bright core-collapse Type-II supernova. Over the 20th century, VY CMa has been undergoing episodic large quasi-periodic light variations. It has experienced two “great dimming” episodes during ∼1920–1950 and ∼1985–1995. During these, the star underwent large (1–2.5 mag) quasi-periodic light variations with dominant periods ranging between ∼1415 and 1565 days. In addition to experiencing large quasi-periodic light variations, VY CMa became fainter by 1.0–1.5 mag during the 1920–1950 episode. There is evidence that the star’s brightness decreased from ∼6.5–7.0 to ∼8.0–8.5 mag from 1850 to after 1900. These long-term dimming events may arise from dust formation from previously expelled gas. The light variations and the “dimmings” of VY CMa far surpass the recent “great dimming” of Betelgeuse.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We explore the post-supernova (SN) outcomes of binary systems using a rapid stellar evolution code to simulate the equivalent of a population of ∼ 10<jats:sup>6</jats:sup>  <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. Here we explore the fraction of binaries that remain intact after the SN, which can potentially be found within supernova remnants. Given the challenges that the observational studies are facing, we use numerical simulations to shed more light on the issue.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The bright star <jats:italic>γ</jats:italic> Psc is among the nearest Population II giants located in the red clump region. Here we demonstrate that <jats:italic>γ</jats:italic> Psc is actually a core-helium burning horizontal branch star. As such, the <jats:italic>τ</jats:italic> ≃ 12 Gyr old <jats:italic>γ</jats:italic> Psc is found to be slightly over-massive at <jats:italic>M</jats:italic> <jats:sub>HB</jats:sub> = 0.97 ± 0.12 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, which suggests that it is possibly a rejuvenated source.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Zinc and Copper abundances are rarely available for normal and Chemically Peculiar A stars because the strongest transitions of Zn <jats:sc>ii</jats:sc> and Cu <jats:sc>ii</jats:sc> fall in the mid-UV. Estimates of the abundances of zinc and copper are derived for 78 Vir (A2p SrCrEu) and <jats:italic>θ</jats:italic> Leo (A2 IV) using mean mid-ultraviolet spectra constructed by coadding individual spectra collected with the Long Wave Prime and Long wavelength Redundant cameras over the 18 yr of the IUE mission. The strong transition of Cu <jats:sc>ii</jats:sc> at 2135.98 Å is present in 78 Vir and <jats:italic>θ</jats:italic> Leo but definitely stronger in 78 Vir, whereas all Zn <jats:sc>ii</jats:sc> lines are blended. Spectral synthesis of the least blended lines yields estimates of the abundances of zinc and copper of about 4.92 and 4.95 respectively in <jats:italic>θ</jats:italic> Leo and 5.82 and 5.19 in 78 Vir (on a scale where log(H) = 12). There is no convincing evidence that these lines varied in the spectra analyzed for both stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In order to investigate the role of the host halo in quenching satellite galaxies, we have characterized a single Milky Way-like host galaxy from the FIRE simulations from <jats:italic>z</jats:italic> = 0–1.76 by quantifying the gas density of the host halo environment with respect to distance from the host and galactocentric latitude. The gas density decreases with increasing distance from the host according to a broken power law. At earlier times (2–10 Gyr ago), the density in the inner regions of the host halo was enhanced relative to <jats:italic>z</jats:italic> = 0. Thus, earlier infalling satellites experienced more ram-pressure and were more efficiently quenched compared to later infalling satellites. We also find that in the inner halo (&lt;150 kpc) the density is 2–3 times larger close to the plane of the host galaxy disk versus above or below the disk, so satellites that orbit at low galactocentric latitudes may be more efficiently quenched.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This is a brief rebuttal to the recent paper by Veena et al. entitled “A Kpc Scale Molecular Wave in the Inner Galaxy: Feather of the Milky Way?” I argue that no robust evidence is presented in the paper to support their claimed discovery of “one of the largest and most intriguing structures identified in the Milky Way,” a structure they call the Gangotri wave.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>An understanding of the dynamical evolution of binary star systems, and their effects on stellar and planetary evolution, requires well-characterized binary populations across stellar ages. However, the observational resources required to find and characterize binaries are expensive. With the release of high-precision Gaia astrometry, the re-normalized unit weight error (RUWE) statistic has been shown to reveal the presence of binary systems, with RUWE values greater than 1.2 indicating the presence of a stellar companion within ∼1″. Our goal is to assess whether this new diagnostic, which was developed for field-age systems (&gt;1 Gyr), applies to young systems; specifically, those that host circumstellar disks. With a control sample of single-star systems, compiled from high-contrast imagining surveys of the Taurus and Upper Scorpius star-forming regions, we compare the RUWE values for systems with and without circumstellar disks. We show that the presence of a protoplanetary disk alone can result in inflated RUWE values. Based on the distribution of the RUWE for disk-bearing single stars, we suggest a more conservative single-star—binary threshold is warranted in the presence of disk material. We place this cutoff at the distribution’s 95th percentile, with RUWE = 2.5.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this work, I estimate the number of close stellar encounters on a specific cross-sectional area that may contain a planetary disk in a crowded star formation cluster. The approximation employs Monte Carlo runs to estimate the most likely value of the number of encounters as a function of stellar densities from 1.6 × 10<jats:sup>5</jats:sup> to 6.2 × 10<jats:sup>5</jats:sup> pc<jats:sup>−3</jats:sup>, velocity dispersions from 0.7 to 1.5 km s<jats:sup>−1</jats:sup>, and the lifetime of a typical star formation environment. I found that the most likely number of encounters on cross-sectional areas with a radius of 400 au goes from one to three. Although, four encounters are also likely to happen. This means that multiple strong stellar could happen on planetary disks in the early epoch of the star formation clusters.</jats:p>