Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Galaxies are surrounded by low-density, highly-ionized clouds of gas, called the Circumgalactic Medium (CGM), which provides insight into galaxy evolution. CGM observations are sensitive to ionization levels, which requires studying ionization types: photoionization (PI), more density-dependent and associated with cooler gas, and collisional ionization (CI), more temperature-dependent and associated with hotter gas. We analyzed PI and CI components for oxygen ionization states using cosmological galaxy simulations. For each ion, we plotted mass distributions into PI and CI phases and created 2D covering-fraction projections of column density at different thresholds. We analyzed changes for different mass-bin galaxies. Our results are: O <jats:sc>vii</jats:sc> and O <jats:sc>ix</jats:sc> are the only predominantly-CI ion states. O <jats:sc>vi</jats:sc> is a local minimum in both PI and CI gas. Column density distributions greatly emphasize higher ion states. Shapes of covering-fraction plots at higher thresholds resemble the 3D-plots. CI gas dominates more in higher mass galaxy simulations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>2MASS J050051.85−093054.9 is the closest known low-mass helium-core white dwarf in a binary system. We used three high-band international Low-Frequency Array stations to perform a targeted search for a pulsar companion, reaching sensitivities of ∼3 mJy for a 10 ms pulsar at a DM = 1 pc cm<jats:sup>−3</jats:sup>. No pulsed signal was detected, confidently excluding the presence of a detectable radio pulsar in the system.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a serendipitous discovery of a new stellar companion to TYC 5493-889-1 detected with the Differential Speckle Survey Instrument at the 4.3 m Lowell Discovery Telescope. We also present photometric observations of TYC 5493-889-1, and determine a spectral type of F1V and a photometric distance of roughly 320 parsecs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Comparison of optical high resolution high signal-to-noise ELODIE spectra of 21 Com taken in 2004 April and separated by about half of the 2 days rotational period, reveals variations of the Eu <jats:sc>ii</jats:sc> resonance and low excitation lines between rotational phases 0.94 and 0.48. All Eu <jats:sc>ii</jats:sc> lines are consistently stronger at phase 0.94. The synthesis of these Eu <jats:sc>ii</jats:sc> lines yields disk-averaged estimates of the abundances of europium: about 50 times solar at phase 0.94 and 25 times solar at phase 0.48.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using the second data release from the Zwicky Transient Facility (ZTF), Chen et al. created a ZTF Catalog of Periodic Variable Stars (ZTF CPVS) of 781,602 periodic variables stars (PVSs) with 11 class labels. Here, we provide a new classification model of PVSs in the ZTF CPVS using a convolutional variational autoencoder and hierarchical random forest. We cross-match the sky-coordinate of PVSs in the ZTF CPVS with those presented in the SIMBAD catalog. We identify non-stellar objects that are not previously classified, including extragalactic objects such as Quasi-Stellar Objects, Active Galactic Nuclei, supernovae and planetary nebulae. We then create a new labeled training set with 13 classes in two levels. We obtain a reasonable level of completeness (≳90%) for certain classes of PVSs, although we have poorer completeness in other classes (∼40% in some cases). Our new labels for the ZTF CPVS are available via Zenodo.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Here we present a catalog of 12,993 photometrically-classified supernova-like light curves from the Zwicky Transient Facility, along with candidate host galaxy associations. By training a random forest classifier on spectroscopically classified supernovae from the Bright Transient Survey, we achieve an accuracy of 80% across four supernova classes resulting in a final data set of 8208 Type Ia, 2080 Type II, 1985 Type Ib/c, and 720 SLSN. Our work represents a pathfinder effort to supply massive data sets of supernova light curves with value-added information that can be used to enable population-scale modeling of explosion parameters and investigate host galaxy environments.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Comparison of high dispersion LWP spectra obtained in 24 hr of monitoring of 21 Com with IUE in April 1991 reveals variations of low excitation Fe <jats:sc>ii</jats:sc> lines at phase 0.65 of the rotational period (FUV minimum flux) compared to phase 0.18 (FUV maximum flux). All 10 Fe <jats:sc>ii</jats:sc> lines of UV Multiplets 1 and 62 are consistently stronger at phase 0.65, which shows that the FUV flux minimum can be partially explained to an increase of the disk averaged iron abundance. In contrast, comparison of optical high resolution high signal-to-noise ELODIE spectra of 21 Com taken in 2004 April and separated by about half of the 2 days rotational period, reveals no significant variations of the Fe <jats:sc>ii</jats:sc> and Fe <jats:sc>i</jats:sc> lines. The lines monitored in the mid UV are strong low-lying transitions which are probably more sensitive to small abundance gradients over the surface of 21 Com.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this study we investigate aspects of orbital stability for the Alpha Centauri and 16 Cygni systems. They are planet-hosting triple star systems of highly hierarchic nature. For each system, orbital stability of the outlying stellar component and the observed exoplanet(s) are explored through assessing Hill stability. Orbital stability is identified for all components, including the observed system planets.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Recent studies using volume-limited samples of brown dwarfs have revealed the photometric evolution of single L and T dwarfs and unresolved binaries as they age and cool, in particular as they transition from L to T spectral types. We demonstrate that the near-infrared photometric evolution of the resolved components of L and T dwarf binaries is consistent with that of single objects using a volume-limited sample. In addition, we provide supporting evidence that the L9 dwarf WISE J185101.83+593508.6 is an unresolved binary and identify three more candidate or confirmed unresolved binaries all from being overluminous for their spectral type. We calculate a new binary fraction of 13.1% ± 1.8% for L0–T8 dwarfs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Cobalt abundances are rarely available for normal and Chemically Peculiar A stars because the strongest transitions of Co <jats:sc>ii</jats:sc> and Co <jats:sc>i</jats:sc> lie in the mid-UV. The abundance of cobalt is derived for 21 Com using a mean mid-ultraviolet spectrum constructed by coadding 28 spectra collected with the Long Wave Prime camera over the 18 yr of the IUE mission. The strong transitions of Co <jats:sc>ii</jats:sc> at 2286.16, 2307.86, 2324.32 and 2580.33 Å are present and usually blended. The least blended, <jats:italic>λ</jats:italic> 2286.16 Å, yields a mean overabundance of cobalt close to 10 times the solar abundance. Over the 24 hr 1991 monitoring of 21 Com, this line may have varied suggesting that cobalt may not be uniformly distributed over the surface of 21 Com.</jats:p>