Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We use a nearest neighbor algorithm combined with the machine learning clustering function Density-Based Spatial Clustering of Applications with Noise to analyze a subset of quasars from the Sloan Digital Sky Survey. Our analysis shows evidence of clustering up to <jats:italic>z</jats:italic> ∼ 2, with evidence of an increase in clustering at lower redshifts (<jats:italic>z</jats:italic> &lt; 0.5). Our findings may suggest that, over time, the gravitational interaction between quasars has led to more clustering at low redshifts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We analyze two sectors of Transiting Exoplanet Sky Survey (TESS) photometry of the nova-like cataclysmic variable star V533 Her. We detect a periodicity consistent with the binary orbital period and estimate a revised value of 3.53709(2) hr. We also detect a strong signal near a period of 3.8 hr that we associate with positive superhumps. The superhump frequency varies over the TESS observations with the fractional difference between the superhump and orbital periods, <jats:italic>ϵ</jats:italic>, ranging between 0.055 ≤ <jats:italic>ϵ</jats:italic> ≤ 0.080. The superhump amplitude is correlated with its frequency such that the amplitude increases as <jats:italic>ϵ</jats:italic> decreases. Positive superhumps result from an instability that generates an eccentric accretion disk and <jats:italic>ϵ</jats:italic> is a measure of the disk precession rate in the binary rest frame. The observed correlation implies that as the disk precession rate slows, the disk eccentricity increases.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A novel method is presented which can pin down the time the accretion disk re-established itself in the RS Oph system after it experienced a nova disruption. The method is based on the re-ionization of the ejecta by photoionization from the radiation released in the boundary layer from accretion.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The analysis of high resolution SWP spectra of the HgMn stars HD 27295 (53 Tau) and HD 33548 obtained through the large aperture recorded by the International Ultraviolet Explorer reveals that the far ultraviolet flux of these two stars remained constant over the various observations with IUE. The TESS lightcurves of 53 Tau show a periodic sine structure with a period estimated to be around 4.43 days whereas that of HD 35548 do not show evidence for periodic variability. The absence of far and mid-UV variability of these two stars precludes the presence of large chemical gradients over their surfaces at the time of the IUE observations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Few stars offer as much toward understanding fundamental aspects of stellar astrophysics and binary star evolution than the eclipsing binary V471 Tauri (DAZ+K2V; <jats:italic>P</jats:italic> = 12.52 hr). V471 Tauri (Tau) is the product of common-envelope binary evolution and a pre-cataclysmic variable. X-ray and UV (291 nm) observations were secured with XMM-Newton over ∼ 62 ks during 2019 September. X-ray and UV photometry show variations over the binary's orbit as well as flares. A precise eclipse timing was obtained from the UV photometry with the Optical Monitor. The timing was added to prior measures and fit with a 35.6 yr Light-Travel-Time-Effect (LTTE) Keplerian orbit of a substellar, tentative brown dwarf companion. However, this companion was not detected by VLT/SPHERE. The LTTE third-body solution appears reliable, now covering ∼50 yr of timings. The non-detection of the companion may be due to changes in its physical properties during the high-mass loss common envelope stage.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We describe the implementation of a new module which can be used to simulate physical systems in which the motion of particles is affected by stochastic forces. Such forces are expected to be present in turbulent circumstellar disks or remnant planetesimal disks. Our implementation offers a convenient way to generate correlated noise with a user-specified amplitude and auto-correlation time for each particle. The module has minimal memory requirements and is freely available within the REBOUNDx additional effects library.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present 370 candidate eclipsing binaries (EBs), identified from ∼510,000 short cadence TESS light curves. Our statistical criteria identify 5105 light curves with features consistent with eclipses (∼1% of the initial sample). After visual confirmation of the light curves, we have a final sample of 2288 EB candidates. Among these, we find 370 sources that were not included in the catalog recently published by Prša et al. We publish our full sample of 370 new EB candidates, and statistical features used for their identification, reported per observation sector.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We measure the anisotropy of the Milky Way stellar halo traced by a dense sample of 18 &lt; <jats:italic>r</jats:italic> &lt; 21 mag F-type main sequence turnoff stars using Gaia eDR3 proper motions and new radial velocity measurements published here.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A gravitational wave pulse from a major merger of massive black holes at the Galactic center induces a permanent increase in the Earth–Moon separation. For black holes of mass ∼10<jats:sup>6</jats:sup>  <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, the shift in the local gravitational potential is comparable to the Earth–Moon potential, leading to the Moon being perturbed relative to the Earth during the passage of the pulse. The permanent increase in the Earth–Moon separation is a fraction of a millimeter, measurable by lunar ranging for future merger events.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Evidence is presented that HD 4065A is a newly discovered HgMn star. The Hg <jats:sc>ii</jats:sc> line at 3983.93 Å is present in two spectra acquired with the High Resolution Spectrograph mounted behind the South African Large Telescope and separated by about 2 months and 25 days. The lines on the second spectrum are redshifted reflecting the orbital motion of HD 4065A around the center of mass of a binary system. The far-ultraviolet spectrum, SWP 20399 collected with IUE, shows a strong resonance line of Ga <jats:sc>ii</jats:sc> usually conspicuous in the far-ultraviolet spectra of HgMn star. A first spectrum synthesis of the spectral range from 3900 up to 4000 Å yields estimates of the abundances of calcium (0.10 solar), zirconium (25 solar) and mercury (50,000 solar).</jats:p>