Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Line variations are studied in the mid-ultraviolet spectra of 78 Vir collected with IUE between phases of far-UV (FUV) maximum and FUV minimum. The mid-UV spectrum of 78 Vir is populated with low-lying transitions of iron-peak elements. The lines of Cr <jats:sc>ii</jats:sc> and Ca <jats:sc>ii</jats:sc> are found to be stronger at phase of FUV minimum, <jats:italic>while the lines of Ni</jats:italic>  <jats:sc>ii</jats:sc> <jats:italic>probably vary in anti phase with those of chromium and calcium. Those of Fe</jats:italic>  <jats:sc>ii</jats:sc> <jats:italic>and Mn</jats:italic>  <jats:sc>ii</jats:sc> <jats:italic>do not show convincing variations between the two phases.</jats:italic> The analysis of these mid-ultraviolet spectra suggests that iron and manganese are uniformly distributed over the surface of 78 Vir, while chromium, calcium and nickel are not but more ultraviolet lines should be studied to confirm this.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>V5588 Sagittarii (Nova Sagittarii 2011 No. 2) was one of the rare novae that undergo outbursts after the initial explosion, and was extreme in that it did so six times. We present 0.8–5.1 <jats:italic>μ</jats:italic>m spectroscopy acquired during the second of these so-called secondary maxima, when the nova was still near its peak brightness and when differences among emission line profiles were most pronounced. Our spectrum supplements and enlarges the wavelength coverage of the extensive observational data set presented by Munari et al. We highlight the differences between the emission line profiles of H <jats:sc>i</jats:sc>, He <jats:sc>i</jats:sc>, and Fe <jats:sc>ii</jats:sc> and point out differences between the narrow and broad line components of the H <jats:sc>i</jats:sc> lines. We also include identifications for a few weak, previously unobserved Fe <jats:sc>ii</jats:sc> features in the midwave-infrared.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Visible and infrared spectra, from two, widely separated epochs, are presented for the nova V606 Vulpeculae. The first, acquired 7 days after the nova reached maximum light, displayed emission from carbon monoxide plus a wealth of low excitation atomic lines characterisic of an Fe <jats:sc>ii</jats:sc>-type novae early in its spectral development. The second, from 80 days later and after additional mass ejection, provided a spectral snapshot of a nova just prior to dust formation. It also was dominated by emission lines of mostly neutral atomic species, many of which included P-Cygni components. However, no spectral features from any molecules were detected, leaving in question what constituted the building blocks of the dust grains that formed shortly thereafter.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Kamath et al. analyzed Gaia EDR3 data of 18 post-asymptotic giant branch (AGB) supergiants having overabundance of <jats:italic>s</jats:italic>-process elements, some of which exhibit unusually low luminosities in disagreement with expectations of <jats:italic>s</jats:italic>-process nucleosynthesis. I have examined the Gaia RUWE statistics of these stars, and find that 13 have RUWE ≫ 1.4, suggesting they are most likely unresolved binaries that contain low-mass companions. The remaining five stars have RUWE &lt; 1.4 and I find that their luminosities are in agreement with post-AGB evolutionary tracks.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Brazilian Meteor Observation Network (BRAMON) is a TV meteor detection network that has been implemented in Brazil since 2014. The BRAMON data made it possible to determine the high-quality orbits of 630 sporadic meteors observed between 2014 and 2021. Using criteria from Jopek &amp; Williams, we assign each of these meteors an asteroidal or cometary origin. Cometary type orbits correspond to slightly more than 60% of sporadic meteors of our sample, a similar percentage to that obtained from other meteor surveys when considering the same magnitude range.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Hobby–Eberly Telescope’s (HET) primary mirror is composed of 91 hexagonal mirror segments aligned in tip/tilt, while piston is manually controlled. BroadBand Phasing (BBP), as used at Keck, may be suitable for HET to sense piston error. Using the procedures laid out in Chanan et al., we modeled diffraction pattern point-spread functions (PSFs) of monochromatic and broadband light through split apertures centered at the edge between two adjacent segments. We simulated 4 sets of PSFs at 21 piston steps, 1 Template group and 3 differing Measurement groups. We determined the cross-correlation of the Template images to each Measurement image using Pearson’s <jats:italic>r</jats:italic> (<jats:italic>r</jats:italic>) and located the two extremes. We subtracted the minimum <jats:italic>r</jats:italic>’s from the largest, fitted a Gaussian curve, and located the peak values. The peak’s location was within ±5 <jats:italic>μ</jats:italic>m from the input piston error for all cases, thereby showing that BBP may adequately measure piston errors down to ±25 <jats:italic>μ</jats:italic>m.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Gaia catalog of nearby stars (GCNS) divided all objects with parallaxes &gt;10 mas into GCNS-selected and GCNS-rejected 100 pc samples. Below the white dwarf (WD) sequence in the complete GCNS color–magnitude diagram (CMD), at <jats:italic>Gabs</jats:italic> &gt; 14.7 + 4.7(<jats:italic>G</jats:italic> − <jats:italic>RP</jats:italic>), there appear 60 GCNS-selected faint blue white dwarfs (FBWDs). However this CMD region is also populated by 411 GCNS-rejected objects, mainly from crowded regions toward the Galactic center and the Magellanic Clouds. The WD catalog of Gentile et al. lists only 47 GCNS-selected but also 8 GCNS-rejected objects. I confirm 59 of the GCNS-selected but none of the GCNS-rejected objects as FBWDs from visual inspection and a proper motion check using additional optical sky surveys. Hence FBWDs form an additional branch in the CMD. Compared to the full GCNS-selected 100 pc sample, FBWDs have relatively high proper motions and tangential velocities. They represent interesting targets for studies of ultracool or infrared-faint, and possibly also ultramassive WDs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We measure the sunspot areas of activity cycle 24 using ten years of continuum images from the Helioseismic and Magnetic Imager, and compare them with the peak flare soft X-ray flux from the Geostationary Operational Environmental Satellite. We find that the sunspot area in our sample is positively correlated with the magnitude of the largest flare they produce. Complex spot groups with <jats:italic>βγδ</jats:italic> magnetic classification tend to be larger and more likely to produce intense flares. Our findings are qualitatively consistent with previous studies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This study analyzes 18 simulated galaxies run using three prescriptions for stellar feedback, including thermal, kinetic, and interstellar medium pre-processing feedback mechanisms. Each simulation set models one of these mechanisms with 6 distinct galaxies, with varying <jats:italic>M</jats:italic> <jats:sub>vir</jats:sub> at <jats:italic>z</jats:italic> = 0. The morphological and thermodynamic quantities and distributions, as well as star formation histories, are compared to understand the impact of each stellar feedback mechanism. We find that the prescription for stellar feedback makes a significant impact on the behavior of galaxies, and observe systematic trends within each simulation and across mass ranges. Specifically, kinetic feedback results in no formation of a disk structure and delayed star formation, and pre-processing of the interstellar medium results in delayed star formation as compared to the thermal feedback mechanisms.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We model the motion of the WE0913A object based on the latest ephemeris and confirm its impact on the far side of the Moon on 2022 March 4. However, this latest ephemeris suggests that the impact will occur at 12:34 pm (UTC) and will be close enough to the lunar limb that the dust cloud could be visible from Earth. The impact could lead to the ejection of a mass of 677 kg, having a velocity in excess of 610 m s<jats:sup>−1</jats:sup>, and 195 kg moving faster than the lunar escape velocity. Such an ejecta cloud could become apparent shortly after impact in ground-based observations slightly above the equator (∼1/8 of the lunar radius) over the dark side of the Moon. In the <jats:italic>V</jats:italic> filter of the Johnson photometric system, the ejecta cloud is expected to be brighter than 4 mag, making possible its detection even at dawn.</jats:p>