Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Height-to-diameter ratios of the enclosures of large refracting telescopes are contrasted with the classical domed structure of the Roman Pantheon. Enclosures whose domes do not sit upon a multi-storied drum, or atop an extended building complex, tend to evince a Pantheon-like ratio.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Ultra-hot Jupiters (UHJs) have recently been the focus of several atmospheric studies due to their extreme properties. While molecular hydrogen (H<jats:sub>2</jats:sub>) plays a key role in UHJ atmospheres, it has not been directly detected on an exoplanet. To determine the feasibility of H<jats:sub>2</jats:sub> detection via transmission spectroscopy of the Lyman and Werner bands, we modeled UHJ atmospheres with H<jats:sub>2</jats:sub> rotational temperatures varying from 2000 to 4000 K orbiting A-type stars ranging from <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> = 8500 K to <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> = 10,300 K. We present simulated transmission spectra for each planet-star temperature combination while adding Poisson noise varying in magnitude from 0.5% to 2.0%. Finally, we cross-correlated the spectra with expected atmospheric H<jats:sub>2</jats:sub> absorption templates for each temperature combination. Our results suggest that H<jats:sub>2</jats:sub> detection with current facilities, namely the Hubble Space Telescope, is not possible. However, direct atmospheric transmission spectroscopy of H<jats:sub>2</jats:sub> may be viable with future UV-capable flagship missions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Proper motion anomalies (PMa) are often useful for identifying companions, but using this technique for large and luminous stars like Asymptotic Giant Branch (AGB) stars is problematic. We studied nearby AGB stars and their potential companions in a PMa catalog derived from Hipparcos and Gaia DR2 proper motion measurements. We found that companion configurations based on PMa for AGB stars are often implausible, such that the radius of the primary star is larger than the orbit of the putative companion. This may suggest an alternative origin of PMa in AGB stars, possibly surface brightness fluctuations due to their large convective surfaces.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The analysis of 14 high resolution spectra of the chemically peculiar star HR 7775 recorded by the International Ultraviolet Explorer reveals large amplitude variations of the far and mid-ultraviolet flux (at minimum the flux is about 70% of its value at maximum) over the various observations with IUE. The lines at minimum flux are redshifted respect to their positions at maximum. These variations probably reflects an eclipse by a cooler and smaller companion of spectral type A or even early F. The absence of TESS observations prevents a search for periodic orbital and rotational variabilities.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the start of science operations of a meteor spectroscopic survey in the Nullarbor region, Western Australia. The observation program consists of well-proven observatories developed as part of the All-Sky Meteor Orbit System (AMOS) project. These comprise high-sensitivity all-sky imaging units, as well as spectroscopic instruments observing brighter meteors. They are co-located with Desert Fireball Network (DFN) instruments, which themselves provide high-resolution astrometry for fireballs. There are two goals for this program. One is to keep a constant watch on meteor activity by always having one AMOS sub-network in the dark. The second is to provide spectroscopic coverage for recovered meteorites by the DFN, establishing essential calibration points between meteoritic samples and fireball spectra.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The utility of the far-infrared lines of oxygen as diagnostics of gas outflows and for other applications depends on accurate descriptions of the rate coefficients for excitation (and relaxation) through collisions with electrons and with hydrogen atoms. For O and H collisions, earlier calculations of rate coefficients show discrepancies leading to ambiguity in astrophysical applications. In this note we introduce a methodology that yields consistent sets of rate coefficients for a number of cases. We then apply our method to the O–H system in order to investigate the discrepancies. The present rate coefficients will be of particular interest for modeling observations of astrophysical environments in the far-infrared.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Standard evolution models of a given age provide a relationship between stellar mass and <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub>. Based on this, Cruz et al. have derived stellar masses and radii for a sample of Kepler stars using photometry alone: their radii are found to be inflated by up to 100% relative to standard models. However, magnetic fields distort the <jats:italic>M–T</jats:italic> <jats:sub>eff</jats:sub> relationship in a systematic way: here, we quantify this distortion, and show that radius inflations in the Cruz et al. stars are likely to be significantly smaller than 100%.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present results about the decrease of stellar activity for stars like the Sun evolving toward the subgiant stage. Specifically, we examine two-component chromosphere models (acoustic and magnetic) for <jats:italic>β</jats:italic> Hydri (G2 IV) based on detailed time-dependent simulations while focusing on Ca <jats:sc>ii</jats:sc> emission. We convey models for two different photospheric magnetic filling factors.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>I show that pair production on sunlight introduces a sizable anisotropy in the cosmic background of TeV gamma-rays. The anisotropy amplitude in the direction of the Sun exceeds the cosmic dipole anisotropy from the motion of the Sun relative to the cosmic rest-frame.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We found a period variation of the close binary of EW type V405 Draconis. From the <jats:italic>O</jats:italic> − <jats:italic>C</jats:italic> diagram built using survey data, data from the literature, and our observations, we calculated a period increase rate (1/<jats:italic>P</jats:italic>)(<jats:italic>dP</jats:italic>/<jats:italic>dt</jats:italic>) of 2.72(0.03) · 10<jats:sup>−6</jats:sup> yr<jats:sup>−1</jats:sup>. Along with the monotonic period increase, TESS data demonstrates a sign of a cyclic variation of the period. We estimated the period of such cyclic variations as 537.9(1.4) days with a semi-amplitude of 0.00200(0.00001) days. This can provide evidence for the presence of the third body in the system.</jats:p>