Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We use ASAS <jats:italic>V</jats:italic>-band and ASAS-SN <jats:italic>g</jats:italic>-band observations to model the long-period detached eclipsing binary ASASSN-21co. ASAS observations show an eclipse of depth <jats:italic>V</jats:italic> ∼ 0.6 mag in 2009 April. ASAS-SN <jats:italic>g</jats:italic>-band observations from 2021 March show an eclipse of similar duration and depth, suggesting an orbital period of 11.9 yr. We combine the <jats:italic>g</jats:italic>-band observations with additional BVRI photometry taken during the eclipse to model the eclipse using PHOEBE. We find that the system is best described by two M giants with a ratio of secondary radius to primary radius of ∼0.61. Optical spectra taken during the eclipse are consistent with at least one component of the binary being an M giant, and we find no temporal changes in the spectral features. The eclipse itself is asymmetric, showing an increase in brightness near mid-eclipse, likely due to rotational variability that is too low amplitude to be observed out-of-eclipse.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>For Cataclysmic Variables (CVs), the record of many eclipse times (as presented in the traditional <jats:italic>O</jats:italic> − <jats:italic>C</jats:italic> curves) often displays a small-amplitude fast jitter on timescales of under a few years, with these often being interpreted as physical effects such as from third bodies in the system (including planets), or from azimuthal movements of the Hot Spot around the edge of the accretion disk. Recently, with the new and excellent light curves from spacecraft missions TESS and Kepler, we can measure large numbers of eclipse times down to orbit-by-orbit timescales. For four representative CVs (DQ Her, U Sco, RW Tri, and UX UMa), I find that the <jats:italic>O</jats:italic> − <jats:italic>C</jats:italic> jitter is constant from one-orbit-to-the-next out to eclipses separated by many years. This demonstrates that the jitter is not caused by physical effects on the orbit, nor by moving Hot Spots. This result was predicted for the expected jitter in eclipse times arising from the ubiquitous flickering in all CV light curves, where random flickers before/after eclipse minima will shift the measured eclipse times later/earlier than the true time of conjunction.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>I report new orbital periods (<jats:italic>P</jats:italic>) for 13 classical novae, based on light curves from TESS, AAVSO, and other public archives. These new nova periods now constitute nearly one-seventh of all known nova periods. Five of my systems have <jats:italic>P</jats:italic> &gt; 1 day, which doubles the number of such systems that must have evolved companion stars. (This is simply because ground-based time series have neither the coverage nor the stability required to discover these small-amplitude long periods.) V1016 Sgr has a rare <jats:italic>P</jats:italic> below the period gap, and suddenly becomes useful for current debates on evolution of novae. Five of the novae (FM Cir, V399 Del, V407 Lup, YZ Ret, and V549 Vel) have the orbital modulations in the tail of the eruption after the transition phase. Soon after the transition, YZ Ret shows a unique set of aperiodic diminishing oscillations, plus YZ Ret shows two highly significant transient periods, 1.1% and 4.5% longer than the orbital period, much like for the superhump phenomenon. I also report an optical 591.27465 s periodicity for V407 Lup, which is coherent and must be tied to the white dwarf spin period.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The objective of this study is to unveil an optimum and precise automated method to model S0 galaxies. Preliminary results of the study confirm that GALFIT—a two-dimensional image decomposition program—with a Sérsic profile can be used to model S0 galaxies. Since the input parameters affect the accuracy of the model, different combinations of parameters were tested to obtain the best-fit model. An automated GALFIT fitting process was developed using Python and Astropy module to increase the efficiency of the process. A sample of S0 galaxy images observed at the Kitt Peak National Observatory was used to test the precision of the implemented method. The accuracy of the created models was tested both visually and statistically. The new method will allow us to model a large sample of S0 galaxies accurately and determine their structure and properties.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Tides can have significant effects on the orbital evolution of close-in planets. The evolution of eccentricity and semimajor axis is usually obtained by numerical integration of a set of coupled differential equations. We present here closed-form solutions to the evolution equations and derive from them an expression of the circularization time.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present near-infrared reflectance spectra from 0.7 to 2.5 <jats:italic>μ</jats:italic>m taken 2021 April 30 at the NASA Infrared Telescope Facility that show strong evidence for water ice within the coma of comet C/2017 K2 (PanSTARRS) at a heliocentric distance of <jats:italic>R</jats:italic> <jats:sub>H</jats:sub> = 6.488 au. This object has likely been active since ∼35 au inbound and this provides a key piece of information to interpreting these early observations, understanding its dust properties, and assessing its overall volatile inventory and release mechanisms. A preliminary spectral model is best-fit with a volume fraction of ice of ∼14% assuming that the refractory and volatile materials are mixed intimately. More sophisticated modeling and a deeper analysis of these data will be presented in a manuscript to be submitted later this year.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Nobel laureate Frances Crick and renowned chemist Leslie Orgel are often credited with introducing the idea of “directed panspermia” in 1973. While they coined the term, the idea itself appeared in the scientific literature almost two decades earlier, and the first allusions can be traced back to 1930.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The USNO ground-based astrometric program URAT-Bright in combination with the Hipparcos mission epoch astrometry provides precise proper motions of a thousand bright stars in the southern hemisphere on a time basis of about 25 yr. Small but statistically significant differences between these proper motions and Gaia EDR3 data can reveal long-period exoplanets similar to Jupiter in the nearest star systems. The presence of such a planet orbiting the magnetically active dwarf <jats:italic>ε</jats:italic> Eri is confirmed from both URAT-Hipparcos-EDR3 data and Hipparcos-EDR3 data with a corresponding projected velocity of (+5, +8) and (+6, +13) m s<jats:sup>−1</jats:sup>, respectively. These signals are formally significant at a 0.989 and 1.0 confidence. We conclude that the newest astrometric results confirm the existence of a long-period exoplanet orbiting <jats:italic>ε</jats:italic> Eri, which was marginally detected from precision radial velocity measurements some 20 yr ago.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Evidence is presented that the detached Algol system OW Hya is a double-lined spectroscopic binary (SB2). The components appear to be closely similar to each other, which is contradicted by the failure so far to detect the secondary eclipse. A sizeable asymmetry in the Mg <jats:sc>ii</jats:sc> <jats:italic>λ</jats:italic>4481 Å line is discussed. The interstellar line of Ca <jats:sc>ii</jats:sc>-K line is present, and the primary star appears to be a late-B giant. OW Hya is the short-period pair of the interferometric triple star, CHR 175, which appears to be hierarchical.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a mosaic of those co-added Full Frame Images acquired by the TESS satellite that had been released in 2020 April. The mosaic shows substantial stray light over the sky. Yet over spatial scales of a few degrees, the background appears uniform. This result indicates that TESS has considerable potential as a Low Surface Brightness Observatory. The co-added images are freely available as a High Level Science Product (HLSP) at MAST and accessible through a Jupyter Notebook.</jats:p>