Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Millisecond pulsar J1713 + 0747 recently underwent a drastic change in its pulse shape. The pulsar has undergone two previous “chromatic timing events,” frequency-dependent changes in pulse arrival times, with some evidence for low-amplitude achromatic changes in the pulse shape. Ongoing monitoring efforts of the pulsar show that the latest significant shape change has persisted for several months, longer than the recovery of the behavior in previous events. I examine profiles from the Nançay Radio Telescope presented in Astronomer’s Telegram #14642 and find evidence for multiple profile shapes after the start of the third event, hinting at the possibility of several new mode changes to consider.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present and publicly release a set of deep, full-sky Wide-field Infrared Survey Explorer (WISE) coadds built from WISE and NEOWISE images spanning from early 2010 through late 2018. This data release uniformly incorporates six years of WISE and NEOWISE exposures at 3.4 <jats:italic>μ</jats:italic>m (W1) and 4.6 <jats:italic>μ</jats:italic>m (W2). These inertial “unWISE” stacks allow for detection of roughly a billion stars and galaxies fainter than the AllWISE catalogs sensitivity limit. Importantly, our six-year unWISE coadds, in combination with the <jats:monospace>crowdsource</jats:monospace> cataloging software, were used to perform deep source detection/deblending for CatWISE2020.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present Gaia DR2 2144465183642117888, a previously unknown, wide white dwarf companion to the HP Dra eclipsing binary system. This companion was discovered through the Backyard Worlds: Planet 9 citizen science collaboration. It has separation of 14.″4 on the sky from the central eclipsing pair, translating to a projected separation of ∼1140 au. We present a review of the orbit and physical parameters of all the components in this now triple system.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> <jats:italic>μ</jats:italic> Cephei is a 4th mag semi-regular variable M2Ia star. It is among the largest, most luminous red supergiants in our galactic neighborhood and a probable SN-II core-collapse progenitor. Analyses of ∼175 yr of photometry were conducted. The observations are mostly from the AAVSO database. Period analyses were conducted using the Period Analysis Software (Peranso-3) package. The CLEANest and Wavelet (WWZ) programs were utilized. Two dominant “periods” were found: <jats:italic>P</jats:italic> = 870 ± 50 days (∼2.39 yr) and a long period of ∼5300 ± 155 days (∼14.5 yr). The long period was prominent during the first ∼90 yr but weakened and was followed by multiple transitory periods ranging from ∼3000 to 4600 days. <jats:italic>μ</jats:italic> Cephei has interesting features including multiple periods, period-splitting, period-merging and period-decays.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>I present WISEA J052305.94–015356.1 as a new candidate extremely metal-poor T subdwarf (esdT), based on its distinctive infrared colors and high proper motion (∼500 mas yr<jats:sup>−1</jats:sup>). Spectroscopic follow-up is now needed to confirm it is a member of this newly discovered class of substellar objects.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The comparison of 10 far ultraviolet spectra of 21 Com taken over continuous 24 hr (half of the recently determined rotational period) reveals large variations shortwards of 1700 Å. In contrast, the flux variations at wavelengths larger then 2200 Å are of smaller amplitudes. The large FUV variability is probably caused by changes in the continuous opacity driven by modest horizontal gradients of the abundances of chemical elements over the surface of 21 Com.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present our analysis of the narrow emission lines produced in the plasma regions within the bright active galactic nucleus of NGC 4151, from an ORBYTS research-with-schools public engagement project. Our goal was to test whether the properties of these plasma regions changed between XMM-Newton observations spanning 15 yr from 2000 to 2015, by measuring the outflow velocities and distances. From this study, we found that NGC 4151 has at least two to three plasma regions. There is no evidence of the outflowing wind properties changing as the velocities and distances are consistent throughout the observations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Blanco 1, a 100 Myr open cluster in the solar neighborhood, is well known for its two 50 pc long tidal tails. Taking Blanco 1 as a reference, we find evidence of early-stage tidal disruption in two other open clusters of ∼120 Myr: the Pleiades and NGC 2516, via Gaia EDR3 data. These two clusters have a total mass of 2–6 times that of Blanco 1. Despite having a similar age as Blanco 1, the Pleiades and NGC 2516 have a larger fraction of their members bound: 86% of their mass is inside the tidal radius, versus 63% for Blanco 1. However, a correlation between Blanco 1's 50 pc long tidal tails and the “kinematic tails” in velocity space is also found for the Pleiades and NGC 2516. This evidence supports the idea that the modest elongation seen in the spatial distribution for the Pleiades and NGC 2516 is a result of early-stage tidal disruption.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The relationship between mass and mass accretion rate in young objects is a powerful tool for interrogating formation and evolution. We analyze a comprehensive database of published accretion diagnostics for ∼400 objects (0.005–2 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>), including 64 brown dwarfs. To eliminate systematics between studies as the source of the four orders of magnitude of observed scatter, we uniformly re-estimate masses and accretion rates from direct observables (e.g., spectral types, line luminosities). In particular, we adopt a single grid of evolutionary models to estimate masses, a single family of scaling relations to estimate accretion luminosity, and update line luminosities using Gaia DR2 distances. We find that this unification produces minimal effects on the observed relation, suggesting systematic and methodological variation is not responsible for the scatter. This paves the way for investigation of physical sources of scatter, including: age variation, intrinsic variability, formation mechanism, and accretion paradigm.</jats:p>