Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Since the first signal in 2015, the gravitational-wave detections of merging binary black holes (BBHs) by the LIGO and Virgo collaborations (LVC) have completely transformed our understanding of the lives and deaths of compact object binaries, and have motivated an enormous amount of theoretical work on the astrophysical origin of these objects. We show that the phenomenological fit to the redshift-dependent merger rate of BBHs from Abbott et al. is consistent with a purely dynamical origin for these objects, and that the current merger rate of BBHs from the LVC could be explained entirely with globular clusters alone. While this does not prove that globular clusters are the dominant formation channel, we emphasize that many formation scenarios could contribute a significant fraction of the current LVC rate, and that any analysis that assumes a single (or dominant) mechanism for producing BBH mergers is implicitly using a specious astrophysical prior.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>I searched for the ground state 6.8 and 9.2 GHz hyperfine transitions of rubidium and cesium toward M- and L-dwarfs that show Rb and Cs optical resonance lines. The optical lines can pump the hyperfine transitions, potentially forming masers. These spin-flip transitions of Rb and Cs are the principal transitions used in atomic clocks (the <jats:sup>133</jats:sup>Cs hyperfine transition defines the second). If they are detected in stellar atmospheres, these transitions would provide exceptionally precise clocks that can be used as accelerometers, as exoplanet detectors, as probes of the predictions of general relativity, as probes of light propagation effects, and as a means to do fundamental physics with telescopes. Observations of 21 M- and L-dwarfs, however, show no evidence for Rb or Cs maser action, and a previous survey of giant stars made no Rb maser detections.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have reprocessed a set of observations of 75 bright, unidentified, steep-spectrum polarized radio sources taken with the Green Bank 43 m telescope to find previously undetected sub-millisecond pulsars and radio bursts. The (null) results of the first search of these data were reported by Schmidt et al.. Our reprocessing searched for single pulses out to a dispersion measure (DM) of 1000 pc cm<jats:sup>−3</jats:sup> which were classified using the Deep Learning based classifier <jats:sc>fetch</jats:sc>. We also searched for periodicities at a wider range of DMs and accelerations. Our search was sensitive to highly accelerated, rapidly rotating pulsars (including sub-millisecond pulsars) in compact binary systems as well as to highly dispersed impulsive signals, such as fast radio bursts. No pulsars or astrophysical burst signals were found in the reprocessing.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>E+A galaxies are post-starburst galaxies that have recently undergone complete quenching of their star formation, making them a valuable source for studying the evolution of galaxies and their environments. Using the Extended Virgo Cluster Catalog, we manually identified 125 “green” and 24 “blue” E+A galaxy candidates within the Virgo Cluster based on their spectral shape, <jats:italic>u</jats:italic> − <jats:italic>r</jats:italic> color, lack of H<jats:italic>α</jats:italic> emission, and hydrogen Balmer absorption. Interestingly, we found a higher density of E+A galaxy candidates in the Virgo Cluster than that of most other low-redshift clusters, and several regions of particularly high E+A density within the Virgo Cluster. The large number of E+As in and around the Virgo Cluster hints at the influence of a dense galaxy environment on the formation of E+A galaxies, and the potential value of E+A galaxies as a diagnostic tool to study the evolution of clusters.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The dark matter halo masses of galaxies can be estimated from their stellar masses via abundance matching (AM). For both the Milky Way and M31, the AM mass is higher than the mass inferred from kinematics. The higher AM masses exacerbate the missing satellite problem. The difference is especially pronounced for M31, for which <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{200}^{\mathrm{AM}}\gtrsim {10}^{13}\,{M}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="rnaasabe1baieqn1.gif" xlink:type="simple" /> </jats:inline-formula> but <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{200}^{\mathrm{kin}}\lt 2\times {10}^{12}\,{M}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="rnaasabe1baieqn2.gif" xlink:type="simple" /> </jats:inline-formula>. This is more than expected from scatter in the AM relation, and may suggest the need for separate AM relations for early and late type galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>I combine duplicate spectroscopic stellar parameter estimates in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 6 Low Resolution Spectral Survey A, F, G, and K Type stellar parameter catalog. Combining repeat measurements results in a factor of two improvement in the precision of the spectroscopic stellar parameter estimates. Moreover, this trivializes the process of performing coordinate-based cross-matching with other catalogs. Similarly, I combine duplicate stellar abundance estimates for the Xiang et al. catalog which was produced using LAMOST Data Release 5 Low Resolution Spectral Survey data. These data have numerous applications in stellar, galactic, and exoplanet astronomy. The catalogs I produce are available as machine-readable tables at <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://doi.org/10.7281/T1/QISGRU" xlink:type="simple">https://doi.org/10.7281/T1/QISGRU</jats:ext-link>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Highly accreting quasars show fairly distinctive properties in their optical, UV, and X spectra, and are easy to recognize because of their specific location in the quasar main sequence: they are the strongest optical FeII emitters. They show a surprisingly high rate of radio detections and, at variance with the classical radio-loud (jetted) sources, the origin of their radio emission is probably “thermal.” The chemical composition of the broad line emitting gas implies high metallicity values, above 10 times solar. A fraction of highly accreting quasars at intermediate and high redshift might therefore be in a particular evolutionary stage that is unobscured albeit still involving a contribution of nuclear and circum-nuclear star formation in their multifrequency properties.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report resolved optical spectroscopy for the nearby low-mass stellar system BD-08 2582AB. We confirm prior unpublished reports of the existence of the secondary, and the spectral data indicate a secondary type of M6 Ve, consistent with spectrophotometric estimates from Gaia astrometry. The secondary exhibits H<jats:italic>α</jats:italic> emission at a level equivalent to other M6 dwarfs, and has a metallicity index in line with its well-studied solar-metallicity K7/M0 primary.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Recently Jiang et al. reported the discovery of a possible short duration transient, detected in a single image, spatially associated with a <jats:italic>z</jats:italic> ∼ 11 galaxy. Jiang et al. and Kann et al. suggested the transient originates from a <jats:italic>γ</jats:italic>-Ray Burst (GRB), while Padmanabhan &amp; Loeb argued the flash is consistent with a supernova shock breakout event of a 300 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> Population III star. Jiang et al. argued against the possibility that this event originated from light reflected off a satellite. Here we show that reflection of sunlight from a high-orbit satellite or a piece of space debris is a valid and reasonable explanation. As shown in recent works, the rate of point-like satellite reflections, brighter than 11th magnitude, is &gt;10 deg<jats:sup>−2</jats:sup> day<jats:sup>−1</jats:sup> near the equatorial plane. At higher declinations the rate is 5–50 times lower, but still significant: about four orders of magnitudes higher than the rate estimated for GRBs.</jats:p>