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Research Notes of the AAS (RNAAS)
Resumen/Descripción – provisto por la editorial en inglés
Research Notes of the AAS is a non-peer reviewed, indexed and secure record of works in progress, comments and clarifications, null results, or timely reports of observations in astronomy and astrophysics.Palabras clave – provistas por la editorial
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Disponibilidad
Institución detectada | Período | Navegá | Descargá | Solicitá |
---|---|---|---|---|
No detectada | desde ene. 2017 / hasta dic. 2023 | IOPScience |
Información
Tipo de recurso:
revistas
ISSN electrónico
2515-5172
Editor responsable
American Astronomical Society (AAS)
País de edición
Estados Unidos
Información sobre licencias CC
Cobertura temática
Tabla de contenidos
Optical Photometry of WR140 as the Dust Formed During the 2016 Periastron Passage
Megan J. Peatt; Noel D. Richardson
<jats:title>Abstract</jats:title> <jats:p>The colliding wind binary WR140 produces dust in its shocked gas every periastron passage. While the infrared light curve is very repeatable, there are noticeable changes every cycle in the optical time-series photometry. In the phases following periastron, there are optical dips in the light curve that were postulated to be caused by localized clumps in the dust produced in our line of sight. We report on the <jats:italic>B</jats:italic>- and <jats:italic>V</jats:italic>-band light curves that were recorded by the American Association of Variable Star Observers after the 2016 periastron event and briefly discuss comparisons to geometric models of the dust production to infer that these features are likely caused by localized dust clumps in the new dust shell.</jats:p>
Palabras clave: General Medicine.
Pp. 20
The Ultraviolet Variability of 78 Vir (A2p SrCrEu) throughout the IUE Mission
Richard Monier
<jats:title>Abstract</jats:title> <jats:p>Forty-one spectra of 78 Vir (A2p ScrCrEu) obtained through the large apertures of the SWP and LWP/LWR cameras on board International Ultraviolet Explorer (IUE) are compared to look for variations of the absolute flux of 78 Vir over the spectral range 1200–3000 Å. Large variations of the spectral energy distribution occur in the far ultraviolet shortwards of 2000 Å. In contrast, the flux at wavelengths larger than 2000 Å does not vary but several lines are variable between phases of far-UV (FUV) maximum and FUV minimum. The large FUV variability is probably caused by changes in the continuous and line opacity driven by modest horizontal gradients of the abundances of chemical elements over the surface of 78 Vir as the star is probably seen at a low inclination angle. The FUV flux at 1500 Å varies in anticorrelation with the FES counts (optical brightness) recorded before each exposure by the Fine Error Sensor on board IUE.</jats:p>
Palabras clave: General Medicine.
Pp. 21
The Ultraviolet Variability of 52 Her (A1p SiSrCr) Throughout the IUE Mission
Richard Monier
<jats:title>Abstract</jats:title> <jats:p>Twenty-four spectra of 52 Her (A1p SiSrCr) obtained through the large apertures of the SWP and LWP cameras on board International Ultraviolet Explorer are compared to look for variations of the absolute flux over the spectral range 1200–3000 Å. Large variations of the spectral energy distribution occur in the far-ultraviolet shortwards of 2000 Å. In contrast, the flux at wavelengths larger than 2000 Å does not vary but several lines are variable between phases of FUV maximum and FUV minimum. The large FUV variability is probably caused by changes in the continuous and line opacity driven by modest horizontal gradients of the abundances of chemical elements over the surface of 52 Her. The TESS lightcurve of 52 Her is slightly asymetric and has a period close to 3.83 days.</jats:p>
Palabras clave: General Medicine.
Pp. 22
Parameterization of Outer-scale on DECam Point-spread Function
Enrico Piperno; Aaron Roodman
<jats:title>Abstract</jats:title> <jats:p>A method to better parameterize the Outer-Scale (<jats:italic>L</jats:italic> <jats:sub>0</jats:sub>) of the Point-Spread Function (PSF) in Dark Energy Camera is described. The PSF characterizes the atmospheric turbulence and diffraction in astronomical images. In particular, the Outer-Scale describes the maximum coherence length in the turbulent atmosphere and leads to a maximum value of the turbulence structure function. We model the PSF by computing a pattern of star features, which are used to fit our PSF model. For each star, we apply a weight function which maximizes the signal-to-noise ratio. We find difficulty in parameterizing <jats:italic>L</jats:italic> <jats:sub>0</jats:sub>, thus, we propose to change the current Gaussian weight function to the von Kaŕmań weight function which extends to larger radii. We find that by changing to the von Kaŕmań, we double our total sensitivity but lose 1st order sensitivity to <jats:italic>L</jats:italic> <jats:sub>0</jats:sub>. Therefore, ulterior methods need to be explored to parameterize <jats:italic>L</jats:italic> <jats:sub>0</jats:sub>.</jats:p>
Palabras clave: General Medicine.
Pp. 23
X-Ray Chronicles of Alpha Centauri: The Swooning of α Cen B
Tom Ayres
<jats:title>Abstract</jats:title> <jats:p>The central AB binary of Alpha Centauri has been visited regularly by Chandra X-ray Observatory since late 2005. Up to mid-2020, the B component, an early K dwarf, had traced out a relatively smooth 8 yr coronal (<jats:italic>T</jats:italic> ∼ 2 MK) activity cycle. Recently, however, B’s X-ray count rate suddenly dipped, from cycle maximum levels to near minimum in just 16 months. Previous cycle decays were 3–4 yr. The significance of the swoon remains to be seen.</jats:p>
Palabras clave: General Medicine.
Pp. 24
Pair-instability Mass Loss for Top-down Compact Object Mass Calculations
M. Renzo; D. D. Hendriks; L. A. C. van Son; R. Farmer
<jats:title>Abstract</jats:title> <jats:p>Population synthesis relies on semi-analytic formulae to determine masses of compact objects from the (helium or carbon-oxygen) cores of collapsing stars. Such formulae are combined across mass ranges that span different explosion mechanisms, potentialy introducing artificial features in the compact object mass distribution. Such artifacts impair the interpretation of gravitational-wave observations. We propose a “top-down” remnant mass prescription where we remove mass from the star for each possible mass-loss mechanism, instead of relying on the fallback onto a “proto-compact-object” to get the final mass. For one of these mass-loss mechanisms, we fit the metallicity-dependent mass lost to pulsational-pair instability supernovae from numerical simulations. By imposing no mass loss in the absence of pulses, our approach recovers the existing compact object masses at the low mass end and ensures continuity across the core-collapse/pulsational-pair-instability regime.</jats:p>
Palabras clave: General Medicine.
Pp. 25
Measuring the Expansion or Contraction of Galaxies
Abraham Loeb
<jats:title>Abstract</jats:title> <jats:p>Galaxies lose mass as a result of their luminosity or gaseous outflows. I calculate the resulting radial migration of stars outwards and show that it could potentially be measured with high resolution spectrographs on the next generation of large telescopes. Substantial accretion of matter in dense cosmic environments could trigger inward stellar migration that would be even more easily measurable.</jats:p>
Palabras clave: General Medicine.
Pp. 26
A Hot Subdwarf Model for the 18.18 minutes Pulsar GLEAM-X
Abraham Loeb; Dan Maoz
<jats:title>Abstract</jats:title> <jats:p>We suggest that the recently discovered, enigmatic pulsar with a period of 18.18 minutes, GLEAM-X J162759.5-523504.3, is most likely a hot subdwarf (proto white dwarf). A magnetic dipole model explains the observed period and period-derivative for a highly magnetized (∼10<jats:sup>8</jats:sup> G), hot subdwarf of typical mass ∼0.5<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and radius ∼0.3<jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub>, and an age of ∼3 × 10<jats:sup>4</jats:sup> yr. The subdwarf spin is close to its breakup speed and its spindown luminosity is near its Eddington limit, likely as a result of accretion from a companion.</jats:p>
Palabras clave: General Medicine.
Pp. 27
PyExoRaMa: An Interactive Tool in Python to Investigate the Radius–Mass Diagram for Exoplanets
Amadori Francesco; Damasso Mario; Zeng Li; Sozzetti Alessandro
<jats:title>Abstract</jats:title> <jats:p>We present the python version of the software originally developed with Mathematica by Zeng et al. The code represents a useful tool for visualizing and manipulating data related to extrasolar planets and their host stars in a multi-dimensional parameter space. Its versatility enables statistical studies based on the large and constantly increasing number of detected exoplanets. It can be used to identify possible interdependence among several physical parameters, and to compare observables with theoretical models describing the exoplanet composition and structure. Our transposition to <jats:sc>python</jats:sc> presents some new features with respect to the original version, and due to the popularity of this programming language in the astrophysics community, the tool is made accessible to a larger number of users interested in exoplanet studies.</jats:p>
Palabras clave: General Medicine.
Pp. 28
Measures of Efficiency of Convection
Adam S. Jermyn; Evan H. Anders; Daniel Lecoanet; Matteo Cantiello; Jared A. Goldberg
<jats:title>Abstract</jats:title> <jats:p>Convection is efficient when advection matters much more than thermal diffusion. Despite this conceptually simple definition, there are several different measures of convective efficiency which are not quite equivalent. Here we recall the definitions of these measures and examine how they are related in different limits.</jats:p>
Palabras clave: General Medicine.
Pp. 29