692 research outputs found
Time domain period determination techniques
Two simple period determination schemes are discussed. They are well suited to problems involving non-sinusoidal periodic phenomena sampled at a few irregularly spaced points. Statistical properties are discussed. The techniques are applied to the double mode Cepheids BK Cen and TU Cas as test cases
Stepping Beyond the Veil and Breaking the Pittsburgh Cycle: The American Dream, Otherness, and Generational Trauma in August Wilson\u27s Cycle Plays
August Wilson’s Pittsburgh Cycle is a series of ten plays that aims to “amend, to explore, and to add to our African consciousness and our African aesthetic” (Wilson qtd. in Gantt 5). Each play is set in a different decade but all share incredibly similar protagonists; all of them are African American men in their mid to late adulthood. The stories are separated by years but all articulate the generational trauma embedded in the African American consciousness in the twentieth century. Wilson’s plays span between the generations of African Americans living in the wake of the Emancipation Proclamation to a group of men living at the start of the new millennium. Each character deals with the struggles of his given time period, but they all experience some form of generational trauma.
An essential part of each characters’ psyche is torn between their African and their American identities, a psychological phenomenon W.E.B. DuBois calls “double consciousness.”
Their American identity pushes them to fulfill their role as the provider, embracing notions of masculinity and the capitalist influence of the “American Dream,” but it is their African identity that prevents them from flourishing in the white American society. They must work to succeed in spite of their identities, crafting their mannerisms and behavior in the form of the “White Man.” These men are also deeply traumatized by their relationships with their fathers. Each man struggles with what Freud would call an Oedipal Complex, attempting to fulfill the paternal role that their fathers failed in. To their own dismay, the generational trauma has already been transposed upon them: they cannot fulfill their fiscal role as the American man because of their blackness. In turn, these men become frustrated, paranoid, anxious, and deeply sad; their self-imposed deficiency separates them from their family, pushing them away from their sons and wives, thereby perpetuating the generational cycle. The Pittsburgh Cycle is truly a cycle of the effects of DuBois’s double-consciousness, demonstrating that these men are always tied to their blackness and the discrimination that is embedded within it
Search for a circum-planetary material and orbital period variations of short-period Kepler exoplanet candidates
A unique short-period Mercury-size Kepler exoplanet candidate KIC012557548b
has been discovered recently by Rappaport et al. (2012). This object is a
transiting disintegrating exoplanet with a circum-planetary material -
comet-like tail. Close-in exoplanets, like KIC012557548b, are subjected to the
greatest planet-star interactions. This interaction may have various forms. In
certain cases it may cause formation of the comet-like tail. Strong interaction
with the host star, and/or presence of an additional planet may lead to
variations in the orbital period of the planet. Our main aim is to search for
comet-like tails similar to KIC012557548b and for long-term orbital period
variations. We are curious about frequency of comet-like tail formation among
short-period Kepler exoplanet candidates. We concentrate on a sample of 20
close-in candidates with a period similar to KIC012557548b from the Kepler
mission.Comment: 19 pages, 75 figures, AN accepte
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On the Impact of Helium Content on the RR Lyrae Distance Scale
Indexación: Scopus.We constructed new sets of He-enhanced (Y = 0.30, Y = 0.40) nonlinear, time-dependent convective hydrodynamical models of RR Lyrae (RRL) stars covering a broad range in metal abundances (Z = 0.0001-0.02). The increase in He content from the canonical value (Y = 0.245) to Y = 0.30-0.40 causes a simultaneous increase in stellar luminosity and in pulsation period. To investigate the dependence of the RRL distance scale on the He abundance, we computed new optical (RI) and near-infrared (JHK) Period-luminosity-metallicity-helium relations. Interestingly enough, the increase in He content causes a minimal change in the coefficients of both period and metallicity terms, since canonical and He-enhanced models obey similar PLZ relations. On the contrary, the classical B-And V-band mean magnitude metallicity relations and the R-band PLZ relation display a significant dependence on the He content. The He-enhanced models are, at fixed metal content, 0.2-0.5 mag brighter than canonical ones. This variation is only marginally affected by evolutionary effects. The quoted distance diagnostics once calibrated with trigonometric parallaxes (Gaia) will provide the opportunity to estimate the He content of field and cluster RRLs. Moreover, the use of either spectroscopic or photometric metal abundances will pave the way to new empirical constraints on the universality of the helium-To-metal enrichment ratio in old (t10 Gyr) stellar tracers. © 2018. The American Astronomical Society. All rights reserved.https://iopscience.iop.org/article/10.3847/2041-8213/aada1
Second Overtone Pulsators Among Delta Scuti Stars
We investigate the modal stability of stellar models at masses and luminosity
levels corresponding to post main sequence luminous delta scuti pulsators. The
envelope models have been computed at fixed mass value, luminosity level and
chemical composition (Y=0.28, Z=0.02). According to a nonlinear approach to
radial oscillations the present investigation predicts the occurrence of stable
second overtone pulsators for the first time. The shape of both light and
velocity curves are presented and discussed, providing a useful tool for the
identification of second overtone pulsators among the known groups of radially
pulsating stars. The period ratios of mixed mode pulsators obtained by
perturbing the first and the second overtone radial eigenfunctions are in
agreement with observative values. Finally, the physical structure and the
dynamical properties of second overtone pulsators are discussed in detail. The
role played by the nodal lines in the destabilization of second overtone
pulsators is also pointed out.Comment: 20 pages, 11 Postscript figures, uses aaspp4.sty and tighten.st
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