Spinning particles in Schwarzschild-de Sitter space-time

After considering the reference case of the motion of spinning test bodies in the equatorial plane of the Schwarzschild space-time, we generalize the results to the case of the motion of a spinning particle in the equatorial plane of the Schwarzschild-de Sitter space-time. Specifically, we obtain the loci of turning points of the particle in this plane. We show that the cosmological constant affect the particle motion when the particle distance from the black hole is of the order of the inverse square root of the cosmological constant.Comment: 8 pages, 5 eps figures, submitted to Gen.Rel.Gra

A causal Schwarzschild-de Sitter interior solution by gravitational decoupling

We employ the minimal geometric deformation approach to gravitational decoupling (MGD- decoupling) in order to build an exact anisotropic version of the Schwarzschild interior solution in a space-time with cosmological constant. Contrary to the well-known Schwarzschild interior, the matter density in the new solution is not uniform and possesses subluminal sound speed. It therefore satisfies all standard physical requirements for a candidate astrophysical object.Comment: 15 pages, 6 figure

Energy exchange between relativistic fluids: the polytropic case

We present a simple, analytic and straightforward method to elucidate the effects produced by polytropic fluids on any other gravitational source, no matter its nature, for static and spherically symmetric spacetimes. As a direct application, we study the interaction between polytropes and perfect fluids coexisting inside a self-gravitating stellar objectComment: 10 pages, 12 figure

The NASA Wallops Arc-Second Pointer (WASP) System for Precision Pointing of Scientific Balloon Instruments and Telescopes

The National Aeronautics and Space Administrations (NASA) Wallops Flight Facility (WFF), part of the Goddard Space Flight Center (GSFC), has developed a unique pointing control system for instruments aboard scientific balloon gondolas. The ability to point large telescopes and instruments with arc-second accuracy and stability is highly desired by multiple scientific disciplines, such as Planetary, Earth Science, Heliospheric and Astrophysics, and the availability of a standardized system supplied by NASA alleviates the need for the science user to develop and provide their own system. In addition to the pointing control system, a star tracker has been developed with both daytime and nighttime capability to augment the WASP and provide an absolute pointing reference. The WASP Project has successfully completed five test flights and one operational science mission, and is currently supporting an additional test flight in 2017, along with three science missions with flights scheduled between 2018 and 2020. The WASP system has demonstrated precision pointing and high reliability, and is available to support scientific balloon missions

Circular motion of neutral test particles in Reissner-Nordstr\"om spacetime

We investigate the motion of neutral test particles in the gravitational field of a mass $M$ with charge $Q$ described by the Reissner-Nordstr\"om (RN) spacetime. We focus on the study of circular stable and unstable orbits around configurations describing either black holes or naked singularities. We show that at the classical radius, defined as $Q^2/M$, there exist orbits with zero angular momentum due to the presence of repulsive gravity. The analysis of the stability of circular orbits indicates that black holes are characterized by a continuous region of stability. In the case of naked singularities, the region of stability can split into two non-connected regions inside which test particles move along stable circular orbits.Comment: 23 pages, 22 figures. To be published Phys. Rev.

Isotropization and change of complexity by gravitational decoupling

We employ the gravitational decoupling appro- ach for static and spherically symmetric systems to develop a simple and powerful method in order to (a) continuously isotropize any anisotropic solution of the Einstein field equa- tions, and (b) generate new solutions for self-gravitating dis- tributions with the same or vanishing complexity factor. A few working examples are given for illustrative purposes

Einstein-Klein-Gordon by gravitational decoupling

We investigate how a spherically symmetric scalar field can modify the Schwarzschild vacuum solution when there is no exchange of energy-momentum between the scalar field and the central source of the Schwarzschild metric. This system is described by means of the gravitational decoupling by Minimal Geometric Deformation (MGD-decoupling), which allows us to show that, under the MGD paradigm, the Schwarzschild solution is modified in such a way that a naked singularity appears.Comment: 16 pages, 2 figures. arXiv admin note: text overlap with arXiv:1804.0346