5827974
Non-supersymmetric extremal multicenter black holes with superpotentials
Using the superpotential approach we generalize Denef’s method of deriving and solving first-order equations describing multicenter extremal black holes in four-dimensional $ \mathcal{N} = 2 $ supergravity to allow non-supersymmetric solutions. We illustrate the general results with an explicit example of the stu model.
124027290
Static, spherically symmetric, charged black holes in four-dimensional N = 2 supergravity
20232952
On anharmonic stabilisation equations for black holes
A bstractWe investigate the stabilisation equations for sufficiently general, yet regular, extremal (supersymmetric and non-supersymmetric) and non-extremal black holes in four-dimensional N = 2 supergravity using both the H-FGK approach and a generalisation of Denef’s formalism. By an explicit calculation we demonstrate that the equations necessarily contain an anharmonic part, even in the static, spherically symmetric and asymptotically flat case.
2507966
The Freudenthal gauge symmetry of the black holes of N = 2, d = 4 supergravity
A bstractWe show that the representation of black-hole solutions in terms of the variables HM which are harmonic functions in the supersymmetric case is non-unique due to the existence of a local symmetry in the effective action. This symmetry is a continuous (and local) generalization of the discrete Freudenthal transformations initially introduced for the black-hole charges and can be used to rewrite the physical fields of a solution in terms of entirely different-looking functions.
118799575
Non-supersymmetric black-hole solutions in N=2,D=4 supergravity
Esta tesis de doctorado se dedica al estudio de los agujeros negros de supergravedad N=2 en cuatro dimensiones. Se concentra principalmente en el analisis de soluciones no supersimetricas, extremas y no extremas, a un solo centro o a multi-centro. Se han utilizado y profundizado nociones importantes como el formalismo de primer orden y el formalismo H-FGK. Se han encontrado nuevas soluciones de agujero negro y nuevas simetrias entre las variables del sistemas.
53957230
A new method for calculating the convergent point of a moving group
Context. Convergent point (CP) search methods are important tools for studying the kinematic properties of open clusters and young associations whose members share the same spatial motion. Aims. We present a new CP search strategy based on proper motion data. We test the new algorithm on synthetic data and compare it with previous versions of the CP search method. As an illustration and validation of the new method we also present an application to the Hyades open cluster and a comparison with independent results. Methods. The new algorithm rests on the idea of representing the stellar proper motions by great circles over the celestial sphere and visualizing their intersections as the CP of the moving group. The new strategy combines a maximum-likelihood analysis for simultaneously determining the CP and selecting the most likely group members and a minimization procedure that returns a refined CP position and its uncertainties. The method allows one to correct for internal motions within the group and takes into account that the stars in the group lie at different distances. Results. Based on Monte Carlo simulations, we find that the new CP search method in many cases returns a more precise solution than its previous versions. The new method is able to find and eliminate more field stars in the sample and is not biased towards distant stars. The CP solution for the Hyades open cluster is in excellent agreement with previous determinations.
54675577
A kinematic study and membership analysis of the Lupus star-forming region
Aims. A precise determination of the distance to individual stars is required to reliably determine the fundamental parameters (mass and age) of young stellar objects. This paper is dedicated to investigating the kinematic properties of the Lupus moving group of young stars with the primary objective of deriving individual parallaxes for each group member. Methods. We identify those stars in the Lupus star-forming region that define the comoving association of young stars by utilizing our new and improved convergent point search method that allows us to derive the precise position of the convergent point of the comoving association from the stars’ proper motions. We used published proper motion catalogs and searched the literature for radial velocities, which are needed to compute individual parallaxes. We supplemented the radial velocity data with new measurements from spectroscopic observations performed with the FEROS spectrograph mounted on the MPG/ESO 2.2 m telescope at La Silla. Results. We identify a comoving group with 109 pre-main sequence stars and candidates that define the kinematic properties of the Lupus low-mass star-forming region. We derive individual parallaxes for stars with known radial velocity and tentative parallaxes for the remaining group members by assuming that all stars share the same space motion. The convergent point method, combined with the k-NN algorithm, makes it possible to distinguish the Lupus and Upper Centaurus Lupus stars from the adjacent ScorpiusCentaurus association. We find significant depth e ects in this region and show that the classical T Tauri stars, located in the close vicinity of the Lupus molecular clouds, form a background population, while the weak-emission line T Tauri stars are dispersed not only in angular extent but also in depth. Conclusions. The newly derived individual parallaxes will be used in a forthcoming paper to refine the masses and ages of Lupus T Tauri stars, with the aim of better constraining the lifetimes of their circumstellar, protoplanetary disks.