arXiv subjects

Diego Hidalgo

Publications and source records attributed to Diego Hidalgo.

25 records · Page 2Linked to original sources

arXiv2019

Stringy (Galilei) Newton-Hooke Chern-Simons Gravities

We construct Chern-Simons gravities in $(2+1)$-dimensional space-time considering the Stringy Galilei algebra both with and without non-central extensions. In the first case, there is an invariant and non-degenerate bilinear form, however, the field equations do not allow to express the spin connections in terms of the dreibeins. In the second case, there is no invariant non-degenerate bilinear form. Therefore, in both cases, we do not have an ordinary gravity theory. Instead, if we consider the stringy Newton-Hooke algebra with extensions as gauge group we have an invariant non-degenerate metric and from the field equations, we express the spin connections in terms of the geometric fields.

hep-th↗

arXiv2019

The Transiting Multi-planet System HD15337: Two Nearly Equal-mass Planets Straddling the Radius Gap

We report the discovery of a super-Earth and a sub-Neptune transiting the star HD 15337 (TOI-402, TIC 120896927), a bright (V=9) K1 dwarf observed by the Transiting Exoplanet Survey Satellite (TESS) in Sectors 3 and 4. We combine the TESS photometry with archival HARPS spectra to confirm the planetary nature of the transit signals and derive the masses of the two transiting planets. With an orbital period of 4.8 days, a mass of 7.51(+1.09)(-1.01) M_Earth, and a radius of 1.64+/-0.06 R_Earth, HD 15337b joins the growing group of short-period super-Earths known to have a rocky terrestrial composition. The sub-Neptune HD 15337c has an orbital period of 17.2 days, a mass of 8.11(+1.82)(-1.69) M_Earth, and a radius of 2.39+/-0.12 R_Earth, suggesting that the planet might be surrounded by a thick atmospheric envelope. The two planets have similar masses and lie on opposite sides of the radius gap, and are thus an excellent testbed for planet formation and evolution theories. Assuming that HD 15337c hosts a hydrogen-dominated envelope, we employ a recently developed planet atmospheric evolution algorithm in a Bayesian framework to estimate the history of the high-energy (extreme ultraviolet and X-ray) emission of the host star. We find that at an age of 150 Myr, the star possessed on average between 3.7 and 127 times the high-energy luminosity of the current Sun.

astro-ph.EP↗

arXiv2018

MuSCAT2: four-color Simultaneous Camera for the 1.52-m Telescopio Carlos Sánchez

We report the development of a 4-color simultaneous camera for the 1.52~m Telescopio Carlos Sánchez (TCS) in the Teide Observatory, Canaries, Spain. The new instrument, named MuSCAT2, has a capability of 4-color simultaneous imaging in $g$ (400--550 nm), $r$ (550--700 nm), $i$ (700--820 nm), and $z_s$ (820--920 nm) bands. MuSCAT2 equips four 1024$\times$1024 pixel CCDs, having a field of view of 7.4$\times$7.4 arcmin$^2$ with a pixel scale of 0.44 arcsec per pixel. The principal purpose of MuSCAT2 is to perform high-precision multi-color exoplanet transit photometry. We have demonstrated photometric precisions of 0.057%, 0.050%, 0.060%, and 0.076% as root-mean-square residuals of 60~s binning in $g$, $r$, $i$ and $z_s$ bands, respectively, for a G0 V star WASP-12 ($V=11.57\pm0.16$). MuSCAT2 has started science operations since January 2018, with over 250 telescope nights per year. MuSCAT2 is expected to become a reference tool for exoplanet transit observations, and will substantially contribute to the follow-up of the TESS and PLATO space missions.

astro-ph.IM↗

arXiv2018

The role of host star variability in the detectability of planetary phase curves

Phase curves, or the change in observed illumination of the planet as it orbits around its host star, help us to characterize their atmospheres. However, the variability of the host star can make their detection challenging: the presence of starspots, faculae, flares and rotational effects introduce brightness variations that can hide other flux variations related to the presence of an exoplanet: ellipsoidal variation, Doppler boosting and a combination of reflected light and thermal emission from the planet. Here we present a study to quantify the effect of stellar variability on the detectability of phase curves in the optical. On a first stage, we simulate ideal data, with different white noise levels, and with cadences and total duration matching a quarter of the \textit{Kepler} mission. We perform injection and recovery tests to evaluate the minimum number of planetary orbits that need to be observed in order to determine the amplitude of the phase curve with an accuracy of 15\%. We also evaluate the effect of a simplistic stellar variability signal with low amplitude, to provide strong constraints on the minimum number of orbits needed under these ideal conditions. On a second stage, we apply these methods to data from the quarter Q9 of the \textit{Kepler} mission, known for its low instrumental noises. The injection and recovery tests are performed on a selected sample of the less noisy stars in different effective temperature ranges. Even for the shortest explored planet period of 1 day, we obtain that observing a single orbit of the planet fails to detect accurately more than 90\% of the inserted amplitude. The best recovery rates, close to 48\%, are obtained after 10 orbits of a 1d period planet with the largest explored amplitude of 150 ppm. The temperature range of the host stars providing better recovery ratios is $5500 \text{K}<T_{eff}<6000 \text{K}$. [Abridged]

astro-ph.EP↗

arXiv2018

Non-Relativistic Maxwell Chern-Simons Gravity

We consider a non-relativistic (NR) limit of $(2+1)$-dimensional Maxwell Chern-Simons (CS) gravity with gauge algebra [Maxwell] $\oplus \ u(1)\oplus u(1)$. We obtain a finite NR CS gravity with a degenerate invariant bilinear form. We find two ways out of this difficulty: To consider i) [Maxwell] $\oplus\ u(1)$, which does not contain Extended Bargmann gravity (EBG); or, ii) the NR limit of [Maxwell] $\oplus\ u(1)\oplus u(1)\oplus u(1)$, which is a Maxwellian generalization of the EBG.

hep-th↗

arXiv2017

Surface Charges for Gravity and Electromagnetism in the First Order Formalism

A new derivation of surface charges for 3+1 gravity coupled to Electromagnetism is obtained. Gravity theory is written in the tetrad-connection variables. The general derivation starts from the Lagrangian and uses the covariant symplectic formalism in the language of forms. For gauge theories surface charges disentangle physical from gauge symmetries through the use of Noether identities and the exactness symmetry condition. The surface charges are quasilocal, explicitly coordinate independent, gauge invariant, and background independent. For a black hole family solution the surface charge conservation implies the first law of black hole mechanics. As a check we show the first law for black hole electrically charged, rotating, and with an asymptotically constant curvature (the Kerr-Newman (anti-)de Sitter family). The charges, including the would-be mass term appearing in the first law, are quasilocal. It is not required a reference to the asymptotic structure of the spacetime nor boundary conditions, and therefore topological terms do not play a rôle. Finally, surface charges formulae for Lovelock gravity coupled to Electromagnetism are exhibited. It generalizes the one derived in a recent work by G. Barnich, P. Mao, and R. Ruzziconi. The two different symplectic methods to define surface charges are compared and shown equivalent.

gr-qc↗

arXiv2017

The Gribov problem in presence of background field for $SU(2)$ Yang-Mills theory

The Gribov problem in the presence of a background field is analyzed: in particular, we study the Gribov copies equation in the Landau-De Witt gauge as well as the semi-classical Gribov gap equation. As background field, we choose the simplest non-trivial one which corresponds to a constant gauge potential with non-vanishing component along the Euclidean time direction. This kind of constant non-Abelian background fields is very relevant in relation with (the computation of) the Polyakov loop but it also appears when one considers the non-Abelian Schwinger effect. We show that the Gribov copies equation is affected directly by the presence of the background field, constructing an explicit example. The analysis of the Gribov gap equation shows that the larger the background field, the smaller the Gribov mass parameter. These results strongly suggest that the relevance of the Gribov copies (from the path integral point of view) decreases as the size of the background field increases.

hep-th↗