arXiv subjects

Carolina Negrelli

Publications and source records attributed to Carolina Negrelli.

6 recordsLinked to original sources

arXiv2023

First results of the glitching pulsars monitoring program at the Argentine Institute of Radioastronomy

We report here on the first results of a systematic monitoring of southern glitching pulsars at the Argentine Institute of Radioastronomy that started in the year 2019. We detected a major glitch in the Vela pulsar (PSR J0835$-$4510) and two small-glitches in PSR J1048$-$5832. For each glitch, we present the measurement of glitch parameters by fitting timing residuals. We then make an individual pulses study of Vela in observations before and after the glitch. We selected 6 days of observations around the major glitch on 2021 July 22 and study their statistical properties with machine learning techniques. We use Variational AutoEncoder (VAE) reconstruction of the pulses to separate them clearly from the noise. We perform a study with Self-Organizing Maps (SOM) clustering techniques to search for unusual behavior of the clusters during the days around the glitch not finding notable qualitative changes. We have also detected and confirm recent glitches in PSR J0742$-$2822 and PSR J1740$-$3015.

astro-ph.HE↗

arXiv2020

Testing Modified Gravity theory (MOG) with Type Ia Supernovae, Cosmic Chronometers and Baryon Acoustic Oscillations

We analyse the MOdified Gravity (MOG) theory, proposed by Moffat, in a cosmological context. We use data from Type Ia Supernovae (SNe Ia), Baryon Acoustic Oscillations (BAO) and Cosmic Chronometers (CC) to test MOG predictions. For this, we perform $χ^2$ tests considering fixed values of $H_0$ and $V_G$, the self-interaction potential of one of the scalar fields in the theory. Our results show that the MOG theory is in agreement with all data sets for some particular values of $H_0$ and $V_G$, being the BAO data set the most powerful tool to test MOG predictions, due to its constraining power.

astro-ph.CO↗

arXiv2020

Solar System tests and chameleon effect in f (R) gravity

Using a novel and self-consistent approach that avoids the scalar-tensor identification in the Einstein frame, we reanalyze the viability of f(R) gravity within the context of solar-system tests. In order to do so, we depart from a simple but fully relativistic system of differential equations that describe a compact object in a static and spherically symmetric spacetime, and then we make suitable linearizations that apply to nonrelativistic objects such as the Sun. We then show clearly under which conditions the emerging chameleonlike mechanism can lead to a post-Newtonian parameter γ compatible with the observational bounds. To illustrate this method, we use several specific f(R) models proposed to explain the current acceleration of the Universe, and we show which of them are able to satisfy those bounds.

gr-qc↗

arXiv2018

Testing MOG theory in the Milky Way

We perform a test of John Moffat's Modified Gravity theory (MOG) within the Milky Way, adopting the well known "Rotation Curve" method. We use the dynamics of observed tracers within the disk to determine the gravitational potential as a function of galactocentric distance, and compare that with the potential that is expected to be generated by the visible component only (stars and gas) under different "flavors" of the MOG theory, making use of a state-of-the-art setup for both the observed tracers and baryonic morphology. Our analysis shows that in both the original and the modified version (considering a self-consistent evaluation of the Milky Way mass), the theory fails to reproduce the observed rotation curve. We conclude that in none of its present formulation, the MOG theory is able to explain the observed Rotation Curve of the Milky Way.

astro-ph.GA↗

arXiv2018

Spatial variation of fundamental constants: testing models with thermonuclear supernovae

Since Dirac stated his Large Number Hypothesis the space-time variation of fundamental constants has been an active subject of research. Here we analyze the possible spatial variation of two fundamental constants: the fine structure constant α and the speed of light c. We study the effects of such variations on the luminosity distance and on the peak luminosity of Type Ia supernovae (SNe Ia). For this, we consider the change of each fundamental constant separately and discuss a dipole model for its variation. Elaborating upon our previous work, we take into account the variation of the peak luminosity of Type Ia supernovae resulting from the variation of each of these fundamental constants. Furthermore, we also include the change of the energy release during the explosion, which was not studied before in the literature. We perform a statistical analysis to compare the predictions of the dipole model for α and c variation with the Union2.1 and JLA compilations of SNe Ia. For this, we also allow the nuisance parameters of the distance estimator $μ_0$ and the cosmological density matter $Ω_m$ to vary. As a result of our analysis we obtain a first estimate of the possible spatial variation of the speed of light c. On the other hand, we find that there is no significant difference between the several phenomenological models studied here and the standard cosmological model, in which fundamental constants do not vary at all. Thus, we conclude that the actual set of data of Type Ia supernovae does not allow to verify the hypothetical spatial variation of fundamental constants.

astro-ph.CO↗

arXiv2014

The variation of the fine structure constant: testing the dipole model with thermonuclear supernovae

The large-number hypothesis conjectures that fundamental constants may vary. Accordingly, the spacetime variation of fundamental constants has been an active subject of research for decades. Recently, using data obtained with large telescopes a phenomenological model in which the fine structure constant might vary spatially has been proposed. We test whether this hypothetical spatial variation of α, which follows a dipole law, is compatible with the data of distant thermonuclear supernovae. Unlike previous works, in our calculations we consider not only the variation of the luminosity distance when a varying α is adopted, but we also take into account the variation of the peak luminosity of Type Ia supernovae resulting from a variation of α. This is done using an empirical relation for the peak bolometric magnitude of thermonuclear supernovae that correctly reproduces the results of detailed numerical simulations. We find that there is no significant difference between the several phenomenological models studied here and the standard one, in which α does not vary spatially. We conclude that the present set of data of Type Ia supernovae is not able to distinguish the standard model from the dipole models, and thus cannot be used to discard nor to confirm the proposed spatial variation of α.

astro-ph.CO↗