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Iara Tosta e Melo

Publications and source records attributed to Iara Tosta e Melo.

5 recordsLinked to original sources

Search for gravitational waves associated with high-energy neutrinos detected by IceCube during the third observing run of LIGO-Virgo

We search for generic gravitational-wave transients associated with high-energy neutrinos detected by the IceCube Neutrino Observatory during the third Observing Run (O3) of Advanced LIGO, Advanced Virgo, and KAGRA. We perform an unmodeled, targeted search, which is sensitive to gravitational-wave signals weaker than those reported in real time or in the gravitional-wave transient catalog, and can thus uncover coincidences missed by typical neutrino follow-up searches. We find no statistically significant gravitational-wave signal and set lower bounds on the distance of possible gravitational-wave sources for different emission models.

astro-ph.HE↗

Search for gravitational-wave bursts in LIGO data at the Schenberg antenna sensitivity range

The Brazilian Mario Schenberg gravitational-wave detector remained operational until 2016 when it was disassembled. To assess the feasibility of reassembling the antenna, its capability to detect GW within its designed sensitivity parameters needs to be evaluated. Although the antenna is currently disassembled, insights can be gleaned from the O3 data of the LIGO detectors, given the similarities between Schenberg's ultimate sensitivity and the interferometers' sensitivity in the [3150-3260] Hz band. The search focused on signals lasting from ms to seconds, with no assumptions about their morphology, polarization, and arrival sky direction. Data analysis was performed using the coherent WaveBurst pipeline in the frequency range between 512 Hz and 4096 Hz, specifically targeting signals with bandwidths overlapping the Schenberg frequency band. However, the O3 data did not yield statistically significant evidence of GW bursts. This null result allowed for the characterization of the search efficiency in identifying simulated signal morphologies and setting upper limits on the GW burst event rate as a function of strain amplitude. The current search is sensitive to sources emitting isotropically $5\times10^{-6} M_{\odot}c^2$ in GWs from a distance of 10 kiloparsecs with a 50\% detection efficiency at a false alarm rate of 1 per 100 years. Moreover, we revisited estimations of detecting f-modes of neutron stars excited by glitches, setting the upper limit of the f-mode energy for the population of Galactic pulsars to $\sim 8 \times 10^{-8} M_{\odot}c^2$ at 3205 Hz. Our simulations suggest f-modes are an unlikely source of gravitational waves for the aSchenberg. Nevertheless, its potential in probing other types of GW short transients, such from giant flares from magnetars, post-merger phase of binary NSs, or the inspiral of binaries of primordial BHs with sub-solar masses, remains promising.

gr-qc↗

Quantum zero point electromagnetic energy difference between the superconducting and the normal phase in a HTc superconducting metal bulk sample

We provide a novel methodological approach to the estimate of the change of the Quantum Vacuum electromagnetic energy density in a High critical Temperature superconducting metal bulk sample, when it undergoes the transition in temperature, from the superconducting to the normal phase. The various contributions to the Casimir energy in the two phases are highlighted and compared. While the TM polarization of the vacuum mode allows for a macroscopic description of the superconducting transition, the changes in the TE vacuum mode induced by the superconductive correlations are introduced within a microscopic model, which does not explicitly take into account the anisotropic structure of the material.

cond-mat.supr-con↗

Scaling Correlations Among Central Massive Objects and Their Host Galaxies

The central regions of galaxies show the presence of super massive black holes and/or very dense stellar clusters. Both such objects seem to follow similar host-galaxy correlations, suggesting that they are members of the same family of Compact Massive Objects. Here we investigate a huge data collection of Compact Massive Objects properties to correlate them with absolute magnitude, velocity dispersion and mass of their host galaxies. We draw also some preliminary astrophysical conclusions.

astro-ph.GA↗

Kinematic study of the parsec-scale jet of the quasar PKS 1741--03

We present 23 interferometric images of parsec-scale jet of the quasar PKS 1741--03 at 15, 24 and 43 GHz spanning about 13 yr. We model the images as a superposition of discrete two--dimensional elliptical Gaussian components, with parameters determined by the cross--entropy technique. All the images present a spatially unresolved component (core) and usually two or three components receding from it. The same components were found in simultaneous 24 and 43 GHz maps, showing the robustness of our model-fitting. The core-shift opacity effect between these frequencies is weak. We have identified seven components moving along straight lines at constant apparent superluminal speeds ($3.5\leβ_\mathrm{obs}\le 6.1$), with different sky position angles ($-186°\le η\le -125°$). The core flux density tracks quite well the fluctuations seen in the historical single-dish light curve at 14.5 GHz, with no measurable delay. The total flux density from the moving jet components is delayed $\sim$2 yr in relation to the core light curve, roughly the same as the lag between the ejection epoch and the maximum flux density in the light curves of the jet components. We propose that there are three non-exclusive mechanisms for producing these delays. From the kinematics of the most robust jet components and the core brightness temperature, we determined the bulk Lorentz factor ($4.8\leγ\le 24.5$) and the jet viewing angle ($0.°35 \le θ\le 4.°2$); these values agree with previous estimates from the spectral energy distribution of PKS 1741--03 and its radio variability.

astro-ph.HE↗