arXiv subjects

R. Casali

Publications and source records attributed to R. Casali.

4 recordsLinked to original sources

arXiv2022

ExoClock Project III: 450 new exoplanet ephemerides from ground and space observations

The ExoClock project has been created with the aim of increasing the efficiency of the Ariel mission. It will achieve this by continuously monitoring and updating the ephemerides of Ariel candidates over an extended period, in order to produce a consistent catalogue of reliable and precise ephemerides. This work presents a homogenous catalogue of updated ephemerides for 450 planets, generated by the integration of $\sim$18000 data points from multiple sources. These sources include observations from ground-based telescopes (ExoClock network and ETD), mid-time values from the literature and light-curves from space telescopes (Kepler/K2 and TESS). With all the above, we manage to collect observations for half of the post-discovery years (median), with data that have a median uncertainty less than one minute. In comparison with literature, the ephemerides generated by the project are more precise and less biased. More than 40\% of the initial literature ephemerides had to be updated to reach the goals of the project, as they were either of low precision or drifting. Moreover, the integrated approach of the project enables both the monitoring of the majority of the Ariel candidates (95\%), and also the identification of missing data. The dedicated ExoClock network effectively supports this task by contributing additional observations when a gap in the data is identified. These results highlight the need for continuous monitoring to increase the observing coverage of the candidate planets. Finally, the extended observing coverage of planets allows us to detect trends (TTVs - Transit Timing Variations) for a sample of 19 planets. All products, data, and codes used in this work are open and accessible to the wider scientific community.

astro-ph.EP↗

arXiv2021

ExoClock project II: A large-scale integrated study with 180 updated exoplanet ephemerides

The ExoClock project is an inclusive, integrated, and interactive platform that was developed to monitor the ephemerides of the Ariel targets to increase the mission efficiency. The project makes the best use of all available resources, i.e., observations from ground telescopes, mid-time values from the literature and finally, observations from space instruments. Currently, the ExoClock network includes 280 participants with telescopes capable of observing 85\% of the currently known Ariel candidate targets. This work includes the results of $\sim$1600 observations obtained up to the 31st of December 2020 from the ExoClock network. These data in combination with $\sim$2350 mid-time values collected from the literature are used to update the ephemerides of 180 planets. The analysis shows that 40\% of the updated ephemerides will have an impact on future scheduling as either they have a significantly improved precision, or they have revealed biases in the old ephemerides. With the new observations, the observing coverage and rate for half of the planets in the sample has been doubled or more. Finally, from a population perspective, we identify that the differences in the 2028 predictions between the old and the new ephemerides have an STD that is double what is expected from gaussian uncertainties. These findings have implications for planning future observations, where we will need to account for drifts potentially greater than the prediction uncertainties. The updated ephemerides are open and accessible to the wider exoplanet community both from our Open Science Framework (OSF) repository and our website.

astro-ph.EP↗

arXiv2013

Hadronic and hybrid stars subject to density dependent magnetic fields

In this work we present a study of magnetars composed of hadronic and quark matter, under the influence of strong magnetic fields. We present our results for hadronic matter taking into account the effects that the inclusion of anomalous magnetic moment corrections may cause on the equations of state (EOS). Particle abundances are also presented and discussed. Additionally, the case of hybrid stars under the influence of strong magnetic fields is considered. We study the structure of hybrid stars based on the Maxwell condition (without a mixed phase), where the hadron phase is described by the non-linear Walecka model (NLW) and the quark phase by the Nambu-Jona-Lasinio model (NJL). The EOS and the mass-radius relation for each case are calculated and discussed. We show that the recently observed high mass neutron stars can be described by both hadronic and hybrid equations of state subject to strong magnetic fields.

astro-ph.SR↗

arXiv1994

Determination of the branching ratios $Γ(K_L \to 3 π^0) / Γ(K_L \to π^+ π^- π^0)$ and $Γ(K_L \to 3 π^0) / Γ(K_L \to πe ν)$

Improved branching ratios were measured for the $K_L \to 3 π^0 $ decay in a neutral beam at the CERN SPS with the NA31 detector: $Γ(K_L \to 3 π^0) / Γ(K_L \to π^+ π^- π^0) = 1.611 \pm 0.037$ and $Γ(K_L \to 3 π^0) / Γ(K_L \to πe ν) = 0.545 \pm 0.010$. From the first number an upper limit for $ΔI =5/2$ and $ΔI = 7/2 $ transitions in neutral kaon decay is derived. Using older results for the Ke3/K$μ$3 fraction, the 3$π^0$ branching ratio is found to be $Γ(K_L \to 3 π^0 )/ Γ_{tot} = (0.211 \pm 0.003)$, about a factor three more precise than from previous experiments.

hep-ex↗