arXiv subjects

José Luis Contreras

Publications and source records attributed to José Luis Contreras.

5 recordsLinked to original sources

arXiv2021

LSTOSA: Onsite processing pipeline for the CTA Larged-Sized Telescope prototype

The prototype of the Large-Sized Telescope (LST) of the Cherenkov Telescope Array (CTA) is presently going through its commissioning phase. A total of four LSTs, among others, will operate together at Observatorio del Roque de Los Muchachos, which will host the CTA North site. A computing center endowed with 1760 cores and several petabytes disk space is installed onsite. It is used to acquire, process, and analyze the data produced, at a rate of 3~TB/hour during operation. The LST On-site Analysis LSTOSA is a set of scripts written in Python which connects the different steps of lstchain, the analysis pipeline developed for the LST. It processes the data in a semiautomatic way producing high-level data and quality plots including detailed provenance logs. Data are analyzed before the next observation night to help in the commissioning procedure and debugging.

astro-ph.IM↗

arXiv2018

Relevance of the fluorescence radiation in VHE gamma-ray observations with the Cherenkov technique

Atmospheric fluorescence is usually neglected in the reconstruction of the signals registered by Cherenkov telescopes, both IACTs and wide-angle detector arrays. In this paper we quantify the fluorescence contribution to the total light recorded in typical observational configurations. To this end we have implemented the production and tracking of fluorescence light in the CORSIKA code. Both the Cherenkov and fluorescence light distributions on ground (2200 m a.s.l.) have been simulated for gamma-ray showers in a wide energy range ($10^{-1} - 10^3$ TeV). The relative fluorescence contribution has been evaluated as a function of the shower energy and zenith angle. Our results indicate that at distances from the impact point smaller than 200 m the fluorescence contamination is negligible in both types of telescopes. However, at about 1000 m, the contamination in IACTs is around 5%. At these core distances, the signals recorded by wide-angle detectors contain around 45% of atmospheric fluorescence in the PeV region.

astro-ph.IM↗

arXiv2018

The relevance of fluorescence radiation in Cherenkov telescopes

Cherenkov telescopes are also sensitive to the atmospheric fluorescence produced by the extensive air showers. However this contribution is neglected by the reconstruction algorithms of imaging air Cherenkov telescopes IACTs and wide-angle Cherenkov detectors WACDs. In this paper we evaluate the fluorescence contamination in the Cherenkov signals from MC simulations in both kinds of Cherenkov telescopes and for some typical observational situations. Results for an observation level of 2200 m a.s.l. are shown. In addition, the feasibility and capabilities of IACTs working as fluorescence telescopes are discussed with the assistance of some geometrical calculations.

astro-ph.IM↗

arXiv2017

A Monte Carlo study of the relevance of fluorescence radiation in VHE gamma ray observations with Cherenkov telescopes

It is generally assumed that fluorescence radiation does not play a significant role in the performance of Cherenkov telescopes. However, this assumption is required to be verified using detailed Monte Carlo simulations. In order to do this, we have implemented the production and tracking of fluorescence radiation inside the CORSIKA code, and simulated gamma-ray induced showers in the very high energy range. The most accurate fluorescence-yield data available so far was used for this purpose. The distribution of both light components on the ground has been studied as a function of various parameters affecting the detection and reconstruction of gamma-ray showers such as the angular aperture. From these distributions, we determined the conditions under which fluorescence radiation becomes significant. These results will also be useful to estimate the corresponding systematic errors in Cherenkov telescope observations. The full simulation results have been cross-checked, on a small sample of events, against numerical calculations based on a one-dimension shower profile and found to be compatible with each other. Both tools can be used for further investigations, like studying the possibility to modify Cherenkov telescopes for the measurement of fluorescence induced by extensive air showers.

astro-ph.IM↗

arXiv2016

Open high-level data formats and software for gamma-ray astronomy

In gamma-ray astronomy, a variety of data formats and proprietary software have been traditionally used, often developed for one specific mission or experiment. Especially for ground-based imaging atmospheric Cherenkov telescopes (IACTs), data and software are mostly private to the collaborations operating the telescopes. However, there is a general movement in science towards the use of open data and software. In addition, the next-generation IACT instrument, the Cherenkov Telescope Array (CTA), will be operated as an open observatory. We have created a Github organisation at https://github.com/open-gamma-ray-astro where we are developing high-level data format specifications. A public mailing list was set up at https://lists.nasa.gov/mailman/listinfo/open-gamma-ray-astro and a first face-to-face meeting on the IACT high-level data model and formats took place in April 2016 in Meudon (France). This open multi-mission effort will help to accelerate the development of open data formats and open-source software for gamma-ray astronomy, leading to synergies in the development of analysis codes and eventually better scientific results (reproducible, multi-mission). This write-up presents this effort for the first time, explaining the motivation and context, the available resources and process we use, as well as the status and planned next steps for the data format specifications. We hope that it will stimulate feedback and future contributions from the gamma-ray astronomy community.

astro-ph.IM↗