Application of the optimised next neighbour image cleaning method to the VERITAS array

Imaging atmospheric Cherenkov telescopes, such as the VERITAS array, are subject to the Night Sky Background (NSB) and electronic noise, which contribute to the total signal of pixels in the telescope camera. The contribution of noise photons in event images is reduced with the application of image cleaning methods. Conventionally, high thresholds must be employed to ensure the removal of pixels containing noise signal. On that account, low-energy gamma-ray showers might be suppressed during the cleaning. We present here the application of an optimised next neighbour image cleaning for the VERITAS array. With this technique, differential noise rates are estimated for each individual observation and thus changes in the NSB and afterpulsing are consistently being accounted for. We show that this method increases the overall rate of reconstructed gamma-rays, lowers the energy threshold of the array and allows the reconstruction of low energy (E > 70 GeV) source events which were suppressed by the conventional cleaning method.Comment: 9 pages, PoS, 38th International Cosmic Ray Conference (ICRC2023

Taxa de sudorese e condição hídrica em atletas de natação

A natação é uma modalidade esportiva na qual seus praticantes não dão a merecida importância ao consumo de líquidos, uma vez que o meio aquático confere uma falsa sensação de hidratação e a percepção de não transpirar. Portanto, o propósito deste estudo foi aferir a taxa de sudorese e observar a condição hídrica de atletas de natação, para que assim, uma reposição hídrica apropriada seja indicada afim de evitar a desidratação. Foram avaliados 9 atletas praticantes de natação (15,4 ± 1,72 anos), onde o peso inicial e final dos mesmos foi aferido para determinar a porcentagem de perda de peso (%pp) e a taxa de sudorese. Durante o treino consumiam água à vontade e ao término da sessão os mesmos eram orientados à urinar em um copo graduado e apresentar a amostra, e então tiras reagentes foram utilizadas para avaliar a densidade urinária. Os resultados mostraram uma %pp inferior à 1,5%, não caracterizando desidratação e tampouco queda do desempenho. A média da taxa de sudorese foi 8ml/min e todos obtiveram aumento da densidade urinária em 0,005, indicando sua concentração após o exercício. Alguns estudos que também visaram aferir a taxa de sudorese e a %pp durante a natação, bem como outros esportes, mostraram resultados semelhantes ao presente estudo. Conclui-se que dentre os avaliados não houve resultados significantes para se caracterizar um quadro de desidratação e que novos estudos devem ser realizados afim de investigar o papel dos eletrólitos e dos carboidratos na hidratação. ABSTRACTSwat rate and hydration status on swimmersThe swimming is a sport in which individuals who practice does not attach too much importance to liquid intake, since the aquatic environment provides a false sense of hydration and a perception that there is no sweating. Therefore, the purpose of this study was to measure the rate of sweating and observe the hydration status on swimmers, so that a properly amount of water be recommended, in order to avoid dehydration. Nine swimmers were evaluated, in which the initial and final weight were scaled to set their weight loss percentage afterwards and sweat rate. During the training time was allowed to consume water ad libitum and at the end of the session they were instructed to urinate into a measuring cup and bring the sample, then, reactant strips were used to measure the urine's specific gravity. The results demonstrated weight loss percentage lower than 1,5%, which does not describe a dehydration process, neither a performance decrease. The sweat rate’s average was 8ml/min and an increase of urine's specific gravity at 0,005, signaling their concentration post workout. Some papers that aimed to measure the rate of sweating and weight loss percentage during the exercise reported similar results. It concludes that among the evaluated, there were no significant results for characterizing a dehydration process and further studies are suggested in order to explore the role of electrolytes and carbohydrates on hydration

A VERITAS/Breakthrough Listen Search for Optical Technosignatures

The Breakthrough Listen Initiative is conducting a program using multiple telescopes around the world to search for "technosignatures": artificial transmitters of extraterrestrial origin from beyond our solar system. The VERITAS Collaboration joined this program in 2018, and provides the capability to search for one particular technosignature: optical pulses of a few nanoseconds duration detectable over interstellar distances. We report here on the analysis and results of dedicated VERITAS observations of Breakthrough Listen targets conducted in 2019 and 2020 and of archival VERITAS data collected since 2012. Thirty hours of dedicated observations of 136 targets and 249 archival observations of 140 targets were analyzed and did not reveal any signals consistent with a technosignature. The results are used to place limits on the fraction of stars hosting transmitting civilizations. We also discuss the minimum-pulse sensitivity of our observations and present VERITAS observations of CALIOP: a space-based pulsed laser onboard the CALIPSO satellite. The detection of these pulses with VERITAS, using the analysis techniques developed for our technosignature search, allows a test of our analysis efficiency and serves as an important proof-of-principle.Comment: 15 pages, 7 figure

Busca indireta de matéria escura em galáxias anãs ultra-fracas

The nature of dark matter is still one of the biggest mysteries of modern cosmology. Unveiling its complexion through indirect observations of gamma-rays requires state of the art observatories, such as the Cherenkov Telescope Array (CTA). The Milky Way satellites constitute a promising target for the search of Weakly Interacting Massive Particles (WIMPs) via indirect searches due to their low astrophysical background. However, the overall census of the dark matter galactic substructures is incomplete. This is owing to the sky coverage and sensitivity limitations of sky-survey experiments. Moreover, N-body simulations indicate that a much higher number of satellites should exist. In this work we present a modelling of the galactic sub-clumps based on statistical estimations of the full Milky Way satellite population. We introduce 10 substructure modellings (SMi, i ∈ {1, . . . , 10}) with the following varying parameters: the substructure inner dark matter profile, its mass and radial distribution around the Milky Way, the expected number of satellites given by various studies and the mass-concentration relation. We simulate hundreds of skymaps with the CLUMPY code based on the sub-halo modellings. We show that the mass-concentration parametrization and the predicted number of sub-halos handed over the most substantial effects on the source J-factor. The sources are then used to investigate the detectability of sub-halos with the CTA. We assume two cases: if a dark matter signal is seen by the CTA or if there is no detection. For both we calculate the sensitivity curves of sources resolved in the simulations for the τ+τ- and bb channels. In general, the τ+τ- channel maintained the most constrained sensitivity curves. There was no substantial difference on the sensitivity curve for sources placed on the north and south hemisphere. In the case of detection of a signal with the CTA, no model was effective to access the thermal values of {σv}. In case of no signal observation, only the model with the highest median J-factcor could probe the thermal values of {σv}.A natureza da matéria escura ainda é um dos maiores mistérios da astrofísica moderna. Rev- elar sua compleição através de observações indiretas de raios gama requer observatórios de última geração, como o CTA (Cherenkov Telescope Array). Os satélites da Via Láctea constituem um alvo promissor para a busca de Partículas Massivas que Interagem Fracamente (WIMPs) através de buscas indiretas devido ao seu baixo ruído astrofísico. Entretanto, o censo geral das subestruturas galácticas de matéria escura é incompleto. Isso se deve a incompleta cobertura do céu e às limitações de sensibilidade dos experimentos de busca de objetos extragalácticos. Além disso, as simulações de N-corpos indicam que deveria existir um número muito maior de satélites. Neste trabalho apresentamos uma modelagem dos subgrupos galácticos com base em estimativas estatísticas da população total de satélites da Via Láctea. Introduzimos 10 modelos de subestruturas (SMi, i ∈ {1, . . . , 10}) com os seguintes parâmetros variáveis: o perfil da subestrutura interna de matéria escura, sua massa e distribuição radial em torno da Via Láctea, o número esperado de satélites dado por differentes estudos e a parametrização entre a massa e concentração de subestruturas. Simulamos centenas de mapas do céu com o código CLUMPY baseando-nos em modelos de subestruturas. Mostramos que a parametrização entre massa e concentração e o número previsto de satélites geram os efeitos mais substanciais sobre o fator J da fonte. As subestruturas são então utilizadas para investigar a detectabilidade de sub-halos com a CTA. Supomos dois casos: se um sinal de matéria escura é visto pela CTA ou se não há detecção. Para ambos, calculamos as curvas de sensibilidade das fontes resolvidas nas simulações para os canais de aniquilação τ+τ- e bb. Em geral, o canal de τ+τ- manteve as curvas de sensibilidade mais restritas. Não houve diferença subestancial na curva de sensibilidade das fontes posicionadas nos hemisférios norte e sul. No caso da detecção de um sinal com a CTA, nenhum modelo foi eficaz em acessar os valores térmicos de {σv}. Em caso de não observação do sinal, somente o modelo com a mediana mais alta do fator J poderia sondar os valores térmicos de {σv}

Gamma-ray Follow-up Observations of Dwarf Nova AT2021afpi as a Possible Neutrino Counterpart with the VERITAS Instrument

AT2021afpi was a 10 mag outburst seen by the MASTER-Tavrida autodetection system in temporal coincidence with the astrophysical neutrino candidate IC211125A. The object was observed as an optical bright transient, initially classified as a classical nova. Follow-up observations by the VERITAS instrument at gamma-ray energies > 100 GeV on the nova location resulted in no detection for an exposure of 5.5 hours. Further spectroscopic reports reclassified AT2021afpi as a dwarf nova of the type WZ Sge-Type, which are not expected to be neutrino emitters. A possible blazar detected by Fermi-LAT, 4FGL J0248.0+2232, which lies within the 90% localisation region of IC211125A, was observed in a flaring radio state four days after the neutrino alert. A further combined analysis with 1 hour of exposure time on 4FGL J0248.0+2232 at the position of AT2021afpi still resulted in no detection

Uncertainties in measuring the dark matter signal from Milky Way satellites using Cherenkov telescopes

In this work, we present a modelling of the galactic sub-clumps based on statistical estimations of the full Milky Way satellite population. We introduce 10 substructure modellings (SM$_{i}$, i $\in$ {1, . . . , 10}) with the following varying parameters: a) subhalos inner profile, b) spatial distribution of subhalos, c) mass distribution of subhalos, d) total number of subhalos and e) concentration parameter. The sensitivity curves of CTA for sources in each model are calculated for the $\tau^{+}\tau^{-}$ and $b\bar{b}$ annihilation channels. With both detection of a signal (5$\sigma$) with the CTA and no signal observation, no model was effective in accessing the thermal values of . We analyse the systematic effects introduced by the substructures models.Comment: Prepared for revision submission to JCAP. 15 pages, 5 figure

Taxa de sudorese e condição hídrica em atletas de natação

Swat rate and hydration status on swimmersThe swimming is a sport in which individuals who practice does not attach too much importance to liquid intake, since the aquatic environment provides a false sense of hydration and a perception that there is no sweating. Therefore, the purpose of this study was to measure the rate of sweating and observe the hydration status on swimmers, so that a properly amount of water be recommended, in order to avoid dehydration. Nine swimmers were evaluated, in which the initial and final weight were scaled to set their weight loss percentage afterwards and sweat rate. During the training time was allowed to consume water ad libitum and at the end of the session they were instructed to urinate into a measuring cup and bring the sample, then, reactant strips were used to measure the urine's specific gravity. The results demonstrated weight loss percentage lower than 1,5%, which does not describe a dehydration process, neither a performance decrease. The sweat rate’s average was 8ml/min and an increase of urine's specific gravity at 0,005, signaling their concentration post workout. Some papers that aimed to measure the rate of sweating and weight loss percentage during the exercise reported similar results. It concludes that among the evaluated, there were no significant results for characterizing a dehydration process and further studies are suggested in order to explore the role of electrolytes and carbohydrates on hydration.A natação é uma modalidade esportiva na qual seus praticantes não dão a merecida importância ao consumo de líquidos, uma vez que o meio aquático confere uma falsa sensação de hidratação e a percepção de não transpirar. Portanto, o propósito deste estudo foi aferir a taxa de sudorese e observar a condição hídrica de atletas de natação, para que assim, uma reposição hídrica apropriada seja indicada afim de evitar a desidratação. Foram avaliados 9 atletas praticantes de natação (15,4 ± 1,72 anos), onde o peso inicial e final dos mesmos foi aferido para determinar a porcentagem de perda de peso (%pp) e a taxa de sudorese. Durante o treino consumiam água à vontade e ao término da sessão os mesmos eram orientados à urinar em um copo graduado e apresentar a amostra, e então tiras reagentes foram utilizadas para avaliar a densidade urinária. Os resultados mostraram uma %pp inferior à 1,5%, não caracterizando desidratação e tampouco queda do desempenho. A média da taxa de sudorese foi 8ml/min e todos obtiveram aumento da densidade urinária em 0,005, indicando sua concentração após o exercício. Alguns estudos que também visaram aferir a taxa de sudorese e a %pp durante a natação, bem como outros esportes, mostraram resultados semelhantes ao presente estudo. Conclui-se que dentre os avaliados não houve resultados significantes para se caracterizar um quadro de desidratação e que novos estudos devem ser realizados afim de investigar o papel dos eletrólitos e dos carboidratos na hidratação.