Performance study update of observations in divergent mode for the Cherenkov Telescope Array

Due to the limited field of view (FoV) of Cherenkov telescopes, the time needed to achieve target sensitivity for surveys of the extragalactic and Galactic sky is large. To optimize the time spent to perform such surveys, a so-called "divergent mode" of the Cherenkov Telescope Array Observatory (CTAO) was proposed as an alternative observation strategy to the traditional parallel pointing. In the divergent mode, each telescope points to a position in the sky that is slightly offset, in the outward direction, from the original center of the field of view. This bring the advantage of increasing the total instantaneous arrays' FoV. From an enlarged field of view also benefits the search for very-high-energy transient sources, making it possible to cover large sky regions in follow-up observations, or to quickly cover the probability sky map in case of Gamma Ray Bursts (GRB), Gravitational Waves (GW), and other transient events. In this contribution, we present the proposed implementation of the divergent pointing mode and its first preliminary performance estimation for the southern CTAO array.Comment: Presented at the 38th International Cosmic Ray Conference (ICRC 2023), 2023 (arXiv:2309.08219

Lung Retransplantation with Positive Crossmatch in Primary Lung Transplantation Complicated by Antibody-Mediated Rejection

La hipertensión arterial pulmonar (HAP) representa el 2,6% de los trasplantes pulmonares (TP), con una mediana de supervivencia condicional(desde los 30 días del TP) de 9,8 años. Son frecuentes, el rechazo celular agudo (ACR) y la disfunción crónica del injerto (CLAD),mientras que es infrecuente el rechazo mediado por anticuerpos (AMR). El retrasplante pulmonar (RTP) constituye el 4% del TP mundial,debido a complicaciones en la vía aérea, disfunción primaria del injerto, ACR y CLAD. Mujer de 22 años, portadora de HAP idiopática(HAPI) desde el año 2013, trasplantada bipulmonar (TBP) en enero de 2018. A los 16 meses presentó neumonía adquirida en la comunidad.En una internación posterior, presentó ACR y a pesar de pulsos de metilprednisolona, progresó a requerimientos de cánula de altoflujo y ventilación mecánica no invasiva hospitalaria, caída del VEF1, y tomografía de tórax con vidrio esmerilado difuso y engrosamientoirregular reticular del intersticio subpleural; interpretándose como CLAD a predominio de síndrome de bronquiolitis obliterante (BOS),con presencia de anticuerpos específicos contra el donante (DSA). En enero de 2020 se realizó nuevo TP y ante cross-match positivo, serealizó plasmaféresis y reposición de IgG. Al mes del egreso, no se observaron signos de rechazo en control de biopsias transbronquiales.Entre 2 y 10% de los pacientes con indicación primaria de TP por HAPI son sometidos a retrasplante pulmonar (RTP). La presencia deDSA y el miss-match de HLA, no son contraindicaciones para el RTP.Pulmonary arterial hypertension (PAH) represents 2.6% of lung transplantations (LT), with a conditional median survival (from 30 days after LT) of 9.8 years. Acute cellular rejection (ACR) and chronic lung allograft dysfunction (CLAD) are common; whereas the antibody-mediated rejection (AMR) is not. Lung retransplantation (LR) accounts for 4% of global LTs for complications in the airways, primary allograft dysfunction, ACR and CLAD. 22-year-old woman with idiopathic PAH (IPAH) since 2013, who underwent a double-lung transplantation (DLT) in January 2018. 16 months after transplantation she presented community-acquired pneumonia. During a subsequent hospitalization, she presented ACR. Despite the fact that she received pulse methylprednisolone, she required high-flow cannula therapy and hospital non-invasive mechanical ventilation; the FEV1 was reduced and she underwent a chest tomography with diffuse ground glass opacities and irregular reticular thickening of the subpleural interstitium; interpreting the predominance of BOS (bronchiolitis obliterans syndrome) as CLAD, with presence of donor-specific antibodies (DSA). In January 2020, she received a new DLT and due to a positive crossmatch, she was treated with plasmapheresis and IgG replacement. One month after hospital discharge, no signs of rejection were observed at the BTB (bone-patellar tendon-bone) control. Between 2 to 10% of patients with primary indication of LT for IPAH are subjected to lung retransplantation (LR). The presence of DSA and HLA (human leucocyte antigen) mismatch aren’t contraindications to LR.Fil: Calderón Soriano, Juan C.. Fundación Favaloro; ArgentinaFil: Nazzo, María V.,. Fundación Favaloro; ArgentinaFil: Pérez Páez, Martha I.. Fundación Favaloro; ArgentinaFil: Virhuez, Yblin. Fundación Favaloro; ArgentinaFil: Balcazar, Jonathan. Fundación Favaloro; ArgentinaFil: Vicente, Luis. Fundación Favaloro; ArgentinaFil: Ahumada, Rosalía. Fundación Favaloro; ArgentinaFil: Osses, Juan M.. Fundación Favaloro; ArgentinaFil: Vigliano, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Medicina Traslacional, Trasplante y Bioingeniería. Fundación Favaloro. Instituto de Medicina Traslacional, Trasplante y Bioingeniería; ArgentinaFil: Bertolotti, Alejandro Mario. Fundación Favaloro; ArgentinaFil: Caneva, Jorge O.. Fundación Favaloro; Argentin

Multiwavelength study of the galactic PeVatron candidate LHAASO J2108+5157

Context. Several new ultrahigh-energy (UHE) γ-ray sources have recently been discovered by the Large High Altitude Air Shower Observatory (LHAASO) collaboration. These represent a step forward in the search for the so-called Galactic PeVatrons, the enigmatic sources of the Galactic cosmic rays up to PeV energies. However, it has been shown that multi-TeV γ-ray emission does not necessarily prove the existence of a hadronic accelerator in the source; indeed this emission could also be explained as inverse Compton scattering from electrons in a radiation-dominated environment. A clear distinction between the two major emission mechanisms would only be made possible by taking into account multi-wavelength data and detailed morphology of the source. Aims. We aim to understand the nature of the unidentified source LHAASO J2108+5157, which is one of the few known UHE sources with no very high-energy (VHE) counterpart. Methods. We observed LHAASO J2108+5157 in the X-ray band with XMM-Newton in 2021 for a total of 3.8 hours and at TeV energies with the Large-Sized Telescope prototype (LST-1), yielding 49 hours of good-quality data. In addition, we analyzed 12 years of Fermi-LAT data, to better constrain emission of its high-energy (HE) counterpart 4FGL J2108.0+5155. We used naima and jetset software packages to examine the leptonic and hadronic scenario of the multi-wavelength emission of the source. Results. We found an excess (3.7σ) in the LST-1 data at energies E > 3 TeV. Further analysis of the whole LST-1 energy range, assuming a point-like source, resulted in a hint (2.2σ) of hard emission, which can be described with a single power law with a photon index of Σ = 1.6 ± 0.2 the range of 0.3 - 100 TeV. We did not find any significant extended emission that could be related to a supernova remnant (SNR) or pulsar wind nebula (PWN) in the XMM-Newton data, which puts strong constraints on possible synchrotron emission of relativistic electrons. We revealed a new potential hard source in Fermi-LAT data with a significance of 4σ and a photon index of Σ = 1.9 ± 0.2, which is not spatially correlated with LHAASO J2108+5157, but including it in the source model we were able to improve spectral representation of the HE counterpart 4FGL J2108.0+5155. Conclusions. The LST-1 and LHAASO observations can be explained as inverse Compton-dominated leptonic emission of relativistic electrons with a cutoff energy of 100-30+70 TeV. The low magnetic field in the source imposed by the X-ray upper limits on synchrotron emission is compatible with a hypothesis of a PWN or a TeV halo. Furthermore, the spectral properties of the HE counterpart are consistent with a Geminga-like pulsar, which would be able to power the VHE-UHE emission. Nevertheless, the lack of a pulsar in the neighborhood of the UHE source is a challenge to the PWN/TeV-halo scenario. The UHE γ rays can also be explained as π0 decay-dominated hadronic emission due to interaction of relativistic protons with one of the two known molecular clouds in the direction of the source. Indeed, the hard spectrum in the LST-1 band is compatible with protons escaping a shock around a middle-aged SNR because of their high low-energy cut-off, but the origin of the HE γ-ray emission remains an open question

Observations of the Crab Nebula and Pulsar with the Large-Sized Telescope Prototype of the Cherenkov Telescope Array

CTA (Cherenkov Telescope Array) is the next generation ground-based observatory for gamma-ray astronomy at very-high energies. The Large-Sized Telescope prototype (\LST{}) is located at the Northern site of CTA, on the Canary Island of La Palma. LSTs are designed to provide optimal performance in the lowest part of the energy range covered by CTA, down to $\simeq 20$ GeV. \LST{} started performing astronomical observations in November 2019, during its commissioning phase, and it has been taking data since then. We present the first \LST{} observations of the Crab Nebula, the standard candle of very-high energy gamma-ray astronomy, and use them, together with simulations, to assess the basic performance parameters of the telescope. The data sample consists of around 36 hours of observations at low zenith angles collected between November 2020 and March 2022. \LST{} has reached the expected performance during its commissioning period - only a minor adjustment of the preexisting simulations was needed to match the telescope behavior. The energy threshold at trigger level is estimated to be around 20 GeV, rising to $\simeq 30$ GeV after data analysis. Performance parameters depend strongly on energy, and on the strength of the gamma-ray selection cuts in the analysis: angular resolution ranges from 0.12 to 0.40 degrees, and energy resolution from 15 to 50\%. Flux sensitivity is around 1.1\% of the Crab Nebula flux above 250 GeV for a 50-h observation (12\% for 30 minutes). The spectral energy distribution (in the 0.03 - 30 TeV range) and the light curve obtained for the Crab Nebula agree with previous measurements, considering statistical and systematic uncertainties. A clear periodic signal is also detected from the pulsar at the center of the Nebula.Comment: Submitted to Ap