CTA Observatory

Abstract In this article, we present the study for the reclassification of the variability of the star CzeV961 by SSV-UAI-GRAV, classified by Variable Star Index as an EW eclipsing binary. In the same field of observation, there were two variable stars already discovered by Gaia but of an undefined type. In examining the comparison stars for our study, we then discovered a new variable star that had not yet been classified. The star CzeV961 turned out to be a Gamma Doradus variable star, like the two Gaia stars, while the newly discovered variable turned out to be an RS Canum Venaticorum type star.

The Barcelona Raman LIDAR (BRL) will provide continuous monitoring of the aerosol extinction profile along the line of sight of the Cherenkov Telescope Array Observatory (CTAO). It will be located at its Northern site (CTAO-N) on the Observatorio del Roque de Los Muchachos. This article presents the performance of the pathfinder Barcelona Raman LIDAR (pBRL), a prototype instrument for the final BRL. Power budget simulations were carried out for the pBRL operating under various conditions, including clear nights, moon conditions, and dust intrusions. The LIDAR PreProcessing (LPP) software suite is presented, which includes several new statistical methods for background subtraction, signal gluing, ground layer and cloud detection and inversion, based on two elastic and one Raman lines. Preliminary test campaigns were conducted, first close to Barcelona and later at CTAO-N, albeit during moonlit nights only. The pBRL, under these non-optimal conditions, achieves maximum ranges up to about 35 km, range resolution of about 50 m for strongly absorbing dust layers, and 500 m for optically thin clouds with the Raman channel only, leading to similar resolutions for the LIDAR ratios and Ångström exponents. Given the reasonable agreement between the extinction coefficients obtained from the Raman and elastic lines independently, an accuracy of aerosol optical depth retrieval in the order of 0.05 can be assumed with the current setup. The results show that the pBRL can provide valuable scientific results on aerosol characteristics and structure, although not all performance requirements could be validated under the conditions found at the two test sites. Several moderate hardware improvements are planned for its final upgraded version, such as gated PMTs for the elastic channels and a reduced-power laser with a higher repetition rate, to ensure that the data acquisition system is not saturated and therefore not affected by residual ringing.

We report on results from the laboratory wide-field phasing testbed that has been constructed to validate the active optics and piston sensing hardware and algorithms to be used on the Giant Magellan Telescope. The GMT is comprised of seven primary (M1) mirror segments, and seven secondary (M2) segments. To maintain a high quality wavefront across the full LTAO field-of-view, telescope aberrations must be controlled at M1 and M2 independently. This will be done on GMT using the 4 off-axis wavefront sensors of the Acquisition, Guiding and Wavefront-sensing System (AGWS). With the double segmented nature of the GMT, the most challenging aberration to control is field-dependent piston, which results from tilts of M1 segments that are compensated by tilts of the corresponding M2 segment. We report here on wavefront sensing experiments conducted with a full-scale prototype AGWS wavefront sensor fed by a GMT optical simulator called the Wide-Field Phasing Testbed (WFPT). With the WFPT we introduce aberrations on M1 and M2, including simulated atmospheric turbulence and a variety of guide-star magnitudes. The AGWS measures the resulting off-axis aberrations, and then corrects the M1 and M2 aberrations. We describe the wavefront reconstructors used to generate the corrections and the performance over a range of conditions.

This proceeding discusses the significance and impact of social media in the field of physics. It explores how platforms such as Facebook, Twitter, and LinkedIn can be used effectively for promoting research interests, simplifying complex concepts, and fostering international collaboration. The proceeding also presents insights from my personal experience as a Social Media Specialist Secondee at the Cherenkov Telescope Array Observatory (CTAO). It highlights successful initiatives like the "Physicists On-Call" program and diversity series at the CTAO, demonstrating the potential of social media in enhancing research visibility, promoting diversity and inclusion, and building an international physics community. The proceeding concludes that the evolution of physics requires physicists to adapt to new communication methods, and embracing social media can lead to new discoveries, collaborations, and a more diverse and inclusive physics community.

ABSTRACT Star-forming regions have been proposed as potential Galactic cosmic ray accelerators for decades. Cosmic ray acceleration can be probed through observations of gamma-rays produced in inelastic proton–proton collisions at GeV and TeV energies. In this paper, we analyse more than 11 yr of Fermi–LAT data from the direction of Westerlund 2, one of the most massive and best-studied star-forming regions in our Galaxy. In particular, we investigate the characteristics of the bright pulsar PSR J1023–5746 that dominates the gamma-ray emission below a few GeV at the position of Westerlund 2 and the underlying extended source FGES J1023.3–5747. The analysis results in a clear identification of FGES J1023.3–5747 as the GeV counterpart of the TeV source HESS J1023-575, through its morphological and spectral properties. This identification provides new clues about the origin of the HESS J1023-575 gamma-ray emission, favouring a hadronic origin of the emission, powered by Westerlund 2, rather than a leptonic origin related to either the pulsar wind nebula associated with PSR J1023–5746 or the cluster itself. This result indirectly supports the hypothesis that star-forming regions can contribute to the cosmic ray sea observed in our Galaxy.

The Cherenkov Telescope Array (CTA), the new-generation ground-based observatory for γ astronomy, provides unique capabilities to address significant open questions in astrophysics, cosmology, and fundamental physics. We study some of the salient areas of γ cosmology that can be explored as part of the Key Science Projects of CTA, through simulated observations of active galactic nuclei (AGN) and of their relativistic jets. Observations of AGN with CTA will enable a measurement of γ absorption on the extragalactic background light with a statistical uncertainty below 15% up to a redshift z=2 and to constrain or detect γ halos up to intergalactic-magnetic-field strengths of at least 0.3 pG . Extragalactic observations with CTA also show promising potential to probe physics beyond the Standard Model. The best limits on Lorentz invariance violation from γ astronomy will be improved by a factor of at least two to three. CTA will also probe the parameter space in which axion-like particles could constitute a significant fraction, if not all, of dark matter. We conclude on the synergies between CTA and other upcoming facilities that will foster the growth of γ cosmology.

Mechanics of the camera for the large size telescopes of CTA must protect and provide a stable environment for its instrumentation. This is achieved by a stiff support structure enclosed in an air and water tight volume. The structure is specially devised to facilitate extracting the power dissipated by the focal plane electronics while keeping its weight small enough to guarantee an optimum load on the telescope structure. A heat extraction system is designed to keep the electronics temperature within its optimal operation range, stable in time and homogeneous along the camera volume, whereas it is decoupled from the temperature in the telescope environment. In this contribution, we present the details of this system as well as its verification based in finite element analysis computations and tested prototypes. Finally, issues related to the integration of the camera mechanics and electronics will be dealt with.

The mass of RR Lyrae variables has been a controversial problem for about a decade: while the stellar evolution theory predicts masses ranging between 0.65 and 0.75 M⊙ for Oosterhoff type I and II clusters respectively, the stellar pulsation theory predicts smaller masses (0.55 and 0.65 respectively) using the double-mode pulsators. Simon (1990, M.N.R.A.S. 246, 70), comparing hydrodynamical models with observed stars by means of Fourier parameters, has found relations between the stellar mass and its luminosity, pulsation period, Helium content and Fourier parameter ϕ31. Combining his equations we obtain:(1)from which one can estimate the stellar mass by using the observable quantities P and ϕ31 and a luminosity scale, e.g. the one derived by Cacciari, Clementini and Fernley (1992, Astrophys. J. in press).