An instrumental puzzle: the modular integration of AOLI

The Adaptive Optics Lucky Imager, AOLI, is an instrument developed to deliver the highest spatial resolution ever obtained in the visible, 20 mas, from ground-based telescopes. In AOLI a new philosophy of instrumental prototyping has been applied, based on the modularization of the subsystems. This modular concept offers maximum flexibility regarding the instrument, telescope or the addition of future developments.Comment: 10 pages, 8 figures, Proc. SPIE 9908, Ground-based and Airborne Instrumentation for Astronomy VI, 99082Z (August 9, 2016

Laboratory and telescope demonstration of the TP3-WFS for the adaptive optics segment of AOLI

AOLI (Adaptive Optics Lucky Imager) is a state-of-art instrument that combines adaptive optics (AO) and lucky imaging (LI) with the objective of obtaining diffraction limited images in visible wavelength at mid- and big-size ground-based telescopes. The key innovation of AOLI is the development and use of the new TP3-WFS (Two Pupil Plane PositionsWavefront Sensor). The TP3-WFS, working in visible band, represents an advance over classical wavefront sensors such as the Shack-Hartmann WFS (SH-WFS) because it can theoretically use fainter natural reference stars, which would ultimately provide better sky coverages to AO instruments using this newer sensor. This paper describes the software, algorithms and procedures that enabled AOLI to become the first astronomical instrument performing real-time adaptive optics corrections in a telescope with this new type of WFS, including the first control-related results at the William Herschel Telescope (WHT)This work was supported by the Spanish Ministry of Economy under the projects AYA2011-29024, ESP2014-56869-C2-2-P, ESP2015-69020-C2-2-R and DPI2015-66458-C2-2-R, by project 15345/PI/10 from the Fundación Séneca, by the Spanish Ministry of Education under the grant FPU12/05573, by project ST/K002368/1 from the Science and Technology Facilities Council and by ERDF funds from the European Commission. The results presented in this paper are based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. Special thanks go to Lara Monteagudo and Marcos Pellejero for their timely contributions

Multiple star systems in the Orion nebula

This is the author accepted manuscript. The final fersion is available from EDP Sciences via the DOI in this record.This work presents an interferometric study of the massive-binary fraction in the Orion Trapezium cluster with the recently comissioned GRAVITY instrument. We observed a total of 16 stars of mainly OB spectral type. We find three previously unknown companions for θ1 Ori B, θ2 Ori B, and θ2 Ori C. We determined a separation for the previously suspected companion of NU Ori. We confirm four companions for θ1 Ori A, θ1 Ori C, θ1 Ori D, and θ2 Ori A, all with substantially improved astrometry and photometric mass estimates. We refined the orbit of the eccentric high-mass binary θ1 Ori C and we are able to derive a new orbit for θ1 Ori D. We find a system mass of 21.7 M⊙ and a period of 53 days. Together with other previously detected companions seen in spectroscopy or direct imaging, eleven of the 16 high-mass stars are multiple systems. We obtain a total number of 22 companions with separations up to 600 AU. The companion fraction of the early B and O stars in our sample is about two, significantly higher than in earlier studies of mostly OB associations. The separation distribution hints toward a bimodality. Such a bimodality has been previously found in A stars, but rarely in OB binaries, which up to this point have been assumed to be mostly compact with a tail of wider companions. We also do not find a substantial population of equal-mass binaries. The observed distribution of mass ratios declines steeply with mass, and like the direct star counts, indicates that our companions follow a standard power law initial mass function. Again, this is in contrast to earlier findings of flat mass ratio distributions in OB associations. We excluded collision as a dominant formation mechanism but find no clear preference for core accretion or competitive accretion.Marie Skłodowska-Curie Grant AgreementFCT-PortugalERC Starting Gran

Diverse Large HIV-1 Non-subtype B Clusters Are Spreading Among Men Who Have Sex With Men in Spain

In Western Europe, the HIV-1 epidemic among men who have sex with men (MSM) is dominated by subtype B. However, recently, other genetic forms have been reported to circulate in this population, as evidenced by their grouping in clusters predominantly comprising European individuals. Here we describe four large HIV-1 non-subtype B clusters spreading among MSM in Spain. Samples were collected in 9 regions. A pol fragment was amplified from plasma RNA or blood-extracted DNA. Phylogenetic analyses were performed via maximum likelihood, including database sequences of the same genetic forms as the identified clusters. Times and locations of the most recent common ancestors (MRCA) of clusters were estimated with a Bayesian method. Five large non-subtype B clusters associated with MSM were identified. The largest one, of F1 subtype, was reported previously. The other four were of CRF02_AG (CRF02_1; n = 115) and subtypes A1 (A1_1; n = 66), F1 (F1_3; n = 36), and C (C_7; n = 17). Most individuals belonging to them had been diagnosed of HIV-1 infection in the last 10 years. Each cluster comprised viruses from 3 to 8 Spanish regions and also comprised or was related to viruses from other countries: CRF02_1 comprised a Japanese subcluster and viruses from 8 other countries from Western Europe, Asia, and South America; A1_1 comprised viruses from Portugal, United Kingom, and United States, and was related to the A1 strain circulating in Greece, Albania and Cyprus; F1_3 was related to viruses from Romania; and C_7 comprised viruses from Portugal and was related to a virus from Mozambique. A subcluster within CRF02_1 was associated with heterosexual transmission. Near full-length genomes of each cluster were of uniform genetic form. Times of MRCAs of CRF02_1, A1_1, F1_3, and C_7 were estimated around 1986, 1989, 2013, and 1983, respectively. MRCA locations for CRF02_1 and A1_1 were uncertain (however initial expansions in Spain in Madrid and Vigo, respectively, were estimated) and were most probable in Bilbao, Spain, for F1_3 and Portugal for C_7. These results show that the HIV-1 epidemic among MSM in Spain is becoming increasingly diverse through the expansion of diverse non-subtype B clusters, comprising or related to viruses circulating in other countries

L'exploration du trou noir super-massif Sgr A* au centre galactic par astrométrie des sursauts

The central parsec is one of the most interesting regions of our Galaxy. It is populated by a nuclear stellar cluster where massive, energetic and young stars coexist with colder evolved stars, hot plasma and streams of interstellar matter. A compact object called SgrA* with a mass of several million solar masses lies in its center becoming the closest supermassive black hole candidate, but being fainter in all wavelengths than other galactic nuclei. One of the closest stars to SgrA*, S2, completes an orbit around it in just 16 years and is bright enough to be used as a robust probe the gravitational potential of the central source by orbit tracking. In the infrared, SgrA* presents a quiescent emission with random short episodes called flares where its brightness sharply increases up to a factor 4, lasting several hours before dimming. The origin of these flares is likely due to the presence of accretion processes in the close environment of the black hole and their study can provide essential information about the exotic nature of SgrA*. Unfortunately, these events are random and require a sufficiently sampled monitoring over time.The GRAVITY instrument, part of the second generation of VLTI, enables the use of optical interferometry to study the Galactic Center. It is able to track the orbit of the star S2 with unprecedented accuracy, up to 10 micro-arcseconds. This thesis work is focused on the data analysis of the first products of the GRAVITY instrument in the Galactic Center.In the first part of the thesis, the astrometry of the star S2 is obtained by the use of the first two years of GRAVITY observations, in which I have actively participated. For that purpose, abinary star model is used to reproduce the interferometric data. Right before and after the pericenter passage, who took place in 2018, I have obtained the positions of S2 with respect to SgrA* reaching an astrometric accuracy of 30 micro-arcseconds, comparable with the expected size of the shadow of the supermassive black hole. In addition, I have obtained a new light curve of SgrA* which complements the data already published and confirms the quiescent-flare scenario. The results obtained are part of a larger study involving orbit fitting where several tests of General Relativity have been successfully performed, as well as interpretations of the flares as a product of accretion processes in the near SgrA* orbit.The second part of the thesis is focused on an evolved star called GCIRS 7, which is also located in the central parsec and serves as a reference for GRAVITY observations. This star, which has a large variability in the infrared, is known to contribute to the interstellar medium of the Galactic Center. By complementing GRAVITY archival data from 2017 with observations I have taken in 2019, I have implemented an atmosphere model, widely used for the study of other advanced stars, to explain the visibility curves of GCIRS 7 obtained by GRAVITY. The model consists of a photosphere and a thin molecular shell. The results show that the data can be interpreted as a photosphere with the same diameter for both epochs, but with a shell being colder and larger in 2019 compared to 2017. An estimation of the density of the thin shell reveals a saturation of the model for 2017 due to a high density, but 2019 data is partially reproduced. The results can be explained by a layer expansion and cooling likely due to an episode of mass loss.Le parsec central est l'une des régions les plus intéressantes de notre Galaxie. Il est peuplé d'un amas stellaire nucléaire où coexistent des étoiles massives, énergétiques et jeunes, des étoiles évoluées plus froides, du plasma chaud et des flux de matière interstellaire. Un objet compact appelé SgrA*, d'une masse de plusieurs millions de masses solaires, se trouve en son centre, devenant ainsi le plus proche candidat au trou noir supermassif, mais étant plus faible dans toutes les longueurs d'onde que les autres noyaux galactiques. L'une des étoiles les plus proches de SgrA*, S2, effectue une orbite autour d'elle en 16 ans seulement et est suffisamment brillante pour être utilisée comme une sonde robuste du potentiel gravitationnel de la source centrale par suivi d'orbite. Dans l'infrarouge, SgrA* présente une émission quiescente avec de courts épisodes aléatoires appelés sursauts où sa luminosité augmente fortement jusqu'à un facteur 4, durant plusieurs heures avant de s'affaiblir. L'origine de ces éruptions est probablement due à la présence de processus d'accrétion dans l'environnement proche du trou noir et leur étude peut fournir des informations essentielles sur la nature exotique de SgrA*. Malheureusement, ces événements sont aléatoires et nécessitent un suivi suffisamment échantillonné dans le temps. L'instrument GRAVITY, qui fait partie de la deuxième génération de VLTI, permet d'utiliser l'interférométrie optique pour étudier le Centre Galactique. Il est capable de suivre l'orbite de l'étoile S2 avec une précision sans précédent, jusqu'à 10 microsecondes d'arc. Ce travail de thèse est axé sur l'analyse des données des premiers produits de l'instrument GRAVITY au Centre Galactique.Dans la première partie de la thèse, l'astrométrie de l'étoile S2 est obtenue par l'utilisation des deux premières années d'observations de la GRAVITY, auxquelles j'ai participé activement. Pour cela, un modèle d’étoile binaire est utilisé pour reproduire les données interférométriques. Juste avant et après le passage du péricentre, qui a eu lieu en 2018, j'ai obtenu les positions de S2 par rapport à SgrA* atteignant une précision astrométrique de 30 microsecondes d’arc, comparable à la taille attendue de l'ombre du trou noir supermassif. En outre, j'ai obtenu une nouvelle courbe de lumière de SgrA* qui complète les données déjà publiées et confirme le comportement quiescent avec des sursauts. Les résultats obtenus font partie d'une étude plus large impliquant l'ajustement de l'orbite où plusieurs tests de relativité générale ont été effectués avec succès, ainsi que des interprétations des sursauts comme produit des processus d’accrétion dans l’orbite proche de SgrA*.La deuxième partie de la thèse est centrée sur une étoile évoluée appelée GCIRS 7, qui est également située dans le parsec central et qui sert de référence pour les observations de GRAVITY. Cette étoile, qui présente une grande variabilité dans l’infrarouge (1 magnitude), est connue pour contribuer au milieu interstellaire du Centre Galactique. En complétant les données d'archives de GRAVITY de 2017 par des observations que j'ai effectuées en 2019, j'ai mis en place un modèle d'atmosphère, largement utilisé pour l'étude d'autres étoiles évoluées, afin d'expliquer les courbes de visibilité de GCIRS 7 obtenues par GRAVITY. Le modèle s'agit d'une photosphère et d'une fine couche moléculaire. Les résultats montrent que les données peuvent être interprétées comme une photosphère avec le même diamètre pour les deux époques, mais la couche étant plus froide et plus grande en 2019 par rapport à 2017. Une estimation de la densité de la couche révèle une saturation du modèle pour 2017 en raison d'une densité élevée, mais les données de 2019 sont partiellement reproduites. Les résultats peuvent être expliqués par une expansion et un refroidissement de la couche probablement dus à un épisode de perte de masse