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Posters
Alan Maciel
The dual null formalism describes the space-time through the evolution of optical scalars associated with two linearly independent families of null curves that are orthogonal to a given family of surfaces. It has been widely used in the study of black hole dynamics, as it conveys a local definition for the black hole horizon. We discuss applications of the dual null formalism beyond the black hole physics, in particular how in this framework the Birkhoff theorem emerges for space-times with two-dimensional spherical, planar or hyperbolic symmetry.

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Alexandre Cabral
MOONS will be the next Multi-Object Optical and Near-infrared Spectrograph for the Very Large Telescope, able to simultaneously observe 1000 targets, feeding a bunch of optical fibres which can be placed at user-specified locations on the Nasmyth focal plane using individual robotic positioners. The sub-fields thus selected are then driven by the fibres into two identical cryogenic spectrographs mounted on the Nasmyth platform of one of the ESO VLT 8 m telescopes. The instrument will provide both medium and high-resolution spectral coverage across the wavelength range of 0.65 μm to 1.8 μm. Such a facility will allow a veritable host of Galactic, Extragalactic and Cosmological questions to be addressed. In this talk we will report on the current status of the instrument, details of the early testing of key components and the major milestones towards its delivery to the telescope, describing the Portuguese contribution.

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André Moitinho
Gaia, with its astrometric data of unprecedentes quality is widely considered a transformative endeavour in Astronomy. The huge data volume delivered in the Gaia data releases is also transforming the way data exploration is done. With almost 1.7 billion sources as of Data Release 2, the information content of the Gaia Archive is unimaginable. In this poster we present the Gaia Archive Visualisation Service (GAVS). GAVS is both a platform for interactive visual exploration of the Gaia data; and a provider of intelligible visual representations of the enourmous information content of the archive. Examples of these representations are the all sky density and flux maps which became the iconic images of the Gaia Data releases. Technical details are given, lessons learned and open challenges for Gaia and future missions are discussed.

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André Moitinho
Gaia, with its astrometric data of unprecedentes quality is widely considered a transformative endeavour in Astronomy. The huge data volume delivered in the Gaia data releases is also transforming the way data exploration is done. With almost 1.7 billion sources as of Data Release 2, the information content of the Gaia Archive is unimaginable. In this poster we present the Gaia Archive Visualisation Service (GAVS). GAVS is both a platform for interactive visual exploration of the Gaia data; and a provider of intelligible visual representations of the enourmous information content of the archive. Examples of these representations are the all sky density and flux maps which became the iconic images of the Gaia Data releases. Technical details are given, lessons learned and open challenges for Gaia and future missions are discussed.

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Beatriz Pereira
Polarimetric studies of astronomical sources might be affected by background sky polarization. For this reason, we formalize how to simulate and analyze the polarization pattern models of the sky with the aim to calibrate and improve polarimetric observations. Using the Rayleigh sky model as a starting point, we develop simulations of the polarization patterns induced by the sun and moon's light. Subsequently, we aim to develop and analyze more complex and realistic models, considering the effects of multiple scattering on the polarization.

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Beatriz Gamboa Pereira
The redshift drift of objects following the Hubble flow provides us with a unique (but still unfulfilled) opportunity to watch the universe expand in real time, and in a model-independent way. The first practical proposal for this measurement emerged in the context of the ELT (the so-called Sandage-Loeb test), but in recent years redshift drift measurements with other facilities have also been proposed. In this contribution we provide a comparative analysis of the constraining power of these measurements for various cosmological scenarios. Our analysis includes the latest techniques and facilities proposed in the Astro 2020 white papers call.

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Bernardo Dias
The time evolution of topological defects formed by symmetry breaking phase transitions in the early Universe depends, among others, on the evolution of the Hubble parameter. We use our recently developed GPU-based field theory code to simulate the evolution of domain walls in contracting Universes, demonstrating their asymmetric evolution in this case. Using the same results, we also verify the predictions of earlier works using analytic models that capture the key properties of topological defect networks, showing an agreement between the two approaches.

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Catarina Marques
We consider spatially homogeneous and isotropic models with torsion, and test them against low-redshift astrophysical observations. We obtain constraints on the allowed amount of torsion (finding that it can only contribute a small fraction of the universe's energy density) and also discuss degeneracies between torsion and other relevant cosmological parameters. Finally, we present forecasts of the improved constraints to be expected from the next generation of observational facilities.

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Ciro Pappalardo
Since 2014, the Institute of Astronomy and Space Sciences of Lisbon has seen its capabilities for ALMA research internationally recognized, being named by ESO as an ALMA Centre of Expertise. This is a result of an objective effort over the last few years to increase the national capability in the exploration of this revolutionary observatory. The Portuguese ALMA Centre of Expertise (PACE) provided along these years face-to-face support to the Portuguese community regarding all stages of ALMA observations: pre-Cycle ALMA promotion, proposal preparation and submission, data reduction and archival research. PACE is also already actively supporting the ALMA project by participating in the task of ALMA data validation and quality assurance. Centres of Expertise are aimed at developing key expertise while supporting their local (national) user community in the use of ALMA. While top-level responsibilities are still reserved to the central ARC node (such as the distribution of calls for proposals or managing the time allocation procedures), others are distributed among the Nodes and Centers of Expertise improving the efficiency of user support (e.g., the speed of data delivery to the PI). The latter include: (i) face-to-face interaction with the community to directly support proposal preparation, data reduction, or archival research; (ii) phase II proposal scheduling and execution; (iii) community preparation via meetings and visits to institutes; (iv) outreach. In this talk I will present the PACE core team, I will describe the computational capabilities provided to the community for computationally expensive data reduction tasks, and finally I will show how PACE has grown in the last years an ALMA user community and has become, in a very short timescale, proficient in the use of a new and revolutionary instrument. PACE will continue the promote ALMA and increase its use by the national community, and as a support facility, welcomes visitors at the Astronomical Observatory of Lisbon, where it is located, and where the community will find dedicated personnel and computer hardware.

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Daniela Cortes Espadinha
General circulation models for planetary atmospheres are a standout amongst the most significant bases and tools of atmosphere dynamics in planetary sciences. Such models are regularly the result of the analysis of great amounts of observations so they can be sufficiently accurate to properly describe and portray circulation on our target planets. There is additionally the possibility of application of these models to other celestial bodies outside of our solar system. Fundamental to this understanding of planetary atmospheres, the cloud-tracking is without doubt a key component. This method makes use of image sequences of the atmosphere of a certain planet to infer and quantify wind characteristics simply by analysing the features shown in these sets of images and knowing the moment they were gathered. One of these characteristics that can be measure is, for example, wind velocity. This method yields significant results that can be crucial for better understanding the cloud circulation on Venus and, consequently, one of its most fascinating and entrancing characteristics: the superrotation of its atmosphere. This work objectives include using Akatsuki’s Ultraviolet Imager (UVI) data to study wind dynamics and velocities on Venus in ultraviolet filters (283nm in this case). Several wind velocity profiles are retrieved using a cutting-edge method of manual cloud tracking in addition to a specifically designed software so that the variability of the winds can be analyzed both spatially and temporally at this cloud level.

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Diogo Silva
Oppenheimer and Snyder in 1939 studied the total collapse of dust matter, by matching an interior Friedman universe to an exterior Schwarzschild solution and, through the understanding of the trajectories of light rays from the center outwards, discovered black holes. The paper was published in Physical Review and nowadays it is considered one of the most important papers in physics and astrophysics. Here, we replace their interior Friedman universe by a thin shell with Minkowski spacetime inside, and make a match too to the exterior Schwarzschild solution. We perform the analysis of outward light rays and unveil in simple terms the formation of a black hole and the causal structure of the spacetime. We trace the event horizon trajectory, the apparent horizon evolution, and the formation of the singularity. We do the analysis in two different coordinate systems, first in Schwarzschild type coordinates for the interior and exterior, and second in comoving coordinates for the interior and Kruskal coordinates for the exterior. In this way we pay homage to Oppenheimer and Snyder work and celebrate 80 years of black holes.

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Francisco Luquet Brasil Atmospheric gravity waves: with Venus GCM simulations and Venus express VMC data
Expandable Content

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Hermano Cardoso de Menezes Valido
Planet encircling dust storms on Mars are somewhat rare events that are not well constrained. The precise feedback mechanisms that allows some storms to evolve to a global scale and that eventually cuts them off along with the interannual variability of the occurrence of these storms are poorly understood (Zurek, R., 1993). Measuring wind speeds during such events is detrimental to the better comprehension of the mechanisms at play. Using ESO's VLT/UVES we were able to successfully observe the 2018 Mars global dust storm (during the month of June), and by adapting the Doppler velocimetry wind retrieval technique successfully used on Venus (Machado, P. et al., 2012), we have been able to use those high resolution observations of mars to derive Doppler shifts and as a result obtain preliminary results. This method should allow us to simultaneously characterize spatial and temporal variations of the zonal winds. Through coordinated observations with ESA's Mars Express space probe (OMEGA) we intend to constrain the altitude of our observations to somewhere in the middle atmosphere The end result we aim to obtain is a latitudinal wind profile of the middle atmosphere of Mars during the development of a global dust storm and velocity field maps that allow us to constraint the wind spatial coverage during these events.

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Jarle Brinchmann
I will show first results of a 11'x11' MUSE mosaic of the Trifid nebula (M20). This is the largest IFU mosaic made thus far and provides a panoramic view of this iconic star forming region.

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Jarle Brinchmann
The advent of ALMA has shown us that many proto-planetary disks have gaps and asymmetries. It is thought that these gaps may be caused by newly forming protoplanets but direct evidence has been missing. Here we present the first ever direct imaging observation of a multiple proto-planetary system. We use the narrow-field mode on the MUSE integral field unit to show that the star PDS 70 has two accreting proto-planets as shown by their Ha emission. The two planets appear to be in a 2-1 resonance which might explain the cavity observed in the disk around PDS 70. We also show that MUSE is an order of magnitude more efficient at this than SPHERE or MagAO and this is opening up an exciting future path for observations of forming exo-planets.

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José Luís Fernandes Ribeiro
With the end of the Cassini-Huygens mission, the only way to obtain information about the chemical and physical properties of the atmosphere of Titan is through ground base observations. Through high-resolution spectroscopy one can probe the atmosphere of the moon at different optical depths based on the wavelength, get its chemical signatures, construct the temperature and pressure profile and constrain its physical properties. The IA's High-Resolution Spectroscopy pipeline is able to produce these high -resolution spectra and measure winds through the Doppler velocimetry method with high quality results, by calculating the wavelength Doppler shift, due to the winds, between the spectrum corresponding to the central pixel and the spectra from the remaining pixels the target occupies in along the slit. This work is the learning and adaptation of the pipeline to the case of Titan using the dedicated VLT-UVES observations with the blue arm in collaboration with the University of Bordeux, the use of the HITRAN and ExoMol databases for the retrieval of relevant chemical species expected to be found in Titan's atmosphere within the UVES blue arm wavelength range and the learning and use of the NEMESIS Radiative Transfer model in order to obtain the temperature and pressure profiles and constrain the altitude level.

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José Manuel Dias Escada
The identification of the state of polarization of X-rays is a very useful tool in the investigation of the physics and geometry of astrophysical compact sources (active galactic nuclei, neutron stars, supermassive black holes, etc), as it add two new parameters – polarization degree and polarization direction – to the three normally considered – time, energy and position. The mission/observatory IXPE/NASA (Imaging X-ray Polarimetry Explorer) will investigate the polarimetry of X-rays in the 2-8 keV range. The polarimeter to be used in this mission is based on the preferential alignment of the direction of emission of photoelectrons with that of the polarization of incident X-rays. The polarimeter’s main element is a gas multipixel detector, in which the gas filling is the key factor for the polarimetric sensitivity, which is expressed by the intrinsic modulation factor (for 100% polarized X-rays) of the direction of emission of the photoelectrons. The ratio between the modulation measured and the intrinsic value provides the degree of polarization of the incident radiation. The purpose of this work is to study the polarimetric potential of a few gaseous media, calculating by Monte Carlo simulation the intrinsic modulation factors in those media: noble gas based mixtures (preferentially with low atomic number noble gas) with a molecular gas (CH4, CF4, CO2, iso-C4H10 e DME). A Monte Carlo simulation model has been developed which considers angular differential diffusion in photoionization of the gas medium which includes dipolar () first order terms and non dipolar ( e ), which are X-ray energy and photoionized subshell dependent. The primary electron cloud formation is reproduced considering the cascade decay process of the ions produced (envolving Auger, shakeoff electron emission as well as fluorescence photon). When, along their drift under the weak electric field, electrons reach subionization energies, their position is assessed and the azimuthal distribution of the cloud is calculated. From this distribution, the modulation factor is determined. We present preliminar results for incident X-ray energies in the 2-15 keV range in noble gas mixtures (Xe, Ar, Ne, He) with CH4.

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José Ricardo Correia
Topological defects are a consequence of early Universe phase transitions, formed by means of the Kibble mechanism. A particular type of defect known as a cosmic string is not only a generic consequence of many GUT theories but also benign (ie. not expected to over-close the Universe). The observational imprints of a network of defects critically depend on many details governing energy losses and overall evolution of the network. One particular way to infer (indirectly) the relative importance of different energy loss mechanisms (loop production, radiation emission, etc.) and the velocity dependence of such mechanisms is to compare a large number of simulations at varying expansion rates with the canonical semi-analytical model for string evolution (Velocity dependent One-Scale model). Here we present the most recent calibration using 1032 field theory high resolution simulations of cosmic strings, and present some properties of the network inferred from the calibration itself.

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José Saraiva
Stories of Tomorrow was an EU-funded project that ran its course between 2017 and 2019 in schools form various European countries, including Portugal. Students in the 5th grade (aged 10-12) were asked to create stories about a journey to Mars and to present them in the shape of an e-book, enriched by images, sounds, and other means of expression. The project made use of some methodologies still unusual in Portuguese schools, and was carried out on a dedicated computer platform. The students received help on space and Mars-related issues, through several activities and hands-on experiments. The main objective of the project was to figure out if an endeavour of this type would influence the interest of young students in science. Though facing some difficulties in its implementation, the project met with much enthusiasm from its subjects, and is seen by those involved at the teaching level as an excellent example of a new way to approach the educational process.

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Karolina Kubiak
The Orion Belt population (OBP, Kubiak et al. 2017) is a newly described young, rich, and massive population in the vicinity of the epsilon Ori supergiant. It has been defined based on the multi-dimensional analysis of colour-magnitude diagrams. Gaia DR2 data revealed significant contamination of our initial sample from foreground stars. The spatial distribution of stars is quite clumpy, with some evidence of mixing populations. There is also some evidence for different spatial motions of stars from different subgroups. In this contribution, I present an atlas and analysis of the spectral energy distributions (SED) of all candidate sources from the OBP.To analyse the nature of the sources, we constructed SEDs for all sources in the selected field using available archival data over a broad spectral range. We looked for signs of strong variability at both optical and infrared wavelengths among the members of the OBP. For a better understanding of the properties of the OBP we decided to use SED modelling to obtain some properties of the sources.

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Maria Prat Colomer
We use recent astrophysical and local tests of the stability of the fine-structure constant, α, to constrain a particular phenomenological but physically motivated class of models in which the dark energy equation of state can undergo a rapid transition at low redshifts, perhaps associated with the onset of the acceleration phase. We set constraints on the phenomenological parameters describing such possible transitions, in particular improving previous constraints (which used only cosmological data) on the present-day value of the dark energy equation of state in these models. We specifically quantify how these constraints are improved by the addition of the α measurements. We find no evidence for a transition associated with the onset of acceleration. In this model the α measurements lead to a bound on Weak Equivalence Principle violations of η<4×10−15 (at 68.3% confidence level), improving on the recent MICROSCOPE bound by about a factor of three. This work has been recently published at Phys.Lett. B791 (2019) 230.

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Mariana Encarnação
Topological defects necessarily form in cosmological phase transitions, via the Kibble mechanism. The simplest of these, domain walls, can be described by a single real scalar field. In addition to their intrinsic relevance, this simplicity makes them a very useful testbed for the physical processes affecting the evolution of other defect networks. In this contribution we report on the results of high-resolution 2D and 3D field theory simulations of domain walls in various cosmological epochs, which have been post-processed with advanced visualization tools, focusing on the energy loss mechanisms for the networks and their dependence on the relevant cosmological and particle physics parameters. Our results are relevant for future accurate estimates of the cosmic microwave and gravitational wave backgrounds produced by these networks.

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Miguel Fernandes Moita
In the multi-messenger era, gamma-ray polarimetry may contribute to a wider understanding of gamma-ray transients associated to gravitational waves detection. Furthermore, allows a deep understanding of the physical processes, geometry and magnetic fields of sources such as pulsars, solar flares, active galactic nuclei or galactic black holes. Herein, we analysed the performances of a prototype in a 2 layers Compton configuration based on two CdTe spectro-imagers operated in coincidence. The two CdTe detectors have an anode segmented in 8´8 pixels (2 mm pitch) on 2 mm thick crystals. The detection system configuration will allow assessing the scattering polarimetric performance of a 3D spectro-imager by changing the distance between the two layers over the 100-600 keV energy range. These conclusions will be of fundamental importance for both high efficiency Laue lens telescope focal plane and all sky advanced Compton telescope design for next generation space mission. The polarimetric modulation factor was evaluated at distances between planes ranging from 8mm up to 16mm at different Compton scattering angles. Results will be presented and discussed.

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Morgan Le Delliou
The generally admitted mathematical structure underlying a gauge theory, of some symmetry group G, will be recalled, that relates to a principal G-bundle and the choice of a connection (the gauge field) on it. I will explain why these requirements are not realized in the usual view of TEGR as a gauge theory of translations and point out that the gauging of the Lorentz symmetry is present from a mathematical point of view. The role of the connection will be questioned and the use the Cartan Geometry and the Cartan connection as the framework for TEGR will be proposed opening the door to some questions about the status of gravity.

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Nuno M. Santos
Kerr black holes are known to support massive bosonic test fields at the threshold of superradiance. The presence of these real-frequency bound states at the linear level, commonly dubbed stationary clouds, is intimately linked to existence of Kerr black holes with bosonic hair at the non-linear level. While the phenomenology of stationary scalar clouds has been widely addressed in the literature over the last years, little is known about the physical properties of their vector counterparts. Following the recent demonstration of the separability of the Proca equation in Kerr spacetime, we compute the existence lines of such stationary vector clouds in a mass vs. angular velocity diagram for Kerr black holes and compare them with those of stationary scalar clouds.

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Ruben Gonçalves
We present new wind velocities and its variability at Venus cloud-tops (~70 km) based on coordinated observations with two complementary techniques: (1) space-based cloud-tracking using JAXA’s Akatsuki/UVI imaging and (2) ground-based Doppler velocimetry using TNG/HARPS-N. This work is based on the first observations of a Solar system planetary atmosphere using HARPS-N. From space, clouds features were tracked on images obtained by the Akatsuki instrument (UVI) operating in the ultraviolet range (365 nm filter), acquired in orbit #39, between 26 and 31 of January 2017. From the ground, data acquired on 28-29 January 2017 using TNG/HARPS-N, Doppler velocimetry measurements are based on high-resolution spectra (resolution of ~115,000) of Fraunhofer lines in the visible range (383-690 nm) using incoming solar radiation scattered by cloud top particles in the observer’s direction. The analysis and results of this new coordinated dataset indicate (1) cross-validation and complementarity of cloud-tracking and Doppler velocimetry measurements; (2) a significant North-South asymmetry of zonal wind circulation, of the order of +10 m/s higher in the South hemisphere in Akatsuki/UVI observations, in accordance with previous detection by Horinouchi et al. (2018); (3) a poleward meridional flow, symmetrical with respect to equator, is clearly measured in both hemispheres; its peaks around 40º N and S with an amplitude of vm = 30±5 m/s. This cloud-top meridional flow is retrieved with unprecedented precision using HARPS-N; (4) spatial and temporal variability of Akatsuki’s zonal and meridional wind flow is also observed, with a significant increase of wind flow near evening terminator, which could be explained by the presence of thermal tide already discussed by other authors.

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Santiago González Gaitán
Dust properties and extinction curves across galaxies are still largely unknown. Although local studies of the Milky Way (MW) and of nearby galaxies point towards standard total-to-selective Rv extinction laws around 3.1, values near the MW bulge and towards some extragalactic highly extinct supernovae (SNe) indicate peculiarly low values that require smaller dust grain sizes. The question arises if such properties are general features of other galaxies or if some nearby process close to the SN creates different types of dust. In both cases, the inferred absolute magnitudes of SNe used for distance estimation are biased by differing color-magnitude relations, with important implications for cosmology. We carry outa study of nearby galaxies with broad-band polarimetry with FORS2/IPOL to obtain maps of continuum polarization and extinction laws from the known relation between maximum polarization wavelength and Rv.

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Sérgio Pereira
"We believe that we need to permanently raise within the society the awareness of the role and relevance of science, and to motivate children and youngsters to follow scientific careers. One of the ways science communication can reach new audiences is through its integration in cultural and artistic activities and entertainment events. With this purpose, the Instituto de Astrofísica e Ciências do Espaço (IA) has been establishing partnerships with art schools, cultural agents and creative agencies. Working with the coordinators of BA and MA in Communication Design, Animation Arts or Multimedia Design, we have been gathering a portfolio of free educational contents in Astronomy, in Portuguese, scientifically validated and with visual quality to attract young audiences in informal contexts. These partnerships have also promoted science communication as one domain of professional development among art students, who may contribute in the future to the material and visual culture in science communication. One of these students has joined the Science Communication team at IA. The return of this work is, so far, two MA projects in science communication, eight short animations, twelve fulldome animations and two educational projects with potential for an international reach. The short animations will likely be presented in cinema festivals, while the fulldome animations are presented daily at Planetário do Porto – Centro Ciência Viva. IA also established a partnership with EGEAC, the public company dealing with major cultural events in Lisbon, which led, so far, to co-organising events with Museu de Lisboa – Teatro Romano promoted through Festas de Lisboa programme. A partnership with the O Cubo agency led to a school workshop about constellations and which output was presented at the Lumina festival in Cascais in 2018, a three-day festival that received 200 000 people and is dedicated to light-based art works. Along the way we have learned the best ways of realising this integration of astronomy and cultural creation, and have received positive feedback both from teachers and cultural agents, acknowledging the specificity and richness of science communication competences and outcomes.

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Tiago Teixeira
A flat LambdaCDM model is, despite an apparent tension in the values of the Hubble constant, the current canonical cosmological model, and deviations from it are tightly constrained. However, some of these constraints come from high-redshift data, especially from the cosmic microwave background. In this work we quantify how well some extensions of LambdaCDM are constrained by current low-redshift data, such as Type Ia supernova and Hubble parameter measurements.

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Vasco Capela Tavares
Rolling tachyon models provide an interesting alternative to LambdaCDM, motivated by string theory. Moreover, they also unavoidably lead to a varying fine-structure constant and naturally predict that the magnitude of its variation is determined by the slope of a potential which also impacts the dark energy equation of state. Therefore, astrophysical tests of the stability of the fine-structure constant and cosmological data jointly constrain these scenarios. In this contribution we present the latest constraints on these models, showing that they require values of the dark energy equation of state that are indistinguishable from LambdaCDM while still allowing for measurable values of the fine-structure constant.

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