Overview of the Gaia mission
Anthony Brown (Univ. Leiden)
I will present an overview of the Gaia spacecraft and survey, highlighting the aspects that make Gaia an excellent transient sky survey machine.
Gaia Photometric Science Alerts: where we were, where we are, where we are going
Simon Hodgkin (Institute of Astronomy, Cambridge)
Gaia continues to monitor the whole sky with cadences of seconds (between CCDs), hours (between fields-of-view) and weeks (between visits), with real-time source detection implemented by a fixed, available, and well-understood on-board algorithm. Every Gaia source obtains near-simultaneous spectrophotometry. The Gaia Alerts system has been running routinely and reliably since January 2016, currently publishing more than 12 transients per day (see http://gsaweb.ast.cam.ac.uk/alerts/home), using well-defined selection criteria. We scan the whole sky exploring into the Galactic plane and crowded regions which are typically hard to do from the ground. We describe the challenges we face in searching through half a billion CCD measurements every day to identify and publish Gaia's transient events. We investigate the properties of the alerts published to date and highlight some of our most interesting discoveries, paying special attention to the overlaps between the Alerts, ground-based follow-up programmes, and the third Gaia Data Release. We examine the completeness and purity of our published alerts, and look ahead to the next years of Gaia Photometric Science Alerts.
Gaia as a black hole discovery machine
Lukasz Wyrzykowski (Warsaw University Astronomical Observatory)
ESA's Gaia space mission monitors the entire sky and provides time-series of brightness, position and spectra of billion of stars. Thanks to the Gaia Science Alerts system, Gaia informs the astronomical community of interesting astrophysical phenomena from the entire sky. Among them, one of the rarest, are gravitational microlensing events - temporal brightenings due to lensing by an invisible object passing in front of a background star. At the same time, Gaia collects positional information, which will yield the most exciting and complete solutions on the nature of the lensing object and an opportunity of finding isolated black holes. I will present the most interesting events found by Gaia so far which were monitored by a ground-based network of telescopes. I will also present the prospects of using Gaia astrometric data for Gaia microlensing events, which will become available with Gaia DR4.
Regular Variable Stars
Marcella Marconi (Osservatorio Astronomico di Capodimonte)
In this review I will focus on regular variable stars in Gaia and their astrophysical uses. As well known, regular variable stars allow us to investigate the properties of their host stellar population and to measure their distance thanks to the existence of relations connecting the pulsation parameters with evolutionary and structural quantities. Moreover the observed oscillation properties provide a fundamental benchmark for stellar evolution and pulsation models predictions. In this context, the astrometric, photometric and spectroscopic Gaia mission and in particular its latest data release (Gaia DR3) are providing fundamental information and constraints that are improving our knowledge of regular variable stars with important implications in several astrophysical fields.
Gaia and the Local Distance scale
Stefano Casertano (Space Telescope Science Institute)
Results from the Gaia mission now play a key role in the accurate determination of the local distance ladder. EDR3 parallaxes now provide the best calibration of the Cepheid Leavitt Law. With addition of DR3 photometry, Gaia will likely also provide one of the strongest calibrations of the Tip of the Red Giant Branch. Recent refinements of the measurement of the Hubble constant in the local Universe appear to confirm and strengthen the well-established tension with the value inferred from Planck and Lambda-CDM cosmology.
Trouble with Hubble
Nils Schoneberg (Institut de Ciencies del Cosmos, Barcelona)
While the LCDM cosmological model has seen an uninterrupted chain of successes over the past decades, in the recent years a tension in the value of the Hubble parameter between inferences from early universe probes and measurements in the late universe has emerged. With the significance of this tension slowly rising to around the 5 sigma mark, it is prudent to re-investigate both the experimental and the theoretical side of this tension. In this presentation I give an overview of the recent efforts to independently corroborate the tension using a variety of experimental probes in the early and late universe and the recent theoretical advancements made in finding a model that would resolve the tension.
A review of tidal disruption events
Thomas Wevers (European Southern Observatory)
I will introduce tidal disruption events and discuss their observational properties across the electromagnetic spectrum, together with our current understanding of the physics underlying them. I will also highlight some key open questions in the field, such as the origin of the UV/optical emission, and recent work that is helping us answer them. I will end with a brief look towards the future, including the potential of TDEs as multi-messenger sources.
AGN, SNe, extended sources, galaxies in the Gaia DR3 variability analysis
Laurent Eyer (Observatoire de Genève)
The third Gaia data release contains a global variability analysis with associated published catalogues. We implemented a supervised classification of the celestial sources into variable stars and extragalactic sources with corresponding training sets based on a compilation of the literature crossmatched Gaia sources. This presentation provides an overview of what was done for the third Gaia data release
QSOs and the Extragalactic Reference Frame
Beatrice Bucciarelli (Osservatorio Astronomico di Torino)
A direct link between the radio and optical realizations of the International Celestial Reference System (ICRS) has been achieved thanks to ESA’s Gaia mission, which at its third data release comprises about 1.6 million QSO-like sources. I will outline the principal steps of this task and present the statistical properties of the defined celestial reference frame; I will also underline some relevant issues related to the astrometric variability of QSOs, such as their internal structure, peculiar motions, and aberration-induced proper motions.
Gaia in the Multi-messenger era
Zuzanna Kostrzewa-Rutkowska (University of Leiden)
The recent discoveries of gravitational wave events and in one case also its electromagnetic (EM) counterpart allow us to study the Universe in a novel way. The increased sensitivity of the LIGO and Virgo detectors has opened the possibility for regular detections of EM transient events from mergers of stellar remnants. Gravitational wave sources are expected to have sky localisation up to a few hundred square degrees, thus Gaia as an all-sky multi-epoch photometric survey has the potential to be a good tool to search for the EM counterparts. I'll present the current status of searches for EM counterparts of GW events and the possibilities of their detections by Gaia.
The SKA Observatory view of transients: synergies with Gaia
Philippa Hartley (SKA Observatory)
The SKA Observatory (SKAO) is building the two largest radio telescope arrays in the world, in an international effort to revolutionise our view of the radio sky. Now under construction in South Africa and Australia, the telescopes will respectively cover the low and mid to high radio frequencies. Large survey programmes will cover a broad range of science objectives, including transient phenomena both galactic and extragalactic. The revolutionary studies of stars, exoplanets and quasars performed by the Gaia mission will be complemented by SKAO studies in the radio, where detection of pulsars, masers and fast radio bursts will likewise probe the nature of our own Galaxy and the nature of spacetime itself. In this talk, I will present an overview of the SKA roadmap before highlighting the synergies that exist with between the SKAO and Gaia relevant to the study of transients.
EUCLID and Gaia
Jarle Brinchmann (Centro de Astrofisica da Universidade do Porto)
I will give a brief overview of what Euclid will provide and how Gaia is indispensable for Euclid and how Euclid will add to the power of Gaia.
PLATO, TESS and Gaia
Susana Barros (Instituto de Astrofísica e Ciências do Espaço)
I will give an overview of Exoplanet research in the context of the current and next space mission. I will explore the expected exoplanet yield by the GAIA mission and the synergies between GAIA, and TESS, CHEOPS and PLATO. GAIA is expected to discover many planets through astrometry and also a few through transit photometry. GAIA astrometry also allows a better characterisation of the orbits and masses of planetary systems and has had a large impact in the characterisation of the exoplanet host stars. This impacts directly the precision of the derived planetary parameters including those discovered by TESS and in the future PLATO. It also provides valuable information about for candidate validation and it has been used to help select the PLATO field of view.
The Rubin LSST transients and variable sky
Federica Bianco (University of Delaware, USA)
Vera C. Rubin Observatory is approaching completion and about to begin the Legacy Survey of Space and Time, LSST, an unprecedented multi-band optical imaging survey. The combination of flux sensitivity – r~25 limiting magnitude for a single image, r~27 for the 10-year stacks –, area coverage – the whole Southern hemisphere sky and extending to special regions above the celestial equator –, and temporal sampling rate – from hours to decades with repeated images within a night and a few nights apart – will reach areas of the Universe and of the discovery parameter space previously entirely unexplored, making this survey potentially transformative for most if not all fields of astronomy and astrophysics. The survey cadence, image resolution and quality, and state-of-the-art rapid image processing will enable the identification of an expected 10M transients and variable phenomena each night, which will be broadcasted worldwide in real-time with an open data policy. I will review the status of Rubin Observatory and its LSST, the data products and data access rules and modalities, the potential for discovery, and emphasize potential synergies that can truly realize the survey’s potential for discovery
