This paper gives a brief overview of the Gaia Research for European Astronomy Training (GREAT) network, including a description of the GREAT-ESF Research Network Programme and the GREAT Initial Training Network (GREAT-ITN). Scientific highlights from the GREAT-ITN are noted.

The temporal evolution of the terrestrial impact cratering rate over the past 250 Myr is dominated by a trend increasing towards the present. We find that the Sun's motion through the Galaxy plays at best a minor role in modulating this cratering rate. Moreover, the solar apex motion can explain the non-uniform longitude distribution of the perihelia of long period comets without invoking a solar companion in the outer Oort cloud.

The ongoing Gaia mission will undertake an astrometric, photometric and spectroscopic survey of the Galaxy. The Gaia consortium will use Gaia-only data to classify objects and to estimate their individual astrophysical parameters. However, one can achieve more reliable estimates of stellar parameters by combining Gaia data with data from other spectroscopic and photometric surveys.

The Gaia “hybrid catalog” project will provide an exquisite value-added catalogs of astrophysical parameters for Gaia targets by taking into account the “obvious” non-Gaia data (e.g., SDSS, WISE, Pan-STARRS, APOGEE, PPMXL, SDSS, 2MASS, Tycho). By including spectroscopic indicators of metallicity when available, or infrared photometry, we can reduce the degeneracies between extinction and temperature and improve the estimation of metallicity and surface gravity.

However, the creation of such catalogs comes with significant challenges. First the cross-matching of catalogs with various selection functions, or photometric depths. Second, we must optimize the data analysis to produce the most accurate information given a specific science goal. Finally, the construction of such catalogs will require significant computation power. The current plan is to do this using the local resources at the Max-Planck-Institut für Astronomie, and then each catalog will go through validation and integration processes to finally be released as part of the value-added Gaia data products. From these challenges, it is clear that hybrid catalogs will not be a copy of the Gaia catalog but must be adapted to support very specific science questions.

In the poster we presented, we details in particular two applicationsof the Gaia hybrid catalogs. First, we considered the addition of WISEdata to the Gaia information. The WISE data enable us to constrainnot only the amount of extinction through the addition of infrareddata, but also allow us to better classify certain spectral types. Forinstance, from the addition of the WISE filters, one can select theOxygen-rich Asymptotic Giant Branch (AGBs) stars to find spatialsubstructures with particular interstellar medium properties. Breaking through the distance-extinction degeneracies will also help finding largescale structures in the disk such as streams or spiral arms, especiallywhen combined with age or metallicity selections for instance.

Second, we presented one aspect of the hybrid catalogs dedicatedto support the analysis of star clusters. Star clusters are not onlycalibrators of stellar evolution models but also references to study starformation in general. We presented one future outcome of the hybridcatalogs, in which we provide for known star clusters, an assessment ofstellar memberships based on a combination of phase-space, and colormagnitudedistribution fitting. In this application, the assumption thata cluster is a “simple” population provides a significant advantage whenderiving individual star properties. Eventually one can imagine thisapplication can be extended to stellar streams.

Hybrid catalogs are meant to be provided along with the Gaia datareleases, and will offer a tremendous source of validation for the GaiaData Processing.

Numerous studies over the past 30 years have suggested there is a causal connection between the motion of the Sun through the Galaxy and terrestrial mass extinctions or climate change. Proposed mechanisms include comet impacts (via perturbation of the Oort cloud), cosmic rays and supernovae, the effects of which are modulated by the passage of the Sun through the Galactic midplane or spiral arms. Supposed periodicities in the fossil record, impact cratering dates or climate proxies over the Phanerozoic (past 545 Myr) are frequently cited as evidence in support of these hypotheses. This remains a controversial subject, with many refutations and replies having been published. Here I review both the mechanisms and the evidence for and against the relevance of astronomical phenomena to climate change and evolution. This necessarily includes a critical assessment of time series analysis techniques and hypothesis testing. Some of the studies have suffered from flaws in methodology, in particular drawing incorrect conclusions based on ruling out a null hypothesis. I conclude that there is little evidence for intrinsic periodicities in biodiversity, impact cratering or climate on timescales of tens to hundreds of Myr. Although this does not rule out the mechanisms, the numerous assumptions and uncertainties involved in the interpretation of the geological data and in particular in the astronomical mechanisms suggest that Galactic midplane and spiral arm crossings have little impact on biological or climate variation above background level. Non-periodic impacts and terrestrial mechanisms (volcanism, plate tectonics, sea level changes), possibly occurring simultaneously, remain likely causes of many environmental catastrophes. Internal dynamics of the biosphere may also play a role. In contrast, there is little evidence supporting the idea that cosmic rays have a significant influence on climate through cloud formation. It seems likely that more than one mechanism has contributed to biodiversity variations over the past half Gyr.

We present the results of a photometric monitoring program of pre-main sequence (PMS) stars in the young (2-4 Myr) open cluster NGC 2264 (d=700 pc). We find that the rotation periods are mass dependent and show a bimodal distribution for higher mass stars with M ≳ 0.3 M⊙ and a unimodal distribution for lower mass stars with M ≲ 0.3 M⊙.