SYRTE and PARSEC Contribution for the GBOT/GAIA Moving Target Astrometry

4 p.International audienceGAIA will measure to unprecedent precision positions, movements, and parallaxes, by the superposition of two fields apart by 174deg, taken from the L2 Earth-Sun, about 1.5 million km from the ground. To achieve the aimed precision for stars, and particularly for solar system bodies, the instantaneous position and speed of the satellite must be known respectively to 150m and 2.5 mm/s. This translates to the GBOT (Ground Base Optical Tracking) requirement to deliver quasi-daily positions of the satellite at the accuracy of 10mas relatively to the GAIA's reference frame itself (Altmann et al., 2010, this proceeding). The challenge increases because the satellite will probably be dimmer than R 17th magnitude and will be moving on average at 30mas/s, and switching hemispheres between summer and winter. We will present the strategies worked out for the satellite centroid's determination, including tracking mode, binning, super-gaussian fit, blind co-addition of images; as well as the astrometric reduction open code designed to cope with this variety of conditions. We will show applications of these resources to observations of the satellites WMAP and PLANCK, and to fast asteroids

Multi-band optical variability of a newly discovered twelve blazars sample from 2013-2019

Here we present the first optical photometric monitoring results of a sample of twelve newly discovered blazars from the ICRF - Gaia CRF astrometric link. The observations were performed from April 2013 until August 2019 using eight telescopes located in Europe. For a robust test for the brightness and colour variability, we use Abbe criterion and F-test. Moreover, linear fittings are performed to investigate the relation in the colour-magnitude variations of the blazars. Variability was confirmed in the case of 10 sources; two sources, 1429+249 and 1556+335 seem to be possibly variable. Three sources (1034+574, 1722+119, and 1741+597) have displayed large amplitude brightness change of more than one magnitude. We found that the seven sources displayed bluer-when-brighter variations, and one source showed redder-when-brighter variations. We briefly explain the various AGN emission models which can explain our results.Comment: 14 pages, 8 figures, 11 tables, 6 supplement figures can be provided on request, MNRAS in pres

Astrometry and Light Curves of Asteroids with the SUBARU Telecope

Program available at: http://www.imcce.fr/hosted_sites/naroo/program.htmlInternational audienceWe present the reductions of observations of a single ecliptic field, carried out over one night in September 2, 2002, at the focus of the SUBARU 8.2 m telescope. The frames necessary for the reduction were retrieved through the database SMOKA (Subaru Mitaka Okayama Kiso Archive System) High frequency multi shots imaging of the fields enable to detect sub-kilometric asteroids and to perform astrometric and photometric reduction, leading in some cases to the extraction of light curves

Ground Based Optical Tracking of Gaia

International audienceGaia's unprecedented ambitions regarding astrometric accuracy and precision require a level of knowledge of the position and velocity vector of the satellite itself not required in other satellite mission. Thus the usual methods of determining these quantities do not suffice and new approaches must be invoked. One of these is the Ground Based Optical Tracking (GBOT) campaign

GBOT - one year before Gaia's launch

International audienceGBOT (Ground Based Optical Tracking, [1]) is a part of the Gaia satellie mission, which is being set up to be able to fully exploit the capabilities of the satellite, even for the best measured stars. The GBOT project consists of about half a dozen small (1-2 m class telescopes), which will make daily observations of the Gaia space craft. From these data, the GBOT group will derive astrometric positions, which will be used in the reconstruction of Gaia's orbit

The ProAm Incentive Multi-Year Action

International audienceThe ProAm Incentive Multi-Year Action (IMYA) of the Paris Observatory manages scientific actions in the framework of Professional-Amateurs collaborations. The goal is to promote collaborations between professional and amateur astronomers on any astronomical topic and with any technique. The 2022 budget of the ProAm IMYA is of 25.000 euros and covers travels of Paris Observatory members, short-term invitations of professional or amateur astronomers, work meetings, material and internships. We will present details and progress for the 4 projects that have been selected after our 2022 Call for Proposals, and funded. We will also open the discussion for ideas for the ProAm IMYA

The ProAm Incentive Multi-Year Action

The ProAm Incentive Multi-Year Action (IMYA) of the Paris Observatory manages scientific actions in the framework of Professional-Amateurs collaborations. The goal is to promote collaborations between professional and amateur astronomers on any astronomical topic and with any technique. The 2022 budget of the ProAm IMYA is of 25.000 euros and covers travels of Paris Observatory members, short-term invitations of professional or amateur astronomers, work meetings, material and internships. We will present details and progress for the 4 projects that have been selected after our 2022 Call for Proposals, and funded. We will also open the discussion for ideas for the ProAm IMYA

Search of a gravitational wave background in timing residuals of PSR 1937 21: minimal model and upper limits on Omega_gr

International audienceAlthough many phenomena can account for pulsar timing residuals, previous upper limits on the amplitude Omega_gr of a gravitational wave background were all obtained with the same decomposition into a measurement noise with known variance and a gravitational noise parametrized by Omega_gr. The justification of this minimal model (MM) is its ability to provide, on average over an infinite set of measurements, the highest upper limits on Omega_gr compared with other models. Keeping with this model, and using free-access Arecibo data concerning PSR 1937 21, we derive a set of 157 estimators of Omega_gr and obtain the 95 per cent confidence upper limit of 1.7x10^-7 using a Bayesian method. We also show evidence of a third term in the residuals (97 per cent confidence), which questions the adequacy of the MM

Long-term R and V -band monitoring of some suitable targets for the link between ICRF and the future Gaia celestial reference frame

International audienc