GaiaData Release 1

Abstract

Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release. Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue. Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the Hipparcos and Tycho-2 catalogues -a realisation of the Tycho-Gaia Astrometric Solution (TGAS) -and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of ∼3000 Cepheid and RR Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr −1 for the proper motions. A systematic component of ∼0.3 mas should be added to the parallax uncertainties. For the subset of ∼94 000 Hipparcos stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr −1 . For the secondary astrometric data set, the typical uncertainty of the positions is ∼10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to ∼0.03 mag over the magnitude range 5 to 20.7. Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data.

Circumbinary, not transitional: on the spiral arms, cavity, shadows, fast radial flows, streamers, and horseshoe in the HD 142527 disc

“…The star itself is a Herbig Fe star of spectral type F6 IIIe (M≈1.8 M ) at a distance of 156 +7 −6 pc (Gaia Collaboration et al 2016) in the Sco-Cen association (Biller et al 2012;Mendigutía et al 2014). Modelling of the Spectral Energy Distribution (SED) suggested a disc gap between 30 and 130 au (Verhoeff et al 2011), confirmed by the initial ALMA observations .…”

Asteroseismic versusGaiadistances: A first comparison

“…Such a model is called an errors-in-variables model (also known as the measurement error model) and has been studied extensively in the statistics literature, see e.g. Fuller (1987). Here, we have the additional feature that the variances of both η i and ε i have been quantified.…”

The Outer Halo of the Milky Way as Probed by RR Lyr Variables from the Palomar Transient Facility*

“…Furthermore, the Hubble Space Telescope Fine Guidance Sensor cameras were used by Benedict et al (2011) to determine trigonometric parallaxes to several of the nearest field RR Lyr, in principle providing a fundamental calibration for all these efforts. Sesar et al (2017a) used the Tycho-Gaia Astrometric Solution (Michalik et al 2015) parallaxes of nearby RR Lyr from the Gaia Data Release 1 (Brown et al 2016) to verify existing period-luminosity-metallicity relationships of previous studies, illustrating the potential for very high accuracy distances for RR Lyr stars with future Gaia releases.…”

“…S. G. Djorgovski) and the Pan-STARRS survey (Hodapp et al 2004;Tonry et al 2012), with the Large Synoptic Survey Telescope (LSST) coming in the next decade. Gaia recently had its first data release as well (Brown et al 2016), with more to follow in due course. These surveys, with their huge databases, can, depending on their cadences and limiting magnitudes, be used to identify ever-larger samples of ever more distant RR Lyr, continuing and expanding on much earlier efforts (see, e.g., Wetterer & McGraw 1996).…”