10 research outputs found
Ground-based CCD astrometry with wide field imagers. III. [email protected] proper-motion catalog of the globular cluster omega Centauri
Omega Centauri is the most well studied Globular Cluster because of its
numerous puzzling features. Intensive spectroscopic follow-up observing
campaigns targeting stars at different positions on the color-magnitude diagram
promises to clarify some of these peculiarities. To able to target cluster
members reliably during spectroscopic surveys and both spatial and radial
distributions in the cluster outskirts without including field stars, a high
quality proper-motion catalog of omega Cen and membership probability
determination are required. The only available wide field proper-motion catalog
of omega Cen is derived from photographic plates, and only for stars brighter
than B~16. Using ESO archive data, we create a new, CCD-based, proper-motion
catalog for this cluster, extending to B~20. We used the high precision
astrometric software developed specifically for data acquired by [email protected]
telescope and presented in the first paper of this series. We achieved a good
cluster-field separation with a temporal base-line of only four years. We
corrected our photometry for sky-concentration effects. We provide calibrated
photometry for UBVRI wide-band data plus narrow-band filter data centered on
H_alpha for almost 360 000 stars. We can confirm that the omega Cen metal-poor
and the metal-rich components have the same proper motion, and demonstrate that
the metal-intermediate component in addition exhibits the same mean motion as
the other RGB stars. We provided membership probability determination for
published omega Cen variable star catalogs. Our catalog extends the
proper-motion measurements to fainter than the cluster turn-off luminosity, and
covers a wide area (~33'x33') around the center of omega Cen. Our catalog is
now electronically available to the astronomical community.Comment: 21 pages, 15 figures (8 in low resolution), shortened abstract,
revised version, accepted (October 3rd, 2008) for publication in A&
Gaia Data Release 3: Reflectance spectra of Solar System small bodies
30 pages, 26 figuresThe Gaia mission of the European Space Agency (ESA) has been routinely observing Solar System objects (SSOs) since the beginning of its operations in August 2014. The Gaia data release three (DR3) includes, for the first time, the mean reflectance spectra of a selected sample of 60 518 SSOs, primarily asteroids, observed between August 5, 2014, and May 28, 2017. Each reflectance spectrum was derived from measurements obtained by means of the Blue and Red photometers (BP/RP), which were binned in 16 discrete wavelength bands. We describe the processing of the Gaia spectral data of SSOs, explaining both the criteria used to select the subset of asteroid spectra published in Gaia DR3, and the different steps of our internal validation procedures. In order to further assess the quality of Gaia SSO reflectance spectra, we carried out external validation against SSO reflectance spectra obtained from ground-based and space-borne telescopes and available in the literature. For each selected SSO, an epoch reflectance was computed by dividing the calibrated spectrum observed by the BP/RP at each transit on the focal plane by the mean spectrum of a solar analogue. The latter was obtained by averaging the Gaia spectral measurements of a selected sample of stars known to have very similar spectra to that of the Sun. Finally, a mean of the epoch reflectance spectra was calculated in 16 spectral bands for each SSO. The agreement between Gaia mean reflectance spectra and those available in the literature is good for bright SSOs, regardless of their taxonomic spectral class. We identify an increase in the spectral slope of S-type SSOs with increasing phase angle. Moreover, we show that the spectral slope increases and the depth of the 1 um absorption band decreases for increasing ages of S-type asteroid families
Gaia Data Release 3: Reflectance spectra of Solar System small bodies
30 pages, 26 figuresThe Gaia mission of the European Space Agency (ESA) has been routinely observing Solar System objects (SSOs) since the beginning of its operations in August 2014. The Gaia data release three (DR3) includes, for the first time, the mean reflectance spectra of a selected sample of 60 518 SSOs, primarily asteroids, observed between August 5, 2014, and May 28, 2017. Each reflectance spectrum was derived from measurements obtained by means of the Blue and Red photometers (BP/RP), which were binned in 16 discrete wavelength bands. We describe the processing of the Gaia spectral data of SSOs, explaining both the criteria used to select the subset of asteroid spectra published in Gaia DR3, and the different steps of our internal validation procedures. In order to further assess the quality of Gaia SSO reflectance spectra, we carried out external validation against SSO reflectance spectra obtained from ground-based and space-borne telescopes and available in the literature. For each selected SSO, an epoch reflectance was computed by dividing the calibrated spectrum observed by the BP/RP at each transit on the focal plane by the mean spectrum of a solar analogue. The latter was obtained by averaging the Gaia spectral measurements of a selected sample of stars known to have very similar spectra to that of the Sun. Finally, a mean of the epoch reflectance spectra was calculated in 16 spectral bands for each SSO. The agreement between Gaia mean reflectance spectra and those available in the literature is good for bright SSOs, regardless of their taxonomic spectral class. We identify an increase in the spectral slope of S-type SSOs with increasing phase angle. Moreover, we show that the spectral slope increases and the depth of the 1 um absorption band decreases for increasing ages of S-type asteroid families
Gaia Data Release 3: Reflectance spectra of Solar System small bodies
30 pages, 26 figuresThe Gaia mission of the European Space Agency (ESA) has been routinely observing Solar System objects (SSOs) since the beginning of its operations in August 2014. The Gaia data release three (DR3) includes, for the first time, the mean reflectance spectra of a selected sample of 60 518 SSOs, primarily asteroids, observed between August 5, 2014, and May 28, 2017. Each reflectance spectrum was derived from measurements obtained by means of the Blue and Red photometers (BP/RP), which were binned in 16 discrete wavelength bands. We describe the processing of the Gaia spectral data of SSOs, explaining both the criteria used to select the subset of asteroid spectra published in Gaia DR3, and the different steps of our internal validation procedures. In order to further assess the quality of Gaia SSO reflectance spectra, we carried out external validation against SSO reflectance spectra obtained from ground-based and space-borne telescopes and available in the literature. For each selected SSO, an epoch reflectance was computed by dividing the calibrated spectrum observed by the BP/RP at each transit on the focal plane by the mean spectrum of a solar analogue. The latter was obtained by averaging the Gaia spectral measurements of a selected sample of stars known to have very similar spectra to that of the Sun. Finally, a mean of the epoch reflectance spectra was calculated in 16 spectral bands for each SSO. The agreement between Gaia mean reflectance spectra and those available in the literature is good for bright SSOs, regardless of their taxonomic spectral class. We identify an increase in the spectral slope of S-type SSOs with increasing phase angle. Moreover, we show that the spectral slope increases and the depth of the 1 um absorption band decreases for increasing ages of S-type asteroid families