Age determination for 269 Gaia DR2 open clusters

Context. The Gaia Second Data Release provides precise astrometry and photometry for more than 1.3 billion sources. This catalog opens a new era concerning the characterization of open clusters and test stellar models, paving the way for better understanding of the disk properties. Aims. The aim of the paper is to improve the knowledge of cluster parameters, using only the unprecedented quality of the Gaia photometry and astrometry. Methods. We have made use of the membership determination based on the precise Gaia astrometry and photometry. We applied an automated Bayesian tool, BASE-9, to fit stellar isochrones on the observed G, GBP, GRP magnitudes of the high probability member stars. Results. We derive parameters such as age, distance modulus, and extinction for a sample of 269 open clusters, selecting only low reddening objects and discarding very young clusters, for which techniques other than isochrone-fitting are more suitable for estimating ages.

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Characterising open clusters in the solar neighbourhood with the Tycho-Gaia Astrometric Solution

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731251 ◽

2018 ◽

Vol 615 ◽

pp. A49 ◽

Cited By ~ 26

Author(s):

T. Cantat-Gaudin ◽

A. Vallenari ◽

R. Sordo ◽

F. Pensabene ◽

A. Krone-Martins ◽

...

Keyword(s):

Monte Carlo ◽

Markov Chain ◽

High Probability ◽

Open Clusters ◽

Distance Modulus ◽

The Sun ◽

Proper Motions ◽

Orbital Parameters ◽

Naval Observatory ◽

Galactic Potential

Context. The Tycho-Gaia Astrometric Solution (TGAS) subset of the first Gaia catalogue contains an unprecedented sample of proper motions and parallaxes for two million stars brighter than G ~ 12 mag. Aims. We take advantage of the full astrometric solution available for those stars to identify the members of known open clusters and compute mean cluster parameters using either TGAS or the fourth U.S. Naval Observatory CCD Astrograph Catalog (UCAC4) proper motions, and TGAS parallaxes. Methods. We apply an unsupervised membership assignment procedure to select high probability cluster members, we use a Bayesian/Markov Chain Monte Carlo technique to fit stellar isochrones to the observed 2MASS JHKS magnitudes of the member stars and derive cluster parameters (age, metallicity, extinction, distance modulus), and we combine TGAS data with spectroscopic radial velocities to compute full Galactic orbits. Results. We obtain mean astrometric parameters (proper motions and parallaxes) for 128 clusters closer than about 2 kpc, and cluster parameters from isochrone fitting for 26 of them located within a distance of 1 kpc from the Sun. We show the orbital parameters obtained from integrating 36 orbits in a Galactic potential.

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A Gaia DR2 view of the open cluster population in the Milky Way

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833476 ◽

2018 ◽

Vol 618 ◽

pp. A93 ◽

Cited By ~ 180

Author(s):

T. Cantat-Gaudin ◽

C. Jordi ◽

A. Vallenari ◽

A. Bragaglia ◽

L. Balaguer-Núñez ◽

...

Keyword(s):

Stellar Evolution ◽

Milky Way ◽

Galactic Plane ◽

Galactic Disk ◽

Open Cluster ◽

Open Clusters ◽

Number Of Clusters ◽

History Of ◽

Gaia Dr2

Context. Open clusters are convenient probes of the structure and history of the Galactic disk. They are also fundamental to stellar evolution studies. The second Gaia data release contains precise astrometry at the submilliarcsecond level and homogeneous photometry at the mmag level, that can be used to characterise a large number of clusters over the entire sky. Aims. In this study we aim to establish a list of members and derive mean parameters, in particular distances, for as many clusters as possible, making use of Gaia data alone. Methods. We compiled a list of thousands of known or putative clusters from the literature. We then applied an unsupervised membership assignment code, UPMASK, to the Gaia DR2 data contained within the fields of those clusters. Results. We obtained a list of members and cluster parameters for 1229 clusters. As expected, the youngest clusters are seen to be tightly distributed near the Galactic plane and to trace the spiral arms of the Milky Way, while older objects are more uniformly distributed, deviate further from the plane, and tend to be located at larger Galactocentric distances. Thanks to the quality of Gaia DR2 astrometry, the fully homogeneous parameters derived in this study are the most precise to date. Furthermore, we report on the serendipitous discovery of 60 new open clusters in the fields analysed during this study.

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The Cepheid period–luminosity–metallicity relation based on Gaia DR2 data

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833478 ◽

2018 ◽

Vol 619 ◽

pp. A8 ◽

Cited By ~ 28

Author(s):

M. A. T. Groenewegen

Keyword(s):

Strong Correlation ◽

Goodness Of Fit ◽

Zero Point ◽

Distance Scale ◽

Distance Modulus ◽

Initial Sample ◽

Classical Cepheids ◽

Data Release ◽

Multi Mode ◽

Gaia Dr2

Aims. We use parallax data from the Gaia second data release (GDR2), combined with parallax data based on HIPPARCOS and HST data, to derive the period–luminosity–metallicity (PLZ) relation for Galactic classical cepheids (CCs) in the V, K, and Wesenheit WVK bands. Methods. An initial sample of 452 CCs are extracted from the literature with spectroscopically derived iron abundances. Reddening values, classifications, pulsation periods, and mean V- and K-band magnitudes are taken from the literature. Based on nine CCs with a goodness-of-fit (GOF) statistic smaller than 8 and with an accurate non-Gaia parallax (σπ comparable to that in GDR2), a parallax zero-point offset of −0.049 ± 0.018 mas is derived. Selecting a GOF statistic smaller than 8 removes about 40% of the sample most likely related due to binarity. Excluding first overtone and multi-mode cepheids and applying some other criteria reduces the sample to about 200 stars. Results. The derived PL(Z) relations depend strongly on the parallax zero-point offset. The slope of the PL relation is found to be different from the relations in the LMC at the 3σ level. Fixing the slope to the value found in the LMC leads to a distance modulus (DM) to the LMC of order 18.7 mag, larger than the canonical distance. The canonical DM of around 18.5 mag would require a parallax zero-point offset of order −0.1 mas. Given the strong correlation between zero point, period and metallicity dependence of the PL relation, and the parallax zero-point offset there is no evidence for a metallicity term in the PLZ relation. Conclusions. The GDR2 release does not allow us to improve on the current distance scale based on CCs. The value of and the uncertainty on the parallax zero-point offset leads to uncertainties of order 0.15 mag on the distance scale. The parallax zero-point offset will need to be known at a level of 3 μas or better to have a 0.01 mag or smaller effect on the zero point of the PL relation and the DM to the LMC.

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White dwarf-open cluster associations based on Gaia DR2

Astronomy and Astrophysics ◽

10.1051/0004-6361/202039276 ◽

2020 ◽

Vol 645 ◽

pp. A13

Author(s):

M. Prišegen ◽

M. Piecka ◽

N. Faltová ◽

M. Kajan ◽

E. Paunzen

Keyword(s):

Open Cluster ◽

Open Clusters ◽

Photometric Data ◽

Mass Relation ◽

Physical Processes ◽

Satellite Mission ◽

Cluster Membership ◽

Fundamental Parameters ◽

Data Release ◽

Gaia Dr2

Context. Fundamental parameters and physical processes leading to the formation of white dwarfs (WDs) may be constrained and refined by discovering WDs in open clusters (OCs). Cluster membership can be utilized to establish the precise distances, luminosities, ages, and progenitor masses of such WDs. Aims. We compile a list of probable WDs that are OC members in order to facilitate WD studies that are impractical or difficult to conduct for Galactic field WDs. Methods. We use recent catalogs of WDs and OCs that are based on the second data release of the Gaia satellite mission (GDR2) to identify WDs that are OC members. This crossmatch is facilitated by the astrometric and photometric data contained in GDR2 and the derived catalogs. Assuming that most of the WD members are of the DA type, we estimate the WD masses, cooling ages, and progenitor masses. Results. We have detected several new likely WD members and reassessed the membership of the literature WDs that had been previously associated with the studied OCs. Several of the recovered WDs fall into the recently reported discontinuity in the initial-final mass relation (IFMR) around Mi ∼ 2.0 M⊙, which allows for tighter constrains on the IFMR in this regime.

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Asteroid phase curve parameters from Gaia photometry

10.5194/epsc2020-654 ◽

2020 ◽

Author(s):

Julia Martikainen ◽

Grigori Fedorets ◽

Antti Penttilä ◽

Karri Muinonen

Keyword(s):

Photometric Data ◽

Surface Scattering ◽

Phase Curve ◽

The Past ◽

Current State ◽

Data Release ◽

Rotation Parameters ◽

Inversion Techniques ◽

Gaia Dr2

<p>Asteroids have remained mostly the same for the past 4.5 billion years, and provide us information on the origin, evolution and current state of the Solar System. For the physical characterization of asteroids, one of the best data sources is photometry: the measurement of the disk-integrated brightness of the asteroid. &#160;An asteroid's lightcurve (i.e. the dependency of the brightness as a function of time) is indicative of its surface scattering properties, as well as its shape and the state of spin.&#160;<br /><br />In this work, we apply novel Bayesian inverse methods (Muinonen et al., A&A 2020, in revision) to derive phase curve parameters from photometric lightcurve observations. Our aim is to validate and expand the existing analyses by applying the methods to of the order of tens to hundreds of asteroids using photometric data from the Gaia Data Release 2 (Gaia Collaboration, Spoto et al., A&A 616, A13, 2018) and ground-based photometry (Durech et al., A&A 513, A46, 2010) from Database of Asteroid Models from Inversion Techniques (DAMIT). We derive phase curve linear slopes by using four techniques: &#160;1) convex inversion on all data, 2) convex inversion on all data with fixed rotation parameters from DAMIT, 3) ellipsoid inversion on Gaia DR2 data only, and 4) ellipsoid inversion on Gaia DR2 data only with fixed rotation parameters from DAMIT. Finally, we compare the obtained slope parameters with the presumed Bus-DeMeo (DeMeo et al., Icarus 202, 160, 2009) taxonomic classes of the asteroids, and study possible correlations with the geometric albedos. The Gaia photometry has milli-magnitude precision and is thus extremely valuable when used to carry out asteroid taxonomic classification.</p>

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AGE DETERMINATION OF OPEN CLUSTERS WITH GAIA DR2

Proceedings of the 48-th International student's conferences "Physics of Space" ◽

10.15826/b978-5-7996-2935-9.38 ◽

2020 ◽

Author(s):

E. O. Dedov ◽

Keyword(s):

Age Determination ◽

Open Clusters ◽

Gaia Dr2

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Physicochemical and bacteriological characterization of hospital effluents and their impact on the environment

10.31221/osf.io/rbka9 ◽

2019 ◽

Author(s):

Chem Int

Keyword(s):

Human Health ◽

Fecal Coliforms ◽

Chemical Pollution ◽

Hospital Effluents ◽

Biological Contaminants ◽

Almost All ◽

Direct Discharge ◽

Significant Chemical

Liquid effluents discharged by hospitals may contain chemical and biological contaminants whose main source is the different substances used for the treatment of patients. This type of rejection can present a sanitary potentially dangerous risk for human health and can provoke a strong degradation of diverse environmental compartments mainly water and soils. The present study focuses on the quality of the liquid effluents of Hassani Abdelkader’s hospital of Sidi Bel-Abbes (West of Algeria). The results reveal a significant chemical pollution (COD: 879 mgO2/L, BOD5: 850 mgO2/L, NH4+ : 47.9 mg/l, NO2- : 4.2 mg/l, NO3- : 56.8 mg/l with respect to WHO standard of 90 mgO2/L, 30 mgO2/L, 0.5 mg/l, 1 mg/l and 1 mg/l respectively). However, these effluents are biodegradable since the ratio COD/BOD5 do not exceeded the value of 2 in almost all samples. The presence of pathogen germs is put into evidence such as pseudomonas, the clostridium, the staphylococcus, the fecal coliforms and fecal streptococcus. These results show that the direct discharge of these effluents constitutes a major threat to human health and the environment.

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