Not an open cluster after all: the NGC 6863 asterism in Aquila

Bidin, C. Moni; Marcos, R. de la Fuente; Marcos, C. de la Fuente; Carraro, G.

doi:10.1051/0004-6361/200912761

Cited by 15 publications

(10 citation statements)

References 37 publications

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“…The errors were computed as the quadratic sum of the most relevant sources of uncertainty, namely the cross-correlation, the wavelength calibration, and the RV zero-point correction (for further details, see ). We estimated the temperature of the targets fitting the wings of the H α line with the same synthetic spectra (see Fuhrmann et al 1994) following the procedure applied in Moni Bidin et al (2010). We varied the gravity and metallicity of the template models and we thus verified that, as expected, the results were largely insensitive to these parameters.…”

Section: Spectroscopymentioning

confidence: 63%

Ghosts of Milky Way’s past: the globular cluster ESO 37-1 (E 3)

Marcos¹,

Marcos²,

Bidin

et al. 2015

A&A

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Context. In the Milky Way, most globular clusters are highly conspicuous objects that were found centuries ago. However, a few dozen of them are faint, sparsely populated systems that were identified largely during the second half of the past century. One of the faintest is ESO 37-1 (E 3) and as such it remains poorly studied, with no spectroscopic observations published so far although it was discovered in 1976. Aims. We investigate the globular cluster E 3 in an attempt to better constrain its fundamental parameters. Spectroscopy of stars in the field of E 3 is shown here for the first time. Methods. Deep, precise VI CCD photometry of E 3 down to V ∼ 26 mag is presented and analysed. Low-resolution, medium signalto-noise ratio spectra of nine candidate members are studied to derive radial velocity and metallicity. Proper motions from the UCAC4 catalogue are used to explore the kinematics of the bright members of E 3. Results. Isochrone fitting indicates that E 3 is probably very old, with an age of about 13 Gyr; its distance from the Sun is nearly 10 kpc. It is also somewhat metal rich with [Fe/H] = −0.7. Regarding its kinematics, our tentative estimate for the proper motions is (μ α cos δ, μ δ ) = (−7.0 ± 0.8, 3.5 ± 0.3) mas yr −1 (or a tangential velocity of 382 ± 79 km s −1 ) and for the radial velocity 45 ± 5 km s −1 in the solar rest frame.Conclusions. E 3 is one of the most intriguing globular clusters in the Galaxy. Having an old age and being metal rich is clearly a peculiar combination, only seen in a handful of objects like the far more conspicuous NGC 104 (47 Tucanae). In addition, its low luminosity and sparse population make it a unique template for the study of the final evolutionary phases in the life of a star cluster. Unfortunately, E 3 is among the most elusive and challenging known globular clusters because field contamination severely hampers spectroscopic studies.

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Section: Spectroscopymentioning

confidence: 63%

Ghosts of Milky Way’s past: the globular cluster ESO 37-1 (E 3)

Marcos¹,

Marcos²,

Bidin

et al. 2015

A&A

Self Cite

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“…Although the observed radial density profiles are well--represented by the King law, which is typical of stellar clusters, and the stellar overdensity associated with VVV CL002 and VVV CL003 is statistically highly significant, we will not rely on stellar counts alone to conclude about the nature of the three cluster candidates, because they can sometimes be misleading (see, for example, Villanova et al 2004;Moni Bidin et al 2010). Unfortunately, the proper motions do not provide useful information about this.…”

Section: The Nature Of the Cluster Candidatesmentioning

confidence: 99%

Three Galactic globular cluster candidates

Bidin

Mauro

Geisler

et al. 2011

A&A

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Context. The census of Galactic globular clusters (GCs) is still incomplete, and about ten new objects are supposed to await discovery, hidden behind the crowded and reddened regions of the Galactic bulge and disk. Aims. We investigated the nature of three new GC candidates, discovered in the frames collected by the Vista Variables in the Via Lactea (VVV) near-infrared survey. They will be called VVV CL002, VVV CL003, and VVV CL004. Methods. We studied the results of point-spread-function near-infrared photometry from VVV data for the three objects and their surrounding fields, the proper motion information available in the literature and, when possible, we derived the cluster parameters by means of calibrated indices measured on the color-magnitude diagrams. Results. The evidence shows that VVV CL002 is a newly discovered, small, moderately metal-rich ([Fe/H] ≈ −0.4) Galactic GC. It is located at a Galactocentric distance of 0.7 ± 0.9 kpc, and it could be one of the nearest GC to the Galactic center. Its characteristics are more similar to those of low-mass, Palomar-like GCs than to more classical, old, and massive bulge GCs. VVV CL003 is the first star cluster discovered in the Galactic disk on the opposite side of the center with respect to the Sun, at a Galactocentric distance of ∼5 kpc. Its high metallicity ([Fe/H] ≈ −0.1) and location point to an open cluster, but a GC cannot be excluded. VVV CL004, on the contrary, is most probably only a random clump of field stars, as indicated by both its low statistical significance and by the impossibility to distinguish its stars from the surrounding field population. Conclusions. We claim the detection of i) a new Galactic GC, deriving an estimate of its basic parameters; ii) a stellar aggregate, probably an open cluster, in the disk directly beyond the Galactic center; and iii) an overdensity of stars, most probably an asterism.

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“…Scan statistics are used to detect clusters in spatial and spatiotemporal data sets and have been applied in fields as diverse as astronomy (Moni Bidin, de la Fuente Marcos, de la Fuente Marcos, & Carraro, 2009), ecology (Tuia, Ratle, Lasaponara, Telesca, & Kanevski, 2008), and criminology (Minamisava, Nouer, de Morais Neto, Melo, & Andrade, 2009). However, the primary use of scan statistics continues to be in public health surveillance, hence, this is the area of application we will focus on to demonstrate the method proposed in this paper.…”

Section: Introductionmentioning

confidence: 99%

An unconditional space–time scan statistic for ZIP‐distributed data

Allévius

Höhle

2018

Scandinavian J Statistics

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A scan statistic is proposed for the prospective monitoring of spatiotemporal count data with an excess of zeros. The method that is based on an outbreak model for the zero‐inflated Poisson distribution is shown to be superior to traditional scan statistics based on the Poisson distribution in the presence of structural zeros. The spatial accuracy and the detection timeliness of the proposed scan statistic are investigated by means of simulation, and an application on the weekly cases of Campylobacteriosis in Germany illustrates how the scan statistic could be used to detect emerging disease outbreaks. An implementation of the method is provided in the open‐source R package scanstatistics available on the Comprehensive R Archive Network.

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Not an open cluster after all: the NGC 6863 asterism in Aquila

Cited by 15 publications

References 37 publications

Ghosts of Milky Way’s past: the globular cluster ESO 37-1 (E 3)

Ghosts of Milky Way’s past: the globular cluster ESO 37-1 (E 3)

Three Galactic globular cluster candidates

An unconditional space–time scan statistic for ZIP‐distributed data

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