A multicolour CCD photometric and mass function study of the distant southern open star clusters NGC 3105, NGC 3603, Melotte 105, Hogg 15, NGC 4815, Pismis 20 and NGC 6253

Sagar, Ram; Munari, U.; Boer, K. S. de

doi:10.1046/j.1365-8711.2001.04438.x

Cited by 73 publications

(94 citation statements)

References 50 publications

(119 reference statements)

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“…NGC 6253 has been studied by several authors in the past, both photometrically (Bragaglia et al 1997;Piatti et al 1998;Sagar et al 2001;Twarog et al 2003;Anthony-Twarog et al 2007;Montalto et al 2009;De Marchi et al 2010), and spectroscopically (Carretta et al 2000(Carretta et al , 2007Sestito et al 2007; Anthony- Twarog et al 2010). In addition, in Montalto et al (2009) we calculated proper-motion membership probabilities.…”

Section: Introductionmentioning

confidence: 99%

VLT multi-epoch radial velocity survey toward NGC 6253

Montalto¹,

Villanova²,

Koppenhoefer³

et al. 2011

A&A

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Context. One of the most metal-rich open cluster of the Galaxy, NGC 6253 is a target of special interest in the search for extrasolar planets, the study of stellar populations, and the chemical/dynamical evolution of the Galactic disk. Aims. We present the results of two photometric campaigns and a VLT multi-epoch radial velocity survey toward the open cluster NGC 6253. We complement our analysis with photometric, proper motion, and radial velocity data available from previous studies of this cluster, and analyze three planetary candidates found in the field of NGC 6253. Methods. We derived homogeneous radial velocity measurements for stars located at the turn-off, sub-giant, red-giant branch, redclump, and blue straggler regions of the cluster. We also analyzed a comparison sample of surrounding field stars. Spectra were obtained with the UVES and GIRAFFE spectrographs at the VLT during three epochs in August 2008. Results. The three UVES measurements acquired for our brightest transiting candidate (V = 15.26) are all consistent within their errors (200 m/s), but were acquired at very similar orbital phases. The mean radial velocity of this object is not consistent with the cluster recession velocity, which rules out cluster membership except in the case of a binary system. This star is worth further analysis with high-precision spectroscopy. For our faintest candidate (V = 18.247), we were able to exclude the observed transits being caused by a close-by stellar companion, but more precise measurements will be needed to derive an orbital fit and to study other possible scenarios. For the remaining candidate, no measurements were acquired probably because of bad fiber positioning. The mean radial velocity of the cluster is (RV cl ± σ cl ) = (−29.11 ± 0.85) km s −1 . Using both radial velocities and proper motions, we identified 35 cluster members. Our results are in good agreement with past radial velocity and photometric measurements. Furthermore, using our photometry, astrometry, and spectroscopy we identified a new eclipsing binary system member of the cluster. Conclusions. We discussed the possibility of detecting substellar companions (brown dwarfs and planets) with the radial velocity technique (both with UVES/GIRAFFE and HARPS) around turn-off stars of old open cluster. We isolated 5 stars that are optimal targets for searching for planetary mass companions with HARPS. Our optimized strategy minimizes the observing time requested to isolate and followup on the best planetary candidates in cluster with high-precision spectrographs, an important aspect given the faint target stars.

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Section: Introductionmentioning

confidence: 99%

VLT multi-epoch radial velocity survey toward NGC 6253

Montalto¹,

Villanova²,

Koppenhoefer³

et al. 2011

A&A

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“…Its role within any coherent model of the chemical evolution of the disk could be downplayed, if not ignored, if it remained the sole example of an old cluster with exceptionally high metallicity, although again the question of its exact metallicity has itself been a matter of controversy. This situation changed with the discovery of a second, old open cluster interior to the Sun, NGC 6253, with indications of a metallicity at least twice that of the Sun (Bragaglia et al 1997;Sagar et al 2001). This claim was confirmed and quantified within this photometric program using CCD intermediateband photometry ( Twarog et al 2003), implying a metallicity at least as high as that claimed for NGC 6791, i.e., [Fe/ H] above +0.4.…”

Section: Introductionmentioning

confidence: 99%

vbyCaHβ CCD Photometry of Clusters. VIII. The Super-Metal-Rich, Old Open Cluster NGC 6791

2007

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For NGC 6791, the metallicity from m 1 is a factor of 2 below that from hk, a result that may be coupled to the consistently low metal abundance from DDO photometry of the cluster and the C-deficiency found from highdispersion spectroscopy. E(B À V ) is the same value predicted from Galactic reddening maps. With E(B À V ) ¼ 0:15 and ½Fe/ H ¼ þ0:45, the available isochrones predict an age of 7:0 AE 1:0 Gyr and an apparent modulus of (m À M ) ¼ 13:60 AE 0:15, with the dominant source of the uncertainty arising from inconsistencies among the isochrones. The reanalysis of NGC 6253 with the revised lower reddening confirms that on both the hk and m 1 metallicity scales, NGC 6253, while less than half the age of NGC 6791, remains at least as metal-rich as NGC 6791, if not richer.

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“…The differential reddening is rather strong throughout the cluster area (1.0 < E(B − V) < 1.5 mag; Turner 1996;Sagar et al 2001) which is due the large distance (3500 pc; Vázquez et al 1995;Turner 1996;Sagar et al 2001) and its low galactic latitude (−1 • ). We have used the reddening maps of Turner (1996) and Sagar et al (2001) to construct our diagnostic diagrams (Fig. 2).…”

Section: Pismis 20mentioning

confidence: 95%

“…2). (2) The following objects have inconsistent (B − V) values in Vázquez et al (1995) and Sagar et al (2001): WEBDA-number 1058WEBDA-number , 1086WEBDA-number , 1088WEBDA-number , 1089WEBDA-number , 1092WEBDA-number , 1094WEBDA-number , 1099WEBDA-number , 1108WEBDA-number , 1129WEBDA-number , 1138 and 1159. We are not able to verify the error source since no other independent measurements for these objects exist.…”

Section: Pismis 20mentioning

confidence: 99%

CCD photometric search for peculiar stars in open clusters

Paunzen

Pintado

Maitzen

2002

A&A

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Abstract. The time scale on which chemical peculiarity in upper main sequence stars begins is unknown. Results from the Hipparcos measurements indicate that the classical chemically peculiar (CP) stars occupy the whole area from the zero age main sequence to the terminal age main sequence (Gómez et al. 1998). However, Hubrig et al. (2000 reported that the magnetic fields appear only in stars that have already completed at least approximately 30% of their main sequence life time. Previous observations in the very young Orion OB1 and Scorpio-Centaurus associations (Joncas & Borra 1981; Borra et al. 1982) reveal a percentage of chemically peculiar stars that is significantly smaller (less than 5%) than that of the galactic field (up to 25%). This already indicates that the phenomenon needs at least several 10 6 yr to appear. Since no further observations have been published since then, we have observed the five very young (1 Myr ≤ age ≤ 25 Myr) open clusters Collinder 272, Pismis 20, Lyngå 14, NGC 6396 and NGC 6611. Photometry from 250 CCD frames in the three filter ∆a-system results in very low detection limits (0.008 to 0.015 mag). We find no single photometrically chemically peculiar candidate in approximately 460 observed cluster members in the five program clusters. From the number of observed objects we deduce upper limits between 0.6% and 2.4% for the incidence of CP stars for the four observed aggregates.

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A multicolour CCD photometric and mass function study of the distant southern open star clusters NGC 3105, NGC 3603, Melotte 105, Hogg 15, NGC 4815, Pismis 20 and NGC 6253

Cited by 73 publications

References 50 publications

VLT multi-epoch radial velocity survey toward NGC 6253

VLT multi-epoch radial velocity survey toward NGC 6253

vbyCaHβ CCD Photometry of Clusters. VIII. The Super-Metal-Rich, Old Open Cluster NGC 6791

CCD photometric search for peculiar stars in open clusters

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