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On physical parameters of the open cluster NGC 6823
No full textОбнаружено значительное различие показателей цвета U—B звезд — членов скопления NGC 6823 по данным разных каталогов. Это обстоятельство ставит под сомнение результаты предыдущих исследований скопления NGC 6823, выполненных с помощью Q-метода. Поэтому был проведен новый отбор членов скопления по ранее разработанной методике на основе кинематических, фотометрических и имеющихся для большинства звезд спектральных данных.Виявлено значні відмінності між показниками кольору U—B зірок—членів скупчення NGC 6823 за даними різних каталогів. Ця обставина ставить под сумнів результати попередніх досліджень скупчення NGC 6823, виконаних з допомогою Q-методу. Тому було проведено новий відбір членів скупчення за раніше розробленою методикою на основі кінематичних, фотометричних та наявних для більшості зірок спектральних даних.Large discrepancies are found to exist in the (U—B) colour indices for the NGC 6823 cluster members if the data are taken from different catalogues. This makes doubtful the results of previous studies of this cluster by the Q method. Therefore, a new selection of cluster members has been carried out by a method elaborated earlier which is based on the kinematic and photometric data, as well as on the spectral data available for the majority of stars
On physical parameters of the open cluster NGC 6823
Get PDFОбнаружено значительное различие показателей цвета U—B звезд — членов скопления NGC 6823 по данным разных каталогов. Это обстоятельство ставит под сомнение результаты предыдущих исследований скопления NGC 6823, выполненных с помощью Q-метода. Поэтому был проведен новый отбор членов скопления по ранее разработанной методике на основе кинематических, фотометрических и имеющихся для большинства звезд спектральных данных.Виявлено значні відмінності між показниками кольору U—B зірок—членів скупчення NGC 6823 за даними різних каталогів. Ця обставина ставить под сумнів результати попередніх досліджень скупчення NGC 6823, виконаних з допомогою Q-методу. Тому було проведено новий відбір членів скупчення за раніше розробленою методикою на основі кінематичних, фотометричних та наявних для більшості зірок спектральних даних.Large discrepancies are found to exist in the (U—B) colour indices for the NGC 6823 cluster members if the data are taken from different catalogues. This makes doubtful the results of previous studies of this cluster by the Q method. Therefore, a new selection of cluster members has been carried out by a method elaborated earlier which is based on the kinematic and photometric data, as well as on the spectral data available for the majority of stars
Younger adult type 2 diabetic patients have poorer glycaemic control: A cross-sectional study in a primary care setting in Singapore
Get PDF10.1186/1472-6823-13-18BMC Endocrine Disorders13-BEDM
Polarization towards the young open cluster NGC 6823
No full textWe present multiwavelength linear polarimetric observations of 104 stars towards the region of young open cluster NGC 6823. The polarization towards NGC 6823 is dominated by foreground dust grains and we found evidence for the presence of several layers of dust towards the line of sight. The first layer of dust is approximately located within 200 pc towards the cluster, which is much closer to the Sun than the cluster itself (~2.1 kpc). The radial distribution of the position angles for the member stars is found to show a systematic change, while the polarization is found to reduce towards the outer parts of the cluster and the average position angle of the coronal region of the cluster is very close to the inclination of the Galactic parallel (~32°). The size distribution of the grains within NGC 6823 is similar to those in the general interstellar medium. The patchy distribution of foreground dust grains is suggested to be mainly responsible for both differential reddening and polarization towards NGC 6823. The majority of the observed stars do not show evidence of intrinsic polarization in their light
uvby beta photoelectric photometry of the open cluster NGC 6823
No full textAbsolute uvbybeta photoelectric photometry of the brightest stars in the direction of the Open Cluster NGC 6823 has been secured and is presented. From the data analysis, reddening, distance, temperature and gravity are determined for the B, A, F stars and, from these, reddening and a mean distance modulus (12.475 +/- 0.414 mag) to the cluster are determined. Also, their membership in the cluster has been established and a numerical value of the age is determined through direct comparison with theoretical models. A brief analysis of the short period variable stars in the direction of NGC 6823 is made. We have concluded that they might not be pre-MS delta Scuti stars
Study of the galactic cluster NGC 6823
No full textPhotoelectric UBV magnitudes have been determined for 41 stars in NGC 6823. The reddening across the cluster field is determined and found that it varies from E(B-V)=0.60 to 1.16 mag. The true distance modulus to the cluster is estimated at 12.7±0.3 mag. It is found that cluster stars are not co-equal in age
Tunneling dynamics, symmetry, and far-infrared spectrum of the rotating water trimer. II. Calculations and experiments
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6823.pdf (Publisher’s version ) (Open Access
Hydrogen Content of Young Stellar Clusters. V. Clusters NGC6604, 6611, and 6823
No full textMeasurements of the total amount of hydrogen gas associated with the O-type clusters NGC 6604, 6611, and 6823 are reported. Only a small part of the large visible nebula in which NGC 6604 appears to be embedded is associated with the cluster. The small ionized nebula associated with NGC6604 has a mass of ~600Mo and is part of a larger neutral cloud. The mass of the ionized nebula associated with NGC 6611 is ~ 5000 M 0, while a neutral hydrogen shell with a total mass of ~ 105 M 0 probably surrounds the ionized nebula. The cluster NGC 6823 is embedded in a bright nebula of mass ~ 1800 Mo. A neutral hydrogen shell of mass ~ 2000 M 0 surrounds the ionized nebula, so that the total mass of hydrogen associated with NGC 6823 is ~ 4000 Mo.</jats:p
Young stellar objects in NGC 6823
Get PDFNGC 6823 is a young open cluster that lies at a distance of ∼2 kpc in the Vulpecula OB1 association. Previous studies using CCD photometry and spectroscopy have identified a Trapezium system of bright O- and B-type stars at its centre, along with several massive O-, B- and A-type stars in the cluster. We present optical VRI and near-infrared JHK photometric observations, complemented with Spitzer/Infrared Array Camera archival data, with an aim to identify the young low-mass population and the disc candidates in this region. Our survey reaches down to I∼ 22 mag and Ks∼ 18 mag. There is significant differential reddening within the cluster. We find a bimodal distribution for AV, with a peak at ∼3 mag and a broader peak at ∼10 mag. We have classified the sources based on the [4.5] − [8] colour, which is least affected by extinction. We find a ∼20 per cent fraction of Class I/Class II young stellar objects (YSOs) in the cluster, while a large 80 per cent fraction of the sources have a Class III classification. We have made use of the INT Photometric Hα Survey (IPHAS) in order to probe the strength in Hα emission for this large population of Class III sources. Nearly all of the Class III objects have photospheric (r′−Hα) colours, implying an absence of Hα in emission. This large population of Class III sources is thus likely the extinct field star population rather than the discless YSOs in the cluster. There is a higher concentration of the Class I/II systems in the eastern region of the cluster and close to the central Trapezium. The western part of the cluster mostly contains Class III/field stars and seems devoid of disc sources. We find evidence of a pre-main-sequence population in NGC 6823, in addition to an upper main-sequence population. The pre-main-sequence population mainly consists of young disc sources with ages between ∼1 and 5 Myr, and at lower masses of ∼0.1–0.4 M⊙. There may be a possible mass-dependent age spread in the cluster, with the older stars being more massive than the younger ones. The presence of young disc sources in NGC 6823 indicates similar star formation properties in the outer regions of the Galaxy as observed for young clusters in the solar neighbourhood
Spectroscopic observations of young open clusters: IC 1805, NGC 654 and NGC 6823
No full textSpectroscopic observations were made for a sample of 263 stars from three young open clusters IC 1805, NGC 654 and NGC 6823 with CCD detectors in the blue and yellow-red spectral regions. MKK types were properly determined for these stars by carefully comparing spectra of program stars with those of a complete grid of MKK standards, which were observed with the same instruments as the program stars. For most of the observed stars precise MKK types were assigned for the first time. A few of early-type emission-line stars were discovered or confirmed. The presence of Be stars in the studied clusters is discussed. Spectra of the observed MKK standards also reveal lots of features showing temperature or luminosity effect in the yellow-red region, which helped in our stellar spectral classification
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