- ID:
- ivo://CDS.VizieR/J/A+AS/122/9
- Title:
- CCD UBVRI Photometry of 4 open clusters
- Short Name:
- J/A+AS/122/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD observations in the U, B, V, R and I passbands have been used to generate colour-colour and deep colour-magnitude diagrams for the young open star clusters NGC 3228, NGC 4103, NGC 5662 and NGC 6087. The sample consists of about 2000 stars reaching down to V=20mag. The interstellar extinction across the face of the imaged cluster regions seems to be uniform with average values of E(B-V)=0.31, 0.34 and 0.22mag for NGC 4103, NGC 5662 and NGC 6087 respectively. The distances to the clusters NGC 3228, NGC 4103, NGC 5662 and NGC 6087 have been estimated as 0.5+/-0.05, 2.0+/-0.3, 0.8+/-0.1 and 1.0+/-0.1kpc respectively, while the corresponding ages estimated from the theoretical stellar evolutionary isochrones fitted to the bright proper motion cluster members are ~100, 30, 80 and 65Myr respectively. Present data are consistent with the membership of the Cepheid variable V Cen to NGC 5662 and of S Norm to NGC 6087. Heavy contamination by foreground and background field stars has unfortunately made it impossible to reach definite conclusions about the faint luminosity function, and the data do not reach faint enough limits to investigate pre-main sequence stars.
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- ID:
- ivo://CDS.VizieR/J/other/BASI/32.295
- Title:
- CCD UBVRI photometry of 3 open clusters
- Short Name:
- J/other/BASI/32.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometric observations of three open clusters Berkeley 15 (= OCl 414), Czernik 18 (= OCl 426) and NGC 2401 (= OCl 588), obtained for the first time in UBVRI filters down to V=20mag, are presented here. They are located at distances of 1259, 955 and 3467 parsecs with their respective ages estimated as ~5x10^9^years, ~0.8 to 1x10^9^years and ~1x10^9^years. While OCl 414 and OCl 426 are in the direction of the Auriga - Perseus constellations, OCl 588 is placed in the direction of Ophiuchus constellation in our Galaxy. The clusters studied here are of intermediate and old age category.
- ID:
- ivo://CDS.VizieR/J/MNRAS/327/23
- Title:
- CCD UBVRI photometry of 7 open star clusters
- Short Name:
- J/MNRAS/327/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive cluster parameters and mass functions from new UBVRI CCD photometric observations of ~3500 stars reaching down to V~20mag for the distant southern open star clusters NGC 3105, NGC 3603, Melotte 105, Hogg 15, NGC 4815, Pismis 20 and NGC 6253. For NGC 3105 and Hogg 15, CCD data are presented for the first time. The observations were carried out in 1992 between February 28 and March 8, June 5 and 9, and July 9 and 12 in the Cousins U, B, V, R and I photometric bands using CCD detector at the 1.0-m Elizabeth Telescope at the South African Astronomical Observatory (SAAO), Sutherland.
- ID:
- ivo://CDS.VizieR/J/ApJS/245/13
- Title:
- CDIPS. I. LCs from TESS sectors 6 and 7
- Short Name:
- J/ApJS/245/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Transiting Exoplanet Survey Satellite (TESS) is providing precise time-series photometry for most star clusters in the solar neighborhood. Using the TESS images, we have begun a Cluster Difference Imaging Photometric Survey, in which we are focusing both on stars that are candidate cluster members and on stars that show indications of youth. Our aims are to discover giant transiting planets with known ages, and to provide light curves suitable for studies in stellar astrophysics. For this work, we made 159343 light curves of candidate young stars, across 596 distinct clusters. Each light curve represents between 20 and 25 days of observations of a star brighter than G_Rp_=16, with 30-minute sampling. We describe the image-subtraction and time-series analysis techniques we used to create the light curves, which have noise properties that agree with theoretical expectations. We also comment on the possible utility of the light-curve sample for studies of stellar rotation evolution and binary eccentricity damping.
- ID:
- ivo://CDS.VizieR/J/AJ/137/3210
- Title:
- Chandra observations of h Persei
- Short Name:
- J/AJ/137/3210
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe Chandra/ACIS-I observations of the massive ~13-14Myr-old cluster, h Persei, part of the famous Double Cluster (h and {chi} Per) in Perseus. Combining the list of Chandra-detected sources with new optical/IR photometry and optical spectroscopy reveals ~165 X-ray bright stars with V<~23. Roughly 142 have optical magnitudes and colors consistent with cluster membership.
- ID:
- ivo://CDS.VizieR/J/AJ/127/2659
- Title:
- CHANDRA observations of NGC 2264
- Short Name:
- J/AJ/127/2659
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a Chandra observation of a field in NGC 2264. The observations were taken with the ACIS-I camera with an exposure time of 48.1ks. We present a catalog of 263 sources, which includes X-ray luminosity, optical and infrared photometry, and X-ray variability information. We found 41 variable sources, 14 of which have a flarelike light curve, and two of which have a pattern of a steady increase or decrease over a 10-hr period. The optical and infrared photometry for the stars identified as X-ray sources are consistent with most of these objects being premain-sequence stars with ages younger than 3Myr.
- ID:
- ivo://CDS.VizieR/J/ApJ/589/509
- Title:
- Chandra observations of Trumpler 14 and 16
- Short Name:
- J/ApJ/589/509
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The region around the {eta} Carinae Nebula has three OB associations, which contain a Wolf-Rayet star and several massive O3 stars. An early Chandra ACIS-I image was centered on {eta} Car and includes Trumpler 16 and part of Trumpler 14. The Chandra image confirms the well-known result that O and very early B stars are X-ray sources with LX~=10^-7^Lbol over an X-ray luminosity range of about 100. Two new, anomalously strong X-ray sources have been found among the hot star population: Tr 16-244, a heavily reddened O3 I star, and Tr 16-22, a heavily reddened O8.5 V star. Two stars have an unusually large LX/Lbol: HD 93162, a Wolf-Rayet star (and possible binary), and Tr 16-22, a possible colliding-wind binary. In addition, a population of sources associated with cool stars is detected. In the color-magnitude diagram, these X-ray sources sit above the sequence of field stars in the Carina arm. The OB stars are on average more X-ray luminous than the cool star X-ray sources. X-ray sources among A stars have X-ray luminosities similar to those of cooler stars and may be due to cooler companions. Upper limits are presented for B stars that are not detected in X-rays. These upper limits are also the upper limits for any cool companions that the hot stars may have. Hardness ratios are presented for the most luminous sources in bands 0.5-0.9, 0.9-1.5, and 1.5-2.04keV. The available information on the binary nature of the hot stars is discussed, but binarity does not correlate with X-ray strength in a simple way.
- ID:
- ivo://CDS.VizieR/J/ApJ/614/267
- Title:
- Chandra sources in Cha I North
- Short Name:
- J/ApJ/614/267
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sensitive X-ray imaging surveys provide a new and effective tool to establish the census of pre-main-sequence (PMS) stars in nearby young stellar clusters. We report here a deep Chandra X-Ray Observatory observation of PMS stars in the Chamaeleon I North cloud, achieving a limiting luminosity of log L_t_~27ergs/s (0.5-8keV band) in a 0.8x0.8pc^2^ region. Of the 107 X-ray sources, 37 are associated with Galactic stars of which 27 are previously recognized cloud members.
- ID:
- ivo://CDS.VizieR/J/ApJ/770/98
- Title:
- Chandra study of NGC 6791
- Short Name:
- J/ApJ/770/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first X-ray study of NGC 6791, one of the oldest open clusters known (8Gyr). Our Chandra observation is aimed at uncovering the population of close interacting binaries down to L_X_~1x10^30^erg/s (0.3-7keV). We detect 86 sources within 8' of the cluster center, including 59 inside the half-mass radius. We identify 20 sources with proper-motion cluster members, which are a mix of cataclysmic variables (CVs), active binaries (ABs), and binaries containing sub-subgiants. With follow-up optical spectroscopy, we confirm the nature of one CV. We discover one new, X-ray variable candidate CV with Balmer and He II emission lines in its optical spectrum; this is the first X-ray-selected CV in an open cluster. The number of CVs per unit mass is consistent with the field, suggesting that the 3-4 CVs observed in NGC 6791 are primordial. We compare the X-ray properties of NGC 6791 with those of a few old open (NGC 6819, M67) and globular clusters (47 Tuc, NGC 6397). It is puzzling that the number of ABs brighter than 1x10^30^erg/s normalized by cluster mass is lower in NGC 6791 than in M 67 by a factor ~3-7. CVs, ABs, and sub-subgiants brighter than 1x10^30^erg/s are under-represented per unit mass in the globular clusters compared to the oldest open clusters, and this accounts for the lower total X-ray luminosity per unit mass of the former. This indicates that the net effect of dynamical encounters may be the destruction of even some of the hardest (i.e., X-ray-emitting) binaries.
- ID:
- ivo://CDS.VizieR/J/ApJ/588/1009
- Title:
- Chandra X-ray observations of NGC 2516
- Short Name:
- J/ApJ/588/1009
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive study of the Chandra X-ray observations of the young open cluster NGC 2516. We have analyzed eight individual Chandra observations. We have combined the data to achieve the greatest sensitivity, reaching down to log f_X_=-14.56(erg/s/cm^2^), or logLX=28.69(erg/s) at the distance of NGC 2516. Out of 284 X-ray sources detected, 155 are identified with photometric cluster members, with very little ambiguity.