- ID:
- ivo://CDS.VizieR/J/MNRAS/341/805
- Title:
- UBVI CCD photometry of Cep OB3b
- Short Name:
- J/MNRAS/341/805
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a low-mass pre-main-sequence (PMS) stellar population in the younger subgroup of the Cepheus OB3 association, Cep OB3b, using UBVI CCD photometry and follow-up spectroscopy. The optical survey covers approximately 1300arcmin^2^ on the sky and gives a global photometric and astrometric catalogue for more than 7000 objects. The location of a PMS population is well defined in a V versus (V-I) colour-magnitude diagram.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/306/361
- Title:
- UBVI CCD photometry of M35 (NGC 2168)
- Short Name:
- J/MNRAS/306/361
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- UBVI CCD photometry has been obtained for the intermediate-age open cluster M35 (NGC 2168). From this new photometry we derived the cluster parameters (Vo-MV= 9.60+/-0.10 mag, E(B-V) = 0.255+/-0.024 mag), age (logAge=8.3+/-0.3) and a photometric abundance (Z~0.008, i.e. [Fe/H]~-0.3) from comparison with theoretical isochrones of the Padova group. A minimum binary frequency (35+/-5%) was estimated from the distribution of distance moduli of unevolved proper motion members. Faint photometric members were selected by using differences in the reddening effect on colour indices.
- ID:
- ivo://CDS.VizieR/J/AJ/123/290
- Title:
- UBVI CCD photometry of NGC 2516
- Short Name:
- J/AJ/123/290
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBVI CCD photometry of the intermediate-age open cluster NGC 2516.
- ID:
- ivo://CDS.VizieR/J/MNRAS/383/1241
- Title:
- UBVIc photometry of cluster Berkeley 59
- Short Name:
- J/MNRAS/383/1241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBVIc CCD photometry of the young open cluster Be 59 with the aim to study the star formation scenario in the cluster. The radial extent of the cluster is found to be ~10arcmin (2.9pc). The interstellar extinction in the cluster region varies between E(B-V)=1.4 to 1.8mag. The ratio of total-to-selective extinction in the cluster region is estimated as 3.7+/-0.3. The distance of the cluster is found to be 1.00+/-0.05kpc. Using near-infrared (NIR) colours and slitless spectroscopy, we have identified young stellar objects (YSOs) in the open cluster Be 59 region. The Midcourse Space Experiment (MSX) and IRAS-HIRES images around the cluster region are also used to study the emission from unidentified infrared bands and to estimate the spatial distribution of optical depth of warm and cold interstellar dust.
- ID:
- ivo://CDS.VizieR/J/A+A/436/527
- Title:
- UBVIc photometry of NGC 4852
- Short Name:
- J/A+A/436/527
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present wide-field deep UBVIc photometry for the previously unstudied open cluster NGC 4852 down to a limiting magnitude Ic~24, obtained from observations taken with the Wide Field Imager camera on-board the MPG/ESO 2.2m telescope at La Silla (ESO, Chile), in the photometric night of July 7, 2002. These data are used to obtain the first estimate of the cluster basic parameters, to study the cluster spatial extension by means of star counts, and to derive the Luminosity (LF) and Mass Functions (MF). The cluster radius turns out to be 5.0+/-1.0arcmin. The cluster emerges clearly from the field down to V=20mag. At fainter magnitudes, it is completely confused with the general Galactic disk field. The stars inside this region define a young open cluster (200 million years old) 1.1kpc far from the Sun (m-M=11.60, E(B-V)=0.45). The Present Day Mass Functions (PDMF) from the V photometry is one of the most extended in mass obtained to date, and can be represented as a power-law with a slope alpha=2.3+/-0.3 and (the Salpeter MF in this notation has a slope alpha=2.35), in the mass range 3.2<=m/m_{sun}_<=0.6. Below this mass, the MF cannot be considered as representative of the cluster MF, as the cluster merges with the field and therefore the MF is the result of the combined effect of strong irregularities in the stellar background and interaction of the cluster with the dense Galactic field. The cluster total mass at the limiting magnitude results to be 2570+/-210M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A50
- Title:
- UBVIc photometry of stars in Westerlund 2
- Short Name:
- J/A+A/555/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new X-ray, UBVIc, and JHKs study of the young cluster Westerlund 2 was undertaken to resolve discrepancies tied to the cluster's distance. Existing spectroscopic observations for bright cluster members and new multi-band photometry imply a reddening relation toward Westerlund 2 described by E(U-B)/E(B-V)=0.63+0.02E(B-V). Variable-extinction analyses for Westerlund 2 and nearby IC 2581 based upon spectroscopic distance moduli and ZAMS fitting yield values of R_V_=A_V_/E(B-V)=3.88+/-0.18 and 3.77+/-0.19, respectively, and confirm prior assertions that anomalous interstellar extinction is widespread throughout Carina. The results were confirmed by applying the color-difference method to UBVRIcJHKs data for 19 spectroscopically observed cluster members, yielding R_V_=3.85+/-0.07. The derived distance to Westerlund 2 of d=2.85+/-0.43kpc places the cluster on the far side of the Carina spiral arm. The cluster's age is no more than {tau}~2x10^6^yr as inferred from the cluster's brightest stars and an X-ray (Chandra) cleaned analysis of its pre-main-sequence demographic. Four Wolf-Rayet stars in the cluster core and surrounding corona (WR20a, WR20b, WR20c, and WR20aa) are very likely cluster members, and their inferred luminosities are consistent with those of other late-WN stars in open clusters. The color-magnitude diagram for Westerlund 2 also displays a gap at spectral type B0.5~V with associated color spread at higher and lower absolute magnitudes that might be linked to close binary mergers. These features, in conjunction with the evidence for mass loss from the WR stars, may help to explain the high flux of {gamma}-rays, cosmic rays, and X-rays from the direction toward Westerlund 2.
- ID:
- ivo://CDS.VizieR/J/PASP/122/288
- Title:
- UBVI_KC_ photometry in NGC 2309
- Short Name:
- J/PASP/122/288
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained CCD UBVI_KC_ photometry down to V~22.0 for the open cluster NGC 2309 and its surrounding field. Twenty three probable cluster members have been identified for the first time on the basis of sound photometric criteria. Because NGC 2309 is a relatively poor cluster projected onto a rich star field showing density fluctuations, the frequently used membership criteria based on stellar density profiles or proper motion measurements would not be enough to assess the star membership status if employed independently. We estimated a cluster radius of 7.9' and a radius at half the maximum of the cluster density profile of 1.7'. Based on the best fits of isochrones computed by the Geneva group to the cluster color-magnitude and color-color diagrams, previously shifted by the cluster reddening (E(B-V)=0.32) and distance (d=2.5kpc), we derived the cluster age (250Myr) and metallicity ([Fe/H]~0.0). If an 8.5kpc distance from the Sun to the center of the Galaxy is assumed, then NGC 2309 is found to be located just in front of the Perseus spiral arm.
- ID:
- ivo://CDS.VizieR/J/A+A/515/A16
- Title:
- UBVI light curves of NGC 884 variables
- Short Name:
- J/A+A/515/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent progress in the seismic interpretation of field beta Cep stars has resulted in improvements of the physics in the stellar structure and evolution models of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance and chemical composition. To improve our comprehension of the beta Cep stars, we studied the young open cluster NGC 884 to discover new B-type pulsators, besides the two known beta Cep stars, and other variable stars. An extensive multi-site campaign was set up to gather accurate CCD photometry time series in four filters (U, B, V, I) of a field of NGC 884. The images were calibrated and reduced to transform the CCD frames into interpretable light curves. Various variability indicators and frequency analyses were applied to detect variable stars in the field.
- ID:
- ivo://CDS.VizieR/J/MNRAS/397/1073
- Title:
- UBVI photometry in NGC 2587
- Short Name:
- J/MNRAS/397/1073
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD photometry in the Johnson U, B and V and Kron-Cousins I passbands for the open cluster NGC 2587. The sample consists of 4406 stars reaching down to V~21.0. We developed a new method to clean statistically the colour-magnitude diagrams. NGC 2587 appears to be a sparse, relatively bright open cluster, with a few tens of members projected on to a populous star field.
- ID:
- ivo://CDS.VizieR/J/ApJ/783/56
- Title:
- UBVI photometry in NGC 6752
- Short Name:
- J/ApJ/783/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper is devoted to photometric study of the Galactic globular cluster (GGC) NGC 6752 in UBVI, focusing on the multiplicity of its stellar population. We emphasize that our U passband is (1) narrower than the standard one due to its smaller extension blueward and (2) redshifted by ~300{AA} relative to its counterparts, such as the HST F336W filter. Accordingly, both the spectral features encompassed by it and photometric effects of the multiplicity revealed in our study are somewhat different than in recent studies of NGC 6752. Main sequence stars bluer in U-B are less centrally concentrated, as red giants are. We find a statistically significant increasing luminosity of the red giant branch (RGB) bump of {Delta}U{approx}0.2mag toward the cluster outskirts with no so obvious effect in V. The photometric results are correlated with spectroscopic data: the bluer RGB stars in U-B have lower nitrogen abundances. We draw attention to a larger width of the RGB than the blue horizontal branch (BHB) in U-B. This seems to agree with the effects predicted to be caused by molecular bands produced by nitrogen-containing molecules. We find that brighter BHB stars, especially the brightest ones, are more centrally concentrated. This implies that red giants that are redder in U - B, i.e., more nitrogen enriched and centrally concentrated, are the main progenitors of the brighter BHB stars. However, such a progenitor-progeny relationship disagrees with theoretical predictions and with the results on the elemental abundances in horizontal branch stars. We isolated the asymptotic giant branch clump and estimated the parameter {Delta}V_ZAHB_^clump^=0.98+/-0.12.
