- 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.
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- ID:
- ivo://CDS.VizieR/J/A+A/553/A40
- Title:
- UBVI light curves of FK Com
- Short Name:
- J/A+A/553/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We apply the continuous period search and carrier fit methods on long-term standard Johnson-Cousins V-observations from the years 1995-2010. The observations were carried out with two automated photometric telescopes, Phoenix-10 and Amadeus T7 located in Arizona. We identify complex phase behaviour in 6 of the 15 analysed data segments. We identify five flip-flop events and two cases of phase jumps, where the phase shift is {Delta}{phi}<0.4. In addition we see two mergers of spot regions and two cases where the apparent phase shifts are caused by spot regions drifting with respect to each other. Furthermore we detect variations in the rotation period corresponding to a differential rotation coefficient of |k|>0.031.
- 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/ApJS/162/49
- Title:
- UBV imaging of irregular galaxies
- Short Name:
- J/ApJS/162/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of UBV imaging of a large sample of irregular galaxies: 94 Im systems, 24 blue compact dwarfs (BCDs), and 18 Sm galaxies. We also include JHK imaging of 42 of these galaxies. The sample spans a large range in galactic parameters. Ellipse fit axial ratios, inclinations, and position angles are derived, integrated photometry and azimuthally averaged surface photometry profiles are determined, and exponential fits give the central surface brightnesses, scale lengths, and isophotal and half-power radii.
- ID:
- ivo://CDS.VizieR/J/A+A/345/505
- Title:
- UBVI magnitudes of NGC 869 B-type pulsators
- Short Name:
- J/A+A/345/505
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the course of the search for B-type pulsators in the central region of h Persei, we discovered two {beta} Cephei stars, Oo692 and Oo992, and one SPB star, Oo893. The first two stars are monoperiodic pulsators with periods of 0.1716946 and 0.1326359 d respectively, and semi-amplitudes smaller than 0.01mag. The light curve of Oo893 can be described by a single 1.193633-day period, slightly non-sinusoidal in shape, and having semi-amplitudes from 19 mmag in I to 48 mmag in U. Oo893 is the first SPB star found in h and {chi} Persei. In addition, we discovered seven other variables, including three eclipsing binaries and one {lambda} Eri star. One of the binaries is a W UMa-type star and a likely cluster member. We also present new UBV photometry for 258 stars in the field. The average reddening, estimated from the cluster colour-colour diagram, amounts to E(B-V)=0.52mag. A 0.1mag dispersion of reddenings within the cluster is also seen.
- ID:
- ivo://CDS.VizieR/J/ApJ/641/763
- Title:
- UBVI photometry for Arp 220 star clusters
- Short Name:
- J/ApJ/641/763
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new optical observations of young massive star clusters in Arp 220, the nearest ultraluminous infrared galaxy, taken in UBVI with the Hubble Space Telescope ACS HRC camera. We find a total of 206 probable clusters whose spatial distribution is centrally concentrated toward the nucleus of Arp 220. We use model star cluster tracks to determine ages, luminosities, and masses for 14 clusters with complete UBVI indices or previously published near-infrared data. We estimate rough masses for 24 additional clusters with I<24mag from BVI indices alone.
- ID:
- ivo://CDS.VizieR/J/AJ/106/220
- Title:
- UBVI photometry in Berkeley 31
- Short Name:
- J/AJ/106/220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometry on the Johnson UBV and on the Kron-Cousins VI systems are presented for 732 stars in and near Be 31, an open cluster located towards the galactic anticenter. The resultant color-magnitude diagrams indicate that the cluster is an old object. From the color-color diagram, the reddening and metallicity parameters are determined to be E(B-V) = 0.13 mag and [Fe/H] = -0.4. By comparing the cluster C-M diagrams with the VandenBerg isochrones, and by assuming a normal reddening law, a distance of 5.2 +/- 0.5 kpc and an age of 8 Gyr are derived.
- ID:
- ivo://CDS.VizieR/J/other/BASI/29.53
- Title:
- UBVI photometry in Berkeley 32
- Short Name:
- J/other/BASI/29.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new CCD photometry of the distant old open star cluster Berkeley 32 in Johnson V and Cousins I passbands. A total of about 3200 stars have been observed in a field of about 13'x13'. The colour-magnitude diagram (CMD) in V, (V-I) has been generated down to V=22mag. A broad but well defined main sequence is clearly visible. Some blue stragglers, a well developed subgiant branch and a Red Clump are also seen. By fitting isochrones to this CMD as well as to other CMDs available in the literature, and using the Red Clump location, the reddening, distance and age of the star cluster have been determined. The cluster has a distance of about 3.3kpc, its radius is about 2.4pc; the reddening E(B-V) is 0.08 mag and the age is about 6.3Gyr. By comparison with theoretical isochrones, a metallicity of [Fe/H]~-0.2dex has been estimated.
- ID:
- ivo://CDS.VizieR/J/A+A/573/A70
- Title:
- UBVI photometry in 3 globular clusters
- Short Name:
- J/A+A/573/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the photometric analysis of the external regions of three Galactic Globular Clusters: NGC 6121, NGC 6397 and NGC 6752. The main goal is the characterization of the multiple stellar populations along the main sequence (MS) and the study of the radial trend of the different populations hosted by the target clusters. The data have been collected using FORS2 mounted at the ESO/VLT@UT1 telescope in UBVI filters. From these data sets we extracted high-accuracy photometry and constructed color-magnitude diagrams. We exploit appropriate combination of colors and magnitudes which are powerful tools to identify multiple stellar populations, like B versus U-B and V versus c_U,B,I_=(U-B)-(B-I) CMDs. We confirm previous findings of a split MS in NGC 6752 and NGC 6121. Apart from the extreme case of omega Centauri, this is the first detection of multiple MS from ground-based photometry. For NGC 6752 and NGC 6121 we compare the number ratio of the blue MS to the red MS in the cluster outskirts with the fraction of first and second generation stars measured in the central regions. There is no evidence for significant radial trend. The MS of NGC 6397 is consistent with a simple stellar population. We propose that the lack of multiple sequences is due both to observational errors and to the limited sensitivity of U,B,V,I photometry to multiple stellar populations in metal-poor GCs. Finally, we compute the helium abundance for the stellar populations hosted by NGC 6121 and NGC 6752, finding a mild ({Delta}Y~0.02) difference between stars in the two sequences.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/194
- Title:
- UBVI photometry in NGC 1252
- Short Name:
- J/MNRAS/434/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- If stars form in clusters but most stars belong to the field, understanding the details of the transition from the former to the latter is imperative to explain the observational properties of the field. Aging open clusters are one of the sources of field stars. The disruption rate of open clusters slows down with age but, as an object gets older, the distinction between the remaining cluster or open cluster remnant (OCR) and the surrounding field becomes less and less obvious. As a result, finding good OCR candidates or confirming the OCR nature of some of the best candidates still remain elusive. One of these objects is NGC 1252, a scattered group of about 20 stars in Horologium. Here we use new wide-field photometry in the UBVI passbands, proper motions from the Yale/San Juan SPM 4.0 catalogue and high-resolution spectroscopy concurrently with results from N-body simulations to decipher NGC 1252's enigmatic character. Spectroscopy shows that most of the brightest stars in the studied area are chemically, kinematically and spatially unrelated to each other. However, after analysing proper motions, we find one relevant kinematic group. This sparse object is relatively close (~1kpc), metal poor and is probably not only one of the oldest clusters (3Gyr) within 1.5kpc from the Sun but also one of the clusters located farthest from the disc, at an altitude of nearly -900pc. That makes NGC 1252 the first open cluster that can be truly considered a high Galactic altitude OCR: an unusual object that may hint at a star formation event induced on a high Galactic altitude gas cloud. We also conclude that the variable TW Horologii and the blue straggler candidate HD 20286 are unlikely to be part of NGC 1252. NGC 1252 17 is identified as an unrelated, Population II cannonball star moving at about 400km/s.
