- ID:
- ivo://CDS.VizieR/J/AJ/130/1194
- Title:
- UBV photometry in Ruprecht 91
- Short Name:
- J/AJ/130/1194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photoelectric UBV photometry and star counts are presented for stars in the previously unstudied open cluster Ruprecht 91, supplemented by observations for stars in adjacent regions surrounding the Cepheids SX Car and VY Car, including new observations for the latter. Ruprecht 91 is typical of groups associated with Cepheids, with an evolutionary age of ~8x10^7^yr, but it is only 980+/-8pc distant, much closer than the Cepheids.
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- ID:
- ivo://CDS.VizieR/J/AJ/102/642
- Title:
- UBV photometry in Westerlund 2
- Short Name:
- J/AJ/102/642
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Two new Galactic Wolf-Rayet stars were found in open clusters: a WN4 star in the O9 cluster Sher 1 and a WN7 star in the O7 cluster Westerlund 2. This confirms a previous trend, namely that fainter, hotter WN stars tend to be older than brighter, cooler WN stars. This may be a consequence of evolution via extreme mass loss.
- ID:
- ivo://CDS.VizieR/J/A+A/409/541
- Title:
- UBV photometry of IC 2395
- Short Name:
- J/A+A/409/541
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report UBV photoelectric photometry for 273 stars in the fields of the open clusters IC 2395 and BH 47. Our postulate is that, rather than two different clusters in this region of Vela, there is only one, which we call IC 2395 = BH 47. The cluster is centered at about RA = 8h 42min 33s, and DE = -48{deg} 06' 48" (2000), its angular diameter being ~19'. The analysis of the photometric data yields 61 probable cluster members and 16 possible members. Photometric membership probabilities show good agreement with those obtained from a proper motion study for 21 stars in common. The reddening across the cluster appears to be uniform, the mean E(B-V) value being 0.09+/-0.02. The true distance modulus is V_0_-Mv=9.52+/-0.10, corresponding to a distance from the Sun of (800+/-40)pc and 48pc below the Galactic plane. The cluster age, determined by fitting isochrones with core overshooting, turns out to be (6+/-2)Myr. There is a strong likelihood that IC 2395 = BH 47 is physically connected to the Vela OB1C association.
- ID:
- ivo://CDS.VizieR/J/A+AS/128/131
- Title:
- UBV photometry of NGC 2323
- Short Name:
- J/A+AS/128/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- UBV and DDO photoelectric photometry in the field of the open cluster NGC 2323 is presented. The analysis yields 109 probable members; one of them being a red giant, and 3 possible members. The basic cluster parameters are derived. NGC 2323 appears not to be physically connected to the CMa OB1 association.
- ID:
- ivo://CDS.VizieR/J/A+A/493/71
- Title:
- UBV photometry of Shorlin 1
- Short Name:
- J/A+A/493/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The detailed spiral structure of the outer Galactic disk remains poorly constrained, and for several line of sights in the Galaxy we depend on model extrapolations. One of these regions is the fourth Galactic quadrant, between Vela and Carina (270{deg}<=l<=300{deg}), where, apart from the conspicuous Carina branch of the Carina Sagittarius arm, no spiral arms have been detected so far in the optical beyond l~270{deg}. By means of deep UBVI photometry, we search for spiral features in known low absorption windows. Although observationally demanding, U photometry constitutes a powerful tool for detecting and characterizing distant aggregates of young stars, and allows firmer distance estimates to be derived. We study a direction close to the tangent (l~290{deg}) of the Carina arm, in an attempt to detect optical spiral tracers far beyond the Carina branch, where radio observations and model predictions appear to indicate the presence of an extension of the Perseus and Norma-Cygnus spiral arms in the fourth quadrant. Along this line of sight, we detect three distinct groups of young stars. Two of them, at distances of ~2.5 and ~6.0kpc, belong to the Carina spiral arm, which is traversed twice in this particular direction. Interestingly, the latter is detected for the first time. The third group, at a distance of ~12.7kpc, is probably related to the Perseus arm which lies beyond the Carina arm, and constitutes the first optical detection of this arm in the fourth Galactic quadrant. The position of this feature is consistent with both HI observations and model predictions. We also present evidence that this extremely distant group, formerly assumed to be a star cluster (Shorlin 1), is a diffuse, young population, typically found in spiral galaxies. In addition, our data-set does not support, as claimed in the literature, the possible presence of the Monoceros Ring in this direction. This study highlights how multicolor optical studies can be effective in probing the spiral structure of the outer Galactic disk. More fields need to be studied in this region of the Galaxy to constrain the spiral structure in the fourth Galactic quadrant more accurately, in particular, the shape and extent of the Perseus arm, and, possibly, to detect the even more distant Norma-Cygnus arm.
- ID:
- ivo://CDS.VizieR/J/AJ/143/46
- Title:
- UBV photometry of stars in Berkeley 55
- Short Name:
- J/AJ/143/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBV photometry of the highly reddened and poorly studied open cluster Berkeley 55 (= C 2115+515), revealing an important population of B-type stars and several evolved stars of high luminosity. Intermediate-resolution far-red spectra of several candidate members confirm the presence of one F-type supergiant and six late supergiants or bright giants. The brightest blue stars are mid-B giants. Spectroscopic and photometric analyses indicate an age 50+/-10Myr. The cluster is located at a distance d~4kpc, consistent with other tracers of the Perseus Arm in this direction. Berkeley 55 is thus a moderately young open cluster with a sizable population of candidate red (super)giant members, which can provide valuable information about the evolution of intermediate-mass stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/466/4960
- Title:
- UBVRI and CT1T2 photometry of 15 open clusters
- Short Name:
- J/MNRAS/466/4960
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBVRI and CT_1_T_2_ photometry for 15 catalogued open clusters of relative high brightness and compact appearance. From these unprecedented photometric data sets, covering wavelengths from the blue up to the near-infrared, we performed a thorough assessment of their reality as stellar aggregates. We statistically assigned to each observed star within the object region a probability of being a fiducial feature of that field in terms of its local luminosity function, colour distribution and stellar density. Likewise, we used accurate parallaxes and proper motions measured by the Gaia satellite to help our decision on the open cluster reality. 10 catalogued aggregates did not show any hint of being real physical systems; three of them had been assumed to be open clusters in previous studies, though. On the other hand, we estimated reliable fundamental parameters for the remaining five studied objects, which were confirmed as real open clusters. They resulted to be clusters distributed in a wide age range, 8.0<=log(t yr^-1^)<=9.4, of solar metal content and placed between 2.0 and 5.5kpc from the Sun. Their ages and metallicities are in agreement with the presently known picture of the spatial distribution of open clusters in the Galactic disc.
- ID:
- ivo://CDS.VizieR/J/AJ/120/333
- Title:
- UBVRI and H{alpha} in NGC 6530
- Short Name:
- J/AJ/120/333
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New UBVRI and H{alpha} photometry has been obtained for the young open cluster NGC 6530 located 10' east of the Lagoon Nebula (M8). We found 37 pre-main-sequence (PMS) stars with H{alpha} emission and nine PMS candidates using the R-H{alpha} color, a measure of H{alpha} emission. From this new photometry we derived the cluster parameters (V_0_-M_V_=11.25+/-0.1mag and E(B-V)=0.35mag), typical age (1.5Myr), and an age spread of about 5Myr. We confirmed the presence of a small amount of differential reddening across the cluster. We also verified the abnormal reddening law for the cluster, especially for a heavily embedded O7 V star, Herschel 36. Comparisons were made for several PMS evolution models with regard to the resulting age distribution and the initial mass function.
- ID:
- ivo://CDS.VizieR/J/AJ/149/190
- Title:
- UBVRI and infrared photometry of NGC 2215
- Short Name:
- J/AJ/149/190
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical UBVRI photometric measurements using the Faulkes Telescope North were taken in early 2011 and combined with 2MASS JHK_s_ and WISE infrared photometry as well as UCAC4 proper motion data in order to estimate the main parameters of the galactic open cluster NGC 2215 of which large uncertainty exists in the current literature. Fitting a King model we estimate a core radius of 1.12'+/-0.04'(0.24+/-0.01pc) and a limiting radius of 4.3'+/-0.5'(0.94+/-0.11pc) for the cluster. The results of isochrone fits indicates an age of log(t)=8.85+/-0.10 with a distance of d=790+/-90pc, a metallicity of [Fe/H]=-0.40+/-0.10dex, and a reddening of E(B-V)=0.26+/-0.04. A proportion of the work in this study was undertaken by Australian and Canadian upper secondary school students involved in the Space to Grow astronomy education project, and is the first scientific publication to have utilized our star cluster photometry curriculum materials.
- ID:
- ivo://CDS.VizieR/J/other/RMxAA/39.89
- Title:
- UBVRI and polarisation in Lynga 1
- Short Name:
- J/other/RMxAA/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD UBVRI (Cousins system) photometric observations complemented with spectroscopy and polarimetric observations that were carried out in the open cluster Lynga 1. Our data indicate that the cluster reddening is E_B-V_=0.45+/-0.03, the ratio A_v_/E_B-V_=R suggests that the extinction law may be slightly anomalous (R~3.5) and that the cluster distance modulus is V_0_-M_v=11.40+/-0.2. The age of Lynga 1 is between 100 and 125Myr according to a fitting of theoretical isochrones, and the slope of its mass spectrum is x~1.7. The brightest red star in the field is a cluster member of spectral type K2 II-Ib.
