- ID:
- ivo://CDS.VizieR/J/ApJS/116/263
- Title:
- VI photometry of open clusters
- Short Name:
- J/ApJS/116/263
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New CCD VI photometric data for 10 template open clusters with accurately determined fundamental parameters are presented. From the observed V versus V-I diagrams of the clusters, fiducial sequences have been defined and transformed into the M_v_ versus (V-I)_0_ diagram by averaging sequences of template open clusters with similar ages. The resulting composite Mv versus (V-I)_0_ diagram presents a homogeneous set of empirical isochrones in the age range between 5Myr and 4Gyr. These empirical isochrones show an overall very good agreement with those computed from stellar evolutionary models. Theoretical isochrones with moderate overshooting fit the observed main sequences better than the canonical ones for clusters older than 600Myr. The present set of empirical isochrones will be useful for the study of faint reddened open clusters
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/464/573
- Title:
- VI photometry of 5 open clusters
- Short Name:
- J/A+A/464/573
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar populations in the outer Galactic disk are a subject of wide interest nowadays. To contribute to a better picture of this part of the Galaxy, we have studied the nature of five marginally investigated star clusters (Collinder 74, Berkeley 27, Haffner 8, NGC 2509, and VdB-Hagen4) by means of accurate CCD photometry in the V and I passbands. These clusters are in fact located in the third Galactic quadrant. We aim to obtain the basic parameters of these objects, which in some cases are still disputed in the literature. In the case of VdB-Hagen 4 we provide the first estimate of its fundamental parameters, while for Haffner 8 we present the first CCD photometry. The analysis is based on the comparison between field star decontaminated color-magnitude diagrams and stellar models. Particular care is devoted to the the assessment of the data quality and the statistical field star decontamination. The Padova library of stellar isochrones is adopted in this study. The analysis we carried out allowed us to solve a few inconsistencies in the literature regarding Haffner 8 and NGC 2509. Collinder 74 is found to be significantly older than reported before. VdB-Hagen 4 is a young open cluster located more than 20kpc from the Galactic center. Such an extreme distance is compatible with the cluster belonging to the Norma-Cygnus arm.
- ID:
- ivo://CDS.VizieR/J/A+AS/127/423
- Title:
- VI photometry of Westerlund 1 and 2
- Short Name:
- J/A+AS/127/423
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out CCD observations of stars in the region of the open cluster Westerlund 1 through the V and I passbands. The direct images were obtained with the 24-inch telescope of the University of Toronto Southern Observatory situated at Las Campanas Observatory, Chile. After cross-correlating all independent V, (V-I) tables we have obtained a improved set of colour and magnitude values as compared to those based on a single measure.
- ID:
- ivo://CDS.VizieR/J/ApJ/754/30
- Title:
- VISTA IR photometry of {sigma} Ori cluster
- Short Name:
- J/ApJ/754/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on our analysis of the VISTA Orion ZY JHK_s_ photometric data (completeness magnitudes of Z=22.6 and J=21.0 mag) focusing on a circular area of 2798.4arcmin^2^ around the young {sigma} Orionis star cluster (~3Myr, ~352pc, and solar metallicity). The combination of the VISTA photometry with optical, WISE and Spitzer data allows us to identify a total of 210 {sigma} Orionis member candidates with masses in the interval 0.25-0.004M_{sun}_, 23 of which are new planetary-mass object findings. These discoveries double the number of cluster planetary-mass candidates known so far. One object has colors compatible with a T spectral type. The {sigma} Orionis cluster harbors about as many brown dwarfs (69, 0.072-0.012M_{sun}_) and planetary-mass objects (37, 0.012-0.004M_{sun}_) as very low mass stars (104, 0.25-0.072M_{sun}_). Based on Spitzer data, we derive a disk frequency of ~40% for very low mass stars, brown dwarfs, and planetary-mass objects in {sigma} Orionis. The radial density distributions of these three mass intervals are alike: all are spatially concentrated within an effective radius of 12' (1.2pc) around the multiple star {sigma} Ori, and no obvious segregation between disk-bearing and diskless objects is observed.
- ID:
- ivo://CDS.VizieR/J/AJ/147/42
- Title:
- V light curves of EP Cep, ES Cep, and V369 Cep
- Short Name:
- J/AJ/147/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 188 is a good laboratory for studying the formation and evolution of W UMa type contact binaries due to its rich populations of them. We present a detailed photometric study of three short-period close binaries, EP Cep, ES Cep, and V369 Cep, in the old open cluster NGC 188 based on our two-set photometric observations. We discovered that both EP Cep and ES Cep are shallow-contact binaries with continuously decreasing periods. The difference is in their mass ratios. EP Cep has an extremely low-mass ratio, q=0.15, while ES Cep has a relatively high-mass ratio, q=0.69, indicating that they lie in different evolutionary stages. ES Cep is likely a newly formed contact binary via a Case A mass transfer, while EP Cep is an evolved system and may be on the oscillations caused by the combined effect of the thermal relaxation oscillation and the variable angular momentum loss. For another system, V369 Cep, we found that it is a primary-filling near-contact binary. Both the semidetached configuration and the continuous decrease in the orbital period indicate that it is undergoing a mass transfer from the primary component to the secondary one. This conclusion is in agreement with the excess luminosity seen in the light curves on the ingress of the secondary minimum produced by the impact of the mass transfer. All of the results suggest that V369 Cep is evolving into contact, and a shallow-contact high-mass ratio system similar to ES Cep will be formed. Then, it will evolve into a low-mass ratio contact binary just like EP Cep, and finally merge into a rapidly rotating single star.
- ID:
- ivo://CDS.VizieR/J/A+A/471/515
- Title:
- V light curves of NGC 6791 variable stars
- Short Name:
- J/A+A/471/515
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This work presents a high-precision variability survey in the field of the old, super metal-rich open cluster NGC 6791. The data sample consists of more than 75,000 high-precision CCD time series measurements in the V band obtained mainly at the Canada-France-Hawaii Telescope, with additional data from S. Pedro Martir and Loiano observatories, over a time span of ten nights. The field covers an area of 42x28arcmin^2^. We have discovered 260 new variables and re-determined periods and amplitudes of 70 known variable stars. By means of a photometric evaluation of the membership in NGC 6791, and a preliminary membership based on the proper motions, we give a full description of the variable content of the cluster and surrounding field in the range 16<V<23.5. Accurate periods can be given for the variables with P<4.0d, while for ones with longer periods the limited time-baseline hampered precise determinations. We categorized the entire sample as follows: 6 pulsating, 3 irregular, 3 cataclysmic, 89 rotational variables and 61 eclipsing systems; moreover, we detected 168 candidate variables for which we cannot give a variability class since their periods are much longer than our time baseline. On the basis of photometric considerations, and of the positions of the stars with respect to the center of the cluster, we inferred that 11 new variable stars are likely members of the cluster, for 22 stars the membership is doubtful and 137 are likely non-members. We also detected an outburst of about 3 mag in the light curve of a very faint blue star belonging to the cluster and we suggest that this star could be a new U Gem (dwarf nova) cataclysmic variable.
- ID:
- ivo://CDS.VizieR/J/AJ/154/256
- Title:
- VLM stars and BDs in Upper Sco using Gaia DR1
- Short Name:
- J/AJ/154/256
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our understanding of the brown dwarf population in star-forming regions is dependent on knowing distances and proper motions and therefore will be improved through the Gaia space mission. In this paper, we select new samples of very low-mass objects (VLMOs) in Upper Scorpius using UKIDSS colors and optimized proper motions calculated using Gaia DR1. The scatter in proper motions from VLMOs in Upper Scorpius is now (for the first time) dominated by the kinematic spread of the region itself, not by the positional uncertainties. With age and mass estimates updated using Gaia parallaxes for early-type stars in the same region, we determine masses for all VLMOs. Our final most complete sample includes 453 VLMOs of which ~125 are expected to be brown dwarfs. The cleanest sample is comprised of 131 VLMOs, with ~105 brown dwarfs. We also compile a joint sample from the literature that includes 415 VLMOs, out of which 152 are likely brown dwarfs. The disk fraction among low-mass brown dwarfs (M<0.05M_{sun}_) is substantially higher than in more massive objects, indicating that disks around low-mass brown dwarfs survive longer than in low-mass stars overall. The mass function for 0.01<M<0.1M_{sun}_ is consistent with the Kroupa Initial Mass Function. We investigate the possibility that some "proper motion outliers" have undergone a dynamical ejection early in their evolution. Our analysis shows that the color-magnitude cuts used when selecting samples introduce strong bias into the population statistics due to varying levels of contamination and completeness. Our understanding of the brown dwarf population in star-forming regions is dependent on knowing distances and proper motions and therefore will be improved through the Gaia space mission. In this paper, we select new samples of very low-mass objects (VLMOs) in Upper Scorpius using UKIDSS colors and optimized proper motions calculated using Gaia DR1. The scatter in proper motions from VLMOs in Upper Scorpius is now (for the first time) dominated by the kinematic spread of the region itself, not by the positional uncertainties. With age and mass estimates updated using Gaia parallaxes for early-type stars in the same region, we determine masses for all VLMOs. Our final most complete sample includes 453 VLMOs of which ~125 are expected to be brown dwarfs. The cleanest sample is comprised of 131 VLMOs, with ~105 brown dwarfs. We also compile a joint sample from the literature that includes 415 VLMOs, out of which 152 are likely brown dwarfs. The disk fraction among low-mass brown dwarfs (M<0.05M_{sun}_) is substantially higher than in more massive objects, indicating that disks around low-mass brown dwarfs survive longer than in low-mass stars overall. The mass function for 0.01<M<0.1M_{sun}_ is consistent with the Kroupa Initial Mass Function. We investigate the possibility that some "proper motion outliers" have undergone a dynamical ejection early in their evolution. Our analysis shows that the color-magnitude cuts used when selecting samples introduce strong bias into the population statistics due to varying levels of contamination and completeness.
- ID:
- ivo://CDS.VizieR/J/A+A/456/623
- Title:
- VLT-FLAMES survey of massive stars
- Short Name:
- J/A+A/456/623
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new observations of 470 stars using the Fibre Large Array Multi-Element Spectrograph (FLAMES) instrument in fields centered on the clusters NGC 330 and NGC 346 in the Small Magellanic Cloud (SMC), and NGC 2004 and the N11 region in the Large Magellanic Cloud (LMC). A further 14 stars were observed in the N11 and NGC 330 fields using the Ultraviolet and Visual Echelle Spectrograph (UVES) for a separate programme. Spectral classifications and stellar radial velocities are given for each target, with careful attention to checks for binarity. In particular, we have investigated previously unexplored regions around the central LH9/LH10 complex of N11, finding ~25 new O-type stars from our spectroscopy. We have observed a relatively large number of Be-type stars that display permitted Fe II emission lines. These are primarily not in the cluster cores and appear to be associated with classical Be-type stars, rather than pre main-sequence objects. The presence of the Fe II emission, as compared to the equivalent width of H{alpha}, is not obviously dependent on metallicity. We have also explored the relative fraction of Be- to normal B-type stars in the field-regions near to NGC 330 and NGC 2004, finding no strong evidence of a trend with metallicity when compared to Galactic results. A consequence of service observations is that we have reasonable time-sampling in three of our FLAMES fields. We find lower limits to the binary fraction of O- and early B-type stars of 23 to 36%. One of our targets (NGC 346-013) is especially interesting with a massive, apparently hotter, less luminous secondary component.
- ID:
- ivo://CDS.VizieR/J/AJ/128/1254
- Title:
- VLT 3.8{mu}m Trapezium catalog
- Short Name:
- J/AJ/128/1254
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep 3.8{mu}m L' imaging observations of the Trapezium cluster in Orion obtained with the ESO VLT. We use these observations to (1) search for infrared excess emission and evidence for protoplanetary disks associated with the faint, substellar population of this young cluster and (2) investigate the nature and extent of a recently discovered population of deeply embedded sources located in dense molecular gas behind the cluster. We detected 38 L' sources with substellar luminosities. In addition, we detected 24 L' sources that were spectroscopically classified as substellar objects in previous studies. Examining the infrared colors of all these sources, we determine an infrared excess fraction of 50%{+/-}20% from the J, H, K_s_ and L' colors for both the luminosity-selected and spectroscopically selected substellar samples.
- ID:
- ivo://CDS.VizieR/J/AJ/161/102
- Title:
- VPDs and CMDs of Berkeley32, Berkeley98 and King23
- Short Name:
- J/AJ/161/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the photometric and kinematical data from Gaia Data Release 2, three old open clusters namely Berkeley32 (Be32), Berkeley98 (Be98), and King23 are investigated. The latter two of these clusters are poorly studied in the literature. The numbers of the most probable cluster members are 563, 260, and 114 for Be32, Be98, and King23, respectively, with membership probabilities higher than 80% and lying within the clusters limiting radii. Mean proper motions (PMs; {mu}_{alpha}_cos_{delta}_ and {mu}_{delta}_) of the clusters are determined as (-0.34{+/-}0.008, -1.60{+/-}0.006), (-1.34{+/-}0.007, -3.22{+/-}0.008), and (-0.46{+/-}0.009, -0.87{+/-}0.012)mas/yr. The errors mentioned in the PMs are the Gaussian fitting errors. The blue straggler stars (BSS) in all three old clusters were found to exhibit centralized radial distribution. The clusters' radii are determined as 9.4', 12.95', and 6.6' for Be32, Be98, and King23 using radial density profiles. Ages of the clusters determined by isochrone fitting are 4.90{+/-}0.22, 3.23{+/-}0.15, and 1.95{+/-}0.22Gyr. The errors given in the clusters ages are the internal errors. The mass function slopes are found to be flatter than Salpeter's value for all three clusters. All three clusters are found to be dynamically relaxed. Galactic orbits are derived for these clusters, which demonstrate that the studied clusters follow a circular path around the Galactic center.