- ID:
- ivo://CDS.VizieR/J/AJ/116/2395
- Title:
- BV photometry in five SMC clusters
- Short Name:
- J/AJ/116/2395
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our analysis of archival Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) observations in F450W (~B) and F555W (~V) of the intermediate-age populous star clusters NGC 121, NGC 339, NGC 361, NGC 416, and Kron 3 in the Small Magellanic Cloud. We use published photometry of two other SMC populous star clusters, Lindsay 1 and Lindsay 113, to investigate the age sequence of these seven star clusters in order to improve our understanding of the formation chronology of the SMC. We analyzed the V versus B-V and M_V_ versus (B-V)_0_ color-magnitude diagrams of these populous Small Magellanic Cloud star clusters using a variety of techniques and determined their ages, metallicities, and reddenings. These new data enable us to improve the age-metallicity relation of star clusters in the Small Magellanic Cloud. In particular, we find that a closed-box continuous star formation model does not reproduce the age-metallicity relation adequately. However, a theoretical model punctuated by bursts of star formation is in better agreement with the observational data presented herein.
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- ID:
- ivo://CDS.VizieR/J/A+A/429/607
- Title:
- BV photometry of Berkeley 36, 73 and 34
- Short Name:
- J/A+A/429/607
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BV photometry of the faint open clusters Berkeley 36, Berkeley 73 and Biurakan 13 are studied. For these clusters no colour-magnitude analyses were previously available. The colour-magnitude Diagrams indicate that they are all old open clusters. The derived ages are ~4Gyr for Berkeley 36, and ~2.3Gyr for both Berkeley 73 and Biurakan 13. The clusters are not very reddened, with E(B-V)=0.25, 0.10 and 0.30 respectively for Berkeley 36, Berkeley 73 and Biurakan 13. Berkeley 36 and Berkeley 73 are located at a distance from the Galactic center of 10kpc, while Biurakan 13 is much farther, at 15kpc. A peak in the age distribution appears at 5Gyr suggesting a distinct star forming event in the disk.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A40
- Title:
- BV photometry of Bochum 7 members
- Short Name:
- J/A+A/616/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We plan to identify the members of the Bochum 7 association by performing simultaneous astrometric and spectrophotometric analyses, and estimate its distance and evolutionary stage. We used our own visual spectroscopic and UBV photometric data of a 30{deg}x30{deg} region centered at RA=8:44:47.2, DE=-45:58:55.5. This information enabled us to estimate the spectral classification and distance of all stars present in the region. The proper motion was analyzed with data of the UCAC 5 catalog and was used to identify the members of this association. We added JHK data from 2MASS and IRAS catalogs to check for the presence of infrared (IR) excess stars. We found that Bochum 7 is an OB association with at least 27 identified stellar members (l=265.12{deg}, b=-2{deg}) at a distance of ~=5640pc. Its proper motion is pm_RA_cosDE=-4.92+/-0.08mas/yr, pm_DE_=3.26+/-0.08mas/yr. We derived an average heliocentric radial velocity of ~35km/s and were able to confirm the binary nature of the (ALS 1135) system and detect four new binary star candidates. Analysis of data for massive Bo 7 star candidates points towards a young age (<=3x10^6^ years old) for the association, although the presence of a previous episode of star formation remains to be analyzed.
- ID:
- ivo://CDS.VizieR/J/AJ/126/237
- Title:
- BV photometry of LW 55 in LMC
- Short Name:
- J/AJ/126/237
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The field of the moderately old open cluster LW 55 in the outer parts of the Large Magellanic Cloud disk was monitored for detection of short-period variable stars over two nights. Eight variables were found; all but one (a detached eclipsing binary) are small-amplitude ({Delta}V<=0.1mag) pulsating stars of the {delta} Scuti, SX Phoenicis, or Doradus type. The BV color-magnitude diagram extends down to the solar-type stars at V=24 (M_V_~5.2). The cluster age is estimated at 1.5Gyr for Z=0.004 ([Fe/H]=-0.67); the surrounding stellar field is older, with an age greater than 4Gyr.
- ID:
- ivo://CDS.VizieR/J/PASP/119/1233
- Title:
- BV photometry of M11 stars
- Short Name:
- J/PASP/119/1233
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- V-band time-series CCD photometric observations of the intermediate-age open cluster M11 were performed to search for variable stars.
- ID:
- ivo://CDS.VizieR/J/A+A/483/253
- Title:
- BV photometry of NGC 2099 variables
- Short Name:
- J/A+A/483/253
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Rotation and solar-type magnetic activity are closely related to each other in main-sequence stars of G or later spectral types. The presence and level of magnetic activity depend on star's rotation, and rotation itself is strongly influenced by strength and topology of the magnetic fields. Open clusters represent especially useful targets to investigate the connection between rotation and activity. The open cluster NGC 2099 has been studied as a part of the RACE-OC project (Rotation and ACtivity Evolution in Open Clusters), which is aimed at exploring the evolution of rotation and magnetic activity in the late-type members of open clusters of different ages. We collected time series CCD photometric observations of this cluster in January 2004, and we determined the presence of periodicities in the flux variation related to the stellar rotation by Fourier analysis. We investigate the relations between activity manifestations, such as the light curve amplitude, and global stellar parameters. We have discovered 135 periodic variables, 122 of which are candidate cluster members. Determination of rotation periods of G- and K-type stars has allowed us to better explore the evolution of angular momentum at an age of about 500Myr. In our analysis, we have also identified 3 new detached eclipsing binary candidates among cluster members. A comparison with the older Hyades cluster (~625Myr) shows that the newly-determined distribution of rotation periods is consistent with the scenario of rotational braking of main-sequence spotted stars as they age. However, a comparison with the younger M34 cluster (~200Myr) shows that the G8-K5 members of these clusters have the same rotation period distribution. That is, G8-K5 members in NGC 2099 seem to have experienced no significant braking in the age range from ~200 to ~500Myr. Finally, NGC 2099 members have a smaller level of photospheric magnetic activity, as measured by light curve amplitude, than in younger stars of the same mass and rotation, suggesting that the activity level also depends on some other age-dependent parameters.
- ID:
- ivo://CDS.VizieR/J/AcA/59/193
- Title:
- BV photometry of stars in NGC 6866
- Short Name:
- J/AcA/59/193
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of 19 variable stars and two blue stragglers in the field of the open cluster NGC 6866. Three of the variable stars we classify as delta Sct, two as g Dor, four as WUMa, two as ellipsoidal variables, and one as an eclipsing binary. Seven stars show irregular variability. Two of the pulsators, delta Sct star NGC 6866-29 and gamma Dor star NGC 6866-21, are multiperiodic.
- ID:
- ivo://CDS.VizieR/J/ApJ/549/578
- Title:
- BV photometry of Trumpler 14 and 16
- Short Name:
- J/ApJ/549/578
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- H-R diagrams are presented for the very young galactic clusters Trumpler 14 and Trumpler 16, which are the two most populous clusters in the region of vigorous star formation surrounding {eta} Carinae. Point spread function photometry of UBV CCD images is presented down to V~19 for over 560 stars in Tr 16 and 290 stars in Tr 14. We have also obtained similar data for a local background field. After determining cluster membership through proper motions from a previous work, we find that the reddening of cluster members is significantly lower than that of the local background stars. Thus, we are able to use individual reddenings to identify likely members at far deeper levels than possible with proper motions. This work has revealed a significant population of pre-main-sequence (PMS) stars in both clusters. The location of the PMS stars in the H-R diagram indicates that the theoretical "stellar birthline" of Palla & Stahler (1990ApJ...360L..47P, follows the locus of stars far better than that of Beech & Mitalas (1994ApJS...95..517B). Comparison with both pre- and post-main-sequence isochrones also reveals that although intermediate-mass stars have been forming continuously over the last 10Myr, the high-mass stars formed within the last 3Myr. There is no evidence that the formation of the intermediate-mass stars was truncated by the formation of the high-mass stars.
- ID:
- ivo://CDS.VizieR/J/A+A/376/144
- Title:
- BV(RI)_C_H{alpha} photometry of NGC 663
- Short Name:
- J/A+A/376/144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new BV(RI)_C_H{alpha} photometry of the young open cluster NGC 663. The H{alpha} photometry is complete down to magnitude R_C_=15.4, corresponding to spectral type A5 for the cluster members. This allows detection of mild and strong H{alpha} emission in all B-type stars in the cluster. In addition to the 22 Be stars known in the observed field of NGC 663, we discovered four new faint stars of this type. We find that Be stars in NGC 663 cover the whole range of the B spectral type. They are, however, most populous among stars with spectral types falling in the range between B0 and B3, where their fraction amounts to 31+/-8%. Among B-type stars later than B3, Be stars are much less abundant: only 7 out of 101 observed stars, that is, 7+/-3%, were detected. About 70% of the observed Be stars in NGC 663 show detectable variations of light. In the time interval covered by our observations, the ranges of the largest variations reach 0.4mag in the I_C_ band. By means of the isochrone fitting, we derived the cluster distance of 2.1kpc, age of 20-25Myr, and the mean colour excess E(R-I)_C_=0.54mag, with a ~0.1mag scatter due to differential reddening.
- ID:
- ivo://CDS.VizieR/J/AJ/123/304
- Title:
- BV(RI)_C_JHK H{alpha} photometry in IC 5146
- Short Name:
- J/AJ/123/304
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The B0V star BD+46 3474 lies near the front surface of a dense molecular cloud and illuminates the emission/reflection nebula IC 5146. The HAeBe variable BD +46 3471 is embedded in the same cloud, about 10' (3.5pc) away. CCD photometry in BV(RI)_C_ (to V=22) and in JHK (to about K=16.5) has been obtained for the young clusters surrounding each of these two bright stars. Some 100 emission-H{alpha} stars brighter than R=20.5 have been found in the area, most of them in IC 5146. (Among these are two that have spectra resembling a high-excitation Herbig-Haro [HH] object plus a stellar continuum).