- ID:
- ivo://CDS.VizieR/J/A+A/567/A1
- Title:
- BVJH photometry of Andrews-Lindsay 1 field
- Short Name:
- J/A+A/567/A1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Andrews-Lindsay 1 is a pertinent open cluster because it may host the planetary nebula (PN) PHR 1315-6555, yet ambiguities linger concerning its fundamental parameters (>50% scatter). New multiband BVJHW_1-4_ photometry for cluster and field stars, in concert with observations of recently discovered classical Cepheids, were used to constrain the reddening and velocity-distance profiles along the sightline. That analysis yielded the following parameters for the cluster: E(J-H)=0.24+/-0.03, d=10.0+/-0.4kpc (d_JH_=9.9+/-0.6kpc, d_BV_=10.1+/-0.5kpc), and log{tau}=8.90+/-0.15. The steep velocity-distance gradient along l~305{deg} indicates that two remote objects sharing spatial and kinematic parameters (i.e., PHR 1315-6555 and Andrews-Lindsay 1) are associated, thus confirming claims that the PN is a cluster member. The new distance for PHR 1315-6555 is among the most precise established yet for a Galactic PN ({sigma}/d=4%).
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- ID:
- ivo://CDS.VizieR/J/A+A/475/539
- Title:
- BV photometry and Li abundances in NGC3960
- Short Name:
- J/A+A/475/539
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Old open clusters are very useful targets to investigate mechanisms responsible for lithium (Li) depletion during the main sequence. Comparison of the Li abundances in clusters of different age allows us to understand the efficiency of the Li destruction process. To determine the membership and Li abundance in a sample of candidate members of the open cluster NGC 3960 (age ~1Gyr), aiming to fill the gap between 0.6 and 2Gyr in the empirical description of the behavior of the average Li abundance as a function of the stellar age. We use VLT/FLAMES Giraffe spectra to determine the radial velocities and thus the membership of a sample of 113 photometrically selected candidate cluster members. From the analysis of the Li line we derive Li abundances for both cluster members and non-members. 39 stars have radial velocities consistent with membership, with an expected fraction of contaminating field stars of about 20%. Li is detected in 29 of the radial velocity members; we consider these stars as cluster members, while we make the reasonable assumption that the remaining 10 radial velocity members without Li are among the contaminating stars. Li abundances of the stars hotter than about 6000K are similar to those of stars in the Hyades, while they are slightly smaller for cooler stars. This confirms that NGC 3960 is older than the Hyades. The average Li abundance of stars cooler than about 6000K indicates that the Li Pop. I plateau might start at ~1Gyr, rather than 2Gyr, which is the upper limit previously derived in the literature. We also find that the fraction of field stars with high Li abundance (>1.5) is about one third of the whole sample, which is in agreement with previous estimates. The fraction of contaminating field stars is consistent with that previously derived by us from photometry.
- 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.
- 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+AS/121/213
- Title:
- BV photometry of Blanco 1 stars
- Short Name:
- J/A+AS/121/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of H{alpha}(6562A) and Li I(6708A) observations of 114 low-mass stars of the young open cluster Blanco 1. We also present observations of 30 stars in Ca II(K). This work extends the first Blanco 1 spectroscopic study of Panagi et al. (1994A&A...285..233D). From a sample of four well-studied clusters, including Blanco 1, we find that the fraction of H{alpha} emission-line stars amongst K dwarfs is a good indicator of relative age, with a smaller fraction indicative of older age. Blanco 1 shows a relatively small fraction of emitters, inconsistent with previous age estimates for the cluster. We estimate the cluster age to to be 90+/-25Myr, slightly older than the Pleiades. The method is shown to be more sensitive to age than lithium and a useful alternative to other age measurement techniques. The variation of H{alpha} with (B-V) is similar to that observed in the older solar neighbourhood dwarfs, suggesting that, at least for the absorption-line stars, the contribution of stellar rotation to the equivalent width is unclear. We combine both spectroscopy and photometry to revise cluster membership and give accurate positions for all these stars.
- 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/AJ/113/1045
- Title:
- BV photometry of NGC 3680
- Short Name:
- J/AJ/113/1045
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new CCD BV color-magnitude diagram (CMD) has been derived for the intermediate age open cluster NGC 3680. The quality of photometry coupled with the best-to-date knowledge of cluster memberships allows for a detailed isochrone fit to the CMD. The theoretical isochrones have been constructed using the Yale Rotating Evolution Code (YREC) in its non-rotating mode and the OPAL opacities (circa 1991). Four sets of isochrones have been calculated: one for the standard stellar model calibrated to the Sun and three others for models with different amounts of convective overshoot at the edge of the convective core, namely, 0.15, 0.20, and 0.25H_p_, where H_p_ is the pressure scale height at the core edge. All four sets of theoretical isochrones were adjusted to an adopted distance modulus of V_0_-M_V_=10.20 and reddening E(B-V)=0.075 which leads to ages of 1.3+/-0.15, 1.5+/-0.15, 1.6+/-0.15, and 1.7+/-0.15Gyr, respectively The uncertainties in age mainly reflect a subjective decision in differentiating a good fit from a poorer one The model with a convective overshoot of 0.20H_p_ seems to yield the best fit to the sharply curved upper main sequence. Hence, the estimated age of NGC 3680 is 1.6+/-0.15Gyr. The adopted overshoot parameter ostensibly is uncertain by +/-0.05H_p_. For comparison, the same stellar models with overshoot of 0.25H_p_ were fit to the color-magnitude diagram of the cluster NGC 752, which is similar in age and composition to NGC 3680 The age estimate for NGC 752 is 1.6+/-0.2Gyr, assuming V_0_-M_V_=8.20 and E(B-V)=0.030 for the cluster.
- ID:
- ivo://CDS.VizieR/J/MNRAS/243/492
- Title:
- BV Photometry of NGC 6791
- Short Name:
- J/MNRAS/243/492
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD BV photometry to V=20.5 of stars in the old open cluster NGC 6791 is presented. Comparison with the theoretical isochrones of VandenBerg gives a cluster age in the range of 10 to 12.5Gyr, and an apparent distance modulus of 13.45mag, adopting a solar metallicity. This cluster is only marginally younger than Palomar 12, which is the youngest globular cluster known. A search for short-period variables in the cluster field led to the discovery of only one low-amplitude variable, probably belonging to the FK Com-type stars. A very blue star was detected which may be an extremely young white dwarf formed in the cluster.
