- ID:
- ivo://CDS.VizieR/J/AJ/122/3219
- Title:
- M3 and M13 CCD BV photometry
- Short Name:
- J/AJ/122/3219
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-precision V, B-V color-magnitude diagrams (CMDs) for the classic second-parameter globular clusters M3 and M13 from wide-field, deep CCD photometry. The data for the two clusters were obtained during the same photometric nights with the same instrument, allowing us to determine accurate relative ages. Based on a differential comparison of the CMDs using the {Delta}(B-V) method, an age difference of 1.7+/-0.7Gyr is obtained between these two clusters. We compare this result with our updated horizontal-branch (HB) population models, which confirm that the observed age difference can produce the difference in HB morphology between the clusters. This provides further evidence that age is the dominant second parameter that influences HB morphology.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/131/2478
- Title:
- M31 and M33 UBVRI photometry
- Short Name:
- J/AJ/131/2478
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBVRI photometry obtained from Mosaic images of M31 and M33 using the Kitt Peak National Observatory 4m telescope. We describe our data reduction and automated photometry techniques in some detail, as we will shortly perform a similar analysis of other Local Group galaxies. The present study covered 2.2deg^2^ along the major axis of M31 and 0.8deg^2^ on M33, chosen so as to include all of the regions currently active in forming massive stars. We calibrated our data using photometry from the Lowell 1.1m telescope, and this external method resulted in millimagnitude differences in the photometry of overlapping fields, providing some assurance that our photometry is reliable. The final catalog contains 371781 and 146622 stars in M31 and M33, respectively, where every star has a counterpart in (at least) the B, V, and R passbands. Our survey goes deep enough to achieve 1%-2% photometry at 21mag (corresponding to stars more massive than 20M_{sun}_) and achieves <10% errors at ~U ~B ~V ~R ~I 23mag.
- ID:
- ivo://CDS.VizieR/J/A+A/570/A82
- Title:
- Mapping accretion variability in NGC 2264
- Short Name:
- J/A+A/570/A82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our study aims at characterizing the accretion properties of several hundred members of the star-forming region NGC 2264 (3Myr). We performed a deep u,g,r,i mapping of the cluster with CFHT/MegaCam, and monitored the simultaneous u+r variability of its members over a baseline of two weeks. Stellar parameters are determined homogeneously for about 750 monitored young objects, 40% of which are accreting T Tauri stars. Accretion properties and accretion variability are investigated and characterized from UV excess measurements. Non-accreting members of the cluster define the reference UV emission level over which flux excess is detected and measured.
- ID:
- ivo://CDS.VizieR/J/AJ/101/1408
- Title:
- Massive stars in Cyg OB2.
- Short Name:
- J/AJ/101/1408
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The galactic association Cygnus OB2, which contains heavily reddened O and B stars, has been studied using CCD UBV photometry and spectroscopy. The file "mt91.dat" contains precise coordinates, UBV photometry, and spectral types from the study of Cygnus OB2, and merges the tables 2, 5 and 6 from the paper.
325. M 68 BVRI photometry
- ID:
- ivo://CDS.VizieR/J/AJ/99/1831
- Title:
- M 68 BVRI photometry
- Short Name:
- J/AJ/99/1831
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present BVRI photometry of the low metallicity globular cluster M68 (NGC 4590) observed with a CCD camera and the 2.2m telescope at ESO/La Silla, and have compared our BV color-magnitude diagrams with the observational results of a previous research. At magnitudes V<22, our BV results, obtained using the INVENTORY code, are in very close agreement with those of the other authors who used DAOPHOT in their reductions. At fainter levels, selection effects appear to affect INVENTORY more than DAOPHOT. We find that V_TO-HB_=3.42+/-0.10, in accord with values found for other clusters. The comparison between our four-color observations and the theoretical isochrones consistently yield a cluster age of 13Gyr with a likely external uncertainty of 2 or 3Gyr. Our derived values for the interstellar reddening at longer wavelengths are generally in agreement (+/-0.02mag) with what would be expected assuming E(B-V)=0.07mag and (m-M)_V_=15.25.
326. M67 CCD photometry
- ID:
- ivo://CDS.VizieR/J/BaltA/7/369
- Title:
- M67 CCD photometry
- Short Name:
- J/BaltA/7/369
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Seven-color CCD photometry in the Vilnius photometric system of 279 stars down to V=15mag in the open cluster M 67 area is obtained. 13 standard stars in the cluster are measured photoelectrically. Photometric spectral types have been determined for all the stars. The reddening of the cluster is found to be E(B-V)=0.045, the true distance modulus is 9.38mag and the age is 4x10^9^ years. For a description of the Vilnius photometric system, see e.g. <GCPD/21>
327. M 4 CCD photometry
- ID:
- ivo://CDS.VizieR/J/AJ/114/189
- Title:
- M 4 CCD photometry
- Short Name:
- J/AJ/114/189
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the ESO NTT, we have obtained accurate CCD UBVI photometry of 1649 stars in an extended field in the globular cluster M 4 = NGC 6121. The position of the main-sequence turnoff is found to be at V_TO_=17.0+/-0.1mag, (B-V)=0.863+/-0.007, (V-I)=1.224+/-0.010, (B-I)=2.084+/-0.010. Our turnoff point is redder and fainter than those found for M 4 in the majority of recent studies, probably because of our field being located in the western, most reddened part of the cluster. The spread of stars around the main-sequence locus has an unusual shape (broadening near the turnoff point and close to the photometric limit), earlier noticed by Richer et al. (1995ApJ...451L..17R) and attributed by them to photometric effects. We have analyzed the possible reasons for this effect and concluded that, at least in our case, it is most probably due to differential absorption. We confirm the deviation of theoretical isochrones from the fainter parts of the M 4 main-sequence locus found by Alcaino et al. (1988ApJ...330..569A). Several curious structural details (a depression and an excess of stars) have been revealed in the brighter parts of the main-sequence luminosity function of M 4.
- ID:
- ivo://CDS.VizieR/J/BaltA/13/1
- Title:
- M67 CCD Vilnius photometry
- Short Name:
- J/BaltA/13/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Seven color CCD photometry in the Vilnius system, supplemented by the Cousins I passband, has been obtained for 412 stars down to V=16mag in the M67 open cluster area. A special method of flat-fielding, giving high accuracy photometry, was used. Photometric spectral types and interstellar reddenings of all stars were determined. The mean mean reddening of the cluster stars is E(B-V)=0.04mag and the distance is 770pc.
- ID:
- ivo://CDS.VizieR/J/PASP/106/486
- Title:
- Mel 66 CCD photometry
- Short Name:
- J/PASP/106/486
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A CCD study of the peculiar open cluster, Melotte 66, on the vbyHbeta system is presented. The V,(b-y) color-magnitude diagram of this metal-deficient, old disk cluster confirms the anomalous features found in photographic BV studies and extends the main sequence to V=20. The main sequence exhibits a (b-y) color range significantly larger than expected from photometric errors alone; the (b-y) colors are correlated with Hbeta implying that the dispersion is real and is not the result of variable reddening across the cluster. The m1 indices for the turnoff stars imply a spread in [Fe/H] too small to explain the color range. Though the subgiant region is poorly defined, the region above the turnoff in the Hertzsprung gap is richly populated by a group of "yellow stragglers" whose membership is confirmed by radial star counts and radial velocities. The giant branch is richly populated but shows a smaller spread in color at a given V than one would expect from the turnoff region. More important, the giants exhibit a large scatter in m1, in contradiction with the turnoff observations. Various explanations for these observations are discussed, including CN variations among the giants triggered by either binary evolution or rapid rotation among the main-sequence stars.
- ID:
- ivo://CDS.VizieR/J/A+A/461/509
- Title:
- Membership and spectroscopy of IC 2391
- Short Name:
- J/A+A/461/509
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young open clusters provide important clues to the interface between the main sequence and pre-main-sequence phases of stellar evolution. The young and nearby open cluster IC 2391 is well-suited to studies of these two evolutionary phases. We establish a bona fide set of cluster members and then analyze this set in terms of binary frequency, projected rotational velocities, [Fe/H], and lithium abundance. In the wake of the Hipparcos distance controversy for the Pleiades, we compare the main-sequence fitting distance modulus to the Hipparcos mean parallax for IC 2391.
