- ID:
- ivo://CDS.VizieR/J/A+AS/125/337
- Title:
- New variables in NGC 288
- Short Name:
- J/A+AS/125/337
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report discovery of 3 new faint variables in the globular cluster NGC 288: 2 SX Phe stars and 1 contact binary. Both SX Phe variables are blue stragglers. The contact binary is located below cluster turnoff, slightly to the red of the main sequence. New photometry of 6 previously known variables is also presented. We note that 26 out of a total 43 SX Phe stars identified recently in {omega} Cen and NGC 288 exhibit V-band light curves with full amplitudes smaller than 0.10mag. The sample of known SX Phe stars is likely to be significantly incomplete in regard to the low amplitude variables.
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Search Results
- ID:
- ivo://CDS.VizieR/J/other/RMxAA/44.365
- Title:
- New variable stars in NGC 6366
- Short Name:
- J/other/RMxAA/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New CCD photometry of NGC 6366 has lead to the discovery of some variable stars. Two possible Anomalous Cepheids (or Pop II Cepheids), three long period variables, one SX Phe and one eclipsing binary have been found. Also a list of 10 candidate variables is reported. The light curve of the RRab star, V1, has been decomposed into its Fourier harmonics, and the Fourier parameters were used to estimate the star's metallicity and distance; [Fe/H]=-0.87+/-0.14 and d=3.2+/-0.1kpc. It is argued that V1 may not be a member of the cluster but rather a more distant object. If this is so, an upper limit for the distance to the cluster of 2.8+/-0.1kpc can be estimated. The P-L relationship for SX Phe stars and the identified modes in the newly discovered SX Phe variable, V6, allow yet another independent determination of the distance to the cluster of d=2.7+/-0.1kpc. The M_V_-[Fe/H] relationship for RR Lyrae stars is addressed and the case of V1 is discussed.
- ID:
- ivo://CDS.VizieR/J/ApJ/658/980
- Title:
- New velocities for 62 globular clusters in M104
- Short Name:
- J/ApJ/658/980
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new velocities for 62 globular clusters in M104 (NGC 4594, the Sombrero Galaxy), 56 from 2dF on the AAT and 6 from Hydra on WIYN. Combined with previous data, we have a total sample of 108 M104 globular cluster velocities, extending to 20' radius (~60kpc), along with BVR photometry for each of these. We use this wide-field data set to study the globular cluster kinematics and dark matter content of M104 out to 10' radius (30kpc).
574. NGC 6440
- ID:
- ivo://CDS.VizieR/J/A+AS/108/653
- Title:
- NGC 6440
- Short Name:
- J/A+AS/108/653
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
575. NGC 6584
- ID:
- ivo://CDS.VizieR/J/AJ/109/1112
- Title:
- NGC 6584
- Short Name:
- J/AJ/109/1112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD photometry in the B and V passbands for the Galactic globular cluster NGC 6584. The color-magnitude diagram reveals a horizontal branch (HB) populated on both the red and blue sides of the RR Lyrae instability strip. The cluster contains 42 confirmed RR Lyrae variables, and we find an additional 56 stars which are possible RR Lyraes. The mean magnitude of the RR Lyraes on our CCD frames is combined with that of the nonvariable stars to yield <V(HB)> = 16.53 +/- 0.03. Using a polynomial fit to the cluster giant stars, we derive the color of the giant branch at the level of the HB to be (B-V)g = 0.89 +/- 0.02. Our photometry has also been used to isolate the red giant branch "clump," which forms when stars pause and sometimes reverse their course as they evolve up the giant branch. Its luminosity is primarily dependent upon the cluster metallicity, and we have used this fact to derive a metallicity of [Fe/H] = -1.44 +/- 0.16 for NGC 6584. Coupled with the color of the giant branch given above, this yields a cluster reddening of E(B-V) = 0.07 +/- 0.04. To the extent that our photometry can be used to study the age of NGC 6584, we find it to be comparable to M3, which is not surprising given their similar HB morphologies. The color-magnitude diagram also exhibits a significant population of blue straggler stars. From a comparison of the blue straggler radial distribution to that of the subgiant stars with similar V magnitudes, we find that the blue stragglers are more centrally concentrated than the subgiants, indicative of a higher mass for the blue stragglers.
- ID:
- ivo://CDS.VizieR/J/A+A/607/A135
- Title:
- NGC 104, 6121 & 6809 AGB and RGB stars Na abundance
- Short Name:
- J/A+A/607/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze high-resolution spectra of a large sample of asymptotic giant branch AGB and red giant branch (RGB) stars in the Galactic GCs NGC 104, NGC 6121, and NGC 6809 obtained with FLAMES/GIRAFFE at ESO/VLT, and determine their Na abundances. This is the first time that the AGB stars in NGC 6809 are targeted. We find that NGC 104 and NG 6809 have comparable AGB and RGB Na abundance distributions, while NGC 6121 shows a lack of very Na-rich AGB stars. Moreover, to investigate the dependence of AGB Na abundance dispersion on GC parameters, we compare the AGB [Na/H] distributions of a total of nine GCs, with five determined by ourselves with homogeneous method and four from literature, covering a wide range of GC parameters. Their Na abundances and multiple populations of AGB stars form complex picture. In some GCs, AGB stars have similar Na abundances and/or second-population fractions as their RGB counterparts, while some GCs do not have Na-rich second-population AGB stars, and various cases exist between the two extremes. In addition, the fitted relations between fractions of the AGB second population and GC global parameters show that the AGB second-population fraction slightly anticorrelates with GC central concentration, while no robust dependency can be confirmed with other GC parameters.
- ID:
- ivo://CDS.VizieR/J/A+A/592/A66
- Title:
- NGC 2808 AGB and RGB stars Na abundance
- Short Name:
- J/A+A/592/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galactic globular clusters (GC) are known to have multiple stellar populations and be characterised by similar chemical features, e.g., O-Na anti-correlation. While second-population stars, identified by their Na overabundance, have been found from the main sequence turnoff up to the tip of the red giant branch in various Galactic GCs, asymptotic giant branch stars have rarely been targeted. Here we present the results of our high-resolution spectroscopic study of a sample of AGB and RGB stars in the Galactic globular cluster NGC 2808. We derived accurate Na abundances for 31 AGB and 40 RGB stars in this cluster. Comparable Na abundance dispersions are found for our AGB and RGB samples, and we conclude that NGC 2808 has Na-rich second-population AGB stars, which turn out to be even more numerous - in relative terms - than their Na-poor counterparts (on the AGB) and the Na-rich stars on the RGB.
- ID:
- ivo://CDS.VizieR/J/ApJ/791/39
- Title:
- NGC 6218 and NGC 5904 lithium abundances
- Short Name:
- J/ApJ/791/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Convergent lines of evidence suggest that globular clusters host multiple stellar populations. It appears that they experience at least two episodes of star formation whereby a fraction of first-generation stars contribute astrated ejecta to form the second generation(s). To identify the polluting progenitors, we require distinguishing chemical signatures such as that provided by lithium. Theoretical models predict that lithium can be synthesized in AGB stars, whereas no net Li production is expected from other candidates. It has been shown that in order to reproduce the abundance pattern found in M4, Li production must occur within the polluters, favoring the AGB scenario. Here, we present Li and Al abundances for a large sample of RGB stars in M12 and M5. These clusters have a very similar metallicity, while demonstrating differences in several cluster properties. Our results indicate that the first-generation and second-generation stars share the same Li content in M12; we recover an abundance pattern similar to that observed in M4. In M5, we find a higher degree of complexity, and a simple dilution model fails in reproducing the majority of the stellar population. In both clusters, we require Li production across the different stellar generations, but production seems to have occurred to different extents. We suggest that such a difference might be related to the cluster mass with the Li production being more efficient in less-massive clusters. This is the first time a statistically significant correlation between the Li spread within a GC and its luminosity has been demonstrated. Finally, although Li-producing polluters are required to account for the observed pattern, other mechanisms, such as MS depletion, might have played a role in contributing to the Li internal variation, though at a relatively low level.
- ID:
- ivo://CDS.VizieR/J/A+AS/127/471
- Title:
- NGC 6380 and Terzan 12 VI photometry
- Short Name:
- J/A+AS/127/471
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present V, I photometry of the bulge globular clusters NGC 6380 and Terzan 12, using the ESO NTT telescope. For the first time colour-magnitude diagrams are obtained for these clusters, allowing us to derive reliable cluster parameters. From the colour-magnitude diagram morphology both clusters result to be metal-rich. For NGC 6380 we estimate [Fe/H]~-0.5, a reddening of E(B-V)=1.07 and a distance of d~9.8 kpc. For Terzan 12 we obtain [Fe/H]~-0.5, E(B-V)=2.06 and d~3.4kpc.
- ID:
- ivo://CDS.VizieR/J/ApJ/297/582
- Title:
- NGC 2213 BR photometry
- Short Name:
- J/ApJ/297/582
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The age of the LMC red globular cluster NGC 2213 has been estimated as 1.3+/-0.5x10^9^yr from a color-magnitude diagram, derived from CCD photometry, that reveals the cluster main sequence. The accuracy of the age estimate, however, is limited by uncertainly in the LMC distance modulus, by uncertainty in the cluster metal abundance which appears to lie in the range one-half to one-sixth solar, by uncertainty in the reddening of the cluster, and by uncertainty in the extent to which the theoretical isochrones used for the age dating are affected by the neglect, in standard stellar models, of the interior mixing caused by convective overshoot in the stellar cores. Using the adopted reddening of E(B-V)=0.09 and assuming Y=0.2, isochrone best fits to the cluster main sequence are found for [M/H]=-0.3 if (m-M)0=18.7 and for [M/H]=-0.7 if (m-M)0=18.2. After allowance for the possible effects of convective overshoot, the corresponding ages are 0.9^+0.5^_-0.3_ and 1.6^+0.8_^-0.4_x10^9^yr. Plausible alterations in the adopted reddening value and the adopted helium abundance also yield ages within these limits.
