scholarly journals Observational Aspects of Slow Variables in Globular Clusters

1973 ◽  
Vol 21 ◽  
pp. 131-144
Author(s):  
M. W. Feast
Keyword(s):  
Radial Velocity ◽  
Compact Group ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Mira Variables ◽  
Period Effects ◽  
Slow Variables ◽  
Red Giant

AbstractThere are up to 14 known Mira variables in seven globular clusters, though several have not yet been confirmed as radial velocity members. The periods of only 5 are known, all near 200 days. The clusters seem to form a compact group of relatively metal rich clusters. In 3 or 4 cases spectroscopy shows that the giant branches of these clusters penetrate into the M types. The Mira-containing clusters also contain red variables of shorter period and smaller amplitude which are generally also M type stars. Stars apparently evolve to the red of the giant tip as variables of increasing amplitude and period. Effects of TiO blanketing on the (B — V) colours may be anticipated in these clusters.Besides variables at the red giant tip the metal poor globular cluster ω Cen contains variables with strong TiO bands. Photometry, including recent J, H, K, L photometry by Glass shows that these stars are very cool objects. They indicate an extension of the giant branch considerably cooler than previously considered for metal poor clusters.V1, NGC 121 in the Small Magellanic Cloud has a spectrum indicative of an SRd variable. It is not yet clear whether galactic stars similar to this star exist or not.

scholarly journals Narrow-Band Photometry of Red Variables in Globular Clusters

1973 ◽  
Vol 21 ◽  
pp. 164-177
Author(s):  
Robert F. Wing
Keyword(s):  
Radial Velocity ◽  
Globular Clusters ◽  
Near Infrared ◽  
Narrow Band ◽  
Small Range ◽  
Mira Variables ◽  
Color System ◽  
Red Giant ◽  
M Stars

AbstractFourteen red variables in the southern globular clusters 47 Tuc, ω Cen, and NGC 362 have been observed on an eight-color system of narrow-band photometry in the near infrared. Temperatures are derived from blackbody fits to the calibrated fluxes, and spectral types are given for the M stars. The types observed for the three Mira variables in 47 Tuc range from M3.1 to M7.5; two small-range variables in the same cluster are later than M4. The variables in ω Cen are mostly earlier than K5, but spectra of types M3 and MO were also encountered among radial-velocity members. In both the metal-rich 47 Tuc and the metal-poor ω Cen, the relation between TiO band strength and temperature is approximately normal. Several of these stars fall well above or below the red giant branches of their clusters in diagrams of infrared magnitude against temperature. Comparisons are made with recent results obtained at Radcliffe Observatory on some of the same stars.

scholarly journals Chemical abundance analysis of red giant branch stars in the globular cluster E3

2018 ◽  
Vol 616 ◽  
pp. A181 ◽  
Author(s):  
L. Monaco ◽  
S. Villanova ◽  
G. Carraro ◽  
A. Mucciarelli ◽  
C. Moni Bidin
Keyword(s):  
Radial Velocity ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Abundance Ratio ◽  
Chemical Abundance ◽  
Chemical Abundances ◽  
Multiple Populations ◽  
Red Giant ◽  
A Minor ◽  
Giant Branch Stars

Context. Globular clusters are known to host multiple stellar populations, which are a signature of their formation process. The globular cluster E3 is one of the few low-mass globulars that is thought not to host multiple populations. Aims. We investigate red giant branch stars in E3 with the aim of providing a first detailed chemical inventory for this cluster, we determine its radial velocity, and we provide additional insights into the possible presence of multiple populations in this cluster. Methods. We obtained high-resolution FLAMES-UVES/VLT spectra of four red giant branch stars likely members of E3. We performed a local thermodynamic equilibrium abundance analysis based on one-dimensional plane parallel ATLAS9 model atmospheres. Abundances were derived from line equivalent widths or spectrum synthesis. Results. We measured abundances of Na and of iron peak (Fe, V, Cr, Ni, Mn), α(Mg, Si, Ca, Ti), and neutron capture elements (Y, Ba, Eu). The mean cluster heliocentric radial velocity, metallicity, and sodium abundance ratio are νhelio = 12.6 ± 0.4 km s−1(σ = 0.6 ± 0.2 km s−1), [Fe/H] = −0.89 ± 0.08 dex, and [Na/Fe] = 0.18 ± 0.07 dex, respectively. The low Na abundance with no appreciable spread is suggestive of a cluster dominated by first-generation stars in agreement with results based on lower resolution spectroscopy. The low number of stars observed does not allow us to rule out a minor population of second-generation stars. The observed chemical abundances are compatible with the trends observed in Milky Way stars.

scholarly journals Red Variables of the Old Disc and Halo Populations

1974 ◽  
Vol 59 ◽  
pp. 93-100
Author(s):  
M. W. Feast
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Magellanic Cloud ◽  
Carbon Stars ◽  
Infrared Observations ◽  
Mira Variables ◽  
Cloud Clusters

This paper discusses the following topics: (1) Mira Variables in Globular Clusters; (2) infrared observations of Globular Cluster Variables; (3) carbon Stars in Magellanic Cloud Clusters; (4) the Se Variables and the superlithium rich Variables.

scholarly journals Strömgren metallicities for intermediate-age and old star clusters

2020 ◽  
Vol 642 ◽  
pp. A114 ◽  
Author(s):  
Andrés E. Piatti
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Star Clusters ◽  
Star Cluster ◽  
Small Magellanic Cloud ◽  
Similar Comparison ◽  
Age Dependent ◽  
Similar Range ◽  
Red Giant ◽  
Selection Of

We report results that show that the straightforward star cluster metallicities obtained from Strömgren vby photometry are age-dependent and need to be corrected for further use. This outcome arises from the comparison of [Fe/H] values derived from Strömgren photometry with those metallicities published in the literature for 26 Large and Small Magellanic Cloud star clusters, whose ages range from ∼1 Gyr up to the oldest-known globular cluster ages in these galaxies. While deriving mean star cluster metallicities, we carried out a thorough selection of red giant branch candidates to comply with the Strömgren metallicity calibration validity regime. We paid attention to the effect of contamination by field stars, particularly those that lie inside the star clusters’ radii, that are distributed along the star cluster red giant branches and that have [Fe/H] values covering a similar range as that for the selected stars. We find that the measured Strömgren metallicities are systematically more metal-poor than the published ones and that a quadratically age-varying function reproduces the relative metallicity values with an overall uncertainty of ∼0.05 dex. We finally performed a similar comparison relying on a fully independent approach, which consisted in using theoretical red giant branches of old globular clusters spanning [Fe/H] values from −2.0 up to 0.0 dex as standards. We then superimposed onto them the red giant branches of star clusters with ages in the range 1.0−12.5 Gyr and estimated their associated metallicities by interpolation. The derived theoretical relative metallicities follow a similar trend as a function of the star clusters’ ages as what has been found from observations of star clusters.

scholarly journals Wolf-Rayet binaries: old friends and new acquaintances

1999 ◽  
Vol 193 ◽  
pp. 26-37 ◽  
Author(s):  
Virpi S. Niemela ◽  
Roberto Gamen ◽  
Nidia I. Morrell ◽  
Sixto Giménez Benítez
Keyword(s):  
Radial Velocity ◽  
Binary Systems ◽  
Magellanic Cloud ◽  
Elliptic Orbit ◽  
Spectral Lines ◽  
Small Magellanic Cloud ◽  
Orbital Elements ◽  
Spectroscopic Observations ◽  
Short Period ◽  
Old Friends

Observations of WR stars in binary systems are discussed, emphasizing constraints on our knowledge of the binary frequency of WR stars, and of WR stars as a distinctive class of objects. Radial velocity orbits of newly discovered binaries, e.g., WR 29, a short period WN7+OB binary in our Galaxy, and SMC/AB 7, a massive WN+O7 binary in the Small Magellanic Cloud, are presented. New spectroscopic observations of binary systems with previously known orbits are also reported, showing in the case of WR 21 evidence of change of the orbital elements as derived from different spectral lines. An elliptic orbit for CV Ser is also illustrated.

scholarly journals Spectroscopy of Overluminous Cepheids in the Magellanic Clouds

1984 ◽  
Vol 108 ◽  
pp. 223-224
Author(s):  
Horace A. Smith ◽  
Leo Connolly
Keyword(s):  
Globular Cluster ◽  
Large Magellanic Cloud ◽  
Variable Stars ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Small Magellanic Cloud ◽  
Single Star ◽  
Rr Lyrae ◽  
Short Period ◽  
The Galaxy

The Small Magellanic Cloud is known to contain types of short period Cepheid variable stars not yet discovered in either the Large Magellanic Cloud or, with the exception of a single star, in the Galaxy. These variables can be divided into two categories: anomalous Cepheids and Wesselink-Shuttleworth (WS) stars. The former, which have also been found in dwarf spheroidal systems and in the globular cluster NGC 5466, have periods of 0.4–3 days, but average 0.7–1.0 mag. brighter than RR Lyrae and BL Her stars of equal period. The stars we call WS stars have periods less than about 1.1 day and, at MV = −1 to −2, are brighter than anomalous Cepheids of equal period.

scholarly journals ACTINIUM ABUNDANCES IN STELLAR ATMOSPHERES

2021 ◽  
Vol 34 ◽  
pp. 70-73
Author(s):  
V. Yushchenko ◽  
V. Gopka ◽  
A.V. Yushchenko ◽  
A. Shavrina ◽  
Ya. Pavlenkо ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Milky Way ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Stellar Atmospheres ◽  
The Other ◽  
Small Magellanic Cloud ◽  
Red Supergiants ◽  
Red Giant

This paper presents a study of radioactive  actinium in the atmospheres of stars located in galaxies with different chemical evolution history – namely, Przybylski's Star (HD 101065) in the Milky Way and the red supergiant PMMR27 in the Small Magellanic Cloud; it also reports the findings of the previous research of the red supergiant RM 1-667 in the Large Magellanic Cloud and the red giant BL138 in the Fornax dwarf spheroidal galaxy. The actinium abundance is close to that of uranium in the atmospheres of certain stars in the Milky Way’s halo and in the atmosphere of Arcturus. The following actinium abundances have been obtained (in a scale of lg N(H) = 12): for the red supergiants PMMR27 and RM 1- 667 lg N(Ac) = -1.7 and lg N(Ac) = -1.3, respectively, and for the red giant BL138 lg N(Ac) = -1.6. The actinium abundance in the atmosphere of Przybylski's Star (HD 101065) is lg N(Ac) = `0.94±0.09, which is more than two orders of magnitude higher than those in the atmospheres of the other studied stars.

scholarly journals New CCD Survey of Globular Clusters in M31

2002 ◽  
Vol 207 ◽  
pp. 46-51 ◽  
Author(s):  
Myung Gyoon Lee ◽  
Sang Chul Kim ◽  
Doug Geisler ◽  
Juan Seguel ◽  
Ata Sarajedini ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Progress Report ◽  
Wide Field

We present a progress report of our wide field CCD survey of globular clusters in M31. We have covered a 3 deg × 3 deg area centered on M31, using the KPNO 0.9m and Washington CMT1 filters. Our survey is much deeper and more sensitive than previous surveys. We have found several hundred new globular cluster candidates in M31 in addition to confirming previously known globular clusters, and also have found a number of interlopers among previous globular cluster catalogs. We have also obtained spectra of about 500 objects among these candidates using HYDRA at the WIYN 3.5m telescope, which are used for classification and measuring the radial velocity of the candidate objects. When completed, a new master catalog of globular clusters in M31 will be made, combining the new globular clusters with the known globular clusters.

scholarly journals IUE observations of stars in NGC 330 in the Small Magellanic Cloud

1991 ◽  
Vol 148 ◽  
pp. 339-340
Author(s):  
V. Caloi ◽  
A. Cassatella ◽  
V. Castellani ◽  
G. Klare
Keyword(s):  
Globular Cluster ◽  
Massive Star ◽  
Magellanic Cloud ◽  
Small Magellanic Cloud ◽  
Low Resolution ◽  
Star Evolution ◽  
Theoretical Predictions ◽  
Effective Temperatures ◽  
Massive Star Evolution ◽  
Hr Diagram

Low resolution spectra from 1200 to 3300Å have been obtained, with the IUE satellite, for seven blue giants and supergiants in the young, metal-poor globular cluster NGC 330 in the Small Magellanic Cloud (SMC). A further three spectra from the IUE archive have been added to the sample, covering a range of 2.5 mag. The effective temperatures and the local reddening in the SMC have been estimated, and the star positions in the theoretical HR diagram determined, and compared with theoretical predictions for massive star evolution. Substantial discrepancies have been found.

scholarly journals Discovery of a nitrogen-enhanced mildly metal-poor binary system: Possible evidence for pollution from an extinct AGB star

2019 ◽  
Vol 631 ◽  
pp. A97 ◽  
Author(s):  
José G. Fernández-Trincado ◽  
Ronald Mennickent ◽  
Mauricio Cabezas ◽  
Olga Zamora ◽  
Sarah L. Martell ◽  
...  
Keyword(s):  
Binary System ◽  
Radial Velocity ◽  
Globular Clusters ◽  
Near Infrared ◽  
Asymptotic Giant Branch ◽  
Main Element ◽  
Large Variability ◽  
Asymptotic Giant Branch Star ◽  
Red Giant ◽  
Branch Star

We report the serendipitous discovery of a nitrogen-rich, mildly metal-poor ([Fe/H] = −1.08) giant star in a single-lined spectroscopic binary system found in the SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE-2) survey, Data Release 14 (DR14). Previous work has assumed that two percent of halo giants with unusual elemental abundances have been evaporated from globular clusters, but other origins for their abundance signatures, including binary mass transfer, must also be explored. We present the results of an abundance reanalysis of the APOGEE-2 high-resolution near-infrared spectrum of 2M12451043+1217401 with the Brussels Automatic Stellar Parameter (BACCHUS) automated spectral analysis code. We manually re-derive the main element families, namely light elements (C, N), elements (O, Mg, Si), the iron-peak element (Fe), s-process element (Ce), and light odd-Z element (Al). Our analysis confirms the N-rich nature of 2M12451043+1217401, which has a [N/Fe] ratio of +0.69, and shows that the abundances of C and Al are slightly discrepant from those of a typical mildly metal-poor red giant branch star, but exhibit Mg, Si, O and s-process abundances (Ce) of typical field stars. We also detect a particularly large variability in the radial velocity of this star over the period of the APOGEE-2 observations; the most likely orbit fit to the radial velocity data has a period of 730.89  ±  106.86 days, a velocity semi-amplitude of 9.92  ±  0.14 km s−1, and an eccentricity of ∼0.1276  ±  0.1174. These data support the hypothesis of a binary companion, which has probably been polluted by a now-extinct asymptotic giant branch star.

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