Variables In Globular Clusters Research Articles

Long-period variables and carbon stars in the Galactic Bulge

The review covers the properties of red variables in globular clusters and the Galactic Bulge. Details are given of our current understanding of the Mira evolutionary phase. There is evidence that Miras in the LMC and the Bulge occupy different parts of the instability strip but obey the same PLC relation. The Bulge contains at least 2 × 104 Miras of which 100 or so have luminosities in excess of Mbol = — 5 mag. The Mira phase lasts more than 105 yr. These objects originate from stars with a wide range of metallicity, but it is currently unclear if the most metal-rich stars reach the top of the AGB to become Miras. Preliminary data suggest that the distribution of the Miras along the minor axis of the Bulge is different from that of the late-M stars but similar to the 2.4 μm luminosity.Our knowledge of the Bulge carbon stars is briefly reviewed. It is suggested that, by analogy with the carbon-rich dwarfs, these stars are probably best understood as the products of binary evolution.

STUDYING CATACLYSMIC VARIABLES WITH THE HUBBLE SPACE TELESCOPE

ABSTRACT The Space Telescope with its UV and imaging capabilities will allow new methods of investigating cataclysmic variables to be used. It provides the first opportunity to obtain high time resolution UV observations of cataclysmic variables, both spectroscopically and photometrically. Phase resolved observations of eclipses can now be obtained which will allow the UV surface brightness distributions in accretion disks to be studied. Eclipses of white dwarfs that were not visible in optical light will be detected in some systems. Other variations such as dips (in dwarf novae, intermediate polars, and polars), flickering and oscillations can also be resolved for the first time in the UV. High spatial resolution, long slit spectroscopy and imaging with the FOC and WF/PC can be used to study the physical condition and morphology of ejected material around novae, recurrent novae and pre-cataclysmic variables. The UV and H-alpha imaging capabilities will also enable searches for cataclysmic variables in globular clusters to be carried out further into their cores than has been possible before.

RR Lyrae variables in the field and the Sandage period-shift effect in globular clusters

view Abstract Citations (29) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS RR Lyrae Varables in the Field and the Sandage Period-Shift Effect in Globular Clusters Caputo, Filippina ; de Santis, Renato Abstract With the goal of obtaining reddening-free luminosity-to-mass ratio of ab-type RR Lyrae variables, the data of Lub (1977) for field RR Lyrae stars with well determined reddening are reanalyzed and the relationships among the period shift Delta log P(Te) and other observational parameters were determined. It is shown that there is a strong correlation among the period, the blue amplitude, and the light-to-mass ratio, which makes it possible to determine the light-to-mass ratio of any ab-type variable once its period and amplitude are known. The analysis of two additional samples of field variables yielded, for both samples, the slope of the relationship between the light-to-mass ratio and the metal content which is very near the slope for the Lub's stars (i.e., -0.10). In contrast, the slope for RR Lyrae variables in globular clusters was found to be -0.05, in close agreement with the prediciton of synthetic horizontal branch computations. Publication: The Astronomical Journal Pub Date: July 1992 DOI: 10.1086/116237 Bibcode: 1992AJ....104..253C Keywords: Cepheid Variables; Globular Clusters; Metallicity; Stellar Luminosity; Stellar Mass; Hydrogen; Iron; Stellar Composition; Astrophysics; STARS: VARIABLES: RR LYRAE; STARS: LUMINOSITY FUNCTION; MASS FUNCTION; GLOBULAR CLUSTERS: GENERAL full text sources ADS | data products SIMBAD (9)

WHT observations of cataclysmic variables in globular clusters - III. V4 in M30 during quiescence

We report the results of William Herschel telescope (WHT) observations of the candidate globular-cluster dwarf nova, V4 in M30. We find that, on the basis of its quiescent magnitude and colours, its outburst magnitude and its radial velocity, V4 is likely to be a foreground object in the field of M30. In addition, it is probably a short-period system near the period gap

Theoretical model of red variables in globular clusters

view Abstract Citations (15) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Theoretical Model of Red Variables in Globular Clusters Perl, M. ; Tuchman, Y. Abstract The common procedure of using the pulsation constant as a tool for the determination of the dominant mode of pulsation in Mira variables is shown to include a large uncertainty. An alternative way based on theoretical mapping of a luminosity-period relation, which is compared with the well-determined observations of these parameters, is presented. It is shown that the peculiar features of the observed distribution of Miras variables in the period-luminosity plane, for Tuc 47, are distinct enough to enable a clear and a definite selection of the dominant mode in these variables - the second overtone for red semiregulars and the first overtone for Miras variables. These results are also confirmed by detailed nonlinear calculations, some of which are presented as well. Publication: The Astrophysical Journal Pub Date: September 1990 DOI: 10.1086/169144 Bibcode: 1990ApJ...360..554P Keywords: Globular Clusters; Mira Variables; Red Giant Stars; Stellar Models; Stellar Interiors; Stellar Luminosity; Stellar Oscillations; Astrophysics; CLUSTERS: GLOBULAR; STARS: INTERIORS; STARS: LONG-PERIOD VARIABLES; STARS: PULSATION full text sources ADS | data products SIMBAD (1)

The horizontal-branch stars in globular clusters. I - The period-shift effect, the luminosity of the horizontal branch, and the age-metallicity relation

Synthetic models of the horizontal branches in globular clusters are constructed from a grid of the standard horizontal branch evolutionary tracks. The models are used to study the period shifts at constant T(eff) between RR Lyrae variables in globular clusters of different metallicities and the variation in horizontal-branch luminosity with the Fe/H ratio. The results suggest that the observed differences in the mean periods of the ab variables and the fraction of c-type variables between the two Oosterhoff groups are caused by a difference in the mean luminosity of the ab variables of about 0.18 bolometric mass and by the uneven distribution of variables across the instability strip in the group II clusters.

WHT observations of cataclysmic variables in globular clusters - I. V101 in M5 during quiescence and outburst

WHT spectroscopy and photometry are used to investigate the structure of the cataclysmic vaiable V101, in the globular cluster M5. An encouraging consistency is found between the properties derived from the color, magnitude, radial-velocity variations and outburst light curve. All these indicate that V101's orbital period lies above the period gap, is at the distance of M5, and is probably a dwarf nova.

Another Look at the RV Tauri Period-Luminosity Relation

The Period-Luminosity (P-L) relation for the RV Tauri variables (DuPuy 1973) contradicts those of other variables in the instability strip as it predicts lower luminosity at longer pulsational periods. It is based primarily upon three globular cluster variables. DuPuy determined secular and statistical parallaxes from 23 field variables, defining a simple P-L relation with a slightly negative slope.

Red variables in globular clusters - Their classification and evidence for mass loss

Red variables in globular clusters - Their classification and evidence for mass loss

Convection, the blue edge of the RR Lyrae gap, and a comparison of one-dimensional and two-dimensional hydrodynamic simulations

view Abstract Citations (13) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Convection, the blue edge of the RR Lyrae gap, and a comparison of one-dimensional and two-dimensional hydrodynamic simulations Deupree, R. G. Abstract Two-dimensional hydrodynamic simulations of the interaction of convection and pulsation at the blue edge of the RR Lyrae gap are performed. These calculations confirm the results found by Stellingwerf that convection makes the blue edge bluer and that the effect is more pronounced for overtone pulsation and for lower helium abundance. This reduces the sensitivity to helium abundance of the blue edge location and of the color width of the instability strip to the extent that neither quantity can be expected to be a reliable indicator of the helium abundance in the surface layers of RR Lyrae variables in globular clusters. Publication: The Astrophysical Journal Pub Date: September 1985 DOI: 10.1086/163430 Bibcode: 1985ApJ...296..160D Keywords: Cepheid Variables; Convection; Hydrodynamic Equations; Stellar Models; Stellar Oscillations; Eddy Viscosity; Helium; Stability; Stellar Cores; Astrophysics full text sources ADS |

A period-luminosity relation for Mira variables in globular clusters and its impact on the distance scale

On presente la photometrie JHKL de 31 variables rouges dans 15 amas globulaires galactiques. On en deduit les magnitudes bolometriques absolues et une relation M bol -log P qui differe de celle des variables Mira du GNM

The evolutionary state and pulsation characteristics of red variables in globular clusters

view Abstract Citations (47) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The evolutionary state and pulsation characteristics of red variablesin globular clusters. Frogel, J. A. Abstract Infrared observations of more than 50 red variables in globular clusters are presented, and the data are examined to ascertain the location of the variables in the H-R diagram and the implications for their evolutionary state, to find evidence of mass loss, and to determine the mode of pulsation. Particular emphasis is given to seven variables which lie considerably to the blue of their cluster giant branches and which may be in an advanced evolutionary state. It is concluded that all of the long-period variables (LPVs) in the clusters have luminosities greater than that corresponding to core helium flash, so they must be asymptotic giant branch stars. With three possible exceptions, all other cluster variables have luminosities less than that corresponding to helium core flash. Red K-L colors for the LPVs are probably indicative of relatively high mass loss rates compared to non-LPV variables. Publication: The Astrophysical Journal Pub Date: September 1983 DOI: 10.1086/161274 Bibcode: 1983ApJ...272..167F Keywords: Abundance; Globular Clusters; Red Giant Stars; Stellar Evolution; Stellar Oscillations; Variable Stars; Asymptotic Giant Branch Stars; Hertzsprung-Russell Diagram; Mass To Light Ratios; Stellar Luminosity; Stellar Mass Ejection; Stellar Spectrophotometry; Stellar Temperature; Astrophysics full text sources ADS | data products SIMBAD (17)

The Period-Luminosity Relation for Red Variables in Globular Clusters

Recent data for red pulsating variables in globular clusters are discussed. There seems to exist a period-luminosity relation in the near-by infrared but not in the visual magnitude.

Variables in Globular Clusters, the Common and the Rare

The title of this talk is really just a different phrasing from one I have used at several IAU meetings on the subject of numbers and kinds of variables in globular clusters. To furnish this material, I have finished the Third Catalogue of Variables in Globular Clusters. Since many of you are coming to this Colloquium with new information, the Catalogue is in draft form with a request that corrections and additions be given me by October 2, after which the draft will go to the printer.The First Catalogue of Variables in Globular Clusters was published at this observatory in 1939 and the Second Catalogue in 1955. In 1966 appeared the excellent Catalogue of Variables South of Declination—29° by Fourcade, Laborde and Albarracin, with splendid large prints of identification charts.

Observational Aspects of Slow Variables in Globular Clusters

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.

On the Changes of Periods of RR Lyrae Variables in the Globular Clusters M5, M53 and NGC 5053

The period of a variable star is very sensitive to extremely minor changes in luminosity, mass, radius, surface temperature, etc. of the star. With new theoretical calculations of the interior structure of stars in the late stages of evolution now available, the investigation of instabilities in the periods of the RR Lyrae variables in globular clusters becomes urgent.

Photometry of variables in globular clusters. III. M14 and the period-luminosity relation of population II cepheids

view Abstract Citations (25) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photometry of variables in globular clusters. III. M 14 and the period-luminosity relation of Population II Cepheids. Demers, S. ; Wehlau, A. Abstract B and V photographic photometry of five Population II Cepheids in M14 is presented. The plates are calibrated with a new photoelectric sequence. The mean magnitudes and colors of the M14 variables are combined with Population II Cepheids in a Cen, M2, and M13. These 17 variables define a period-lumi- nosity relation given as (Mv = -0.16-1.65 logP. No period-color relation is evident for all stars but the M14 and co Cen variables do follow a P-C relation with almost identical slope. Publication: The Astronomical Journal Pub Date: November 1971 DOI: 10.1086/111200 Bibcode: 1971AJ.....76..916D full text sources ADS | data products SIMBAD (5) GCPD (1) Related Materials (2) Part 1: 1969AJ.....74..925D Part 2: 1971AJ.....76..445D

An investigation of the variable stars in the globular cluster NGC 6712.

view Abstract Citations (7) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An Investigation of the Variable Stars in the Globular Cluster NGC 6712. Smith, L. L. ; Sandage, A. R. ; Lynden-Bell, D. ; Norton, R. H. Abstract The variable stars in the moderately strong metallic- lined globular cluster NGC 6712 previously studied (Smith and Sandage, Astron. J. 67,121,1962) have been investigated using photographic plates and a photoelectric sequence obtained with the 200-inch telescope between 1955 and 1961. A number of variables were found in a blink survey and we confirm all of Sawyer's previous discoveries. Seven of the variables appear to be RR Lyrae members of the cluster. Periods and light curves in the B and V bandpass were obtained for all seven members, six of which are of Bailey type a or b, and one is of type c. Four variables are of long period and lie at the end of the red-giant branch in the color-magnitude diagram. The purpose of the study was to see if the group characteristics of the variables in NGC 6712 differ from the characteristics in metal-weak clusters such as M3 or in very metal weak clusters such as M 15. Although it appears to be well established that the mean period of type a or b variables in globular clusters correlates well with the metal abundance (longer mean period occurs in the metal- poorer clusters), the six variables in NGC 6712 are not a large enough sample to apply the test because the observed Pa ,~ = 0d54 has little weight. A more stringent test is the differences of the period- amplitude relation between weak- and strong-lined clusters. Defining P1,0 as the period at which the amplitude in blue light is 1.0 mag., we get P3.0 values of 0d66, 0d65, 0d,60, and 0d,57 for M15, M92, M3, and NGC 6712, respectively, placed in the order of increasing metal abundance from the spectroscopic evidence. This decrease of P3.0 may be significant. It agrees with a model designed to explain the difference in mean period Pa,b between clusters (Sandage, 1958 Vatican Symposium on Stellar Populations, p. 51) but accurate data for more clusters are needed before the test can be said to be satisfactory. Publication: The Astronomical Journal Pub Date: September 1963 DOI: 10.1086/109107 Bibcode: 1963AJ.....68R.293S full text sources ADS | data products SIMBAD (2)

THE PERIOD-LUMINOSITY RELATION OF THE CEPHEIDS

Around the turn of the century two investigations were started at the Harvard Observatory that had a far-reaching influence on the further development of astronomy: Henrietta S. Leavitt's investigation of the variable stars in the two Magellanic Clouds and Solon I. Bailey's investigation of the variable stars in globular clusters. The Magellanic Clouds turned out to be veritable mines of cepheids with periods longer than one day. In contrast, the overwhelming majority of the variables in globular clusters were cepheids with periods shorter than one day ; they were so characteristic of globular clusters that Bailey proposed for them the name cluster -type variables. Further investigations of these variables led to two very remarkable results. The most striking was Miss Leavitt's discovery that the brightness of the cepheids in the Magellanic Clouds is a function of the period of the lightvariation (the observed brightness increases with the period). Since there was every reason to believe that the objects in each Cloud are at practically the same distance from us, the observed period-brightness relation clearly implied a period-luminosity relation for the cepheids with periods longer than one day. Once established, this period-luminosity relation obviously would provide a simple and very powerful tool for determining the distance of any cepheid of known apparent brightness and period.

Photoelectric light and color curves of V Vulpeculae.

view Abstract Citations (2) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photoelectric light and color curves of V Vulpeculae. Kameny, Franklin E. Abstract The RV Tauri variable V Vulpeculae was observed photoelectrically from September 3 until December 4, 1952, at the Agassiz Station of Harvard College Observatory. The observations were made with a I P2 I photomultiplier with a Corning 3384 yellow filter and a Corning 5543 blue filter. The 6i-inch and the ~~-inch reflectors, with aluminized mirrors, were employed. As comparison stars, BD ~ 2504312 and BD 2504306 were used. The international visual magnitude and the color of these two stars were found to be: V P-V +25~3I2 6.99 +1.19 +25~3o6 8.8~ +0.98 The observed magnitudes and colors were converted to the international system by means of a tie-in with C-I 2. Eggen's magnitudes were used.1 The individual probable errors of the 16 observed points averaged about 0.02 magnitude, with many smaller than 0.01, and some as large as 0.04 magnitude. The star was observed through three maxima and two minima. The curves of yellow light, blue light, and color parallel each other approximately, but not accurately. The blue maxima usually occurred on the same day as the yellow ones, but the blue minima preceded the yellow ones by about 3 days. The maxima of color preceded the maxima in yellow light by about 2 days; the color minlma, I.e. reddest color, preceded the yellow minima by about 6 days. The following table gives the magnitudes of the maxima and minima of yellow light with their dates, together with the magnitudes of the associated maxima and minima of blue light and color, although without dates. JD 1952 V P P-V 2434259 Sept. 4 Maximum 8w33 8w95 +O~63 289 Oct. 4 Minimum 9.20 10.40 +1.28 304 Oct. 19 Maximum 8.32 9.28 +0.99 323 Nov. 7 Minimum 8.78 9.92 +1.17 340 Nov. 24 Maximum 8.34 9.23 +0.90 The interval between the maxima before and after the deep minimum is 45 days, as compared with an interval of only 36 days between the maxima on either side of the shallow minimum. The star seems to be behind schedule by about I 1 days, as computed from the epoch and period given in the Kukarkin and Parenago General Catalogue of Va4able Stars. The unusual blueness of the maximum of Sept. 4 seems to have been caused almost entirely by excess light in the blue; the yellow maximum of that date was very similar in brightness to the other two which were observed. This star is decidedly redder than the RV Tauri variables in globular clusters, as observed by Arp. The differences between the blue and the yellow curves suggest that photoelectric observations of RV Tauri variables in several colors might well prove fruitful, especially if these observations could be combined with simultaneous spectrographic observations. I.Ap. J. "4, 143, 1951. Harvard College Observatory, Cambridge, Mass. Publication: The Astronomical Journal Pub Date: December 1953 DOI: 10.1086/106862 Bibcode: 1953AJ.....58..217K full text sources ADS | data products SIMBAD (3)