scholarly journals New Pulsational Constraints to the Distance of Globular Clusters and the MV(RR)–[Fe/H] Relation

2000 ◽  
Vol 176 ◽  
pp. 263-263
Author(s):  
Vincenzo Ripepi ◽  
Filippina Caputo ◽  
Vittorio Castellani ◽  
Marcella Marconi
Keyword(s):  
Globular Clusters ◽  
Apparent Distance ◽  
Chemical Compositions ◽  
Distance Modulus ◽  
Instability Strip ◽  
Rr Lyrae ◽  
Visual Magnitude ◽  
The Absolute ◽  
Galactic Globular Clusters

AbstractWe applied the pulsational method (Caputo 1997) to derive the distances to a sample of galactic globular clusters with well-observed RR Lyrae populations. To apply the method we calculated a set of pulsational theoretical boundaries of the instability strip for the range of masses and chemical compositions spanned by the analysed clusters. In this way we were able to fix simultaneously the apparent distance modulus and the absolute visual magnitude of the RR Lyrae population of each cluster in the sample. As a result we derived the following relations:

scholarly journals Pulsating Stars and the Distance Scale - II

1995 ◽  
Vol 155 ◽  
pp. 209-220
Author(s):  
Michael Feast
Keyword(s):  
Globular Clusters ◽  
Zero Point ◽  
Distance Scale ◽  
Age Difference ◽  
Distance Modulus ◽  
Pulsating Stars ◽  
Rr Lyrae ◽  
Galactic Globular Clusters

AbstractThe current Cepheid zero-point is equivalent to an LMC distance modulus of 18.57 ± 0.10. The zero-point from corrected Baade-Wesselink data is probably not significantly different from this. A reexamination of the Baade-Wesselink data for RR Lyrae variables leads to an LMC modulus of 18.51, an age difference between β- and α-group galactic globular clusters of +1.46±0.70 Gyr, and an Mv - [Fe/H] slope in agreement with theory. Other questions discussed include; Avoiding bias in using the Cepheid PL relation; Metallicity spread amongst Cepheids; Cepheids and Ho.

The Luminosity-Metallicity Relation for RR Lyrae Stars and its Implications for the Astronomical Distance Scale

1989 ◽  
Vol 111 ◽  
pp. 255-255
Author(s):  
G. Clementini ◽  
C. Cacciari
Keyword(s):  
Globular Clusters ◽  
Galactic Center ◽  
Absolute Magnitude ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Visual Magnitude ◽  
Phase Range ◽  
The Absolute ◽  
Lyrae Stars ◽  
Magnitude Difference

AbstractThe surface brightness version of the Baade-Wesselink method, has been applied to 7 field RR Lyrae stars with metallicity ranging from [Fe/H]= −0.2 to −1.5. V magnitudes, V-R and V-I colors and CORAVEL radial velocities were used, and the analysis was performed over a restricted phase range in order to avoid the complications caused by the pulsating atmospheres. The combination with previous results of the B-W method, which used comparable criteria (Jones, Carney, & Latham, 1988, preprint; Jameson, Fernley, & Longmore 1987, in press M.N.R.A.S; Cohen & Gordon 1987, Ap.J., 318, 215) leads to the following relation between the absolute luminosity and metallicity:Mv = (1.0 ± 0.05) + (0.17 ± 0.05) [Fe/H]This relation is in very good agreement with the preliminary results found by Liu and Janes (this volume). The application of the above relation to the RR Lyraes in M31 and the Magellanic Clouds leads to distance moduli of (m–M)o= 24.21 ± 0.20 for M31, (m–M)o = 18.26 ± 0.20 for the LMC, and (m–M)o =18.85 ± 0.20 for the SMC, and the distance to the galactic center turns out to be approximately 7.2 kpc. From the absolute magnitude of the RR Lyraes and adopting a constant visual magnitude difference between the RR Lyraes and the turn-off ΔV = 3.55 (Buonanno 1986, Mem.S.A.It., 57, 333), we estimate ages of 18.8 and 15.7 Gyr for globular clusters of metallicity [Fe/H] = −2.2 (e.g. M92) and [Fe/H] = −0.8 (e.g. 47 Tuc) respectively, using the age-turnoff luminosity relation derived by Sandage (1982, Ap.J., 252, 553) or 20.9 and 16.9 Gyr using Buonanno’s relation.

scholarly journals The Period-Luminosity Relation for Cepheids in Globular Clusters

1973 ◽  
Vol 21 ◽  
pp. 180-184
Author(s):  
B. V. Kukarkin ◽  
A. S. Rastorgouev
Keyword(s):  
Globular Clusters ◽  
Apparent Distance ◽  
Absolute Magnitude ◽  
Rr Lyrae ◽  
Method Of Determination ◽  
The Absolute ◽  
Absolute Magnitudes

The period-luminosity relation for Cepheids in globular clusters has been investigated many times (e.g. Fernie, 1964; Kwee, 1968; Frolov, 1970; Demers, 1971).The method of determination of the apparent distance moduli was recently revised by Kukarkin and Russev (1972). Instead of using a single absolute magnitude for RR Lyrae variables, the magnitudes according to pulsation theory (Christy, 1966, 1971) were adopted. The inhomogeneity of the absolute magnitudes of the RR Lyrae variables had already been established long ago (Pavlovskaya, 1953), but it attracted attention only recently. The different methods for determining the distance moduli of globular clusters were calibrated according to the new absolute magnitudes of the RR Lyrae variables. The problem consisted in the determination of the absolute magnitudes of the Cepheids in globular clusters according to the apparent distance moduli.

scholarly journals RR Lyrae variables in Galactic globular clusters

2005 ◽  
Vol 437 (3) ◽  
pp. 1017-1021 ◽  
Author(s):  
M. Castellani ◽  
V. Castellani ◽  
S. Cassisi
Keyword(s):  
Globular Clusters ◽  
Rr Lyrae ◽  
Galactic Globular Clusters

scholarly journals The Absolute Magnitudes of RR Lyrae Stars and the Age of the Galaxy

1989 ◽  
Vol 111 ◽  
pp. 121-140
Author(s):  
Allan Sandage
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Main Sequence ◽  
Absolute Magnitude ◽  
Cluster System ◽  
Apparent Magnitude ◽  
Rr Lyrae ◽  
Globular Cluster System ◽  
The Absolute ◽  
Absolute Magnitudes

AbstractIt is shown that the intrinsic spread in the absolute magnitudes of the RR Lyrae variables in a given globular cluster can reach 0.5 magnitudes at a given period or at a given color, due to luminosity evolution away from the zero age horizontal (ZAHB). The size of this intrinsic luminosity spread is largest in clusters of the highest metallicity.The absolute magnitude of the ZAHB itself also differs from cluster to cluster as a function of metallicity, being brightest in clusters of the lowest metallicity. Three independent methods of calibrating the ZAHB RR Lyrae luminosities each show a strong variation of MV(RR) with [Fe/H]. The pulsation equation of P<ρ>0.5 = Q(M,Te, L) used with the observed periods, temperatures, and masses of field and of cluster RR Lyraes gives the very steep luminosity-metallicity dependence of dMv(RR)/d[Fe/H] = 0.42. Main sequence fitting of the color-magnitude diagrams of clusters which have modern main-sequence photometry gives a confirming steep slope of 0.39. A summary of Baade-Wesselink MV(RR) values for field stars determined in four independent recent studies also shows a luminosity-metallicity dependence, but less steep with a slope of dMV(RR)/d[Fe/H] = 0.21.Observations show that the magnitude difference between the main sequence turn-off point and the ZAHB in a number of well observed globular clusters is independent of [Fe/H], and has a stable value of dV = 3.54 with a disperion of only 0.1 magnitudes. Using this fact, the absolute magnitude of the main sequence turn-off is determined in any given globular cluster from the observed apparent magnitude of the ZAHB by adopting any particular MV(RR) = f([Fe/H]) calibration.Ages of the clusters are shown to vary with [Fe/H] by amounts that depend upon the slopes of the MV(RR) = f([Fe/H]) calibrations. The calibrations show that there would be a steep dependence of the age on [Fe/H] if MV(RR) does not depend on [Fe/H]. No dependence of age on metallicity exists if the RR Lyrae luminosities depend on [Fe/H] as dMV(RR)/d[Fe/H] = 0.37. If Oxygen is not enhanced as [Fe/H] decreases, the absolute average age of the globular cluster system is 16 Gyr, independent of [Fe/H], using the steep MV(RR)/[Fe/H] calibration that is favored. If Oxygen is enhanced by [O/Fe] = – 0.14 [Fe/H] + 0.40 for [Fe/H] < –1.0, as suggested from the observations of field subdwarfs, then the age of the globular cluster system decreases to 13 Gyr, again independent of [Fe/H], if the RR Lyrae ZAHB luminosities have a metallicity dependence of dMV(RR)/d[Fe/H] = 0.37.

scholarly journals RR Lyrae Stars in Galactic Globular Clusters. II. A Theoretical Approach to Variables in M3

2003 ◽  
Vol 596 (1) ◽  
pp. 299-313 ◽  
Author(s):  
M. Marconi ◽  
F. Caputo ◽  
M. Di Criscienzo ◽  
M. Castellani
Keyword(s):  
Theoretical Approach ◽  
Globular Clusters ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Galactic Globular Clusters ◽  
Lyrae Stars

scholarly journals Globular clusters in the Sagittarius stream

2020 ◽  
Vol 636 ◽  
pp. A107 ◽  
Author(s):  
M. Bellazzini ◽  
R. Ibata ◽  
K. Malhan ◽  
N. Martin ◽  
B. Famaey ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Main Body ◽  
Rr Lyrae ◽  
The Galaxy ◽  
Tidal Stream ◽  
Galactic Globular Clusters

We reconsider the case for the association of Galactic globular clusters to the tidal stream of the Sagittarius dwarf spheroidal galaxy (Sgr dSph) using Gaia DR2 data. We used RR Lyrae variables to trace the stream in 6D and we selected clusters matching the observed stream in position and velocity. In addition to the clusters residing in the main body of the galaxy (M 54, Ter 8, Ter 7, Arp 2) we confirm the membership of Pal 12 and Whiting 1 to the portion of the trailing arm populated by stars lost during recent perigalactic passages. NGC 2419, NGC 5634, and NGC 4147 are very interesting candidates, possibly associated with more ancient wraps of the Sagittarius stream. With the exception of M 54, which lies within the stellar nucleus of the galaxy, we note that all these clusters are found in the trailing arm of the stream. The selected clusters are fully consistent with the [Fe/H] versus [Mg/Fe], [Ca/Fe] patterns and the age-metallicity relation displayed by field stars in the main body of Sgr dSph.

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