/ 97 09 02 4 v 1 3 S ep 1 99 7 Evolution of Horizontal Branch Stars in Globular Clusters
نویسندگان
چکیده
New observations of variable stars in the globular cluster M3 reveal that the RR Lyrae variable V79 is a double-mode (RRd) variable with the first overtone mode dominating. In all previous studies, V79 was found to be a fundamental mode (RRab) pulsator with an irregular light curve. This is the first observed mode switch for an RR Lyrae variable and it is direct observational evidence for blueward evolution of horizontal branch stars in the Oosterhoff type I cluster M3. It also demonstrates that there is a connection between the Blazhko effect and pulsational mode mixing in RR Lyrae variables. These new observations also show that the strength of the overtone oscillations in the RRd star V68 in M3 may have increased in the last 70 years, thus indicating blueward evolution for V68 as well. Affiliated with the Department of Astronomy, University of Toronto and Department of Physics and Astronomy, York University
منابع مشابه
ar X iv : a st ro - p h / 99 03 43 7 v 1 2 9 M ar 1 99 9 Striking Photospheric Abundance Anomalies in Blue Horizontal - Branch Stars in Globular Cluster
High-resolution optical spectra of thirteen blue horizontal-branch (BHB) stars in the globular cluster M13 show enormous deviations in element abundances from the expected cluster metallicity. In the hotter stars (Teff > 12000K), helium is depleted by factors of 10 to 100 below solar, while iron is enhanced to three times the solar abundance, two orders of magnitude above the canonical metallic...
متن کامل00 02 11 9 v 1 4 F eb 2 00 0 Rotations and Abundances of Blue Horizontal - Branch Stars in Globular Cluster
High-resolution optical spectra of eighteen blue horizontal-branch (BHB) stars in the globular cluster M15 indicate that their stellar rotation rates and photospheric compositions vary strongly as a function of effective temperature. Among the cooler stars in the sample, at Teff ∼ 8500K, metal abundances are in rough agreement with the canonical cluster metallicity, and the v sin i rotations ap...
متن کاملar X iv : a st ro - p h / 97 08 21 0 v 1 2 2 A ug 1 99 7 Multimodal Distributions along the Horizontal Branch 1 Francesco
We report on HST/WFPC2 U, V and far-ultraviolet observations of two Galactic Globular Clusters (GGCs), NGC6205 = M13 and NGC6093 = M80. Both of these clusters have horizontal-branch (HB) tails that extend to the helium-burning main sequence, with the hottest stars reaching theoretical effective temperatures above 35,000K. In both clusters, groups of stars are found to be separated by narrow gap...
متن کاملar X iv : a st ro - p h / 97 01 04 5 v 1 9 J an 1 99 7 Blue Horizontal Branch Stars in M 92 1
We have analyzed high dispersion and high precision spectra of 5 blue horizontal branch stars in the globular cluster M92 to establish that the projected rotational velocity for these stars ranges from 15 to 40 km s. This is larger than that expected based on the rotation of their main sequence progenitors, the spin down of rotation with age, and the conservation of angular momentum. Possible e...
متن کاملar X iv : a st ro - p h / 01 05 14 5 v 1 9 M ay 2 00 1 Hot Stars in Globular Clusters – A Spectroscopist ’ s View
Globular clusters are ideal laboratories to study the evolution of low-mass stars. In this work we concentrate on three types of hot stars observed in globular clusters: horizontal branch stars, UV bright stars, and white dwarfs. After providing some historical background and information on gaps and blue tails we discuss extensively hot horizontal branch stars in metal-poor globular clusters, e...
متن کامل