THE VARIABLE STAR POPULATION OF THE GLOBULAR CLUSTER B514 IN THE ANDROMEDA GALAXY

Journal Article · Tue Oct 20 00:00:00 EDT 2009 · Astrophysical Journal (Online)

DOI:https://doi.org/10.1088/0004-637X/704/2/L103· OSTI ID:21367329

Clementini, Gisella; Contreras, Rodrigo; Federici, Luciana; Cacciari, Carla; Merighi, Roberto; Fusi Pecci, Flavio ^[1]; Smith, Horace A ^[2]; Catelan, Marcio ^[3]; Marconi, Marcella ^[4]; Kinemuchi, Karen ^[5]

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1. INAF, Osservatorio Astronomico di Bologna, Bologna (Italy)
2. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)
3. Pontificia Universidad Catolica de Chile, Departamento de AstronomIa y AstrofIsica, Santiago (Chile)
4. INAF, Osservatorio Astronomico di Capodimonte, Napoli (Italy)
5. Universidad de Concepcion, Departamento de AstronomIa, Concepcion (Chile)

A rich harvest of RR Lyrae stars has been identified for the first time in B514, a metal-poor ([Fe/H] approx- 1.95 +- 0.10 dex) globular cluster (GC) of the Andromeda galaxy (M31), based on Hubble Space Telescope Wide Field Planetary Camera 2 and Advanced Camera for Surveys time-series observations. We have detected and derived periods for 89 RR Lyrae stars (82 fundamental-mode, RRab, and 7 first-overtone, RRc, pulsators, respectively) among 161 candidate variables identified in the cluster. The average period of the RR Lyrae variables ((Pab) = 0.58 days and (Pc) = 0.35 days, for RRab and RRc pulsators, respectively) and the position in the period-amplitude diagram both suggest that B514 is likely an Oosterhoff type I cluster. This appears to be in disagreement with the general behavior of the metal-poor GCs in the Milky Way, which show instead Oosterhoff type II pulsation properties. The average apparent magnitude of the RR Lyrae stars sets the mean level of the cluster horizontal branch at (V(RR)) = 25.18 +- 0.02 (sigma = 0.16 mag, on 81 stars). By adopting a reddening E(B - V) = 0.07 +- 0.02 mag, the above metallicity and M {sub V} = 0.44 +- 0.05 mag for the RR Lyrae variables of this metallicity, we derive a distance modulus of mu{sub 0} = 24.52 +- 0.08 mag, corresponding to a distance of about 800 +- 30 kpc, based on a value of M {sub V} that sets mu{sub 0}(LMC)=18.52 mag.

• OSTI ID: 21367329
• Journal Information: Astrophysical Journal (Online), Vol. 704, Issue 2; Other Information: DOI: 10.1088/0004-637X/704/2/L103; ISSN 1538-4357
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
DISTANCE
METALS
MILKY WAY
PULSATIONS
TELESCOPES
VARIABLE STARS
ELEMENTS
GALAXIES
STARS