Bibcode
DOI
Dall'Ora, M.; Ripepi, V.; Caputo, F.; Castellani, V.; Bono, G.; Smith, H. A.; Brocato, E.; Buonanno, R.; Castellani, M.; Corsi, C. E.; Marconi, M.; Monelli, M.; Nonino, M.; Pulone, L.; Walker, A. R.
Referencia bibliográfica
The Astronomical Journal, Volume 126, Issue 1, pp. 197-217.
Fecha de publicación:
7
2003
Número de citas
72
Número de citas referidas
54
Descripción
We present new BV time series data of the Carina dwarf spheroidal galaxy
(dSph). Current data cover an area of ~0.3 deg2 around the
center of the galaxy and allow us to identify 92 variables. Among them
75 are RR Lyrae stars, 15 are bona fide anomalous Cepheids, one might be
a Galactic field RR Lyrae star, and one is located along the Carina red
giant branch. Expanding upon the seminal photographic investigation by
Saha, Monet, & Seitzer we supply, for the first time, accurate
estimates of their pulsation parameters (periods, amplitudes, mean
magnitudes, and colors) on the basis of CCD photometry. Approximately
50% of both RR Lyrae stars and anomalous Cepheids are new
identifications. Among the RR Lyrae sample, six objects are new
candidate double-mode (RRd) variables. On the basis of their pulsation
properties we estimate that two variables (V158, V182) are about 50%
more massive than typical RR Lyrae stars, while the bulk of the
anomalous Cepheids are roughly a factor of 2 more massive than
fundamental-mode (RRab) RR Lyrae stars. This finding supports the
evidence that these objects are intermediate-mass stars during central
He-burning phases. We adopted three different approaches to estimate the
Carina distance modulus, namely, the first-overtone blue edge method,
the period-luminosity-amplitude relation, and the
period-luminosity-color relation. We found DM=20.19+/-0.12, a result
that agrees quite well with similar estimates based on different
distance indicators. The data for Carina, together with data available
in the literature, strongly support the conclusion that dSph's can
barely be classified into the classical Oosterhoff dichotomy. The mean
period of RRab's in Carina resembles that found for Oosterhoff type II
clusters, whereas the ratio between first-overtone (RRc) pulsators and
the total number of RR Lyrae stars is quite similar to that found in
Oosterhoff type I clusters.
Based on observations collected at the European Southern Observatory, La
Silla, Chile, on Osservatorio Astronomico di Capodimonte guaranteed
time.