The Carina project. I. Bright variable stars

被引:53
作者
Dall'Ora, M
Ripepi, V
Caputo, F
Castellani, V
Bono, G
Smith, HA
Brocato, E
Buonanno, R
Castellani, M
Corsi, CE
Marconi, M
Monelli, M
Nonino, M
Pulone, L
Walker, AR
机构
[1] Osserv Astron Capodimonte, Inst Nazl Astrofis, I-80131 Naples, Italy
[2] Osserv Astron Roma, Ist Nazl Astrofis, I-00040 Monte Porzio Catone, Italy
[3] Univ Roma Tor Vergata, I-00133 Rome, Italy
[4] Ist Nazl Fis Nucl, Sez Ferrara, I-44100 Ferrara, Italy
[5] Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA
[6] Ist Nazl Astrofis, Osservatorio Astron Collurania, I-64100 Teramo, Italy
[7] Ist Nazl Astrofis, Osservatorio Astron Trieste, I-40131 Trieste, Italy
[8] Cerro Tololo Interamer Observ, Natl Opt Astron Observ, La Serena, Chile
关键词
galaxies : dwarf; galaxies : individual(Carina); Local Group; stars : distances; stars : horizontal-branch; stars : oscillations;
D O I
10.1086/374943
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present new BV time series data of the Carina dwarf spheroidal galaxy (dSph). Current data cover an area of approximate to0.3 deg(2) around the center of the galaxy and allow us to identify 92 variables. Among them 75 are RR Lyrae stars, 15 are bona. de 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 Oosterho. type I clusters.
引用
收藏
页码:197 / 217
页数:21
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