1 Introduction

$\rm NGC\;5904=M\,5=C1516\!+\!022$ is one of the richest globular clusters in the northern hemisphere. It is placed only 7 kpc from the Sun, 5.5 kpc from the Galactic Center and 4.9 kpc above the plane of the Galactic disc (Zinn 1985), and thus has low reddening, E(B-V)=0.03 (Harris 1996). The above properties make M 5 an excellent target for detailed studies, especially in the field of variable stars.

Spectroscopic investigations of M 5 yield metallicity determinations varying from ${\rm [Fe/H]}=-1.0$ (Butler 1975) to ${\rm [Fe/H]}=-1.4$(Zinn 1985). Carretta & Gratton (1997) obtained ${\rm [Fe/H]}=-1.11\pm 0.03$ on their newly introduced scale of GC metallicities.

M 5 is known to contain more than 140 RR Lyr variables (Clement 1997; Sandquist et al. 1996; Caputo et al. 1999). CCD VI photometry for 49 of them was recently presented by Reid (1996) who gives references to earlier papers dealing with RR Lyr stars in M 5. Recently, Kaluzny et al. (1999) reported the discovery of 5 faint variables in the cluster field: four SX Phe stars and one eclipsing binary. They also showed that several candidate eclipsing binaries identified by Reid (1996) and Yan & Reid (1996) are non-variable objects. Drissen & Shara (1998) used HST images to look for variable stars in the core of M 5. They identified one variable blue straggler, probably an eclipsing binary, and several new RR Lyr stars. New BV photometry of the M 5 RR Lyr variables was also reported by Caputo et al. (1999). And recently Olech et al. (1999b) using newly developed image subtraction method discovered four new variables in this cluster.

 

Table 1: Light curve parameters for RRc variables from M 5

Star	Period	AV	A0	A1	R21	$\sigma_{R_{21}}$	$\phi_{21}$	$\sigma_{\phi_{21}}$	$\phi _{31}$	$\sigma_{\phi_{31}}$	$\phi_{41}$	$\sigma_{\phi_{41}}$
V15	0.336776	0.41	15.064	0.206	0.087	0.010	3.067	0.117	7.130	0.142	3.571	0.243
V31	0.300575	0.50	15.069	0.261	0.157	0.004	3.100	0.019	6.117	0.028	3.356	0.042
V35	0.308177	0.46	14.967	0.234	0.154	0.004	3.431	0.045	6.542	0.073	3.644	0.106
V40	0.317334	0.43	15.051	0.220	0.114	0.005	3.147	0.034	6.549	0.046	3.975	0.091
V44	0.329576	0.42	15.027	0.214	0.107	0.009	2.899	0.080	6.967	0.128	4.026	0.259
V55	0.328938	0.41	15.086	0.210	0.119	0.010	3.438	0.080	7.132	0.133	4.024	0.188
V57	0.284673	0.49	15.050	0.246	0.179	0.004	3.305	0.032	6.065	0.065	3.256	0.076
V62	0.281412	0.53	15.099	0.262	0.187	0.004	3.107	0.030	5.808	0.067	3.036	0.079
V66	0.350658	0.44	15.032	0.225	0.053	0.005	3.299	0.122	7.343	0.095	4.113	0.216
V73	0.340111	0.51	14.974	0.262	0.095	0.008	3.364	0.085	7.047	0.098	3.854	0.150
V76	0.432544	0.40	14.828	0.192	0.036	0.005	5.524	0.201	8.276	0.109	5.315	0.212
V78	0.264798	0.39	15.094	0.196	0.158	0.005	3.090	0.038	6.209	0.137	2.698	0.173
V79	0.333089	0.35	14.947	0.177	0.147	0.011	3.134	0.151	7.033	0.237	3.379	0.388
V80	0.336549	0.39	15.042	0.196	0.117	0.005	2.998	0.057	7.194	0.116	4.014	0.146
V88	0.328070	0.43	15.034	0.220	0.123	0.014	3.496	0.100	6.626	0.183	4.045	0.285
V130	0.326624	0.42	14.882	0.212	0.033	0.028	4.460	0.876	7.544	0.395	4.464	0.776
Mean	0.324994	0.44	15.015	0.221	0.117	-	3.429	-	6.849	-	3.798	-

In this paper we present results based on time-series photometry of RR Lyr stars in M 5 obtained in 1997 at Las Campanas Observatory. The detailed description of the observational runs and reduction process were published elsewhere (Kaluzny et al. 1999). In short, the observing material consisted of 275 V-band frames collected during the period from May 9 through August 13 1997. Most of the data were taken during a single sub-run in May 1997. Two fields with a significant overlap at the cluster center were monitored.