### Abstract

Aims. We present the analysis of 11 nights of V and I time-series observations of the globular cluster NGC 1904 (M 79). Using this we searched for variable stars in this cluster and attempted to refine the periods of known variables, making use of a time baseline spanning almost 8 years. We use our data to derive the metallicity and distance of NGC 1904. Methods. We used difference imaging to reduce our data to obtain high-precision light curves of variable stars. We then estimated the cluster parameters by performing a Fourier decomposition of the light curves of RR Lyrae stars for which a good period estimate was possible. Results. Out of 13 stars previously classified as variables, we confirm that 10 are bona fide variables. We cannot detect variability in one other within the precision of our data, while there are two which are saturated in our data frames, but we do not find sufficient evidence in the literature to confirm their variability. We also detect a new RR Lyrae variable, giving a total number of confirmed variable stars in NGC 1904 of 11. Using the Fourier parameters, we find a cluster metallicity [Fe/H] _{ZW} =-1.63 ± 0.14, or [Fe/H] _{UVES} =-1.57 ± 0.18, and a distance of 13.3 ± 0.4 kpc (using RR0 variables) or 12.9 kpc (using the one RR1 variable in our sample for which Fourier decomposition was possible).

Original language | English |
---|---|

Article number | A92 |

Journal | Astronomy and Astrophysics |

Volume | 548 |

DOIs | |

Publication status | Published - 5 Dec 2012 |

Externally published | Yes |

### Fingerprint

### Keywords

- Globular clusters: individual: NGC 1904
- Stars: variables: RR Lyrae

### ASJC Scopus subject areas

- Astronomy and Astrophysics
- Space and Planetary Science

### Cite this

*Astronomy and Astrophysics*,

*548*, [A92]. https://doi.org/10.1051/0004-6361/201220217

**Constraining the parameters of globular cluster NGC 1904 from its variable star population.** / Kains, N.; Bramich, D. M.; Figuera Jaimes, R.; Arellano Ferro, A.; Giridhar, S.; Kuppuswamy, K.

Research output: Contribution to journal › Article

*Astronomy and Astrophysics*, vol. 548, A92. https://doi.org/10.1051/0004-6361/201220217

}

TY - JOUR

T1 - Constraining the parameters of globular cluster NGC 1904 from its variable star population

AU - Kains, N.

AU - Bramich, D. M.

AU - Figuera Jaimes, R.

AU - Arellano Ferro, A.

AU - Giridhar, S.

AU - Kuppuswamy, K.

PY - 2012/12/5

Y1 - 2012/12/5

N2 - Aims. We present the analysis of 11 nights of V and I time-series observations of the globular cluster NGC 1904 (M 79). Using this we searched for variable stars in this cluster and attempted to refine the periods of known variables, making use of a time baseline spanning almost 8 years. We use our data to derive the metallicity and distance of NGC 1904. Methods. We used difference imaging to reduce our data to obtain high-precision light curves of variable stars. We then estimated the cluster parameters by performing a Fourier decomposition of the light curves of RR Lyrae stars for which a good period estimate was possible. Results. Out of 13 stars previously classified as variables, we confirm that 10 are bona fide variables. We cannot detect variability in one other within the precision of our data, while there are two which are saturated in our data frames, but we do not find sufficient evidence in the literature to confirm their variability. We also detect a new RR Lyrae variable, giving a total number of confirmed variable stars in NGC 1904 of 11. Using the Fourier parameters, we find a cluster metallicity [Fe/H] ZW =-1.63 ± 0.14, or [Fe/H] UVES =-1.57 ± 0.18, and a distance of 13.3 ± 0.4 kpc (using RR0 variables) or 12.9 kpc (using the one RR1 variable in our sample for which Fourier decomposition was possible).

AB - Aims. We present the analysis of 11 nights of V and I time-series observations of the globular cluster NGC 1904 (M 79). Using this we searched for variable stars in this cluster and attempted to refine the periods of known variables, making use of a time baseline spanning almost 8 years. We use our data to derive the metallicity and distance of NGC 1904. Methods. We used difference imaging to reduce our data to obtain high-precision light curves of variable stars. We then estimated the cluster parameters by performing a Fourier decomposition of the light curves of RR Lyrae stars for which a good period estimate was possible. Results. Out of 13 stars previously classified as variables, we confirm that 10 are bona fide variables. We cannot detect variability in one other within the precision of our data, while there are two which are saturated in our data frames, but we do not find sufficient evidence in the literature to confirm their variability. We also detect a new RR Lyrae variable, giving a total number of confirmed variable stars in NGC 1904 of 11. Using the Fourier parameters, we find a cluster metallicity [Fe/H] ZW =-1.63 ± 0.14, or [Fe/H] UVES =-1.57 ± 0.18, and a distance of 13.3 ± 0.4 kpc (using RR0 variables) or 12.9 kpc (using the one RR1 variable in our sample for which Fourier decomposition was possible).

KW - Globular clusters: individual: NGC 1904

KW - Stars: variables: RR Lyrae

UR - http://www.scopus.com/inward/record.url?scp=84870318004&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84870318004&partnerID=8YFLogxK

U2 - 10.1051/0004-6361/201220217

DO - 10.1051/0004-6361/201220217

M3 - Article

VL - 548

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

M1 - A92

ER -