Browsing by Author "Storm, J"

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    A direct distance to the Large Magellanic Cloud Cepheid HV 12198 from the infrared surface brightness technique
    (2000) Gieren, WP; Storm, J; Fouqué, P; Mennickent, RE; Gómez, M
    We report on the first application of the infrared surface brightness technique on a Cepheid in the Large Magellanic Cloud, the variable HV 12198 in the young globular cluster NGC 1866. From this one star, we determine a distance modulus of 18.42 +/- 0.10 (random and systematic uncertainty) to the cluster. When the results on further member Cepheids in NGC 1866 become available, we expect to derive the distance to the LMC with a +/-3%-4% accuracy, including systematic errors, from this technique.
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    Cepheid variables in the Large Magellanic Cloud cluster NGC 1866.: I.: New BVRI CCD photometry
    (2000) Gieren, WP; Gómez, M; Storm, J; Moffett, TJ; Infante, L; Barnes, TG; Geisler, D; Fouqué, P
    We report BV(RI)(C) CCD photometric data for a group of seven Cepheid variables in the young, rich cluster NGC 1866 in the Large Magellanic Cloud. The photometry was obtained as part of a program to determine accurate distances to these Cepheids by means of the infrared surface brightness technique and to improve the LMC Cepheid database for constructing Cepheid P-L and P-L-C relations. Using the new data together with data from the literature, we have determined improved periods for all variables. For five fundamental mode pulsators, the light curves are now of excellent quality and will lead to accurate distance and radius determinations once complete infrared light curves and radial velocity curves for these variables become available.
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    The Araucaria Project
    (2004) Gieren, W; Pietrzynski, G; Walker, A; Bresolin, F; Minniti, D; Kudritzki, RP; Udalski, A; Soszynski, I; Fouqué, P; Storm, J; Bono, G
    In a previous paper, we reported on the discovery of more than a hundred new Cepheid variables in the Sculptor Group spiral galaxy NGC 300 from wide-field images taken in the B and V photometric bands at ESO/La Silla. In this paper, we present additional VI data, derive improved periods and mean magnitudes for the variables, and construct period-luminosity relations in the V, I, and the reddening-independent V - I Wesenheit bands using 58 Cepheid variables with periods between 11 and 90 days. We obtain tightly defined relations, and by fitting the slopes determined for the LMC Cepheids by the OGLE II Project we obtain reddening-corrected distances to the galaxy in all bands, which show a slight offset to each other in the sense that the Wesenheit relation yields the smallest distance, whereas the I- and V-band distances are larger by 0.094 and 0.155 mag, respectively. We adopt as our best value the distance derived from the reddening-free Wesenheit magnitudes, which is 26.43 +/- 0.04( random) +/- 0.05( systematic) mag. The distance moduli from both the V and I bands agree perfectly with the Wesenheit value if one assumes an additional reddening of E( B - V) = 0.05 mag intrinsic to NGC 300, in addition to the Galactic foreground reddening toward NGC 300 of 0.025 mag. Such a modest intrinsic reddening is supported by recent Hubble Space Telescope (HST) images of NGC 300, which show that this galaxy is relatively dustfree but also reveal that there must be some dust absorption in NGC 300. We argue that our current distance result for NGC 300 is the most accurate that has so far been obtained using Cepheid variables and that it is largely free from systematic effects due to metallicity, blending, and sample selection. It agrees very well with the recent distance determination from the tip of the red giant branch method obtained from HST data by Butler and coworkers, and it is consistent with the Cepheid distance to NGC 300 that was derived by Freedman and coworkers from CCD photometry of a smaller sample of stars.