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J/PASP/111/812 V(RI)C Phot of Cepheids in the Magellanic Clouds (Barnes+ 1999)
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V(RI)C Photometry of Cepheids in the Magellanic Clouds
Barnes T. G. III, Ivans I. I., Martin J. R., Froning C. S.,
Moffett T. J.
<Publ. Astron. Soc. Pac., 111, 812 (1999)>
=1999PASP..111..812B
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ADC_Keywords: Stars, fundamental; Magellanic Clouds; Photometry, Cousins
Keywords: Cepheids, Magellanic Clouds, stars: fundamental parameters
Abstract:
We present V(RI)C data for 13 Cepheids in the Large Magellanic Cloud and
eight in the Small Magellanic Cloud. The total number of new measures is
55 in each wavelength band. The median uncertainty in the photometry is
±0.03 mag. These results supplement a larger photometric program
presented in the second paper in this series which contained 1000 measures
(±0.01 mag) in each wavelength band on 22 variables with periods in the
range 8133 days.
Description:
This is the fourth paper in a program to determine distances to the Large
and Small Magellanic Clouds using the visual surface brightness technique.
This technique provides Cepheid distances which are essentially
independent of reddening and are independent of the
period-luminosity-color relation and its calibration. The visual surface
brightness technique requires radial velocities and photometric values of
high quality. Fortunately, there are velocity curves for 14 LMC and eight
SMC Cepheids from the work of the CORAVEL group (Imbert et al. 1985, 1989)
and from Caldwell et al. (1986). On the other hand, existing BV(RI)C
photometry of these stars (Caldwell et al. 1986; Caldwell & Coulson 1986)
samples the light curves too sparsely for our analysis, hence our present
program to improve the available photometry.
In Paper I (Barnes, Moffett, & Gieren 1993) we demonstrated the surface
brightness technique for distance determination on HV 829 in the SMC using
preliminary photometric data. For HV 829 we obtained a distance modulus
of 18.9 ± 0.2 mag. Because HV 829 may not lie at the centroid of the
SMC, this may not be the mean distance to the SMC.
In Paper II (Moffett, Gieren, & Barnes 1998) we presented new Cousins
BV(RI)C photometry of 14 Magellanic Cloud Cepheids and eight Small
Magellanic Cloud Cepheids which yielded light curves of high quality,
consistent with the quality of the radial velocity curves and sufficient
for surface brightness analysis.
In Paper III (Gieren, Moffett, & Barnes 1999) we used the new photometry
and existing radial velocities to determine radii for 16 Magellanic Cloud
Cepheids and to compare those radii with results for Galactic Cepheids.
In this paper we present additional Cousins V(RI)C photometric data for
all but one of the stars in Paper II. The present data were actually the
first to be obtained in our CCD observing program, but because the
observing program shifted to another telescope for all subsequent runs,
the present data became "orphaned" and have only now been reduced for
publication. A follow-up paper will use the full set of photometry to
determine individual Cepheid distances from the visual surface brightness
technique. These data are also useful for other distance techniques, e.g.,
the infrared flux method.
Table1.dat gives our photometric results. Separate Julian Dates are given
for each passband because of the long integration times in some of the
exposures. The magnitude uncertainty given for each Cepheid is the
standard deviation in the comparison star values on the appropriate image.
Because comparison star magnitudes (on the Cousins system) were adopted
from Paper II, the scatter in their individual measures about the adopted
means is a reasonable representation of the uncertainty in a single
stellar magnitude measurement on that image, incorporating the errors in
magnitude determination, atmospheric extinction, and transformation to the
standard system. The Cepheid was almost always the brightest star on the
image, making the quoted uncertainties conservative estimates. The median
standard deviation in the comparison star measures is ±0.043 mag in V,
±0.033 mag in RC, and ±0.034 mag in IC.
A check on how well the present photometry fits the photometric system
of Paper II was made by comparing the values in Table1.dat to the light
curves in Paper II. We formed a difference (Table1.dat minus Paper II) for
all measures in Table1.dat which fell within 0.02 in phase to a value in
Paper II. Based on 35 differences, we found V = 0.006 ± 0.050 mag,
R = 0.009 ± 0.034 mag, and I = 0.005 ± 0.034 mag. The current
photometry clearly matches the V(RI)C photometric system of Paper II.
This is also illustrated in Figure 1 of the original source reference.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 86 55 Photometry of Magellanic Cloud Cepheids
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See also:
http://www.physics.mcmaster.ca/Cepheid/ :
McMaster Cepheid Photometry and Radial Velocity Data Archive
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Galaxy SMC or LMC
5- 12 A8 --- Name Cepheid
14- 20 F7.3 d HJD_V *V heliocentric Julian date
22- 27 F6.3 mag V V magnitude
29- 33 F5.3 mag e_V Uncertainty in V
35- 41 F7.3 d HJD_R(c) *R_c heliocentric Julian date
43- 48 F6.3 mag R(c) R-c magnitude
50- 54 F5.3 mag e_R(c) Uncertainty in R_c
56- 62 F7.3 d HJD_I(c) *I_c heliocentric Julian date
64- 69 F6.3 mag I(c) I_c magnitude
71- 75 F5.3 mag e_I(c) Uncertainty in I_c
77- 81 F5.3 mag V-R V-R color
83- 87 F5.3 mag V-I V-I color
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Note on HJD_V, HJD_R(c), HJD_I(c):
All Julian Dates given as HJD - 2,448,000.
References:
Barnes, T. G., & Moffett, T. J. 1979, PASP, 91, 289 =1979PASP...91..289B
Barnes, T. G., Moffett, T. J., & Gieren, W. P. 1993, ApJ, 405, L51
(Paper I) =1993ApJ...405L..51B
Caldwell, J. A. R., & Coulson, I. M. 1986, South African Astron. Obs. Circ.,
8, 1
Caldwell, J. A. R., Coulson, I. M., Spencer Jones, J. H., Black, C. A., &
Feast, M. W. 1986, MNRAS, 220, 671 =1986MNRAS.220..671C
Gieren, W. P., Moffett, T. J., & Barnes, T. G. 1999, ApJ, 512, 553
(Paper III) =1999ApJ...512..553G
Imbert, M., et al. 1985, A&AS, 61, 259 =1985A&AS...61..259I
Imbert, M. 1989, A&AS, 81, 339 =1989A&AS...81..339I
Landolt, A. U. 1992, AJ, 104, 340 =1992AJ....104..340L
Moffett, T. J., Gieren, W. P., & Barnes, T. G. 1998, ApJS, 117, 135
(Paper II) =1998ApJS..117..135M
Stetson, P. B. 1987, PASP, 99, 191 =1987PASP...99..191S
Tody, D. 1993, in ASP Conf. Ser. 52, Astronomical Data Analysis Software
and Systems II, ed. R. J. Hanisch, R. J. V. Brissenden, & J. Barnes
(San Francisco: ASP), 173
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(End) Gail L. Schneider [SSDOO/ADC] 15-May-2000