J/PASP/111/812 V(RI)C Phot of Cepheids in the Magellanic Clouds (Barnes+ 1999)
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 1999PASP..111..812B
ADC_Keywords: Stars, variable; 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. 1985A&AS...61..259I 1985A&AS...61..259I, 1989A&AS...81..339) and from
Caldwell et al. (1986MNRAS.220..671C 1986MNRAS.220..671C). On the other hand, existing
BV(RI)C photometry of these stars (Caldwell et al.
1986MNRAS.220..671C 1986MNRAS.220..671C; 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 1993ApJ...405L..51B 1993ApJ...405L..51B) 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 1998ApJS..117..135M 1998ApJS..117..135M) 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 1999ApJ...512..553G 1999ApJ...512..553G) 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 99 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- 24 F11.3 d HJD_V V heliocentric Julian date
26- 31 F6.3 mag Vmag V magnitude
33- 37 F5.3 mag e_Vmag Uncertainty in V
39- 49 F11.3 d HJD_R(c) Rc heliocentric Julian date
51- 56 F6.3 mag R(c) R-c_ magnitude
58- 62 F5.3 mag e_R(c) Uncertainty in R_c
64- 74 F11.3 d HJD_I(c) Ic heliocentric Julian date
76- 81 F6.3 mag I(c) Ic magnitude
83- 87 F5.3 mag e_I(c) Uncertainty in Ic
89- 93 F5.3 mag V-R V-R color
95- 99 F5.3 mag V-I V-I color
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References:
Barnes, T. G., & Moffett, T. J. 1979, PASP, 91, 289 =1979PASP...91..289B 1979PASP...91..289B
Barnes, T. G., Moffett, T. J., & Gieren, W. P. 1993, ApJ, 405, L51
(Paper I) =1993ApJ...405L..51B 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 1986MNRAS.220..671C
Gieren, W. P., Moffett, T. J., & Barnes, T. G. 1999, ApJ, 512, 553
(Paper III) =1999ApJ...512..553G 1999ApJ...512..553G
Imbert, M., et al. 1985, A&AS, 61, 259 =1985A&AS...61..259I 1985A&AS...61..259I
Imbert, M. 1989, A&AS, 81, 339 =1989A&AS...81..339
Landolt, A. U. 1992, AJ, 104, 340 =1992AJ....104..340L 1992AJ....104..340L
Moffett, T. J., Gieren, W. P., & Barnes, T. G. 1998, ApJS, 117, 135
(Paper II) =1998ApJS..117..135M 1998ApJS..117..135M
Stetson, P. B. 1987, PASP, 99, 191 =1987PASP...99..191S 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
(End) Gail L. Schneider [SSDOO/ADC] 15-May-2000