J/ApJS/117/135 Photometry of Cepheids in Magellanic Clouds (Moffett+ 1998)
BV(RI)C Photometry of Cepheids in the Magellanic Clouds
Moffett T.J., Gieren W.P., Barnes T.G. III, Gomez M.
<Astrophys. J. Suppl. 117, 135 (1998)>
=1998ApJS..117..135M 1998ApJS..117..135M
ADC_Keywords: Stars, variable; Magellanic Clouds ; Photometry, Cousins
Keywords: stars: variables: cepheids - galaxies: magellanic clouds - stars:
fundamental parameters
Abstract:
We report BV(RI)C data for a select group of 14 Cepheids in the Large
Magellanic Cloud and eight in the Small Magellanic Cloud that have
preexisting radial velocity curves. The photometry was obtained as
part of a program to determine distances to these Cepheids by means of
the visual surface brightness technique and to improve significantly
the optical BV(RI)C light curves of Magellanic Cloud Cepheids. The
data were acquired on the 0.9 m telescope at Cerro Tololo
Inter-American Observatory with the CFCCD instrument and with the 1 m
photometric telescope at ESO using aperture photometry. The median
number of measures per Cepheid is 46 in each band, and the uncertainty
in the photometry is typically 0.01 mag. Using these data together
with data from the literature, we determined improved periods for all
variables. For most of the Cepheids, these revised periods lead to
excellent, low-noise light curves, but for a few variables, the
periods are obviously variable.
Introduction:
In this paper we present the new photometric data, demonstrate the
consistency among the data obtained from CCD and aperture photometry,
and determine improved periods for all of the variables. In follow-up
papers we will use these observations to determine individual Cepheid
distances and radii from the visual surface brightness technique and
also from the infrared surface brightness technique (Welch
1994AJ....108.1421W 1994AJ....108.1421W; Fouque & Gieren 1997A&A...320..799F 1997A&A...320..799F).
Table 1 gives our final photometric results. All entries in Table 1 having
B magnitudes are CCD observations (CTIO), and the ones lacking B magnitudes
are photoelectric observations (ESO).
The uncertainties in the CCD results are dominated by the uncertainty
in the aperture correction. The standard deviation in the comparison
stars on a particular image is typically ±0.004 mag and always less
than ±0.01 mag. The aperture correction to the zero point of each
frame is estimated to be better than ±0.01 mag. We adopt ±0.01 mag
as the typical uncertainty in all magnitudes.
For the photoelectric observations, we inferred the uncertainties from
scatter in the observations of the Cepheids themselves, finding
±0.010 mag in V and ±0.012 mag in R and I.
We combined our new photometry with existing photoelectric photometry
from the literature to determine a new period for each Cepheid. This
was greatly aided by the McMaster Cepheid Data Archive maintained by
Doug Welch at http://www.physics.mcmaster.ca/Cepheid/. (The data
reported here will be added to the McMaster archive.) Periods were
found using an algorithm due to T. Deeming given in Bopp et al.
(1970MNRAS.147..355B 1970MNRAS.147..355B) and are listed in Table 2. The uncertainty of
each period is reflected in the number of digits given in the table.
For most of the Cepheids in our sample, the new periods lead to
excellent light curves of very low scatter, which indicates that the
periods for these variables are both correct and stable over the time
of our observations. For the Cepheids with comments in Table 2,
however, the periods appear to be changing in time. The existing data
set is insufficient to describe fully the nature of these period
changes.
Also in Table 2 we compare our intensity mean V magnitudes with those
from the literature, as represented by an extensive, private data base
maintained by J.A.R. Caldwell (1997, private communication). The
intensity means were determined from Fourier fits to the
(intensity-converted) light curves. The agreement is very good. The
mean difference between the data sets is -0.005 mag, and the standard
deviation is 0.019 mag. For Cepheids with the best new data, we have
listed a value to 0.001 mag, while for stars with less complete light
curves, the values are listed to 0.01 mag only.
Table 2: New Periods and Mean V Magnitudes for Magellanic Cloud Cepheids
Period V(new) V(SAAO)
Cepheid (days) Comment (mag) (mag)
---------------------------------------------------------
LMC
---------------------------------------------------------
HV 879... 36.827 13.332 13.35
HV 883... 133.585 12.14
HV 899... 31.0461 13.433 13.43
HV 900... 47.5085 12.766 12.78
HV 909... 37.5654 12.774 12.74
HV 2257... 39.3699 13.031 13.06
HV 2338... 42.1944 12.759 12.78
HV 2447... 118.3115 11.990 12.00
HV 2827... 78.77 Variable? 12.280 12.30
HV 2864... 10.9845 14.651 14.65
HV 2883... 108.968 12.41
HV 5497... 98.975 Variable? 11.92 11.94
HV 12815.. 26.1157 13.506 13.48
HV 12816.. 9.1089 14.500 14.52
---------------------------------------------------------
SMC
---------------------------------------------------------
HV 821... 127.314 Variable? 11.93 11.94
HV 824... 65.8635 12.36 12.37
HV 829... 85.199 Variable? 11.93 11.91
HV 834... 73.639 Variable? 12.21 12.21
HV 837... 42.6954 13.24 13.23
HV 1338... 8.49503 15.12 15.16
HV 1365... 12.4117 Variable? 15.04 15.02
HV 11157.. 69.0872 12.93 12.94
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 54 1002 Photometry of Magellanic Cloud Cepheids
--------------------------------------------------------------------------------
See also:
http://www.physics.mcmaster.ca/Cepheid/ :
McMaster Cepheid Photometry and Radial Velocity Data Archive
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Galaxy SMC or LMC
5- 12 A8 --- Name Cepheid Name
15- 26 F12.4 d HJD Heliocentric Julian date
28- 33 F6.3 mag Bmag ? B magnitude
35- 40 F6.3 mag Vmag ? V magnitude
42- 47 F6.3 mag R(c)mag ? Rc magnitude
49- 54 F6.3 mag I(c)mag Ic magnitude
--------------------------------------------------------------------------------
History:
From ApJ electronic edition
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
=1993ApJ...405L..51B 1993ApJ...405L..51B
Bopp, B.W., Evans, D.S., Laing, J.D., & Deeming, T.J. 1970, MNRAS, 147, 355
=1970MNRAS.147..355B 1970MNRAS.147..355B
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
Fouque, P., & Gieren, W.P. 1997, A&A, 320, 799 =1997A&A...320..799F 1997A&A...320..799F
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..339I 1989A&AS...81..339I
Landolt, A.U. 1992, AJ, 104, 340 =1992AJ....104..340L 1992AJ....104..340L
Menzies, J.W., & Laing, J.D. 1988, MNRAS, 231, 1047 =1988MNRAS.231.1047M 1988MNRAS.231.1047M
Mermilliod, J.-C., Turon, C., Robichon, N., & Arenou, F. 1997, in Proc. of
the ESA Symp. Hipparcos-Venice 1997 (ESA SP-402), 643
Welch, D.L. 1994, AJ, 108, 1421 =1994AJ....108.1421W 1994AJ....108.1421W
(End) Gail Schneider [SSDOO/ADC] 26-Sep-2000