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J/ApJ/449/164 Variable Stars in MC Clusters. II (Sebo+ 1995)
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Variable Stars in Magellanic Cloud Clusters. II. NGC 1850
Sebo P.R., Wood K.M.
<Astrophys. J. 449, 164 (1995)>
=1995ApJ...449..164S
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ADC_Keywords: Magellanic Clouds ; Stars, variable ; Clusters, open ;
Photometry, CCD
Keywords: Cepheids - Magellanic Clouds - open clusters and associations:
individual (NGC 1850) - stars: evolution
Abstract:
We present the results of a study aimed at identifying variable stars
in the rich LMC cluster NGC 1850. V and I band CCD imaging spanning
more than 5 years in a 10'x10' field surrounding the cluster has
allowed us to identify more than 30 variable stars, including seven
classical Cepheids, one anomalous Cepheid, two RR Lyrae variables, 19
long-period variables (LPVs), one blue eclipsing binary, one possible
pair of eclipsing giants, and several peculiar variables. The only
likely cluster member is a Cepheid.
Isochrone fitting to the cluster CMD yields an age of 80 Myr if an LMC
distance modulus of 18.5 is adopted. A comparison of pulsation and
evolution masses for the Cepheids still yields a ratio of evolution to
pulsation mass of ~1.2 for evolution models computed with core
overshoot parameter Lambda = 0.5, where Lambda = 2d_ov/H_p, d_ov is
the distance that convection overshoots beyond the Schwarzschild
boundary and H_p is the pressure scale height. An overshoot parameter
Lambda ~ 1.0 would be required to bring the evolution and pulsation
masses into agreement. One of the Cepheids in the field is a bump
Cepheid. A calculation of the bump mass yields a value in reasonable
agreement with the pulsation mass. We show that detailed modelling of
individual bump Cepheids is capable of providing very tight
constraints on the LMC distance modulus. The Cepheid
period-luminosity-color relation compared to the theoretical relation
yields a LMC distance modulus of 18.60. Finally, arguments are
presented which suggest that the LPVs are a mixture of fundamental
mode pulsators and small-amplitude overtone pulsators.
Description:
In the case where there are differing numbers of data points
in each color, the color with the fewer data points has been
padded with zeros.
Objects:
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RA (2000) DE Cl* NGC 1850 SW
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05 08 18.4 -68 46 46 9
05 08 44.1 -68 45 28 17
05 08 28.2 -68 48 24 39
05 08 43.6 -68 45 33 58
05 09 16.0 -68 44 30 110
05 09 24.3 -68 47 24 120
05 08 54.9 -68 43 10 269
05 08 07.3 -68 41 09 341
05 08 12.9 -68 41 03 347
05 08 16.4 -68 48 38 349
05 08 39.6 -68 43 46 395
05 09 08.8 -68 48 53 441
05 09 35.8 -68 41 43 502
05 09 38.4 -68 48 07 504
05 08 05.0 -68 42 12 558
05 08 09.4 -68 43 22 574
05 08 14.5 -68 44 55 587
05 08 28.3 -68 45 04 652
05 08 32.5 -68 44 30 670
05 08 35.4 -68 48 59 679
05 09 28.3 -68 47 51 1038
05 09 41.6 -68 45 26 1078
05 09 42.5 -68 45 16 1084
05 08 14.3 -68 49 42 1135
05 09 00.5 -68 47 02 1847
05 09 05.6 -68 46 30 1906
05 09 10.1 -68 41 38 1956
05 09 20.5 -68 45 54 2093
05 09 31.8 -68 48 52 2199
05 09 30.5 -68 42 27 2202
05 09 39.7 -68 45 35 2268
05 09 47.9 -68 45 08 9276
05 08 19.6 -68 44 44 10753
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
idata.dat 30 1575 I photometry
vdata.dat 30 1537 V photometry
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Byte-by-byte Description of file: vdata.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Star Number of star
7- 17 F11.3 d JD Julian date of V observation
19- 24 F6.3 mag Vmag V magnitude
26- 30 F5.3 mag e_Vmag V magnitude error
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Byte-by-byte Description of file: idata.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Star Number of star
7- 17 F11.3 d JD Julian date of I observation
19- 24 F6.3 mag Imag I magnitude
26- 30 F5.3 mag e_Imag I magnitude error
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Origin: AAS CD-ROM series, Volume 5, 1995 Lee Brotzman [ADS] 10-Oct-95
Historical Notes:
The original 34 files were merged into two files.
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(End) [CDS] 29-Jan-1996