J/ApJ/449/164 Variable Stars in MC Clusters. II (Sebo+ 1995)
Variable Stars in Magellanic Cloud Clusters. II. NGC 1850
Sebo P.R., Wood K.M.
<Astrophys. J. 449, 164 (1995)>
=1995ApJ...449..164S 1995ApJ...449..164S
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 = 2dov/Hp, 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 Name in SIMBAD
----------------------------------------------------
05 08 18.4 -68 46 46 Cl* NGC 1850 SW 9
05 08 44.1 -68 45 28 Cl* NGC 1850 SW 17
05 08 28.2 -68 48 24 Cl* NGC 1850 SW 39
05 08 43.6 -68 45 33 Cl* NGC 1850 SW 58
05 09 16.0 -68 44 30 Cl* NGC 1850 SW 110
05 09 24.3 -68 47 24 Cl* NGC 1850 SW 120
05 08 54.9 -68 43 10 Cl* NGC 1850 SW 269
05 08 07.3 -68 41 09 Cl* NGC 1850 SW 341
05 08 12.9 -68 41 03 Cl* NGC 1850 SW 347
05 08 16.4 -68 48 38 Cl* NGC 1850 SW 349
05 08 39.6 -68 43 46 Cl* NGC 1850 SW 395
05 09 08.8 -68 48 53 Cl* NGC 1850 SW 441
05 09 35.8 -68 41 43 Cl* NGC 1850 SW 502
05 09 38.4 -68 48 07 Cl* NGC 1850 SW 504
05 08 05.0 -68 42 12 Cl* NGC 1850 SW 558
05 08 09.4 -68 43 22 Cl* NGC 1850 SW 574
05 08 14.5 -68 44 55 Cl* NGC 1850 SW 587
05 08 28.3 -68 45 04 Cl* NGC 1850 SW 652
05 08 32.5 -68 44 30 Cl* NGC 1850 SW 670
05 08 35.4 -68 48 59 Cl* NGC 1850 SW 679
05 09 28.3 -68 47 51 Cl* NGC 1850 SW 1038
05 09 41.6 -68 45 26 Cl* NGC 1850 SW 1078
05 09 42.5 -68 45 16 Cl* NGC 1850 SW 1084
05 08 14.3 -68 49 42 Cl* NGC 1850 SW 1135
05 09 00.5 -68 47 02 Cl* NGC 1850 SW 1847
05 09 05.6 -68 46 30 Cl* NGC 1850 SW 1906
05 09 10.1 -68 41 38 Cl* NGC 1850 SW 1956
05 09 20.5 -68 45 54 Cl* NGC 1850 SW 2093
05 09 31.8 -68 48 52 Cl* NGC 1850 SW 2199
05 09 30.5 -68 42 27 Cl* NGC 1850 SW 2202
05 09 39.7 -68 45 35 Cl* NGC 1850 SW 2268
05 08 58.4 -68 47 18 Cl* NGC 1850 SW 7254
05 09 47.9 -68 45 08 Cl* NGC 1850 SW 9276
05 08 19.6 -68 44 44 Cl* NGC 1850 SW 10753
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
idata 30 1575 I photometry
vdata 30 1537 V photometry
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Byte-by-byte Description of file: vdata
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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
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
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 at CDS.
(End) [CDS] 29-Jan-1996