J/AJ/103/460 CCD photometry of M 71 (Hodder+, 1992)
Deep CCD photometry and variable stars in the metal-rich globular cluster M 71
HODDER P.J.C., NEMEC J.M., RICHER H.B., FAHLMAN G.G.
<Astron. J. 103, 460 (1992)>
=1992AJ....103..460H 1992AJ....103..460H (SIMBAD/NED Reference)
ADC_Keywords: Clusters, globular; Photometry, CCD; Stars, variable
Abstract:
Two sets of observations of the metal-rich globular cluster M 71 are
presented. The first uses deep CCD exposures to derive a fiducial
in V, B-V and compares this with a cluster of similar metallicity,
47 Tuc. Comparison with oxygen enhanced theoretical isochrones leads
to age estimates for M 71 of from ∼14±2Gyr to ∼16±2Gyr. Within
the limits imposed by the quality of the data, no significant age
difference between the two clusters is found. The second set of
73 frames is used to search an overlapping 67"x104" area of the cluster
for variable stars. Light curves and phase diagrams (where appropriate)
are presented for all four of the variables discovered. One variable
blue straggler (or SX Phe star) has been identified with a period of
0.050d. Values for its mass depend, of course, on the assumed pulsation
mode-(0.90±0.47)M☉ for the first overtone mode, and
(1.57±0.83)M☉ for the fundamental mode. One of the variables,
with a 0.0582d period, but with a magnitude 1.75mag below the main
sequence turnoff may be a field star. Two candidate eclipsing binary
systems were also found. The most likely orbital period of one is 0.372d.
This value, and the shape of the light curve, suggest that it could be
a W UMa type variable. No period was obtainable for the other candidate
binary due to a lack of phase coverage. Further data is needed to confirm
and strengthen these claims, and to check for cluster membership.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2 47 1861 Photometry of M71
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- ID Identification number
5 A1 --- Cud [*] A '*' indicates Cudworth stars that have a
cluster membership probability of 50% or more
7- 8 A2 --- n_ID Note on the stars (1)
12- 16 F5.1 pix X X position
18- 23 F6.1 pix Y Y position
27- 31 F5.2 mag Vmag V magnitude
36- 40 F5.2 mag B-V B-V colour
43- 47 F5.2 mag U-B U-B colour
--------------------------------------------------------------------------------
Note (1): Name of the variables discussed in section 4.
--------------------------------------------------------------------------------
References: Cudworth K.M., 1985, AJ, 90, 65
--------------------------------------------------------------------------------
Historical note: Keypunched at CDS
(End) Marie-Jose Wagner, Patricia Bauer [CDS] 05-Dec-1994