J/AJ/124/1486 M4 UBV color-magnitude diagrams (Mochejska+, 2002)
Clusters ages experiment: hot subdwarfs and luminous white dwarf candidates
in the field of the globular cluster M4.
Mochejska B.J., Kaluzny J., Thompson I., Pych W.
<Astron. J. 124, 1486 (2002)>
=2002AJ....124.1486M 2002AJ....124.1486M
ADC_Keywords: Clusters, globular ; Photometry, UBV ; Stars, white dwarf
Keywords: globular clusters: individual (M4) - Hertzsprung-Russell diagram -
subdwarfs - white dwarfs
Abstract:
We present UBV color-magnitude diagrams (CMDs) for the globular
cluster M4. The CMDs show a sequence of four luminous blue stars
(V<20, U-V←0.6), which appear to be cluster hot subdwarfs. We present
spectra for the three brightest ones. We also note the presence of a
population of faint blue objects, likely to be hot, young white dwarfs
belonging to the cluster. We have selected five objects above V=22mag,
bright enough for follow-up ground-based spectroscopy, and present
their coordinates and finding charts. We show a spectrum for variable
V46, which suggests that it is a hot subdwarf, along with a new light
curve obtained with the ISIS image subtraction package. The light
curve is unstable, but only one period of variability is apparent. Two
new variables have been discovered, both located on the cluster red
giant branch. We also present a differential E(B-V) reddening map and
a fiducial sequence for the main sequence, subgiant branch, and red
giant branch on the V/B-V CMD for a selected region with uniform
reddening. Based on a comparison with the M5 fiducial sequence, we
obtain a reddening estimate of E(B-V)=0.41mag toward M4, consistent
with previous determinations.
Description:
The photometric data were obtained with the 2.5m du Pont telescope at
Las Campanas Observatory. An 8.8x8.8 field centered on the cluster was
monitored during five consecutive nights, from 1995 June 1 to 5.
Observations were made through Johnson UBV filters.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
m4wd.dat 87 37 UBV photometry and astrometry of the white dwarfs
m4ubv.dat 114 12121 Astrometry and UBV photometry for 12121 stars in M4
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See also:
J/PAZh/22/847 : Identification and coordinates in M4 (Shokin+, 1996)
J/AJ/114/189 : M 4 CCD photometry (Alcaino+, 1997)
J/ApJS/120/265 : HST photometry of M4 (Ibata+, 1999)
J/AJ/127/2771 : HST proper-motions of M4 main-sequence stars (Richer+, 2004)
Byte-by-byte Description of file: m4wd.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- --- [WD]
3- 4 I2 --- MKTWD Sequential WD number,
Cl* NGC 6121 MKTWD NN in Simbad
6- 15 F10.6 deg RAdeg Right ascension (J2000)
18- 27 F10.6 deg DEdeg Declination (J2000)
29- 34 F6.3 mag Vmag Johnson V magnitude
37- 41 F5.3 mag e_Vmag rms uncertainty on Vmag
43- 48 F6.3 mag B-V ?=-9.999 Johnson B-V colour index
50- 55 F6.3 mag e_B-V ?=-9.999 rms uncertainty on B-V
57- 62 F6.3 mag U-B ?=-9.999 Johnson U-B colour index
64- 69 F6.3 mag e_U-B ?=-9.999 rms uncertainty on U-B
71- 76 F6.3 mag U-V ?=-9.999 Johnson U-V colour index
78- 83 F6.3 mag e_U-V ?=-9.999 rms uncertainty on U-V
87 A1 --- Class [A-C] Class of the object (1)
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Note (1): Class as follows:
A = very good candidates
B = good candidates
C = poorer candidates
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Byte-by-byte Description of file: m4ubv.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- MKT Sequential number,
Cl* NGC 6121 MKT NNNNN in Simbad
7- 13 F7.2 pix Xpos X position
15- 21 F7.2 pix Ypos Y position
23- 32 F10.6 deg RAdeg Right ascension (J2000)
34- 43 F10.6 deg DEdeg Declination (J2000)
45- 50 F6.3 mag Vmag Johnson V magnitude
53- 57 F5.3 mag e_Vmag rms uncertainty on Vmag
59- 64 F6.3 mag B-V ?=-9.999 Johnson B-V colour index
66- 71 F6.3 mag e_B-V ?=-9.999 rms uncertainty on B-V
73- 78 F6.3 mag U-B ?=-9.999 Johnson U-B colour index
80- 85 F6.3 mag e_U-B ?=-9.999 rms uncertainty on U-B
87- 92 F6.3 mag U-V ?=-9.999 Johnson U-V colour index
94- 99 F6.3 mag e_U-V ?=-9.999 rms uncertainty on U-V
101-114 A14 --- Note Hot subdwarf candidate (BN) or Variable (VNN)
identification
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History:
From electronic version of the journal
(End) James Marcout, Patricia Bauer [CDS] 08-Nov-2002