J/AJ/113/2104 UBV photometry of 163 stars around SU Cyg (Turner+ 1997)
Galactic clusters with associated Cepheid variables. V. The case of SU Cygni
Turner D.G., Mandushev G.I., Welch G.A.
<Astron. J. 113, 2104 (1997)>
=1997AJ....113.2104T 1997AJ....113.2104T (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Photometry, UBV ; Radial velocities
Abstract:
Photoelectric, CCD, and photographic photometry is presented for a
sample of 163 stars in the field of the short-period Cepheid SU Cyg
for the purpose of searching for a putative cluster that might be
associated with the Cepheid. Although the variable is situated in a
clump of stars that has the appearance of a sparse cluster, the
photometric evidence indicates that they are not a physical group.
About two dozen B and A-type stars randomly distributed in the field
lie at a common distance of 1086±60pc (V0-MV= 10.18±0.12 for
R=2.94±0.38), but they are likely to represent at best a segment of
the Vul OB4 association, which overlaps the region. SU Cyg is unlikely
to be a member of that group. The close optical companion to SU Cyg,
an A2 V star with a radial velocity (=-23.6±7.1km/s) close to
the systemic velocity of the Cepheid, is a spectroscopic binary that
might be physically related to the variable. Its primary importance is
for helping to establish a space reddening of E(B-V)=0.15±0.01 for
SU Cyg. Despite the lack of related cluster stars to SU Cyg, its two
unresolved companions can be used to place restrictions on the likely
luminosity of the Cepheid. The resulting value of <MV>≤-3.02±0.23
relative to its companions agrees closely with a value of
(PLC)=-3.03±0.07 obtained from the Cepheid PLC relation.
Objects:
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RA (2000) DE Designation(s)
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19 44 48.6 +29 15 53 SU Cyg = HD 186688 = HR 7518
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1 40 14 Photoelectric UBV data for stars in the field
of SU Cyg
table2 18 52 CCD BV photometry for faint stars near SU Cyg.
table3 27 101 Photographic UBV photometry for stars near SU Cyg
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Byte-by-byte Description of file: table1
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Bytes Format Units Label Explanations
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1- 4 A4 --- Star Star name
6- 11 I6 --- HDE ? HDE number
13- 17 F5.2 mag Vmag V magnitude
20- 23 F4.2 mag B-V B-V colour index
25- 29 F5.2 mag U-B colour index
31 I1 --- n_Vmag ? Number of nights of observations
for stars 1 to 10
32 I1 --- NUBV ? Number of published UBV observations
for FM stars
34 I1 --- Ntsc ? Number of transformed system colors
for FM stars
37- 40 A4 --- SpType Available spectral type (MK/HDE)
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Byte-by-byte Description of file: table2 table3
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Bytes Format Units Label Explanations
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1- 3 I3 --- Star Star number
4 A1 --- n_Star [cd] Note on star (1)
6- 10 F5.2 mag Vmag ? V magnitude
11 A1 --- u_Vmag Uncertainty flag on Vmag
12 A1 --- n_Vmag [ab] Note on Vmag (2)
14- 17 F4.2 mag B-V ? B-V colour index
18 A1 --- u_B-V Uncertainty flag on B-V
19 A1 --- n_B-V [ab] Note on B-V (2)
21- 25 F5.2 mag U-B ? U-B colour index
26 A1 --- u_U-B Uncertainty flag on U-B
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Note (1): c: HDE 332544, Spectral type G5.
d: HDE 332543, Spectral type A0.
Note (2): a: Has close companion. Corrected values: V=12.13, B-V=1.15.
b: V and B-V from CCD photometry.
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Table 4: Radial velocity data for star 1.
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JD Radial velocity (km/s)
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2445906.909 -5.2 ± 4.5
2445908.762 -19.3 ± 4.1
2445909.781 -43.0 ± 3.8
2445910.882 -47.1 ± 2.9
2445911.777 +12.5 ± 5.1
2446327.770 -43.5 ± 5.0
2446328.689 -9.5 ± 3.8
2446330.740 -14.3 ± 5.3
2446331.689 -42.8 ± 3.3
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History: Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer [CDS] 10-Oct-1997