J/A+A/314/448 UBV photometry of a blue straggler in NGC 2354 (Lapasset+, 1996)
Discovery of an eclipsing blue straggler in NGC 2354
Lapasset E., Ahumada J.
<Astron. Astrophys. 314, 448 (1996)>
=1996A&A...314..448L 1996A&A...314..448L (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, eclipsing ; Stars, blue ; Photometry, UBV
Keywords: stars: binaries: close - stars: binaries: eclipsing -
stars: blue stragglers - stars: evolution -
galaxy: open clusters and associations: individual: NGC 2354
Abstract:
A photometric search for variable stars among the blue stragglers (BS)
in southern open clusters of old and intermediate age led to the
discovery of one eclipsing binary BS in NGC 2354. The star D266 is 1.5
magnitudes brighter than the cluster turn-off while its angular
distance to the cluster center is about seven tenths of the estimated
cluster radius. This star was observed for several nights and a total
of 422 UBV measurements were obtained. The coverage of the orbital
cycle was almost completed, a period of 0.6388228 days was determined,
and finally the first light curves of this eclipsing variable star
were obtained. They show the typical characteristics of an EB-class
close binary with minima about 0.4 and 0.1 magnitudes deep. The
photometric analysis by means of the Wilson-Devinney code allowed to
define a set of ten possible solutions for assumed values of the
mass-ratio between 0.2 and 5.0. Two minima of the quality-of-fit
function for q=0.30 and q=3.0 indicate the best solutions we could
obtain. Regardless of the value of q, the following features could be
established: a) both components are very close to the critical contact
lobes and both detached or semidetached configurations fit the light
curves in an acceptable way; b) the temperature difference between the
components is one of the highest among this type of stars; c) the
primary component always remains in the BS zone of the cluster
colour-magnitude diagram. If we assume that D266 is a member of NGC
2354, we may conclude that mass-exchange between the components of
this system is the most probable cause of its present BS state.
Objects:
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RA (2000) DE Name
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07 14 07 -25 44.4 NGC 2354
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2 36 422 UBV data of D266
table3 30 71 Normal points of D266
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Byte-by-byte Description of file: table2
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Bytes Format Units Label Explanations
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1- 12 F12.4 d HJD Julian Day heliocentric
16- 20 F5.3 mag Vmag Differential V-magnitude (D266-minus-comparison)
24- 28 F5.3 mag Bmag Differential B-magnitude (D266-minus-comparison)
32- 36 F5.3 mag Umag Differential U-magnitude (D266-minus-comparison)
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Byte-by-byte Description of file: table3
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Bytes Format Units Label Explanations
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1- 6 F6.4 --- Phase [0/1[ Phases
10- 14 F5.3 mag Vmag Differential V-magnitude (D266-minus-comparison)
18- 22 F5.3 mag Bmag Differential B-magnitude (D266-minus-comparison)
26- 30 F5.3 mag Umag Differential U-magnitude (D266-minus-comparison)
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(End) Patricia Bauer [CDS] 15-Apr-1996