57 Cyg: A spectroscopic
binary star
57 Cyg characteristics:
RA: 20h53.2
DEC: +44°23'
Magnitude: 4.72
Spectral type: B5V+B5V
Period: 2.8548 days
Half amplitude of the radial velocity curve: 111.9 km/s (primary) and
126.0 km/s (secondary)
Instrumentation:
Flat-field camera 19-cm F/D=4
Audine CCD camera (CCD
KAF-0401E)
R3000 spectrograph
Observatory location: Ramonville Saint Agne (near Toulouse, France)
Journal of observations:
Date
JD
25/07/1999 20H56UT 2451385.370 (phase
0 point)
01/08/1999 20H08UT 2451392.337
20/08/1999 21H30UT 2451411.396
21/08/1999 19H51UT 2451412.327
22/08/1999 20H15UT 2451413.343
23/08/1999 20H19UT 2451414.347
24/08/1999 20H24UT 2451415.350
29/08/1999 20H52UT 2451420.369
31/08/1999 20H06UT 2451422.337
01/09/1999 20H07UT 2451423.338
02/09/1999 20H28UT 2451424.352
11/09/1999 19H54UT 2451433.329
Animation of the 57 Cyg spectrum. One can see
the separation of the H-alpha (6563A) and HeI (6678A) lines according to
the configuration of the orbital couple. The small lines visibles particulary
on the left side of H-alpha correspond to telluric lines (H2O). The variation
of their intensity is caused by the evolution of the content of humity
of the atmosphere.
Graphics of the relative radial speed between
two stars in km/s (the whole of the observations made between July and
September were gathered here). The rotation period adopted is 2.8548 days.
The maximum amplitude radial speed measured is about 450 km/s, whereas
the value raised in the catalogues is of 2*(111.9*126.0)=475.8 km/s. The
agreement is reasonably correct! A simple sinusoidal curve (in red) is
fitted.
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