J/A+A/627/A2 New V-band photometry of Cyg OB2 5 (V729 Cyg) (Rauw+, 2019)
Quest for the tertiary component in Cyg OB2 #5.
Rauw G., Naze Y., Campos F.
<Astron. Astrophys. 627, A2 (2019)>
=2019A&A...627A...2R 2019A&A...627A...2R (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Photometry
Keywords: stars: early-type - stars: winds, outflows - X-rays: stars -
binaries: spectroscopic - binaries: eclipsing -
stars: individual: Cyg OB2 #5
Abstract:
The Cyg OB2 #5 system is thought to consist of a short-period (6.6d)
eclipsing massive binary associated with an OB-star orbiting it with a
period of ∼6.7yr, themselves orbited by a distant early B-star (with
thousands of years period). However, while the inner binary has been
studied many times, information is missing on the other stars, in
particular the third one whose presence was indirectly postulated from
recurrent modulations in the radio domain. Besides, to this date, the
X-ray lightcurve could not be fully interpreted, e.g. in the framework
of colliding-wind emission linked to one of the systems.
We obtained new optical and X-ray observations of Cyg OB2 #5, which we
combined to archival data. We performed a thorough and homogeneous
investigation of all available data, notably revisiting the times of
primary minimum in photometry.
In the X-ray domain, XMM-Newton provides scattered exposures over
∼5000d whilst Swift provides a nearly continuous monitoring for the
last couple of years. Though the X-ray lightcurve reveals clear
variability, no significant period can be found hence the high-energy
emission cannot be explained solely in terms of colliding winds
varying along either the short or intermediate orbits. The optical
data reveal for the first time clear signs of reflex motion: the
photometry indicates the presence of a 2366d (i.e. 6.5yr) period
while the associated radial velocity changes are detected at the
3σ level in the systemic velocity of the HeII 4686 emission
line. With the revised period, the radio lightcurve is interpreted
consistently in terms of a wind interaction between the inner binary
and the tertiary star. From the optical and radio data, we derive
constraints on the physical properties of the tertiary star and its
orbit.
Description:
Table 1 contains the new photometric time series of Cyg OB2 #5
collected through a V-band filter. The first column lists the
heliocentric Julian date of the observation. The second column lists
the V-band magnitude of Cyg OB2 #5 calibrated against star SAO 49783.
The third column provides an estimate of the photometric error.
Objects:
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RA (2000) DE Designation(s)
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20 32 22.42 +41 18 19.0 Cyg OB2 #5 = Schulte 5
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 29 773 Time series of V-band photometry of Cyg OB2 #5
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See also:
J/other/NewA/31.32 : V729 Cyg UBVRI light curves (Yasarsoy+, 2014)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d HJD Heliocentric Julian Date
17- 21 F5.3 mag Vmag V-band magnitude
25- 29 F5.3 mag e_Vmag Photometric error on V magnitude
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Acknowledgements:
Gregor Rauw, g.rauw(at)uliege.be
(End) Patricia Vannier [CDS] 19-May-2019