J/A+A/686/A199 MACHO 80.7443.1718 UBV light curves (Kolaczek-Szymanski+, 2024)
Exploring extreme brightness variations in blue supergiant MACHO 80.7443.1718:
Evidence for companion-driven enhanced mass loss.
Kolaczek-Szymanski P.A., Lojko P., Pigulski A., Rozanski T., Mozdzierski D.
<Astron. Astrophys. 686, A199 (2024)>
=2024A&A...686A.199K 2024A&A...686A.199K (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Stars, supergiant ; Photometry, UBV
Keywords: binaries: close - stars: early-type - stars: emission-line, Be -
stars: massive - stars: mass-loss -
stars: individual: MACHO80.7443.1718
Abstract:
Evolution of massive stars is dominated by interactions within binary
and multiple systems. In order to accurately model this evolution, it
is necessary to investigate all possible forms of interaction in
binary systems that may affect the evolution of the components. One of
'laboratories' plausible for this kind of investigation is the
massive eccentric binary system MACHO 80.7443.1718 (ExtEV), which
exhibits an exceptionally large amplitude of light variability close
to the periastron passage of its 32.8-day orbit.
We examine whether the light variability of the ExtEV can be explained
by a wind-wind collision (WWC) binary system model. We also critically
review other models proposed to explain the light curve of ExtEV.
We conducted an analysis of (i) broadband multi-color photometry of
ExtEV spanning a wide range of wavelengths from ultraviolet to
near-infrared, (ii) time-series space photometry from Transiting
Exoplanet Survey Satellite (TESS), (iii) ground-based Johnson UBV
photometry, and (iv) time-series high-resolution spectroscopy. To
derive the parameters of the primary component of the system, we
fitted spectral energy distribution (SED) and calculated evolutionary
models of massive stars that included mass loss. Using radial-velocity
data, we determined the spectroscopic parameters of the system. We
also fitted an analytical model of light variations to the TESS light
curve of ExtEV.
The ExtEV system exhibits an infrared excess, indicating an increased
mass- loss rate. The system does not match the characteristics of B[e]
stars, however. We rule out the possibility of the presence of a
Keplerian disk around the primary component. We also argue that the
scenario with periodic Roche-lobe overflow at periastron may not be
consistent with the observations of ExtEV. Analysis of SED suggests
that the primary component has a radius of about 30R☉ and a
luminosity of ∼6.6x105L☉. With the analysis of the radial-
velocity data, we refine the orbital parameters of ExtEV and find
evidence for the presence of a tertiary component in the system. Using
evolutionary models we demonstrate that the primary component's mass
is between 25 and 45M☉. We successfully reproduce the light
curve of ExtEV with our analytical model, showing that the dominant
processes shaping its light curve can be attributed to atmospheric
eclipse and light scattered in the WWC cone. We also estimate the
primary's mass-loss rate due to stellar wind for
4.5x10-5M☉/yr.
ExtEV is most likely not an extreme eccentric ellipsoidal variable,
but rather an exceptional WWC binary system. The mass loss rate we
derived exceeds theoretical predictions by up to two orders of
magnitude. This implies that the wind in the system is likely enhanced
by tidal interactions, rotation, and possibly also tidally excited
oscillations. Therefore, ExtEV represents a rare evolutionary phase of
a binary system that may help to understand the role of a
companion-driven enhanced mass loss in the evolution of massive binary
systems.
Description:
Here, we provide the time-series differential photometry of MACHO
80.7443.1718 in Johnson UBV passbands that we extracted based on the
data collected at the Las Cumbres Observatory Global Telescope (LCOGT)
network. More details regarding the extraction of the light curves can
be found in Sect. 2.1 of our paper.
Based on observations made with the LCOGT network of 1-meter
telescopes with SINISTRO detectors, under the OPTICON RadioNet Pilot
program 22A006 (PI: Piotr Kolaczek-Szymanski).
Objects:
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RA (2000) DE Designation(s)
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05 26 24.46 -68 47 04.94 MACHO 80.7443.1718 = TIC 373840312
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
lcogt.dat 80 136 LCOGT UBV light curves of ExtEV (MACHO 80.7443.1718)
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Byte-by-byte Description of file: lcogt.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d BJD-U Middle-exposure BJD times for U passband
15- 20 F6.3 mag dUmag Differential magnitude in Johnson U passband
22- 26 F5.3 mag e_dUmag Photometric error in Johnson U passband
28- 40 F13.5 d BJD-B Middle-exposure BJD times for B passband
42- 47 F6.3 mag dBmag Differential magnitude in Johnson B passband
49- 53 F5.3 mag e_dBmag Photometric error in Johnson B passband
55- 67 F13.5 d BJD-V Middle-exposure BJD times for V passband
69- 74 F6.3 mag dVmag Differential magnitude in Johnson V passband
76- 80 F5.3 mag e_dVmag Photometric error in Johnson V passband
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Acknowledgements:
Piotr Kolaczek-Szymanski, piotr.kolaczek-szymanski(at)uwr.edu.pl
(End) Piotr Kolaczek-Szymanski [UWr, Poland], Patricia Vannier [CDS] 15-Mar-2024