GG Carinae: orbital parameters and accretion indicators from phase-resolved spectroscopy and photometry

Abstract

B[\,e\,] supergiants are a rare and unusual class of massive and luminous stars, characterised by opaque circumstellar envelopes. GG Carinae is a binary whose primary component is a B[\,e\,] supergiant and whose variability has remained unsatisfactorily explained. Using photometric data from ASAS, OMC, and ASAS-SN, and spectroscopic data from the Global Jet Watch and FEROS to study visible emission lines, we focus on the variability of the system at its $\sim$31-day orbital period and constrain the stellar parameters of the primary. There is one photometric minimum per orbital period and, in the emission line spectroscopy, we find a correlation between the amplitude of radial velocity variations and the initial energy of the line species. The spectral behaviour is consistent with the emission lines forming in the primary's wind, with the variable amplitudes between line species being caused by the less energetic lines forming at larger radii on average. By modelling the atmosphere of the primary, we are able to model the radial velocity variations of the wind lines in order to constrain the orbit of the binary. We find that the binary is even more eccentric than previously believed ($e=0.5\pm 0.03$). Using this orbital solution, the system is brightest at periastron and dimmest at apastron, and the shape of the photometric variations at the orbital period can be well described by the variable accretion by the secondary of the primary's wind. We suggest that the evolutionary history of GG Carinae may need to be reevaluated in a binary context.

23 pages, 26 figures. Accepted for publication in MNRAS

References in corpus (15)

• The Gaia mission
• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• On the formation of Be stars through binary interaction
• Python Leap Second Management and Implementation of Precise Barycentric Correction (barycorrpy)
• Interacting Binaries with Eccentric Orbits. Secular Orbital Evolution Due To Conservative Mass Transfer
• Orbital eccentricities of binary systems with a former AGB star
• Interacting Binaries with Eccentric Orbits II. Secular Orbital Evolution Due To Non-Conservative Mass Transfer
• Investigating the lack of main-sequence companions to massive Be stars
• The pre- versus post-main sequence evolutionary phase of B[e] stars: Constraints from 13CO band emission
• On the formation of eccentric millisecond pulsars with helium white-dwarf companions
• Fluctuations and symmetry in the speed and direction of the jets of SS433 on different timescales
• Constraining Dust Extinction Properties via the VVV Survey
• Molecular emission from GG Car's circumbinary disk
• Inhomogeneous molecular ring around the B[e] supergiant LHA 120-S 73
• Resolved imaging of the AR Puppis circumbinary disk

Cited by in corpus (3)

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• The circumbinary rings of GG Carinae: indications of disc eccentricity growth in the B[e] supergiant's atomic emission lines