Evidence for conservative mass transfer in the classical Algol system δ Librae from its surface carbon-to-nitrogen abundance ratio

Abstract

Algol-type binary systems are the product of rapid mass transfer between the initially more massive component to its companion. It is still unknown whether the process is conservative, or whether substantial mass is lost from the system. The history of a system prior to mass exchange is imprinted in the photospheric chemical composition, in particular in the carbon-to-nitrogen (C/N) ratio. We use this to trace the efficiency of mass-transfer processes in the components of a classical Algol-type system, δ Librae. The present analysis is based on new spectroscopic data (groundbased high-resolutionéchelle spectra) and extracted archival photometric observations (space-based measurements from the STEREO satellites). In the orbital solution, non-Keplerian effects on the radial-velocity variations were taken into account. This reduces the primary's mass by 1.1 M ⊙ (∼23%) significantly in comparison to previous studies, and removes a long-standing discrepancy between the radius and effective temperature. A spectral disentangling technique is applied to theéchelle observations and the spectra of the individual components are separated. Atmospheric and abundance analyses are performed for the mass-gaining component and we found C/N = 1.55 ± 0.40 for this star. An extensive set of evolutionary models (3.5 × 10 6 ) for both components are calculated from which the best-fitting model is derived. It is found that β, the parameter which quantifies the efficiency of mass-loss from a binary system, is close to zero. This means that the mass-transfer in δ Lib is mostly conservative with little mass loss from the system.

Spectroscopic long-term monitoring of RZ Cas

“…In that case, the surface carbon abundance of the gainer cannot be lower than that of the donor star, however. Multiple authors have used the sketched scenario to explain the surface abundance anomalies observed in several other Algol-type stars; these include Ibanoǧlu et al (2012) for GT Cep, AU Mon, and TU Mon, Kolbas et al (2014) for u Her, and Dervişoglu et al (2018) for δ Lib.…”

“…Tkachenko et al (2008Tkachenko et al ( , 2009 confirmed the finding of the two spots, resuming the interpretation. Dervişoglu et al (2018) and Berdyugin et al (2018), on the other hand, give an alternative explanation, showing for the short-period Algols δ Lib and λ Tau that the mass stream can produce a light scattering cloud in front of the surface of the Roche lobe filling secondary facing the primary.…”

Space-Based Photometry of Binary Stars: From Voyager to TESS

“…In semi-detached and contact binaries one or both components fills their Roche lobe and mass can be transferred between them or lost from the system. These objects are laboratories for tidal effects, case A mass transfer (during the main sequence), case B mass transfer (during evolution to the giant phase), mass loss, and orbital angular momentum loss (e.g., [27]). When mass is stripped from the originally more massive star it reveals the deep interior and gives a window onto thermonuclear fusion in stars [28][29][30].…”

“…Evolved binaries. Mass transfer in semi-detached and contact binaries remains poorly understood [27,352] and can lead to stellar mergers [353]. The common-envelope phase of binary evolution is also difficult [354,355], and once a binary has got past these obstacles it exhibits many complex phenomena [356].…”

Dynamical parallax, physical parameters and evolutionary status of the components of the bright eclipsing binary α Draconis

“…To explore the parameter space, as well as to obtain error estimates, many researchers utilize Markov-Chain Monte-Carlo (MCMC; Goodman & Weare 2010) based optimisers (e.g. Lehmann et al 2020, Dervişoǧlu et al 2018. For the purpose of optimising the aforementioned nine free parameters, we developed a Python framework (LC MCMC ) which uses PyWD2015 To obtain a good fit, we sampled parameter priors with a normal distribution around 10 % sigma.…”