Carbon deficiencies in the primaries of some classical Algols★

İbanoǧlu, C.; Dervişoğlu, Ahmet; Çakırlı, Ö.; Sipahi, E.; Yüce, Kutluay

doi:10.1111/j.1365-2966.2011.19812.x

Cited by 12 publications

(8 citation statements)

References 26 publications

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“…Since the transferred material from the evolved donor star is C poor, when this is mixed with the original matter of the gainer the C amount appears to decrease (de Greve & Sarna 1997). Thus, Ibanoglu et al (2012) found a correlation between the EWs of the C II 4267 Å line and the mass transfer rate. As the mass transfer rate increases, the EW of C II 4267 Å decreases.…”

Section: Accretion Discmentioning

confidence: 94%

“…Using the correlation EW s/Ṁ for the Algols studied by Ibanoglu et al (2012) we measured a mean value of the EW/λ of −4.7 ± 0.3 and thus we estimate a mass transfer rate aroundṀ = −5 × 10 −8 M /yr. This mass transfer rate is lower than the value predicted from the evolutionary analysis of DQ Vel with the gainer star in synchronous rotation (see Sect.…”

Section: Ibanoglumentioning

confidence: 99%

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Exploring the long-term variability and evolutionary stage of the interacting binary DQ Velorum

Barría

Mennickent

Graczyk

et al. 2014

A&A

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Aims. In order to better understand the double periodic variable (DPV) phenomenon, we analyse a series of optical spectra of the DPV system DQ Velorum during much of its long-term cycle. In addition, we investigate the evolutionary history of DQ Vel using theoretical evolutionary models to obtain the best representation for the current observed stellar and orbital parameters of the binary. We investigate the evolution of DQ Vel through theoretical evolutionary models to estimate the age and the mass transfer rate which are then compared with those of its twin V393 Scorpii. Methods. We subtracted the donor star contribution from the composite spectra of DQ Vel using a synthetic spectrum as a donor template. Donor-subtracted spectra covering around 60% of the long-term cycle allowed us to investigate time-modulated spectral variations of the gainer star plus the disc. We used Gaussian fits to measure the equivalent widths (EWs) of Balmer and helium lines in the separated spectra during the long-term cycle and thus analyse EW variabilities. We compared the observed stellar parameters of the system with a grid of theoretical evolutionary tracks computed under a conservative and a non-conservative evolution regime. Results. We have found that the EW of Balmer and helium lines in the donor-subtracted spectra are modulated with the long-term cycle. We observe a strengthening in the EWs in all analysed spectral features at the minimum of the long-term cycle which might be related to an extra line emission during the maximum of the long-term variability. Difference spectra obtained at the secondary eclipse support this scenario. We have found that a non-conservative evolutionary model where DQ Vel has lost mass at some stage of its binary history, is a better representation of the current observed properties of the system. The best evolutionary model suggests that DQ Vel has an age of 7.40 × 10 7 yr and is currently in a low mass transfer rate (−9.8 × 10 −9 M /yr) stage, after a mass transfer burst episode. Comparing the evolutionary stages of DQ Vel and V393 Sco we observed that the former is an older system with a lower mass transfer rate. This might explain the differences observed in the physical parameters of their accretion discs.

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Section: Accretion Discmentioning

confidence: 94%

Section: Ibanoglumentioning

confidence: 99%

Exploring the long-term variability and evolutionary stage of the interacting binary DQ Velorum

Barría

Mennickent

Graczyk

et al. 2014

A&A

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“…In a period analysis of ten semi-detached Algol-type binaries, Ibanoǧlu et al (2012) found u Her to be the system with the small- est period changes. We used their ephemeris 3 during our analysis; Tprim.min.…”

Section: Light Curve Modellingmentioning

confidence: 99%

Tracing CNO exposed layers in the Algol-type binary system u Her

Kolbas

Dervişoğlu

Pavlovski

et al. 2014

Monthly Notices of the Royal Astronomical Society

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The chemical composition of stellar photospheres in mass-transferring binary systems is a precious diagnostic of the nucleosynthesis processes that occur deep within stars, and preserves information on the components' history. The binary system u Her belongs to a group of hot Algols with both components being B-stars. We have isolated the individual spectra of the two components by the technique of spectral disentangling of a new series of 43 high-resolutioń echelle spectra. Augmenting these with an analysis of the Hipparcos photometry of the system yields revised stellar quantities for the components of u Her. For the primary component (the mass-gaining star) we find M A = 7.88 ± 0.26 M ⊙ , R A = 4.93 ± 0.15 R ⊙ and T eff,A = 21 600 ± 220 K. For the secondary (the mass-losing star) we find M B = 2.79 ± 0.12 M ⊙ , R B = 4.26 ± 0.06 R ⊙ and T eff,B = 12 600 ± 550 K. A non-LTE analysis of the primary star's atmosphere reveals deviations in the abundances of nitrogen and carbon from the standard cosmic abundance pattern in accord with theoretical expectations for CNO nucleosynthesis processing. From a grid of calculated evolutionary models the best match to the observed properties of the stars in u Her enabled tracing the initial properties and history of this binary system. We confirm that it has evolved according to case A mass transfer. A detailed abundance analysis of the primary star gives C/N = 0.9, which supports the evolutionary calculations and indicates strong mixing in the early evolution of the secondary component, which was originally the more massive of the two. The composition of the secondary component would be a further important constraint on the initial properties of u Her system, but requires spectra of a higher signal to noise ratio.

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“…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.…”

Section: Discussionmentioning

confidence: 99%

Spectroscopic long-term monitoring of RZ Cas

Lehmann

Dervişoğlu

Mkrtichian

et al. 2020

A&A

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Context. RZ Cas is a short-period Algol-type system showing episodes of mass transfer and δ Sct-like oscillations of its massgaining primary component. This system exhibits temporal changes in orbital period, v sin i, and the oscillation pattern of the primary component. Aims. We analyse high-resolution spectra of RZ Cas that we obtained during a spectroscopic long-term monitoring lasting from 2001 to 2017. In this first part we investigate the atmospheric parameters of the stellar components and the time variation of orbital period, v sin i, and radial velocities (RVs), searching for seasonal changes that could be related to episodes of mass exchange and to a possible activity cycle of the system triggered by the magnetic cycle of the cool companion. Methods. We used spectrum synthesis to analyse the spectra of both components of RZ Cas. The study of variations of the orbital period is based on published times of primary minima. We used the LSDbinary program to derive separated RVs and least-squares deconvolved (LSD) profiles of the components. From the LSD profiles of the primary we determined its v sin i. Using Markov Chain Monte Carlo simulations with the PHOEBE program, we modelled the RV variations of both components. Results. Spectrum analysis resulted in precise atmospheric parameters of both components, in particular in surface abundances below solar values. We find that the variation of orbital period is semi-regular and derive different characteristic timescales for different epochs of observation. We show that the RV variations with orbital phase can be modelled when including two cool spots on the surface of the secondary component. The modelling leads to very precise masses and separation of the components. The seasonal variation of several parameters, such as v sin i, rotation-orbit synchronisation factor, strength of the spots on the cool companion, and orbital period, can be characterised by a common timescale of the order of nine years. Conclusions. We interpret the timescale of nine years as the magnetic activity cycle of the cool companion. In particular the behaviour of the dark spots on the cool companion leads us to the interpretation that this timescale is based on an 18-year magnetic dynamo cycle. We conclude that the mass-transfer rate is controlled by the variable depth of the Wilson depression in the magnetic spot around the Lagrangian point L1. In the result, based on available data, we observe a damped activity cycle of the star, starting with a high mass-transfer episode around 2001 with a calculated mass-transfer rate of 1.5 × 10 −6 M yr −1 , followed by quiet periods in 2006 and 2009, slightly higher activity around 2013 and 2014, and again followed by quiet periods in 2015 and 2016. However, owing to missing data for years 2010 and 2011, we cannot exclude that a second high mass-transfer episode occurred within this time span.

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Carbon deficiencies in the primaries of some classical Algols★

Cited by 12 publications

References 26 publications

Exploring the long-term variability and evolutionary stage of the interacting binary DQ Velorum

Exploring the long-term variability and evolutionary stage of the interacting binary DQ Velorum

Tracing CNO exposed layers in the Algol-type binary system u Her

Spectroscopic long-term monitoring of RZ Cas

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