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Khalesseh, B.

doi:10.1023/a:1001705122297

Cited by 5 publications

(6 citation statements)

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“…For this reason, we decided to adopt the parameters of Ca ii 8542 for the RVC of the secondary. The resulting parameters are in good agreement with those obtained by Khalesseh (1999). The RVC is shown in Fig.…”

Section: Discussionsupporting

confidence: 84%

“…Given the quality of the radial velocity curves published by Khalesseh (1999), well sampled in orbital phase for both stars, we rely mainly on their derived radial velocity amplitudes to derive the stellar masses adopted in the light‐curve analysis. Adopting the values K 1 ≃ 96 km s −1 , K 2 ≃ 214–223 km s −1 , i ≃ 79.5°, e ≃ 0.0 and P (d) = 1.198 81 d, the well‐known relations allow us to derive for the primary stellar mass: M 1 ≃ 2.86 M ⊙ with a mass ratio q = M 2 / M 1 = K 1 / K 2 ≃ 0.43–0.45…”

Section: Discussionmentioning

confidence: 99%

“…The latest radial velocity curves of AI Dra components have been published by Khalesseh (1999), who reports the following velocity amplitudes: K 1 = 95.9 ± 2.0 km s −1 and K 2 = 213.9–223.5 ± 1.7 km s −1 , and a mass ratio of q = m 1 / m 2 = 2.23–2.33. Richards & Albright (1999) obtained Hα spectra with orbital resolution of AI Dra, as part of a programme to determine the morphologies of the accretion regions in a group of Algol‐type binaries.…”

Section: Introductionmentioning

confidence: 99%

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The fundamental parameters of the Algol binary AI Draconis revisited

Lázaro¹,

Martínez‐País²,

Arévalo³

2004

Monthly Notices of the Royal Astronomical Society

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We present the results of an analysis of our infrared light curves of the Algol-type binary AI Draconis in the J, H and K bands, and of published light curves in the B, V and Strömgren uvby bands, together with spectra obtained by us. The analysis of the light curves was carried out using a code based on ATLAS model atmospheres and Roche geometry.The small contribution of the secondary cool component to the total light of the system in the visible, producing light curves with very shallow secondary eclipses, makes the stellar and orbital parameters derived from light-curve analysis in the visible spectral range uncertain. The larger contribution of the secondary star to the infrared fluxes makes this range particularly well suited to the derivation of precise orbital and stellar parameters in binaries of Algol type. From the simultaneous solution of the infrared JHK light curves, we derive the following absolute orbital and stellar parameters for the two components: T eff,1 = 10 160 ± 160 K, R eq,1 = 2.12 ± 0.04 R , log( g ) 1 = 4.23; T eff,2 = 5586 ± 110 K, R eq,2 = 2.36 ± 0.04 R , log( g ) 2 = 3.76; M 1 = 2.86 ± 0.09 M , q = M 2 /M 1 = 0.44 ± 0.03; a = 7.62 ± 0.09 R , i = 76.53 • ± 0.3 • , e 0.0. Here, T eff and log( g ) indicate average surface values, R eq is the equivalent radius of the deformed star and a is the orbital size.In our light-curve solutions, the secondary star of AI Dra fills its Roche lobe (as also indicated by the spectroscopy), thus discounting claims, based on UBV light curves, that both components of the binary are located within their Roche lobes. The visible and infrared photometry show no evidence of any significant infrared excess in the system, and the distance of AI Dra is estimated as d = 169 ± 17 pc.Based on the spectra of AI Dra and template stars in the ranges 8210-9060, 6250-7130 and 4040-4920 Å, we classify the stellar components of AI Dra and find that the most probable spectral types are A0V (or perhaps A1V) for the primary and F9.5V for the secondary (although it could reach as far as G4V), respectively. From our spectroscopic observations, the spectral evolution of AI Dra with orbital phase is also presented. Furthermore, we obtain the projected rotational velocity of the secondary, whose value turns out to be compatible with the star filling its Roche lobe.

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Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The fundamental parameters of the Algol binary AI Draconis revisited

Lázaro¹,

Martínez‐País²,

Arévalo³

2004

Monthly Notices of the Royal Astronomical Society

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“…The CCT has been proven to be very powerful for detecting the RVs of the secondary components of Algol systems (e.g. Holmgren 1988;Khalesseh & Hill 1992;Hill 1993;Maxted & Hilditch 1995).…”

Section: R a D I A L V E L O C I T I E S A N D O R B I T S O L U T I mentioning

confidence: 99%

A spectroscopic study of the Algol-type binaries S Equulei and KO Aquilae: absolute parameters and mass transfer

Soydugan

Frasca

Soydugan

et al. 2007

Monthly Notices of the Royal Astronomical Society

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We present and analyse high‐resolution optical spectra of two Algol binaries, namely S Equ and KO Aql, obtained with the echelle spectrograph at Catania Astrophysical Observatory. New accurate radial velocities (RVs) for the hotter primary components are obtained. Thanks to the cross‐correlation procedure, we were able to measure, for the first time to our knowledge, RVs also for the cool secondary components of S Equ and KO Aql. By combining the parameters obtained from the solution of the RV curves with those obtained from the light‐curve analysis, reliable absolute parameters of the systems have been derived. The rotational velocity of the hotter components of S Equ and KO Aql has been measured and it is found that the gainers of both systems rotate about 30 per cent faster than synchronously. This is likely due to mass transfer across the Lagrangian L1 point from the cooler to the hotter component. The lower luminosity of the mass‐gaining components of these systems compared to normal main‐sequence stars of the same mass can also be an effect of the mass transfer. The Hα profiles were analysed with the ‘synthesis and subtraction’ technique and reveal clear evidence of mass transfer and accretion structures. In both systems, especially before the primary eclipses and afterwards, we clearly observed extra absorption lines. From the integrated absorption and the RV variations of these features, we found that the mass accretion is very dense around the impact region of the hotter components. A double‐peaked emission in the spectra of S Equ was seen outside the eclipses. One of these peaks is likely originated in a region between the centre of mass and the cooler component, which is occupied by the flowing matter. Furthermore, the Hα difference spectra of S Equ and KO Aql also display emission features, which should be arising from the magnetic activity of the cooler components.

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“…Our light-curve analysis was made separately for each passband with the fixed, spectroscopically estimated mass ratio of the components q = m c /m h = 0.43 (Khalesseh 1999). The adopted value of the temperature of the primary was T h = 9800 K in agreement with its spectral type B9.6 V (Degirmenci et al 2000).…”

Section: Xz Puppismentioning

confidence: 99%

Gravity-darkening exponents in semi-detached binary systems from their photometric observations. II.

Djurašević

Rovithis‐Livaniou²,

Rovithis

et al. 2005

A&A

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This second part of our study concerning gravity-darkening presents the results for 8 semi-detached close binary systems. From the light-curve analysis of these systems the exponent of the gravity-darkening (GDE) for the Roche lobe filling components has been empirically derived. The method used for the light-curve analysis is based on Roche geometry, and enables simultaneous estimation of the systems' parameters and the gravity-darkening exponents. Our analysis is restricted to the black-body approximation which can influence in some degree the parameter estimation. The results of our analysis are: 1) For four of the systems, namely: TX UMa, β Per, AW Cam and TW Cas, there is a very good agreement between empirically estimated and theoretically predicted values for purely convective envelopes. 2) For the AI Dra system, the estimated value of gravity-darkening exponent is greater, and for UX Her, TW And and XZ Pup lesser than corresponding theoretical predictions, but for all mentioned systems the obtained values of the gravity-darkening exponent are quite close to the theoretically expected values. 3) Our analysis has proved generally that with the correction of the previously estimated mass ratios of the components within some of the analysed systems, the theoretical predictions of the gravity-darkening exponents for stars with convective envelopes are highly reliable. The anomalous values of the GDE found in some earlier studies of these systems can be considered as the consequence of the inappropriate method used to estimate the GDE. 4) The empirical estimations of GDE given in Paper I and in the present study indicate that in the light-curve analysis one can apply the recent theoretical predictions of GDE with high confidence for stars with both convective and radiative envelopes.

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Cited by 5 publications

References 0 publications

The fundamental parameters of the Algol binary AI Draconis revisited

The fundamental parameters of the Algol binary AI Draconis revisited

A spectroscopic study of the Algol-type binaries S Equulei and KO Aquilae: absolute parameters and mass transfer

Gravity-darkening exponents in semi-detached binary systems from their photometric observations. II.

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