A Spectroscopic Study of Algol

Hill, Graham; Barnes, J. V.; Hutchings, J. B.; Pearce, J. A.

doi:10.1086/151100

Cited by 35 publications

(41 citation statements)

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“…The simultaneous light-curves analysis of β Per was made with the photometrically estimated mass ratio of q = m c /m h = 0.227 (Kim 1989). This value is in good agreement with the mass ratio q = m c /m h = 0.217 ± 0.005 which is obtained from spectroscopic work done by Hill et al (1971) and Tomkin & Lambert (1978). The temperature of the primary star was taken to be T h = 12 000 K (Kim 1989).…”

Section: Results Of the Light-curve Analysissupporting

confidence: 84%

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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Section: Results Of the Light-curve Analysissupporting

confidence: 84%

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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“…The agreement of the Algol V sin i determinations with respect to the three standard stars ¡a Lep, 53 Tau, and m Cet, which have V sin i equal to 20, 10, and 15 km s -1 , respectively (Uesugi and Fukuda 1982), shows that this result is independent of the choice of standard star, so long as the V sin i value of the standard is much smaller than that of the program star. We also note that the V sin i value from comparison with ¡i Lep and 53 Tau, in which the He i line is weaker than in Algol, and the V sin i value from comparison with 7T Cet, in which the He i line is stronger than in Algol, are in good agreement, which indicates that the He i lines in the program, and standard, stars do Hill et al (1971), andRucinski (1979) suggested that the rotation of Algol is synchronous and estimated the synchronous V as 50, 55, and 53 km s -1 , respectively. We adopt a synchronous V of 52 ± 3 km s -1 , which is based on the separation between the primary and secondary, a sini = (9.66 ± 0.29) X 10 6 km, determined by Tomkin and Lambert (1978); the inclination i = 82 ?4 (Wilson et al 1972); and a primary fractional radius of 0.211, which is the mean of the determinations of 0.…”

Section: Analysis and Resultssupporting

confidence: 54%

The rotation of the primary of Algol

Tomkin¹,

Tan²

1985

PASP

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“…We have computed theoretical X-ray light curves for Algol using a spherically symmetric, optically thin emitting shell coronal model. The model assumes that Algol A is 100% X-ray-dark and uses the following physical and orbital parameters: M B ¼ 0:81 M , M A ¼ 3:7 M , R B ¼ 3:5 R , R A ¼ 2:9 R , P ¼ 2:867 days, and i ¼ 81 :4 (Hill et al 1971;Tomkin & Lambert 1978;Richards et al 1988). Theoretical light curves were calculated for an array of Algol B coronal scale heights, ranging from 0.1 to 4.0 stellar radii.…”

Section: Rotational Broadening and Coronal Scale Heightmentioning

confidence: 99%

Doppler Shifts and Broadening and the Structure of the X‐Ray Emission from Algol

Chung

Drake

Kashyap

et al. 2004

ApJ

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In a study of Chandra High Energy Transmission Grating spectra of Algol, we clearly detect Doppler shifts caused by the orbital motion of Algol B. These data provide the first definitive proof that the X-ray emission of Algol is dominated by the secondary, in concordance with expectations that the primary B8 component should be X-ray-dark. However, the measured Doppler shifts are slightly smaller than might be expected, implying an effective orbital semimajor axis of about 10 R instead of 11.5 R for the Algol B center of mass. This could be caused by a small contribution of Algol A, possibly through accretion, to the observed X-ray flux, in which case such a contribution does not exceed 10%-15%. We suggest that the more likely explanation is an asymmetric corona biased toward the system center of mass by the tidal distortion of the surface of Algol B. A detailed analysis of the profiles of the strongest lines indicates the presence of excess line broadening amounting to approximately 150 km s À1 above that expected from thermal motion and surface rotation. Possible explanations for this additional broadening include turbulence, flows or explosive events, or rotational broadening from a radially extended corona. We favor the latter scenario and infer that a significant component of the corona at temperatures less than 10 7 K has a scale height of order the stellar radius. This interpretation is supported by the shape of the X-ray light curve and tentative detection of a shallow dip at secondary eclipse. We also examine the O vii intercombination and forbidden lines in a Low Energy Transmission Grating Spectrograph observation and find no change in their relative line fluxes as the system goes from quadrature to primary eclipse. Since these lines appear to be strongly affected by UV irradiation from Algol A through radiative excitation of the 2 3 S ! 2 3 P transition, this supports the conjecture that the corona of Algol B at temperatures of several million kelvins must be significantly extended and /or located toward the poles to avoid being shadowed from Algol A during primary eclipse.

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A Spectroscopic Study of Algol

Cited by 35 publications

References 0 publications

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

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

The rotation of the primary of Algol

Doppler Shifts and Broadening and the Structure of the X‐Ray Emission from Algol

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