Classical Algol Research Articles

Analysis of δ Librae including Hipparcos astrometry

New spectroscopy of the classical Algol system δ Lib, combined with high-quality optical and infrared photometry, provides the basis for a good understanding of the close binary system's main parameters. Detailed analysis of the photometry reveals the significant role of a third light source, pointing to the existence of a companion to the eclipsing system of mass ∼1 M ⊙ . We review the methodology of applying high-accuracy positional information, available from the Hipparcos Intermediate Astrometric Data archive, to stars that may have such companions. Analysis of the astrometry of δ Lib also points to a third star similar to the one already identified by Worek from radial-velocity data, although with slightly revised parameters. O-C data do not contradict this, but their general precision (while confirming the close pair's Algol status) fails to allow a decision on the third orbit parameters: Worek's or revised ones. Taking the photometry, spectroscopy and astrometry together, however, the existence of a third star of comparable mass to the Sun, as a relatively close companion to the eclipsing binary (∼4 au), is confirmed.

Optical Photometry and X-Ray Monitoring of the "Cool Algol" BD +05706: Determination of the Physical Properties

We present new photometric observations in the BVRI bands of the double-lined eclipsing binary BD +05°706 conducted over three observing seasons, as well as new X-ray observations obtained with ROSAT covering a full orbital cycle (P = 18.9 days). A detailed light-curve analysis of the optical data shows the system to be semidetached, confirming indications from an earlier analysis by Torres et al. (published in 1998), with the less massive and cooler star filling its Roche lobe. The system is a member of the rare class of cool Algol systems, which are different from the classical Algol systems in that the mass-gaining component is also a late-type star rather than a B- or A-type star. By combining the new photometry with a reanalysis of the spectroscopic observations reported by Torres et al., we derive accurate absolute masses for the components of M1 = 2.633 ± 0.028 M⊙ and M2 = 0.5412 ± 0.0093 M⊙, radii of R1 = 7.55 ± 0.20 R⊙ and R2 = 11.02 ± 0.21 R⊙, as well as effective temperatures of 5000 ± 100 and 4640 ± 150 K, for the primary and secondary, respectively. There are obvious signs of activity (spottedness) in the optical light curve of the binary. Our X-ray light curve clearly shows the primary eclipse but not the secondary eclipse, suggesting that the primary star is the dominant source of the activity in the system. The depth and duration of the eclipse allow us to infer some of the properties of the X-ray–emitting region around that star.

Be Stars in Roche-Lobe Interacting Binaries

AbstractDifferent types of massive interacting binaries with Be components are discussed. Due to mass exchange, Be stars in these systems have some peculiar characteristics. Often it is even difficult to find traces of the Be star and/or mass-losing star in the optical region of the spectrum. Using the value of the orbital period as a primary parameter, it is possible to divide all massive interacting binaries into two large groups: short-period or classical Algols and long-period binaries. The last group includes a number of very active mass transfer systems named as W Serpentis. There is also a small group of double systems whose stars do not fill their Roche lobes but have emission lines in the spectrum. Properties of their spectral variability are discussed. Analysis of each group lets us find different behaviours in mass exchange that depend on the size of their Roche lobes.

Further Discussion of Binary Star Radio Survey Data

AbstractStatistical information on 8280 individual radio observations of binary stars, predominantly at 8·4 GHz using the Parkes 64 m antenna, is presented. Three main groups are distinguished: (i) RS CVn stars, (ii) classical Algol binaries (EA2s), and (iii) detached pairs of generally early type (ETBs).The RS CVn stars more frequently gave rise to detectable fluxes, while the ETBs, in these data, are a small and rather heterogeneous class. The Algols' emission appears to increase near conjunction phases, though we cannot clearly distinguish any special property of the Algols' phase-dependent behaviour that is not also shared by the RS CVn binaries. Both these categories' data show a bimodal, phase-dependent pattern to the distribution of detections, suggesting that these binary types share similar underlying physical properties, though there could also be other factors at play. The sample sizes of the Algols and particularly the ETB detections are too small for effective, discriminatory statistics, however.

A photometric investigation of the eclipsing binary V505 Sagittarii

view Abstract Citations (15) References (35) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Photometric Investigation of the Eclipsing Binary V505 Sagittarii Chambliss, C. R. ; Walker, R. L. ; Karle, J. H. ; Snodgrass, H. B. ; Vracko, Y. A. Abstract V505 Sgr is a classical Algol system consisting of an A2 V primary and a G5 IV secondary that fills its Roche lobe. New times of minimum light are presented. The period of the eclipsing system (1.18287d) varies, due in part to an orbital light-time effect. A third component has been detected that orbits the eclipsing pair. This investigation uses the SIMPLEX algorithm (Kallrath & Linnell, 1987) and the Differential Correction code (Wilson, 1979) to analyze two separate datasets. The results indicate the third component, an F8 V star, contirbutes about 5% of the light to the system. The minimum projected distance between the third component and the eclipsing pair is 37 AU. This implies an orbital period of about 105 years, a value that differs with the O-C data. The photometric solution, combined with recent spectroscopic data yields R1 = 2.14 solar radius and R2 = 2.24 solar radius and M1 = 2.20 solar mass and M2 = 1.15 solar mass. Publication: The Astronomical Journal Pub Date: November 1993 DOI: 10.1086/116785 Bibcode: 1993AJ....106.2058C Keywords: A Stars; Astronomical Photometry; Eclipsing Binary Stars; F Stars; G Stars; Light Curve; Simplex Method; Triple Stars; Orbital Mechanics; Photoelectric Emission; Radial Velocity; Speckle Interferometry; Astrophysics; STARS: INDIVIDUAL: V505 SAGITTARII; BINARIES: ECLIPSING full text sources ADS | data products SIMBAD (1) CDS (1)

Photometric Analysis of Wide and Narrow Hα Band Observations of R Canis Majoris

Wide and narrow Hα lightcurves of R CMa were analysed using Wilson-Devinney (WD) and Information Limit Optimisation Technique (ILOT) approaches. A range of mass ratios, tested by both methods, led to an optimal estimate of around 0.45, at variance with the spectroscopic value. The distortion on the light curve affects the modelling, and so, in a second fitting, this was represented by a ‘hot spot’, associated with mass transfer effects. A semi-detached configuration was then derived. This is supported by the form of the Hα index variation, which has also been modelled. Although thus appearing as a ‘classical Algol’ system, R CMa retains its inherent peculiarity of low mass ratio with low period, which cannot be reconciled with conservative evolution scenarios.

UBV photometry of AW Pegasi

NewUBV observations of the classical Algol system AW Peg were presented. The photometric minima times were collected and used together with the new determinations in a period study. No sign of any period change was found from observations covering more than sixty years. TheB andV light curves are analyzed by means of the Wilson-Devinney approach. It was verified that the system is semi-detached with a Roche lobe filling secondary.

Observations and analysis of the Southern binary R Arae

This paper investigates the nature of the relatively bright (≃ 7th magnitude) eclipsing variable R Arae (HD 149730A), which has an orbital period of 4d.42509, from the analysis of photometricUBV observations. The main objective behind such an analysis is to determine whether the system qualifies for a classical Algol of semi-detached status. An analysis has been performed twice on each of theUBV curves as well as the light curve due to Gaposchkin, utilising a light curve optimisation procedure. In the first analysis the presence of the visual companion (HD 1497330B) to R Arae (angular separation = 3′'.6), whose light was present in all observations, was not accounted for. The second analysis attempts to account for this third light source. All the analyses indicate the relative radius of the secondary star, is of the order of 0.20. This value is well below the limit which would classify the system as a semi-detached binary. These results do, however, seem to be somewhat discordant with the spectroscopic and general photometric nature of the system, all of which suggest mass transfer processes to be occuring (therefore a possible semi-detached status). This is seen in several features, especially a marked increase in the system's mean orbital period, which tends to corroborate mass transfer from the secondary star.

Statistical study of semi-detached and near contact semi-detached binaries

We carried out a statistical study of 107 semi-detached with combined light curve solutions. 1. We derived an empirical period-dependent mass-radius relation, thereby revealing the impossibility of having evolved semi-detached systems with very short periods. 2. Statistically, the near-contact semi-detached systems have the common properties of nearly equal mass densities of the components, larger mass-ratios, shorter periods and smaller specific angular momenta and their A- F-type secondaries generally have greater densities than the secondaries of classical Algol systems of the same spectral types. A detailed discussion is also made in this paper on the evolution of near-contact semi-detached binaries.

Observations and analysis of MT Her

Previously reportedBV photometry of MT Her is analysed with the aid of efficient curve-fitting techniques. There is insufficient overall data to allow a definitive parametrization of the binary, but we can confidently rule out the possibility of a classical Algol.

Radio Emission from EA Eclipsing Binaries: Evidence for Kilogauss Early- and Late-Type Stars

A recent survey of EA eclipsing binaries by the Parkes 64-m telescope operating at 8.4 GHz detected 15 out of 47 systems on at least one out of the 10 nights surveyed. The detected systems were HD 6882 (ξ Phe), HD 36486 (δ Ori A), HD 39780 (TZ Men), HD 57167 (R CMa), HD 58713 (RY Gem), HD 74307 (S Cnc), HD 132742 (δ Lib), HD 147683 (V769 Sco), HD 161741 (V393 Sco), HD 163708 (V1647 Sgr), HD 16871Q(XZ Sgr), HD 183794 (V822 Aql), HD 187949 (V505 Sgr), HD 199005 (KZ Pav), and HD 207098 (δ Cap).A full account of the observations and interpretation has been submitted to The Astrophysical Journal.About one-half of the 15 detections refer to main-sequence pairs of spectral types earlier than F and the remainder are classical Algols.

Classical Algol systems (invited review)

Progress in the study of Algol-type binaries is looked at both in the light of more general efforts at compilation and categorization, and also some specific new and important observational results.

Photometry and discussion of the classical Algol systems U Sge and U Cep

The (in many respects, similar) classical Algol-type eclipsing binary systems U Sge and U Cep are studied and compared against a background of photometric evidence, both broadhand and narrowband. Broadband photometry of the primary minimum of U Sge over a four year period fails clearly to confirm Olson's (1982b) finding of radial variations.

ABSOLUTE PARAMETERS OF STARS IN SEMIDETACHED ECLIPSING BINARY SYSTEMS.

ABSTRACT A number of questions concerning the absolute parameters of stars in semidetached binary systems are addressed. Consideration is given to: similarities between Algol-type binaries and unevolved detached binaries with respect to the mass-luminosity law; and the single-line classical Algol candidates with known mass functions and photometric solutions for mass ratio. It is shown that the validity of the mass luminosity-law cannot be verified for individual Algol-type binaries though it does hold well on average; and (2), the existence of a definite class of sd-binaries not containing a proportion of significantly undersize types is apparent. The conclusions are found to be in general agreement with the observations of Hall and Neff (1979).

Simultaneous differential photometry with the St. Andrews twin photometric telescope - I. The eclipsing binary TT Aurigae

The refurbished Twin Photometric Telescope at St. Andrews has been used to obtain a complete B light curve (∼ 1150 observations) of the B-type interacting binary system TT Aurigae. Analysis of the light curve by the synthesis code LIGHT (Hill 1979) results in an rms scatter of the individual observations about the theoretical model fit of ±0.005 mag. The system is shown to be in a semi-detached state but with too large a mass ratio to be considered as a classical Algol system.

Theq-log P distribution of classical Algols

Data on a large sample (~400) of candidates for the classical Algol-type eclipsing binary configurations have been collected. The mass-ratio q has been calculated on the assumption of their semi-detached nature, and then compared with corresponding period for some subsets of the sample. The tendency to slight overluminosity (compared with corresponding MS stars) of the primaries in classical Algols is confirmed.

The q-Log P Distribution of Classical Algols

AbstractData on a large sample (∼400) of candidates for the classical Algol-type eclipsing binary configurations have been collected. The mass-ratio q has been calculated on the assumption of their semi-detached nature, and then compared with corresponding period for some subsets of the sample. The tendency to slight overluminosity (compared with corresponding MS stars) of the primaries in classical Algols is confirmed.The role of the loss of angular momentum in classical Algol evolution is considered, together with a method for determining representative parameters to characterize such effects using the sample data. The possible existence of a class of post-contact classical Algols is noted.

General properties of Algol binaries

view Abstract Citations (107) References (113) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS General properties of Algol binaries. Giuricin, G. ; Mardirossian, F. ; Mezzetti, M. Abstract Theoretical computations on close binary evolution have made it possible to obtain a general understanding of the evolutionary scenario of Algol variables in terms of mass exchange. The present investigation has the objective to draw attention to some important discrepancies between the observational data of Algol variables and the relevant theoretical results. A compilation of the observed properties of 101 Algol variables is presented. This term is used to denote binaries related to the classical Algol variables from the evolutionary point of view. Attention is given to the statistical properties of the binaries of the selected sample, taking into account a comparison of the binaries with similar available statistical analyses of a large sample of eclipsing and spectroscopic binaries. An order-of-magnitude estimate is provided of the amount of mass ejected into the interstellar space by Algol binaries as a result of nonconservative mass-transfer processes. Publication: The Astrophysical Journal Supplement Series Pub Date: May 1983 DOI: 10.1086/190858 Bibcode: 1983ApJS...52...35G Keywords: Astronomical Catalogs; Eclipsing Binary Stars; Stellar Evolution; Data Sampling; Statistical Analysis; Stellar Luminosity; Stellar Mass; Stellar Mass Ejection; Astrophysics full text sources ADS | data products SIMBAD (103)

S Cnc as a Case Study of Classical Algol Evolution

AbstractBasic information on empirical determinables for the system S Cnc are reviewed. Whilst the photometric information can be clearly analysed along well known lines, the spectrographic information is far from clear and requires further study, though a semi-detached configuration, at least, can be confidently deduced.The potentially important question of some physical relationship of the variable to the open cluster Praesepe is considered, but the result is in the negative.The evolutionary status of the binary is examined in a general way by making use of some summary formulae, some guidelines for which were taken from previous more general work of Refsdal and Weigert. S Cnc is in good overall agreement with the low mass Case B theoretical mode of binary evolution, and even the absence of a detectable rate of period variation is shown to be not in serious conflict with this picture. Interesting close comparisons with the well known example AS Eri are possible.