UMa System Research Articles

The Nature of RW Sextantis

AbstractPhotometry and first results of extensive CCD-spectroscopy of the UX UMa system RW Sex are presented. The period is found to be P = 0.24486 days and the semi-amplitude of the radial velocity is K1 = 101 km s−1. The mass of a Roche-lobe filling secondary is M2 = (0.54±0.09) Mo and, for M1 ≧ M2, the mass ratio is M1/M2 = 1.5±0.5. The accretion rate is about (2–3) 1017 g/s. The model for RW Sex by Greenstein and Oke is discussed and rejected.

A NOTE ON LITHIUM ABUNDANCE AND CHROMOSPHERIC ACTIVITY IN THE QUADRUPLE SYSTEM XI URSAE MAJORIS.

ABSTRACT The ξ UMa system consists of a visual binary, each component of which is a spectroscopic binary. The visual components have usually been assigned identical spectral types of G0 V. Surprisingly, the lithium λ6708 line has been found in absorption only in ξ UMa A. This small puzzle has been solved by means of new CCD scans, obtained during an interval of excellent seeing when the visual pair was completely resolved. The new data show the spectral types of ξ UMa A, B to be nearer G0 V and G5 V, suggesting that the lack of a detectable lithium line in component B is explained most simply by its lower temperature and deeper convection zone. At the same time, the core of the Hα absorption feature in the chromospherically active ξ UMa B is noticeably filled by emission, confirming results by Herbig (1985).

The combined photometric and spectroscopic solutions for contact binaries BV DRA and BW DRA

view Abstract Citations (33) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The combined photometric and spectroscopic solutions for contact binaries BV DRA and BW Dra. Kaluzny, J. ; Rucinski, S. M. Abstract Extant light curves and new very precise radial-velocity curves of two W UMa systems (which form the visual binary ADS 9537) have been solved simultaneously using the Wilson-Devinney synthesis code. The absolute parameters of both systems suggest moderately advanced interior evolution and lowered metallicity; the kinematic properties of ADS 9537 are in agreement with the advanced global age. BV Dra and BW Dra are truly different and cannot be transformed into each other by conceivable evolutionary changes; thus, they do not represent different stages of the same evolutionary path. Publication: The Astronomical Journal Pub Date: September 1986 DOI: 10.1086/114200 Bibcode: 1986AJ.....92..666K Keywords: Binary Stars; Light Curve; Radial Velocity; Stellar Spectra; Metallicity; Stellar Evolution; Astrophysics full text sources ADS | data products SIMBAD (2)

THE SPECTROSCOPIC ORBIT OF THE W URSAE MAJORIS SYSTEM V508 OPHIUCHI.

ABSTRACT The spectroscopic orbit of the W UMa system V508 Oph has been studied using spectrograms obtained in 1985 with a 1.8-m telescope and the intensified Reticon detector at the Dominion Astrophysical Observatory. Orbital elements were derived separately for each component of the system, assuming a circular orbit. The spectroscopic orbital elements, determined for the first time, are T0 = 2446254.8384, K1 = 119.1 km/s, and K2 = 229.2 km/s, with the systemic velocity estimated to be approximately -36.4 km/s. Spectroscopic measurements yielded a value for the luminosity ratio (in blue light) of 1.69. The components of V508 Oph are classified as G0 V (the more massive as well as more luminous star) and G2 V. Thus, V508 Oph is an A-type W UMa system.

FO Virginis - A pre-contact binary

view Abstract Citations (13) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS FO Virginis : a pre-contact binary. Mochnacki, S. W. ; Fernie, J. D. ; Lyons, R. ; Schmidt, F. H. ; Gray, R. O. Abstract The star FO Vir, a recently discovered eclipsing binary with a period of 0.776 days, has been observed photometrically and spectroscopically. Light-curve and line-profile synthesis shows that FO Vir is semidetached with a mass ratio of 0.15 + or - 0.02. The A7 V primary component very nearly fills its Roche lobe. Radial velocities from the observed and synthesized profiles have been measured by cross correlation. The theoretical radial-velocity curve fits the observations well, to yield a mass of 1.9 + 0.9 or - 0.6 solar mass for the primary and 0.29 + 0.08 or - 0.06 solar mass for the secondary. The mean density is 0.17 + or - 0.02 g/cu cm for the primary, 0.33 + or - 0.03 g/cu cm for the secondary, with log g about 3.9 and Mv about 1.7 for the primary. This suggests the primary has evolved off the zero-age main sequence, while the secondary has a density that shows that for its mass it is highly evolved. The period and mass ratio are typical of the more extreme 'A-type' W UMa systems, which suggests that FO Vir will evolve into a contact binary of this type. Short-period semidetached binaries may be the progenitors of at least some W UMa systems. Publication: The Astronomical Journal Pub Date: May 1986 DOI: 10.1086/114094 Bibcode: 1986AJ.....91.1221M Keywords: Eclipsing Binary Stars; Stellar Evolution; Stellar Spectrophotometry; Curve Fitting; Light Curve; Radial Velocity; Stellar Mass; Stellar Models; Astrophysics full text sources ADS | data products SIMBAD (3)

THE SPECTROSCOPIC ORBITS OF BV AND BW DRACONIS.

ABSTRACT Reticon spectra of high dispersion and time resolution have been obtained of BV an BW Draconis, which together form a visual binary and each of which is a W UMa system. The spectra were measured by cross-correlation. The orbital elements of BV Dra have been revised to the values T0 = 2446127.6888, K1 = 93.9 km s-1 and K2 = 233.6 km s-1, while those of BW Dra, determined for the first time, are T0 = 2446135.8067, K1 = 70.5 km s-1 and K2 = 251.5 km s-1. A circular orbit is adopted for each system. Different values of V0 are obtained from each component of each system, but V0 for each pair is close to -60 km s-1. Radial velocities confirm the proper motions in identifying the two systems as a genuine binary (ADS 9537) whose space velocity with respect to the Sun is over 90 km s-1. From spectrophotometry, the components of BV Dra are classified as F9 (more massive star) and F8, with a luminosity ratio (in blue light) of 1.78 (Δm = 0.63), while the components of BW Dra are G3 (more massive star) and G0, with a luminosity ratio (also in blue light) of 1.52 (Δm = 0.45). All four stars are of luminosity class V.

A NEW SPECTROSCOPIC ORBIT OF THE W URSAE MAJORIS SYSTEM U PEGASI.

ABSTRACT High-dispersion spectra have been obtained for the W UMa system U Peg. Time resolution was kept high by means of an image tube coupled to a Reticon. All the spectra were measured by cross-correlation techniques. The orbital elements for both components of the system have been determined to be: T0 = 2445956.983, V0 = 28.5 km/s, K1 = 77.6 km/s, K2 = 246.5 km/s. A circular orbit is adopted. From the semiamplitudes of the two components, an accurate mass ratio m1/m2 = 3.18 is deduced. Spectrophotometric measurements were also carried out from which the luminosity ratio (determined from line-strength ratios) is deduced to be 1.47, corresponding to a difference of 0.42 mag in the blue region of the spectrum. Both stars are found to be on the main sequence; their spectral types are each close to G2 with the secondary a little earlier.

New photoelectric observations of four W UMa systems: OO aql, V839 Oph, V566 Oph, and SW Lac

The W UMa-type systems (OO Aql, V839 Oph, V566 Oph, and SW Lac) were observed photoelectrically in two wavebands (B andV) during the years 1982–1983. The light curves of these systems are analysed using Kopal's frequency-domain technique and the optimisation method. New geometrical and physical elements have been determined. The absolute elements and the period variations of these systems are discussed.

A new photometric study of the binary U Pegasi

Over four hundred photoelectric observations of U Peg in B and V were secured with a 0.6M reflector at Beijing Observatory in 1978. Four times of minima were determined. A period study of the times of minima from 1896 to 1980 was performed. The system was found to have a secular period decrease, Δp/ p of −1.32 ¢ 10 −1 or −4.16 × 10 −3 sec/yr, as well as a short term (17 years) sinusoidal oscillation with a semi-amplitude of 0.00323 day. It is suggested that oscillating term is caused by the light-time effect of an unseen third body. The third body may be a M6 main sequence star with a mass of 0.16 M ⊙. The longterm secular change in period may be associated with slow mass transfer. The analysis of the 1978 light curves together with the 1958 light curves of Binnendijk suggest that the system U Peg has an overcontact configuration of about 9%. It has the characteristics of a W-type W UMa system. The photometric mass ratio, m 2 m 1 , is between 3 and 2.5. If we correct the Struve et al. γ-velocity from 0 km/sec to about −40 km/sec the estimated spectroscopic mass ratio would agree with the photoelectric value. Based on the above assumption the absolute dimensions of U Peg are of 0.6 and 1.8 M ⊙ and of 0.8 and 1.4 R ⊙, for components 1 and 2 respectively. The physical dimensions indicate that the components are main sequence stars.

Two very similar late-type contact systems - BX and BB Pegasi

view Abstract Citations (15) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Two very similar late-type contact systems : BX and BB Pegasi. Leung, K. -C. ; Zhai, D. ; Zhang, Y. Abstract V and B observations of BX and BB Pegasi secured at Beijing Observatory were analyzed with the Wilson and Devinney method. An extensive search for reliable photometric mass ratios was performed. Both systems were found to be in contact with small degrees of overcontact, 10 percent and 12 percent, for BX and BB Peg, respectively. Their mass ratios were, respectively, 2.80 and 2.81. The eclipse at primary minimum was found to be total for both systems. They have the characteristics of W-type W UMa systems. The computed light curves fit the observations very well for BX Peg. The light curves of BB Peg are very complex: there is large asymmetry in the maxima, and significant discrepancy in the differential eclipse depths (Min I and Min II) between the V and B curves. As a result of these complications, the computed light curves do not fit the observations well. Adopted photometric parameters for BX Peg are similar to those obtained by Kaluzny, who used the Rucinski method. It is believed that adopted photometric parameters for BB Peg are more reliable than those obtained by Cerruti-Sola et al. Publication: The Astronomical Journal Pub Date: March 1985 DOI: 10.1086/113759 Bibcode: 1985AJ.....90..515L Keywords: Astronomical Photometry; Eclipsing Binary Stars; Electrophotometry; Late Stars; Light Curve; Mass Ratios; Astrophysics full text sources ADS | data products SIMBAD (4)

Photometric solution for the eclipsing binary system AO Camelopardalis

UBV light curves of AO Cam were analyzed with Wilson and Devinney's model. The system was found to be a contact configuration with a degree of overcontact of 1.4%. The mass ratio of the system is about 1.30, and the inclination is 75.09. The primary eclipse appears to be an occultation. Thus AO Cam has the characteristics of a W-type W UMa system. Its location in a period-spectral type diagram suggests that the system may be a zero-age contact system.

UBV photometric analysis of V758 Centauri

Classical R-M and synthetic W-D analysis of V758 Centauri are presented. Two solutions (semi-detached and contact) were found from differential corrections approach. The semi-detached model is physically acceptable since the system is thermally decoupled. The solution for this case and the photometric data are consistent with a B9 primary and A9 secondary components having parameters close to Main-Sequence values. It is suggested that V758 Centauri is a B-type W UMa system at the brokencontact phase predicted by the Thermal Relaxation Oscillations theory.

The peculiar behaviour of the photometric variability of V508 Ophiuchi

RecentUBV observations of the eclipsing binary V508 Oph are presented. The obtained partial light curves show the typical behaviour of W UMA systems. The amplitudes of light variation are about 0 . 80, 0 . 86, and 0 . 94 inV, B, andU, respectively. This is not consistent with older photographic and photoelectricBV data which showed amplitudes of about 0 . 6 and 1 . 1 inV andB. Furthermore, the shapes of the light curves are not similar to the older ones. It is concluded that a strong change in the photometric behaviour of V508 Oph has probably occurred between 1981 and 1984.

A disk origin for superhumps in Ursae Majoris variables

As cataclysmic variables, SU Ursae Majoris stars1,2 are short-period binary systems consisting of a red dwarf star that fills its Roche-lobe and spills material to an accretion disk around a white dwarf. SU UMa systems undergo outbursts (episodes of increased mass transfer in the disk) of two distinct types: normal outbursts that last a few days, and superoutbursts that last up to 2 weeks. Superhumps are periodic ∼30% brightness variations of unknown origin seen only during the superoutbursts. The superhump period is several per cent longer than the binary orbital period. Both the accretion disk3,4 and the red dwarf5 have been proposed as possible sites for the superhump. Although superhumps occur in both eclipsing and non-eclipsing systems, observations of the eclipsing systems Z Cha and OY Car may help to discriminate between these two classes of models. Whitehurst et al.5 have shown that the superhumps in Z Cha are not deeply eclipsed, and argue that superhumps therefore cannot originate in the accretion disk. In their starspot model, superhumps arise in a bright active region located in the equatorial belt of the red dwarf. By contrast, the light curve synthesis results reported here show explicitly that disk models produce a shallow partial eclipse of the superhump light, compatible with the eclipse depth measurements of Whitehurst et al., provided the superhump source is not concentrated into a small region of the disk. The starspot model is shown to be inconsistent with the observed shapes of superhumps unless radiation emerges from the starspot in a narrow (≲35°) fan beam with its long axis in the direction of stellar latitude.

A STUDY OF PHOTOELECTRIC OBSERVATIONS OF SW LACERTAE.

ABSTRACT SW Lac is a well-known late-type close binary system with large variation in its light curve. New photoelectric observations in B and V were obtained in 1978 at the Beijing Observatory. The authors attempted to derive a consistent photometric solution by analyzing individually three separate sets of light curves (1953, 1961, and 1978). All the solutions suggest that the system is overcontact and belongs to the W-type W UMa systems. The 1961 and 1978 light curves have essentially identical photometric parameters. The derived mass ratio is identical with the spectroscopic value. However, the 1953 light curves have distinctly different parameters from those of the later years. Two different interpretations are discussed.

Red component activity in dwarf novae

SU Ursae Majoris systems are short-period binary dwarf novae characterized by two distinct classes of outbursts: ‘normal outbursts’ of duration ∼2 days and less frequent ‘superoutbursts’ which last ∼12 days. Superoutbursts may be present in longer-period systems but could be classified as wide outbursts1. Superoutbursts require enhanced mass transfer rates for an extended period of ∼10 days to explain their sustained activity2,3. During superoutbursts, ‘superhumps’ are observed4–6 which modulate the visible light by ≲40% with a period 3–7% longer than the binary period. Measurement of eclipse depths in the two eclipsing SU UMa systems during superoutburst should show whether or not the superhump light is eclipsed and hence make it possible to infer its location either in the eclipsed disk or in the uneclipsed red component. Study of the available eclipse data reported here shows that the superhump light is not eclipsed, so that the red component is the location of the superhump.

Constraints for cataclysmic binary evolution as derived from space distributions

Space densities and galactic z-distributions of novae, recurrent novae, dwarf novae and symbiotic stars are newly determined and discussed in the context of earlier determinations. The data are then compared with the distributions of single and binary stars of possibly related types (late type giants, Mira variables, Algol systems, W UMa systems).

Constraints for Cataclysmic Binary Evolution as Derived from Space Distributions

AbstractSpace densities and galactic z-distributions of novae, recurrent novae, dwarf novae and symbiotic stars are newly determined and discussed in the context of earlier determinations. The data are then compared with the distributions of single and binary stars of possibly related types (late type giants, Mira variables, Algol systems, W UMa systems).Novae and dwarf novae have similar distributions, those of fairly young stellar populations. The observed space density of potential novae (novalike objects) indicates that the mean recurrence time of novae might be as small as a few hundred years, which leads, with given nova shell masses and mass transfer rates in the minimum stage, to a secular decrease of the masses of the components undergoing nova outbursts.Recurrent novae and symbiotic stars have distributions of older stellar populations, similar to those of late type giants and Mira variables.On the basis of galactic distribution, novae and dwarf novae are closely related and may be final stages of W UMa systems, as well as progenitors of supernovae of type I. A small fraction of W UMa systems seems to belong to an older population. If evolutionary transitions between these types of stars can be substantiated, the presence of a minority of novae and dwarf novae in globular clusters and of supernovae I in elliptical galaxies can be explained.Due to the lack of sufficiently well determined space distributions of Algol binaries, the suggestion that long-period Algol systems might be the progenitors of cataclysmic binaries can as yet neither be substantiated nor refuted. A very high space density of long-period Algol systems in the solar neighbourhood is derived. The observed space density of cataclysmic binaries could be explained by the transformation of a small percentage of the long-period Algol systems by common envelope evolution.

V758 Centauri:UBV photometry

The W UMa system V758 Centauri has been observed photoelectrically in theUBV system at Bosque Alegre Station, and the comparison and check stars at Cerro Tololo Observatory. Full light curves were constructed from 1043 differentialUBV observations. A study of 11 photoelectric times of minimum light and of earlier photographic data shows that the period remained constant in the last century, V758 Cen shows a total occultation at secondary minimum, thus being an A-type W UMa system. Asymmetries are observed at primary minima whereas maxima are of different heights. Thermal decoupling of the components is suggested by the depth ratio of the minima; V758 Cen may be at the broken phase (or marginal contact) of a thermal relaxation oscillation.

X-ray emission from the W UMa system TZ Bootis

HEAO-B (Einstein) satellite measurements with the Imaging Proportional Counter revealed the W UMa binary system TZ Bootis as an X-ray source. It is estimated that the luminosity ratioLx/Lvof this system is about 10−3.8 indicating that TZ Bootis is in the transition region between A- and W-type W UMa systems.