Red Companion Research Articles

CW 1103+254 : A NEW CATACLYSMIC AT HIGH GALACTIC LATITUDE.

ABSTRACT The discovery and observation of a probable old nova CW 1103+254, which is at high galactic latitude is discussed. It is shown that the properties of this star are consistent with the classical old nova phenomenology. Some estimates on the evolutionary status of the red companion and on the various system parameters are given. The object is a morphologically similar star to GK Per although not a known variable. Some suggestions for future observations are made.

Radii and luminosities of classical cepheids

The radiii of 17 classical Cepheids are determined. The linear surface brightness-colour relationS v=b(B−V)o+const is accepted. The present method permits the determination of the coefficientb for each star separately and the obtaining of the absolute magnitude of Cepheids. The coefficientb shows a slight dependence on the periodP of stars. The period-luminosity relation is approximately the same as the one obtained by van den Bergh (1976) for Cepheids in open clusters. The simultaneous radial velocity and photoelectric observation may show the phase shifts between motions of the continuum layer and of the level where the Fe I line is formed. The Cepheidl Car is outside the instability strip, and probably has a red companion as was suggested by Schmidt (1980a). Conclusions about the existence of overtone pulsators cannot probably be drawn only from the scattering in the period-radius relation.

A quest for the red companion in six cataclysmic binaries

view Abstract Citations (85) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A quest for the red companion in six cataclysmic binaries. Young, P. ; Schneider, D. P. Abstract Near-infrared CCD spectra of six cataclysmic binaries have been obtained in an attempt to detect their red dwarf components. Similar observations of M dwarfs yield a classification scheme, based on TiO bands, which can be used to describe the red dwarfs in cataclysmic binaries. Observations of AM Her while in its low state revealed a red dwarf of type M4(+) V and a distance of 80 pc. The red dwarf in DQ Her was detected in an observation centered on mid-eclipse. The red star in DQ Her has a spectral type of M3(+) V, a mass = 0.32 solar mass, and a radius = 0.45 solar radius. The red star in DQ Her does not lie on the main sequence; although its temperature is correct for its mass, the radius is 25% too large. A spectroscopic distance estimate of 400 pc to the DQ Her binary system was obtained; in four additional systems, the red dwarf defied detection. Lower limits to their distances are given. Publication: The Astrophysical Journal Pub Date: August 1981 DOI: 10.1086/159105 Bibcode: 1981ApJ...247..960Y Keywords: Companion Stars; Dwarf Stars; Infrared Spectra; Novae; Stellar Spectrophotometry; Charge Coupled Devices; Near Infrared Radiation; Stellar Magnitude; Stellar Mass Accretion; Titanium Oxides; Astronomy full text sources ADS | data products SIMBAD (13)

Nova Modeling

The mass and energy of nova ejecta are 10-5 - 10-4M⊚ and 1044 - 1045 ergs, respectively (Payne-Gaposchkin 1957). Comparison of these quantities with the mass (1 M⊚) and binding energy (1051 erg) of the erupting white dwarf implies that the nova outburst is a surface event. From an average of two or three novae detected each year, it is estimated that the rate of novae is 40-50 per year in our galaxy (Payne-Gaposchkin 1954) . Comparing this rate with a white dwarf birth rate of 2 per year in our galaxy (Weidemann 1968), we conclude that the nova outburst is a recurrent phenomenon (cf. Ford 1978). The recurrent nature also implies that the white dwarf cannot be drastically altered from event to event, thus giving further evidence for a surface event. The argument of recurrency become even stronger when it is realized that observations strongly indicate a close binary structure for the nova candidates—the white dwarf and a red companion (Kraft 1964).Kraft (1963) proposed the following hypothesis. The red companion overflows its Roche lobe and supplies hydrogen-rich material to an accretion disk around the white dwarf. This material eventually accretes onto the white dwarf, forming an hydrogen-rich envelope whose base is electron-degenerate. As the accretion proceeds, the temperature at the base of this envelope increases. This has little effect on the pressure, but greatly increases the thermonuclear energy generation. The thermonuclear energy generation, in turn, increases the temperature. This positive feedback loop leads to a thermonuclear runaway, which Kraft proposed as the cause of the nova outburst. A large number of theoretical studies based on this model have been carried out. These studies are presented in order of increasing realism and complexity in the following sections.

AZ CASSIOPEIAE AT THE 1956 - 57 ECLIPSE.

ABSTRACT The spectrum of AZ Cas at the time of the 1956-57 eclipse can be described as a combination of an F8 Ib star and a main-sequence B0-I companion. The latter star is ejecting matter with approximately spherical symmetry at some 50-60 km/sec, while the former has a very extended atmosphere. The whole system seems to be also surrounded by an expanding envelope. Determinations of the spectral type of the red companion range from early-M, well before eclipse, to F8, in the present material, with a Ib-luminosity class sensibly constant. This variation is interpreted as indicating changes in the optical thickness of the envelope surrounding the late-type companion, either intrinsic (rho Cas episode) or related to the binary nature of the system.

Periodicities and Disks in Dwarf Novae

The outbursts of dwarf novae are suggested as being due to the liberation of energy in the accretion disk surrounding the white dwarf component following unstable mass outflow by the red companion. The periodicities observed in dwarf novae near maximum light are shown to be consistent with periodic eclipses of temperature fluctuations in the innermost region of the disk.