Mass Transfer Events Research Articles

The light-curve properties of mass-transfer events in cataclysmic variables

Etude de la forme des courbes de lumiere lors d'eruptions produites par des evenements avec transfert de masse dans des novae naines

On the evolution of binary components which first fill their Roche lobes after the exhaustion of central helium

view Abstract Citations (34) References (42) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Evolution of Binary Components Which First Fill Their Roche Lobes after the Exhaustion of Central Helium Iben, I., Jr. Abstract The evolution of model close binary components of initial mass 3-7 Msun and of Population I composition is followed from the beginning of the core helium-burning phase. For one set of models, mass loss is initiated at an arbitrary point during the early AGB phase (early case C events) and evolution is followed to the degenerate dwarf stage. For another set of models, mass loss is initiated when hydrogen is reignited and thermal pulses begin (late case C events). It is found that the inclusion of overshoot and semiconvection during the core helium-burning phase has little effect on the relationship between progenitor mass and final degenerate dwarf mass. A new channel for producing both oxygen-neon (ONe) degenerate dwarfs and neutron stars is identified. Involved are stars of initial mass 7. 8.5 Msun which undergo early case C events. For such stars, mass loss from the surface proceeds sufficiently more rapidly than the mass of the hydrogen-exhausted core can be decreased by convective dredge-up that carbon ignition at the center occurs before degeneracy sets in; the remnant of the mass transfer event can evolve into either an ONe degenerate dwarf or a neutron star at a combined frequency that is comparable to the observed rate of supernova formation in the Galaxy. In binary systems in which the primary becomes a neutron star or an ONe degenerate dwarf, the secondary will normally evolve into a CO degenerate dwarf, and common envelope action will lead in some instances to small enough orbital separations that orbital shrinkage due to gravitational wave radiation will again lead to Roche-lobe filling by the CO dwarf. If before the merging and explosion process begins, the heavier compact component is an ONe degenerate dwarf, a supernova-like explosion fueled by the conversion of carbon and oxygen into iron peak nuclei may result, and the light curve and spectrum may be of the Type I "peculiar" variety. The compact remnant remaining after the explosion may be either an ONe degenerate dwarf or a neutron star. Publication: The Astrophysical Journal Pub Date: May 1986 DOI: 10.1086/164154 Bibcode: 1986ApJ...304..201I Keywords: Binary Stars; Neutron Stars; Stellar Evolution; Stellar Models; White Dwarf Stars; Convective Heat Transfer; Helium; Hertzsprung-Russell Diagram; Roche Limit; Stellar Mass; Astrophysics; STARS: BINARIES; STARS: EVOLUTION; STARS: INTERIORS; STARS: NEUTRON; STARS: SUPERNOVAE; STARS: WHITE DWARFS full text sources ADS |

RECENT OPTICAL SPECTRA OF THE SYMBIOTIC OBJECT R AQUARII.

ABSTRACT Spectroscopic observations of R Aqr and its nearby 'jet' between 1980 and 1984 are presented. As first reported by Sopka et al. (1982), a significant difference between the velocity of the jet and the inner nebula associated with the star is found. Spectra at high resolution show that many emission lines are double with one component near that of the star and one near that of the jet; however, forbidden lines favored by high density do not show the latter component. Profiles of the single Ne III forbidden lines from the inner nebula indicate an expansion velocity no greater than 12.5 km/s in 1984. An assembly of absorption-line velocities for the long-period variable obtained during the past 40 years is consistent with a 44-year period, and a velocity amplitude of 7 km/s. A highly eccentric orbit, which might explain the outbursts by a mass-transfer event at periastron, is not likely to be consistent with the absorption-line data.

A remarkable H-alpha outburst in the RS CVn binary SZ PISCIUM - A transient mass-transfer event

The very unusual spectroscopic behavior of the RS CVn binary SZ Psc (K1IV + F8V; P = 3.97 days) is described. For much of the time the Ha line in the K star appears as a weak absorption feature, presumably partially filled by chromospheric emission. The Hα equivalent width ordinarily shows small variations that may be adequately explained by stellar surface activity. During a single month in 1978, however, the appearance and behavior of the Hα feature were bizarre. Over the course of a few nights the line profile changed from the expected weak absorption feature to a broad (∼300 km s<SUP>-1</SUP>) double-peaked emission. This emission profile persisted, weakening slowly, for several weeks. Velocity measures indicate the K star was the source of the emission. Such an Ha outburst, with its unusual profile and temporal behavior, has never been seen in other, more intensively observed RS CVn systems. An explanation in the strict context of surface phenomena does not appear feasible. Instead, we propose that the emission is circumstellar in origin, produced from a ring or shell of gas around the primary K component. We examine the possibility that this Hα outburst may have signaled a transient mass-transfer event in this barely detached system.

RECENT PERIOD CHANGES IN U CEPHEI.

ABSTRACT The influence of photometric contamination accompanying recent mass-transfer events on times of minima and period changes in U Cep is discussed. A simple criterion is proposed to separate disturbed and undisturbed eclipses. By using times of minima from essentially undisturbed eclipses, it is found that a large period decrease occurred in early 1972, before evidence of mass transfer was observed. This decrease was followed in 1974 by a period increase of much smaller magnitude, after which the period has remained constant. The sporadic nature of the transfer activity from 1974 through 1977 is demonstrated.

THE ORBITAL PERIOD OF ALGOL: 1964 TO 1978.

ABSTRACT A photoelectric observation of minimum light for Algol is reported: JD 2443565.5785 (visual) and JD 2443565.5802 (blue). The times of minima obtained between 1964 and 1978 indicate that a period decrease may have occurred about 1975. It is suggested that this period change, as well as the radio and X-ray activity and spectroscopic anomalies observed during 1975, may have been due to a mass-transfer event that occurred around that time.

U Cephei - A mass-transfer event. I

view Abstract Citations (28) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS U Cephei: a mass-transfer event. I. Olson, E. C. Abstract A major mass-transfer event, with accompanying photometric anomalies, occurred in U Cep in late 1974. Four-color uvby observations during this outburst have been interpreted by a simple quantitative model containing a mass-transferring stream and a hot spot and equatorial disk associated with the primary star. A lower limit to the peak mass-transfer rate of 0.00003 solar masses per year is deduced. Publication: The Astrophysical Journal Pub Date: February 1976 DOI: 10.1086/154158 Bibcode: 1976ApJ...204..141O Keywords: Astronomical Models; Cepheid Variables; Eclipsing Binary Stars; Mass Transfer; Stellar Mass Ejection; Astronomical Photometry; H Beta Line; Optical Thickness; Stellar Spectra; Astrophysics full text sources ADS |