scholarly journals History of the Light Curves and Molecular Maser Emission of the Miras U Ori and R Leo

1993 ◽  
Vol 155 ◽  
pp. 323-323
Author(s):  
I. L. Andronov ◽  
L. S. Kudashkina ◽  
G. M. Rudnitskij
Keyword(s):  
Radio Emission ◽  
Molecular Species ◽  
Light Curves ◽  
Evolutionary Status ◽  
Maser Emission ◽  
Radio Line ◽  
History Of ◽  
Maser Radio

We have collected all the available data on light curves, OH, H2O and SiO maser observations for a sample of Mira-type variables. We consider in detail the data on two stars, U Ori and R Leo. There is a net correlation between optical and radio line variations for all the three molecular species in these stars. More pronounced maser flares seem to follow brighter-than-average visual maxima of the stars. We discuss also the drastic changes in the type of the OH maser radio emission which happened in these stars some years ago. Implications for the mechanisms of maser pumping and the evolutionary status of these stars (probably undergoing the helium flash) are discussed.

History of the Light Curves and Molecular Maser Emission of the Miras U Ori and R Leo

1993 ◽  
pp. 323-323
Author(s):  
I. L. Andronov ◽  
L. S. Kudashkina ◽  
G. M. Rudnitskij
Keyword(s):  
Light Curves ◽  
Maser Emission ◽  
History Of

scholarly journals On the Short Time Scale Evolutionary History of the Contact Binary VW Cephei

1998 ◽  
Vol 11 (1) ◽  
pp. 396-396
Author(s):  
I. Pustylnik
Keyword(s):  
Evolutionary History ◽  
Light Curves ◽  
Published Data ◽  
Short Time Scale ◽  
Flare Activity ◽  
Considerable Portion ◽  
History Of ◽  
Contact Binary ◽  
Elongation Phase ◽  
Short Time

We study the short-time evolutionary history of the well-known contact binary VW Cep. Our analysis is based partly on the numerous UBV lightcurves obtained at Tartu Observatory, IUE spectra, and samples from the published data. Special attention is given to the effects of asymmetry of the light curves. A higher degree of asymmetry outside the eclipses along with the significant displacements of the brightness maxima in respect to the elongation phase is interpreted as evidence that a considerable portion of the flaring source is concentrated close to the neck connecting the components. We discuss the nature of asymmetry in terms of possible mass exchange and the flare activity and compare the results of our model computations with the record of orbital period variations over the last 60 years.

scholarly journals Bulge δ Scuti stars in the MACHO database

1997 ◽  
Vol 189 ◽  
pp. 293-298
Author(s):  
D. Minniti ◽  
C. Alcock ◽  
D.R. Alves ◽  
T.S. Axelrod ◽  
A.C. Becker ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
High Amplitude ◽  
Light Curves ◽  
Evolutionary Status ◽  
Absolute Magnitudes ◽  
Scuti Stars ◽  
Δ Scuti Stars

We describe the search for δ Scuti stars in the MACHO database of bulge fields. Concentrating on a sample of high amplitude δ Scutis, we examine the light curves and pulsation modes. We also discuss their spatial distribution and evolutionary status using mean colors and absolute magnitudes.

scholarly journals High Redshift Radio Galaxies

1996 ◽  
Vol 175 ◽  
pp. 571-576
Author(s):  
K. Meisenheimer ◽  
H. Hippelein ◽  
M. Neeser
Keyword(s):  
Radio Emission ◽  
Electromagnetic Waves ◽  
High Redshift ◽  
Radio Galaxies ◽  
Early History ◽  
Radio Telescopes ◽  
Radio Waves ◽  
History Of ◽  
The Universe ◽  
Travel Distances

One hundred years after G. Marconi recorded radio waves over a distance of more than 1000 m, the most sensitive radio telescopes are able to detect the radio emission from light travel distances at least 1.4 × 1023 times greater. The electromagnetic waves from these distant objects are red shifted by Δλ/λ = z > 4. It is not the mere distance of high redshift objects which is fascinating, but rather the fact that one looks back into the early history of the universe by observing them: Objects at a redshift of 4 shined at a time when the universe had reached only about 1/5 of its present age.

scholarly journals Whence the pulses?

1996 ◽  
Vol 160 ◽  
pp. 139-146 ◽  
Author(s):  
D.B. Melrose
Keyword(s):  
Radio Emission ◽  
Pair Production ◽  
Emission Mechanism ◽  
Maser Emission ◽  
Light Cylinder

AbstractRadio emission mechanisms for pulsars are reviewed with emphasis on five possible sites for the emission: the pair production front (PPF), two regions in the relativistically outflowing plasma (denoted ROP1 and ROP2) between the PPF and the light cylinder (LC), and two sited near the LC. Several maser emission mechanism are viable for ROP1, where radius-to-frequency mapping applies. Suggested Schott radiation from outside the LC is discussed critically.

scholarly journals Some patterns in the development of centers of solar activity, 1962–66

1968 ◽  
Vol 35 ◽  
pp. 56-63 ◽  
Author(s):  
Helen W. Dodson ◽  
E. Ruth Hedeman
Keyword(s):  
Solar Activity ◽  
Radio Emission ◽  
Differential Rotation ◽  
Graphical Representation ◽  
Past History ◽  
The Sun ◽  
Active Centers ◽  
Opposite Hemisphere ◽  
The Past ◽  
History Of

A graphical representation of the 66 solar rotations (Carrington) between January 1, 1962 and December 31, 1966 has been prepared. It includes all centers of activity for which the calcium plage attained an area of at least 1000 millionths of the solar hemisphere and/or intensity 3 (McMath scale). In this study the antecedents, descendents, and neighbors of each region can easily be discerned. The work shows clearly that zones of activity, apparently closely related and much larger than single plages existed for long intervals of time. For example, the significant increases in solar activity in February, May, and October of 1965 occurred in a ‘family’ of calcium plages apparently related through similarities of position and strong radio emission.The members of ‘families’ of centers of activity are found at systematically changing longitudes. For some ‘families’ the change of longitude appears to be primarily a consequence of differential rotation; for others, the pattern of formation of active centers dominates.According to the data for 1962–66 a meaningful study of the development of a center of activity may require consideration not only of the past history of the zone of the Sun in which it occurs but also of the zone approximately 180° away on the opposite hemisphere.

Flares of H2O maser radio line in the sources GDD 25 and Sgr B2

Astrophysics ◽  
1989 ◽  
Vol 30 (1) ◽  
pp. 71-75
Author(s):  
I. V. Gosachinskii ◽  
R. A. Kandalyan ◽  
F. S. Nazaretyan ◽  
N. A. Yudaeva
Keyword(s):  
Radio Line ◽  
Maser Radio

scholarly journals Radio Supernovae

1983 ◽  
Vol 101 ◽  
pp. 171-176
Author(s):  
K. W. Weiler ◽  
R. A. Sramek ◽  
J. M. van der Hulst ◽  
N. Panagia
Keyword(s):  
Radio Emission ◽  
Light Curves ◽  
Type I ◽  
Extensive Data ◽  
Radio Range ◽  
One Year

Three supernovae have so far been detected in the radio range shortly after their optical outbursts. All are Type IIs. A fourth supernova, a Type I, is being monitored for radio emission but, at an age of approximately one year, has not yet been detected. For two of the supernovae, extensive data are presented on their “light curves” and spectra and models which have been suggested in the literature are discussed.

scholarly journals On the evolutionary status and instability mechanism of the Luminous Blue Variables (LBV)

1989 ◽  
Vol 113 ◽  
pp. 15-26
Author(s):  
André Maeder
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Light Curves ◽  
Evolutionary Status ◽  
Average Mass ◽  
Luminous Blue Variables ◽  
Ir Sources ◽  
Order Of Magnitude ◽  
Lower Luminosity

AbstractVarious evolutionary sequences leading to LBV are examined. The sequence O-Of-LBV-WR-SN is well supported by the models; some LBV with relatively lower luminosity may turn into OH/IR sources. The overall duration of the LBV phase depends mainly on the average mass loss rate; for <Ṁ> = 10−3M⊙y−1, it lasts about 104y.Very massive stars undergo, when they reach logTeff= 3.9, strong departure from hydrostatic equilibrium due to supra-Eddington luminosities at some depth in the outer layers. This results in heavy mass loss, as the growth rate of the instability is very fast. We suggest that the amount of mass ejected in a shell episode is mainly determined by the mass of such a layer that its thermal adjustment timescale is within an order of magnitude of the stellar dynamical timescale. Simulations of B-light curves due to shell ejections by LBV are performed and some sensitive properties are identified.

scholarly journals An Update on Radio Supernovae

1998 ◽  
Vol 164 ◽  
pp. 357-358 ◽  
Author(s):  
Schuyler D. Van Dyk ◽  
Richard A. Sramek ◽  
Kurt W. Weiler ◽  
Marcos J. Montes ◽  
Nino Panagia
Keyword(s):  
Synchrotron Radiation ◽  
Radio Emission ◽  
Brightness Temperature ◽  
Power Law ◽  
Progress Report ◽  
Light Curves ◽  
High Brightness ◽  
Turn On ◽  
Distance Indicators ◽  
Circumstellar Environment

AbstractThe radio emission from supernovae (SNe) is nonthermal synchrotron radiation of high brightness temperature, with a “turn-on” delay at longer wavelengths, power-law decline after maximum with index β, and spectral index α asymptotically decreasing with time to a final, optically thin value. Radio supernovae (RSNe) are best described by the Chevalier (1982) “mini-shell” model, with modifications by Weiler et al. (1990). RSNe observations provide a valuable probe of the SN circumstellar environment and constraints on progenitor masses. We present a progress report on a number of recent RSNe, as well as on new behavior from RSNe 1979C and 1980K, and on RSNe as potential distance indicators. In particular, we present updated radio light curves for SN 1993J in M81.

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