Stellar flares represent one of the most challenging problems of contemporary astrophysics. Both solar and stellar observations have shown the flare phenomenon to be very complex, and in recent years important progress has been made from simultaneous observations over wide wavelength ranges. Some similarities exist between solar and stellar flares, but im- portant differences have also been established. Such topics, as well as theoretical aspects, were discussed in detail at the Palo Alto IAU Colloquium No. 104, Solar and Stellar Flares, in 1988. Another approach to the study of stellar flares is through observations of flare stars in physical systems. The possibility of detecting flare stars in star clusters and associations with wide angle telescopes have allowed observations of systems with quite different ages. The classical works of G. Haro and V. A. Ambartsumian demonstrated the evolutionary nature of the flare phenomenon. Flares occur at the earliest stages of dwarf star evolution. The photographic observations of flare stars in systems of different ages turned out to be significant not only for the evolutionary study of flare stars, but also for the study of their physical nature. This observational fact was conditioned by very large diversity of flare star luminosities, i.e. of scales of flares produced by them and by peculiarities of stellar flares observed in star clusters and associations.
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Space Science Reviews 61:422 (1992)
I. Flare Stars. Optical Observations and Flare Statistics.- Flare stars in star clusters, associations and solar vicinity (Invited paper).- The flare activity of AD Leo1972-1988.- Photometrical, spectral and radio monitoring for EV Lac in 1986 and 1987.- Electrophotometric observations of the EV Lac flares in U, H? and H?.- Rapid spike flares on AD Leo and EV Lac.- Photoelectric observations of flares on UV Ceti.- Two-colour observations of spikes and flares with high time resolution.- A short-lived flare on EV Lacertae.- Diagnostic possibilities of the Walrawen photometric system.- The flare activity of two peculiar red dwarfs.- Statistics of flares observed for UV Ceti type stars YZ CMi, AD Leo, and EV Lac at the Okayama Observatory.- Flare activity levels for fully convective red dwarfs.- Some physical consequences from the flare statistics of the UV Cet type stars in the solar neighbourhood.- Search for slow light variations of red-dwarf stars.- Distribution of red dwarfs in general galactic field on the basis of stellar star statistics.- New observations of flare stars in the Pleiades by the method of stellar tracks.- Possible new, bright flare star in the Pleiades region.- Data filtering in statistical studies of flares recorded in sky fields of stellar aggregates - demonstrated with the example of the Pleiades.- On two possible groups of flare stars in Pleiades.- Flare activity of stars in the Taurus region.- An automatic search for flare stars in southern stellar aggregates of different ages.- Spectral observations of flare stars.- NTT spectra of the flare stars HM1 and HM2 in the R Coronae Austrinae aggregate.- Catalog of flare stars in Orion nebula region.- A catalogue of flare stars in the Cygnus region.- Slow flares in stellar aggregates and solar vicinity.- A prediction of the flare activity of stellar aggregates.- Flare stars as age indicators in open clusters.- The relative number of flare stars in systems of different ages.- Flare stars at radio wavelengths (Invited paper).- Broadband spectral radio observations of flare stars.- Radio flare on eta Gemini star.- X-ray emission from solar neighbourhood flare stars.- Balmer and soft X-ray emission from solar and stellar flares.- X-ray variability in the Orion nebula.- II. Flare Stars and Related Objects. T Tauri Stars..- Some resolutions on T Tauri stars (Invited paper).- The variability of T Tauri stars.- Periodical variations of the brightness of T Tauri.- The polarization discovery and investigation of T Tau stars in Byurakan.- Recent results on polarization of T Tauri stars and other young stellar objects.- The UBVRI photometric and Polarimetric observations of the T Tau star HDE 283572.- Axial rotation of BY Dra-type stars and related objects.- Flares on T Tauri stars (Invited paper).- T Tauri stars and flare stars: common properties and differences.- Circumstellar phenomena and the position of T Tauri stars in the colour-magnitude diagram.- High resolution spectroscopy of RY Tauri: variability of the Na D line profiles.- Herbig-Haro phenomena associated with T Tauri: evidence for a precessing jet?.- Survey observations of emission line stars and Herbig-Haro objects at the Kiso Observatory.- III. Flare Stars and Related Objects. Fuors and Other Non-Stable Objects..- FU Orionis eruptions and early stellar evolution (Invited paper).- Subfuors in Orion association.- Slow flares and eruptive phenomena in early stages of stellar evolution.- A new fuor?.- Correlation between flare stars and other populations in young clusters and star forming regions.- The results of spectral observations of collimated outflows.- H2O megamaser in Orion KL.- Flares of radio line emission H2O in Ori A and W49N.- On the connection between the IRAS point sources and galactic nonstable objects.- The statistical analysis of the optical and infrared luminosities of young stars.- Far infrared emission from post-T Tauri stars.- Residual extinction effects in spectra of newly formed stars.- IV. Theoretical Problems and Interpretation of Observations..- Review of the theoretical models of flares of the UV Ceti-type stars (Invited review).- Quiescent chromospheric response to the (E)UV/optical flare radiation field on dMe stars.- The hydrogen atom kinetics in flare star chromospheres.- The Balmer decrement in red dwarfs spectra during the flares and quiescent state.- A model for the observed periodicity in the flaring rate on YY Gem.- Pinch-model of flares and its observational consequences.- On the gamma-activity of stellar flares.- On a differential equation for electromagnetic wave transmission in flare stars and the possible existance of cohesive wave solutions.- The stochastical approach to the modelling of the line profiles in T Tauri stellar winds.- On the origin of dwarf stars (Invited review).- Magnetic activity and evolution of low-mass young stars.- V. Prospects for Stellar Flare Research and Concluding Remarks..- Prospects for studies of UV Cet-type flare stars (Invited review).- Closing remarks.- Author index.- Object index.
Series: International Astronomical Union Symposia
Number Of Pages: 410
Published: 30th June 1990
Country of Publication: NL
Dimensions (cm): 22.86 x 15.24
Weight (kg): 0.63