scholarly journals Double-Peaked Flare Events on red Dwarf Stars and Solar ‘Sympathetic’ Flares

1976 ◽  
Vol 71 ◽  
pp. 475-475
Author(s):  
M. Rodonò
Keyword(s):  
Proximity Effect ◽  
Binary Systems ◽  
Angular Separation ◽  
Dwarf Stars ◽  
Multiple Systems ◽  
Photometric Observations ◽  
Red Dwarfs ◽  
Flare Stars ◽  
Red Dwarf Stars ◽  
The Individual

About 50% of the flare events observed on red dwarfs are at least double-peaked. As the majority of flare stars are members of double or multiple systems, the possibility that time-overlapping flares originate quasi-simultaneously on the individual components is discussed.Assuming a poissonian occurrence of flares in both components, the expected probability of observing double-peaked flares is lower than 1% for the most active binary systems.However, from photometric observations of the double flare star EQ Peg (BD +19°5116 AB) carried out by the author with an area scanner (the components' angular separation is 3.7″) about 20% of the observed flares have been found to be double-peaked flares resulting from separate flares, one in each component. A direct flare triggering of the following flare by the preceding one can be ruled out since the light travel-time between the two components is 3.5 h, while the observed time delay between the flare peaks is about 10 min. Moreover, the proximity effect does not seem to play an important triggering role.It is concluded that, although the analogy with solar ‘sympathetic’ flares is not always applicable, it is the most promising framework within which the majority of double-peaked flare events on red dwarfs must be interpreted.

scholarly journals Flare Activity Among Nearby Stars

1995 ◽  
Vol 151 ◽  
pp. 61-62 ◽  
Author(s):  
N.I. Shakhovskaya
Keyword(s):  
Background Radiation ◽  
Flare Activity ◽  
Dwarf Stars ◽  
Photometric Variability ◽  
Red Dwarfs ◽  
Nearby Stars ◽  
Flare Stars ◽  
The Common ◽  
Red Dwarf Stars ◽  
Absolute Magnitudes

I selected the common objects from our Data Base on 234 UV Cet Flare Stars and Related Objects and the Third Catalogue of Nearby Stars by Gliese & Jahreiss (CNS-3). It is found that manifestation of flare activity (FA) (flares in any spectral region or photometric variability caused by spots) is observed on 143 flare stars (FS) out of the 3803 CNS-3 stars within 25 pc of the Sun with absolute magnitudes Mv from 5.2 (Sp G2 V) to 18.8 (Sp dM5e − dM6e).Magnitudes and spectra of flare stars: For each MV-interval, Table 1 gives the “mean” spectral class (Sp), the number of FS (Nf) and the portion of FS among other red dwarf stars from CNS-3 (Nf/N). Absolutely fainter stars include a higher portion of known FS. However, observational selection effects can cause this dependence, because the probability is higher to register flares over the background radiation of a faint star. The observed portion of FS among all red dwarfs from CNS-3, which are fainter than Mv=5, is about 5%.

scholarly journals Wide-Field Photographic Versus Wide-Field CCD Techniques in the Activity Analysis of dM Stars

1994 ◽  
Vol 161 ◽  
pp. 61-64
Author(s):  
G. Szécsényi-Nagy
Keyword(s):  
Variable Stars ◽  
Activity Level ◽  
Wide Field ◽  
Dwarf Stars ◽  
Photoelectric Photometry ◽  
Stellar Flares ◽  
Red Dwarfs ◽  
The Galaxy ◽  
Flare Stars ◽  
Red Dwarf Stars

The Galaxy is abundant in red dwarf stars. According to statistical analyses, their majority is unstable. Simultaneously, more than 60% of the variable stars known in the solar vicinity (r < 20 pc) are flare stars and taking into account the number of BY Dra stars too the proportion of red dwarfs amongst local variables is superior to three quarters. Their absolute visual magnitudes range from +6 to +17.5 or even more (Szécsényi-Nagy 1986a). During flare events their brightness may reach a maximum corresponding to an enhancement of 1000–10,000 times. The amplitude of a large flare in the U band may be as high as 8–10 magnitudes. The events take place nonperiodically in unpredictable moments; no unquestionable periodicity has been found in the time distribution of stellar flares. However the activity level of various flare stars is considerably different. Some of them show observable flare ups with a mean frequency of 1 per hour whilst others produce only one event per annum. For the scarcity of the phenomenon, traditional photoelectric photometry of individual stars is not an adequate means to a better understanding of flare stars.

scholarly journals Interferometric Investigations of Eclipsing Binaries as a Key to an Improved Distance Scale

2006 ◽  
Vol 2 (S240) ◽  
pp. 496-498
Author(s):  
K. Shabun ◽  
A. Richichi ◽  
U. Munari ◽  
A. Siviero ◽  
B. Pacsysnki
Keyword(s):  
Spectral Type ◽  
Effective Temperature ◽  
Binary Systems ◽  
Angular Separation ◽  
Eclipsing Binaries ◽  
Multiple Systems ◽  
Long Baseline ◽  
Global Calibration ◽  
Empirical Calibration ◽  
Full Solution

AbstractBinary and multiple systems constitute one of the main tools for obtaining fundamental stellar parameters, such as masses, radii, effective temperatures and distances. One especially fortunate, and at the same time rare, occurrence is that of double-lined eclipsing binaries with well-detached components. In this special case, it is possible to obtain a full solution of all orbital and stellar parameters, with the exception of the effective temperature of one star, which is normally estimated from spectral type or derived from atmospheric analysis of the spectrum. Long-baseline interferometry at facilities such as the ESO VLTI is beginning to have the capability to measure directly the angular separation and the angular diameter of some selected eclipsing binary systems, and we have proposed such observations with the AMBER instrument. In particular, we aim at deriving directly the effective temperature of at least one of the components in the proposed system, thereby avoiding any assumptions in the global solution through the Wilson–Devinney method. We will also obtain an independent check of the results of this latter method for the distance to the system. This represents the first step towards a global calibration of eclipsing binaries as distance indicators. Our results will also contribute to the effective temperature scale for hot stars. The extension of this approach to a wider sample of eclipsing binaries could provide an independent method to assess the distance to the LMC. The observations will extend accurate empirical calibration to spectral type O9 – B0.

scholarly journals Origin of Binary Systems

1992 ◽  
Vol 151 ◽  
pp. 9-19
Author(s):  
Peter Bodenheimer
Keyword(s):  
Angular Momentum ◽  
Binary Systems ◽  
Theoretical Calculations ◽  
Pressure Effects ◽  
Close Binaries ◽  
Rotating Stars ◽  
Multiple Systems ◽  
The Individual ◽  
Protostellar Collapse ◽  
Three Body

Recent observational studies of the properties of binary systems among young stars indicate that the majority of binaries are formed very early in the history of a star, perhaps during the protostellar collapse. Major observational facts to be explained include the overall binary frequency, the non-negligible occurrence of multiple systems, and the distributions of period, eccentricity, and mass ratio among the individual binaries. Theoretical calculations of the collapse of rotating protostars during the isothermal phase indicate instability to fragmentation into multiple systems. This process in general produces systems with periods greater than a few hundred years, although somewhat shorter periods are possible. Fragmentation during later, optically thick, phases of collapse tends to be suppressed by pressure effects. Therefore, major theoretical problems remain concerning the origin of close binaries. Fission of rapidly rotating stars, tidal capture, and three-body capture have been shown to be improbable mechanisms for formation of close binaries. Mechanisms currently under study include gravitational instabilities in disks, orbital interactions and disk-induced captures in fragmented multiple systems, hierarchical fragmentation, and orbital decay of long-period systems. Single stars, on the other hand, could result by escape from multiple systems or by the collapse of clouds of low angular momentum, coupled with angular momentum transport after disk formation.

scholarly journals The Red Dwarf Star Population in the Galaxy

1995 ◽  
Vol 151 ◽  
pp. 55-56 ◽  
Author(s):  
L.V. Mirzoyan
Keyword(s):  
Star Clusters ◽  
Space Distribution ◽  
Dwarf Star ◽  
Star Clusters And Associations ◽  
Dwarf Stars ◽  
The Galaxy ◽  
Flare Stars ◽  
Red Dwarf Stars ◽  
T Tau ◽  
Stellar Associations

Red dwarf stars in the Galaxy occur in three forms: as flare stars, T Tau stars and red dwarf stars of constant brightness. Haro (1957) suggested that all these stars present regular evolutionary stages of red dwarf stars.The space distribution of UV Cet flare stars in the solar vicinity indicates that these low luminosity stars belong to the disk population of the Galaxy. Therefore one can suppose that all red dwarf stars have a space distribution which is similar to that of the flare stars (Mirzoyan et al. 1988a). Only a small part of them is found in star clusters and associations. The T Tau stars are an exception: because of their very short lifetime, all of them are found in stellar associations.The space distribution of red dwarf stars is determined by the fact that all of them are formed in star clusters and associations and are finally lost from their stellar systems and merge into the general galactic field (Mirzoyan 1995).

scholarly journals A Report on Flare Stars on the Sproul Astrometric Program

1971 ◽  
Vol 15 ◽  
pp. 109-109
Author(s):  
Sarah Lee Lippincott
Keyword(s):  
Long Range ◽  
Dwarf Stars ◽  
Nearby Stars ◽  
Flare Stars ◽  
Red Dwarf Stars ◽  
O 10 ◽  
Photographic Records

The long range program of the Sproul Observatory initiated in 1937 by P. VAN DE KAMP has been primarily devoted to a detailed astrometric study of the positions of nearby stars from photographs taken with the 24-inch refractor. By now there are 30 years of observations on most stars with parallaxes greater than + O″10 and brighter than the 12th magnitude which are observable at latitude +40°. It follows therefore that there are long series of photographic records of many red dwarf stars.

scholarly journals Distribution of red dwarfs in general galactic field on the basis of stellar star statistics

1990 ◽  
Vol 137 ◽  
pp. 59-62
Author(s):  
A.T. Garibjanian ◽  
V.V. Hambarian ◽  
L.V. Mirzoyan ◽  
A.L. Mirzoyan
Keyword(s):  
Uniform Distribution ◽  
Total Mass ◽  
Luminosity Function ◽  
Stellar Flare ◽  
Dwarf Stars ◽  
Galactic Field ◽  
Red Dwarfs ◽  
The Galaxy ◽  
Ceti Type ◽  
Red Dwarf Stars

The mathematical expectation for detection of stellar flare on UV Ceti type stars in the solar vicinity during photographic patrol observations with 40″ Shcmidt camera of the Byurakan Astrophysical Observatory is estimated. We use the luminosity function of the flaring red dwarfs the assume a uniform distribution in the general galactic field. Comparison with the results of photographic patrol supports this assumption. The numbers and total mass of the flare and non-flare red dwarf stars in the Galaxy for the uniform distribution are determined. They are not in contradiction with Oort's estimate of total mass of red dwarfs.

scholarly journals Radio Continuum Observations of Stellar Sources

1974 ◽  
Vol 60 ◽  
pp. 377-381
Author(s):  
L. L. E. Braes
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Early Stage ◽  
Planetary Nebulae ◽  
Radio Continuum ◽  
Red Dwarfs ◽  
Red Supergiants ◽  
Flare Stars ◽  
Stellar Sources

Thirty optically visible stellar sources have been observed in the radio continuum: four red dwarf flare stars, three novae, two red supergiants, eight binary systems, and 13 related peculiar objects. The observations of red dwarfs, novae, and supergiants are briefly reviewed. Their emission seems reasonably well understood. Binary systems such as Algol show erratic flaring; consistent explanations have not yet been given. The related peculiar objects, such as V1016 Cyg and MWC 349, are even less well understood. Some of them may have just arrived on the main sequence; others may be planetary nebulae in an early stage of formation.

Flare stars and the evolution of red dwarf stars

Astrophysics ◽  
1994 ◽  
Vol 36 (2) ◽  
pp. 170-191 ◽  
Author(s):  
A. V. Mirzoyan
Keyword(s):  
Dwarf Stars ◽  
Flare Stars ◽  
Red Dwarf Stars

ENVIRONMENTAL EFFECTS OF FLARES FROM RED DWARF STARS

2011 ◽  
Vol 20 (supp02) ◽  
pp. 37-41
Author(s):  
LIUBA PEÑATE ◽  
ROLANDO CÁRDENAS ◽  
OSMEL MARTÍN
Keyword(s):  
Environmental Effects ◽  
Life Forms ◽  
Habitable Zone ◽  
Dwarf Stars ◽  
Planet Surface ◽  
Star Evolution ◽  
Stellar Flares ◽  
Red Dwarfs ◽  
Red Dwarf Stars ◽  
Radiative Perturbation

We examine some environmental effects appearing on exoplanets in the habitable zone of red dwarfs, during the first billion years of the star evolution. We focus on the radiative perturbation that the frequent stellar flares would cause on the planet surface and down the assumed planetary ocean, with some insight on the affectation of potential life forms.

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