6.2.3.8 UV Ceti type stars (flare and flash stars) - UV

2005 ◽  
pp. 560-561
Author(s):  
M. Beyer
Keyword(s):  
Ceti Type ◽  
Stars Flare

scholarly journals By Draconis and RS Canum Venaticorum Stars: The Discoveries of Classical Photometry and Spectroscopy

1980 ◽  
Vol 5 ◽  
pp. 847-848 ◽  
Author(s):  
Bernard W. Bopp
Keyword(s):  
Spectroscopic Binaries ◽  
Physical Parameters ◽  
Late Type ◽  
Double Line ◽  
Strong Emission ◽  
Rs Cvn Stars ◽  
Ceti Type ◽  
The Common ◽  
Orbital Periods ◽  
Detached Binaries

Physically quite dissimilar, the BY Dra and RS CVn stars have the common characteristic of extraordinarily high levels of stellar surface activity.The RS CVn group, as defined by Hall, consists of detached binaries both components of types F, G, or K. The orbital periods are from a few days to a few weeks, and the mass ratios are generally near unity. Spectroscopically, the stars are remarkable in that they show very strong Ca II H and K emission outside eclipse. Masses and radii are known for many of these systems; physical parameters indicate these systems contain a moderately evolved subgiant, with mass slightly greater than 1 M⊚. The ages (which may be verified by data on visual companions) are a few 10 years.In contrast, the BY Dra variables are late-type dwarfs, with spectral types ranging from dK5e to dM4e. The e designation indicates the presence of Balmer emission, which is generally visible in moderate strength at Ha and only very weakly present in the blue. The BY Dra stars do exhibit strong emission at H and K, however, and also show UV Ceti-type flares. Approximately 75% of the BY Dra variables are known as double-line spectroscopic binaries.

scholarly journals Quiescent and flaring lyman-α radiation of host stars and effects on exoplanets

2015 ◽  
Vol 11 (S320) ◽  
pp. 391-396
Author(s):  
Jeffrey L. Linsky ◽  
Kevin France ◽  
Yamila Miguel ◽  
Lisa Kaltenegger
Keyword(s):  
Emission Lines ◽  
Late Type ◽  
Chemical Abundances ◽  
Interstellar Absorption ◽  
Ultraviolet Spectra ◽  
M Stars ◽  
Host Stars ◽  
Stars Flare ◽  
Photochemical Models

AbstractLyman-α radiation dominates the ultraviolet spectra of G, K, and M stars and is a major photodissociation source for H2O, CO2, and CH4 in the upper atmospheres of exoplanets. We obtain intrinsic Lyman-α line fluxes for late-type stars by correcting for interstellar absorption or by scaling from other spectroscopic observables. When stars flare, all emission lines brighten by large factors as shown by HST spectra. We describe photochemical models of the atmosphere of the mini-Neptune GJ 436b (Miguel et al. 2015) that show the effects of flaring Lyman-α fluxes on atmospheric chemical abundances.

FLARES OF STARS OF THE UV CETI TYPE

1967 ◽  
Vol 10 (3) ◽  
pp. 307-312
Author(s):  
Roald E Gershberg
Keyword(s):  
Ceti Type

scholarly journals Flare Stars Database

1994 ◽  
Vol 161 ◽  
pp. 380-382
Author(s):  
M. Tsvetkov ◽  
M. Chukova ◽  
K. Tsvetkova
Keyword(s):  
Wide Field ◽  
Flare Activity ◽  
The Galaxy ◽  
Statistical Regularities ◽  
Ceti Type ◽  
Formation And Evolution ◽  
Flare Stars ◽  
Machine Readable

The important role of flare stars (UV Ceti type variables) in astrophysics is due to the fact that the flare activity is not only typical for red stars with small masses but is a necessary stage during their evolution. The flare star search in stellar aggregates has led to the accumulation of rich observational material allowing us to look for statistical regularities in star formation and evolution. At present, there are more than 1500 known flare stars in the Galaxy; these were discovered mainly during the last 30 years. Most results of the long term monitoring with wide-field telescopes are listed in existing catalogues of flare stars in stellar aggregates and in the solar neighbourhood. These catalogues and their machine-readable versions were the basis for the present database of flare stars in the Galaxy.

scholarly journals Multiwavelength Studies of Mira Ceti-type Variable Stars

1999 ◽  
Vol 191 ◽  
pp. 201-206 ◽  
Author(s):  
V.F. Esipov ◽  
M.I. Pashchenko ◽  
G.M. Rudnitskij ◽  
M.V. Kozin ◽  
E.E. Lekht ◽  
...  
Keyword(s):  
Time Series ◽  
Emission Intensity ◽  
Variable Stars ◽  
Optical Variability ◽  
Line Flux ◽  
Maser Line ◽  
Type Variable ◽  
Hα Emission ◽  
Ceti Type ◽  
Spectral Ranges

Since 1994, observations of a sample of about 20 Mira Ceti-type and semiregular variables have been carried out in three spectral ranges: radio (H2O maser line λ = 1.35 cm), optical (spectroscopy and UBV photometry) and infrared (JHKLM photometry). Time series of the Hα emission intensity and H2O line flux, covering several periods of the stars, have been obtained. Correlation of the intensity variations of the H2O maser with optical variability in the maser stars RR Aql, U Ori, VX Sgr and others was confirmed. One of the most interesting results is the flare of the H2O maser emission in R Leo, which happened in autumn 1997, 14 months after a flare of the Hα emission.

scholarly journals X-ray flares on the UV Ceti-type star CC Eridani: a “peculiar” time-evolution of spectral parameters

2007 ◽  
Vol 471 (3) ◽  
pp. 929-939 ◽  
Author(s):  
I. Crespo-Chacón ◽  
G. Micela ◽  
F. Reale ◽  
M. Caramazza ◽  
J. López-Santiago ◽  
...  
Keyword(s):  
Time Evolution ◽  
Type Star ◽  
Spectral Parameters ◽  
X Ray ◽  
Ceti Type

scholarly journals X-Ray Superflares from Pre-main-sequence Stars: Flare Energetics and Frequency

2021 ◽  
Vol 916 (1) ◽  
pp. 32
Author(s):  
Konstantin V. Getman ◽  
Eric D. Feigelson
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
X Ray ◽  
Stars Flare

Vibrational Instabilities and Pulsational Properties of Cool White Dwarfs

1979 ◽  
Vol 53 ◽  
pp. 359-373 ◽  
Author(s):  
W. Dziembowski
Keyword(s):  
Mode Coupling ◽  
White Dwarfs ◽  
Dominant Role ◽  
Nonlinear Effects ◽  
Resonant Mode ◽  
Finite Amplitude ◽  
Oscillation Modes ◽  
Type Variable ◽  
Ceti Type ◽  
Cool White Dwarfs

AbstractAttention is focused on those aspects of the theory that may be relevant in understanding the nature of ZZ Ceti-type variable white dwarfs. Recent calculations show that the opacity mechanism can drive a large variety of oscillation modes, including the ones that fit observed periods. An estimate of nonlinear effects shows that resonant mode coupling plays a dominant role in determining the finite amplitude behaviour of oscillations and is also probably responsible for rapid amplitude changes observed in these variables.

scholarly journals Statistics of flares observed for UV Ceti type stars YZ CMi, AD Leo, and EV Lac at the Okayama Observatory

1990 ◽  
Vol 137 ◽  
pp. 43-47
Author(s):  
K. Ishida
Keyword(s):  
Time Resolution ◽  
High Time ◽  
High Time Resolution ◽  
Ceti Type ◽  
Flare Stars ◽  
Ev Lac

Photoelectric monitoring of flare stars YZ CMi, AD Leo, and EV Lac has been done at the Okayama Observatory since early 1970s. This is a simultaneous UBV observations with a high time resolution. Some statistics of the flares of the UV Ceti type stars are presented.

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.

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