Characteristics of activity energetics of the UV cet-type flare stars

Гершберг, Р. Е.; Shakhovskaya, N. I.

doi:10.1007/bf00653631

Cited by 87 publications

(72 citation statements)

References 16 publications

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“…The flare energy, which is expressed by Equation (2) given by Gershberg (1972), has generally been used to examine the level of flare activity in many studies (see, e.g., Mazeh et al 2001;Lacy et al 1976;Walker 1981;Gershberg & Shakhovskaya 1983;Pettersen et al 1984;Mavridis & Avgoloupis 1986). The luminosity parameter L occurs in the expression of the energy E, as in all these and other studies.…”

Section: Resultsmentioning

confidence: 99%

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Saturation Levels for White-Light Flares of Flare Stars: Variation of Minimum Flare Duration for Saturation

Dal¹,

Evren²

2010

The Astronomical Journal

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Taking into account results obtained from models and from statistical analyses of obtained parameters, we discuss flare activity levels and flare characteristics of five UV Ceti stars. We present the parameters of unpublished flares detected over two years of observations of V1005 Ori. We compare parameters of the U-band flares detected over several seasons of observations of AD Leo, EV Lac, EQ Peg, V1054 Oph, and V1005 Ori. Flare frequencies calculated for all program stars and maximum energy levels of the flares are compared, and we consider which is the most correct parameter as an indicator of flare activity levels. Using the One Phase Exponential Association function, the distributions of flare equivalent duration versus flare total duration are modeled for each program star. We use the Independent Samples t-Test in the statistical analyses of the parameters obtained from the models. The results reveal some properties of flare processes occurring on the surfaces of UV Ceti type stars. (1) Flare energies cannot be higher than a specific value regardless of the length of the flare total duration. This must be a saturation level for white-light flares occurring in flare processes observed in the U band. Thus, for the first time it is shown that white-light flares have a saturation in a specific energy range. (2) The span values, which are the difference between the equivalent durations of flares with the shortest and longest total durations, are almost equal for each star. (3) The half-life values, minimum flare durations for saturation, increase toward the later spectral types. (4) Both maximum total durations and maximum rise times computed from the observed flares decrease toward the later spectral types among the UV Ceti stars. According to the maximum energy levels obtained from the models, both EV Lac and EQ Peg are more active than the other three program stars, while AD Leo is the most active flare star according to the flare frequencies.

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Section: Resultsmentioning

confidence: 99%

“…However, observations made over 50 years show that flare energies of UV Ceti stars rise from 10 28 erg to 10 34 erg (Gershberg 2005). Moreover, when flare stars in young clusters such as the Pleiades cluster and Orion association are considered, their flare energies can reach 10 36 erg (Gershberg & Shakhovskaya 1983).…”

Section: Introductionmentioning

confidence: 99%

Saturation Levels for White-Light Flares of Flare Stars: Variation of Minimum Flare Duration for Saturation

Dal¹,

Evren²

2010

The Astronomical Journal

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“…Lacy et al (1976) and Gershberg & Shakhovskaia (1983) found high optical flare rates, however, at the lowest flare energies in their samples of UV Ceti stars. Robinson et al (1995) analyzed UV flare events on CN Leo down to the microflare scale observed with the High Speed Photometer onboard HST.…”

Section: The Active M Dwarf Cn Leomentioning

confidence: 90%

Multiwavelength observations of a giant flare on CN Leonis

Liefke¹,

Fuhrmeister²,

Schmitt³

2010

A&A

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Context. Stellar flares affect all atmospheric layers from the photosphere over chromosphere and transition region up into the corona. Simultaneous observations in different spectral bands allow to obtain a comprehensive picture of the environmental conditions and the physical processes going on during different phases of the flare. Aims. We investigate the properties of the coronal plasma during a giant flare on the active M dwarf CN Leo observed simultaneously with the UVES spectrograph at the VLT and XMM-Newton. Methods. From the X-ray data, we analyze the temporal evolution of the coronal temperature and emission measure, and investigate variations in electron density and coronal abundances during the flare. Optical Fe xiii line emission traces the cooler quiescent corona.Results. Although of rather short duration (exponential decay time τ LC < 5 min), the X-ray flux at flare peak exceeds the quiescent level by a factor of ≈100. The electron density averaged over the whole flare is greater than 5 × 10 11 cm −3 . The flare plasma shows an enhancement of iron by a factor of ≈2 during the rise and peak phase of the flare. We derive a size of <9000 km for the flaring structure from the evolution of the the emitting plasma during flare rise, peak, and decay. Conclusions. The characteristics of the flare plasma suggest that the flare originates from a compact arcade instead of a single loop. The combined results from X-ray and optical data further confine the plasma properties and the geometry of the flaring structure in different atmospheric layers.

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“…A typical value of ?7-band energy released in a flare is 10 32 ergs. Previous calculations have shown a relationship between the rate of flaring and the energy released in the flare (Gershberg and Shakhovskaya 1983). That relationship is…”

Section: Application To Flare Star Observationsmentioning

confidence: 91%

Flare Star Observations with a Single-Photon Counting Imaging Detector

Casperson

Priedhorsky

Baron

et al. 1995

International Astronomical Union Colloquium

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At Los Alamos National Laboratory we are developing a new imaging sensor which combines high spatial and high temporal resolution over a large area format, while maintaining single-photon counting sensitivity and sustaining a high count rate. The detector is called a microchannel plate with crossed delay line readout, or MCP/CDL. This detector is ideally suited to the observation of weak transient events, such as stellar flares from red dwarf flare stars in our Galaxy. At present we are initiating an experiment with the MCP/CDL detector which will utilize a 30-cm aperture f/7 telescope to characterize {/-band, S-band, and V-band emission from such low-luminosity flare stars, and to search for weak optical transients associated with other astrophysical sources. The MCP/CDL DetectorOver the past several years, new photon-counting microchannel plate imagers have been developed that allow the location and time-tagging of individual photons with high accuracy (Baron & Priedhorsky 1993). The newest version utilizes a crossed delay line for readout of individual photon events, and so it is designated as an MCP/CDL detector.The current MCP/CDL design uses a transmissive S-20 visible photocathode deposited on the inside surface of the vacuum window of the detector. Photoelectrons emitted from this surface are accelerated across a narrow gap to the 40-millimeter active diameter microchannel plates in a z-stack (three plates in series) configuration, providing an electron gain of 10 7 . Each incident photoelectron on the front surface of the stack generates a cloud of electrons out the back that passes through a pair of orthogonal helical windings -one in the ^-direction and the other in the y-direction. Readout of each photon is accomplished by precisely measuring, at the ends of each delay line, the time difference of arrival of the electron-cloud induced pulses.The maximum photon counting rate available from the detector is presently one-half million per second, limited by pileup of events on the 100-ns long delay lines. Within a few months a new front-end electronics package will boost this rate to approximately five million photons per second. The demonstrated spatial resolution in our prototype detector is better than 20 microns, corresponding to of use, available at https://www.cambridge.org/core/terms. https://doi

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Characteristics of activity energetics of the UV cet-type flare stars

Cited by 87 publications

References 16 publications

Saturation Levels for White-Light Flares of Flare Stars: Variation of Minimum Flare Duration for Saturation

Saturation Levels for White-Light Flares of Flare Stars: Variation of Minimum Flare Duration for Saturation

Multiwavelength observations of a giant flare on CN Leonis

Flare Star Observations with a Single-Photon Counting Imaging Detector

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