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Abranin, E. P.; Bazelyan, L. L.; Alekseev, I. Yu.; Гершберг, Р. Е.; Avgoloupis, S.; Seiradakis, J. H.; Mavridis, L. N.; Beskin, G.; Митронова, С. Н.; Panferova, I. P.; Kidger, M.

doi:10.1023/a:1001192915841

Cited by 13 publications

(15 citation statements)

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“…The reddening of the continuum in the gradual phase was suggested to be the result of the presence of two (or more) competing emission mechanisms, including a contribution from Hydrogen (Paschen continuum) recombination radiation. Other studies have similarly concluded from colorimetry that flare radiation consists of a combination of the hot blackbody emission and optically thin Balmer continuum recombination radiation, while speculating that the blackbody is short-lived and the Balmer continuum becomes more dominant in the gradual phase (Abdul-Aziz et al, 1995, see also Abranin et al (1997); Zhilyaev et al (2007)). A two-component model was first proposed using simultaneous colorimetry and spectra of dMe flares by Kunkel (1970) -see also Moffett & Bopp (1976) -who concluded that a single, isothermal (T e = 3000 − 30 000 K) optically thin hydrogen emission (bf+ff) model was too blue to explain the observed flare colors, nor could it account for the spread of colors among a sample of flares.…”

Section: Acknowledgmentsmentioning

confidence: 92%

“…Self-consistent models that use realistic flare heating mechanisms typically result in a white-light continuum that is dominated by a strong Hydrogen recombination component (Hawley & Fisher, 1992). The sophisticated one-dimensional RHD models of Abbett & Hawley (1999) and Allred et al (2005Allred et al ( , 2006 used the RADYN code (Carlsson & Stein, 1994, 1995, 1997 to simulate flares on an M dwarf and on the Sun using moderate (10 10 ergs s −1 cm −2 , F10) and large (10 11 ergs s −1 cm −2 , F11) fluxes of mildly relativistic electrons injected at the top of a semi-circular flare loop. The RADYN models employ the thick-target formulae of Emslie (1978), Canfield (1983), and that describe how the nonthermal electron beam deposits energy throughout the atmosphere.…”

Section: Acknowledgmentsmentioning

confidence: 99%

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TIME-RESOLVED PROPERTIES AND GLOBAL TRENDS IN dMe FLARES FROM SIMULTANEOUS PHOTOMETRY AND SPECTRA

Kowalski

Hawley

Wisniewski

et al. 2013

ApJS

228

399

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We present a homogeneous survey of near-ultraviolet (NUV) /optical line and continuum emission during twenty M dwarf flares with simultaneous, high cadence photometry and spectra. These data were obtained to study the white-light continuum components to the blue and red of the Balmer jump to break the degeneracy with fitting emission mechanisms to broadband colors and to provide constraints for radiative-hydrodynamic flare models that seek to reproduce the white-light flare emission. The main results from the continuum analysis are the following: 1) the detection of Balmer continuum (in emission) that is present during all flares, with a wide range of relative contribution to the continuum flux in the NUV; 2) a blue continuum at the peak of the photometry that is linear with wavelength from λ = 4000 − 4800Å, matched by the spectral shape of hot, blackbody emission with typical temperatures of 10 000 − 12 000 K; 3) a redder continuum apparent at wavelengths longer than Hβ; this continuum becomes relatively more important to the energy budget during the late gradual phase. The hot blackbody component and redder continuum component (which we call "the conundruum") have been detected in previous U BV R colorimetry studies of flares. With spectra, one can compare the properties and detailed timings of all three components. Using time-resolved spectra during the rise phase of three flares, we calculate the speed of an expanding flare region assuming a simple geometry; the speeds are found to be ∼5 -10 km s −1 and 50 -120 km s −1 , which are strikingly consistent with the speeds at

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Section: Acknowledgmentsmentioning

confidence: 92%

Section: Acknowledgmentsmentioning

confidence: 99%

TIME-RESOLVED PROPERTIES AND GLOBAL TRENDS IN dMe FLARES FROM SIMULTANEOUS PHOTOMETRY AND SPECTRA

Kowalski

Hawley

Wisniewski

et al. 2013

ApJS

228

399

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“…However, it does provide the correct overall shape of the continuum and allows us to investigate the possible evolution of the flare temperature and area coverage. Other mechanisms have been tried by several authors, with marginal results (see, e.g., Abranin et al 1997). A description of the exact nature of the blue continuum emission, as well as the underlying physical mechanism that produces it, remains elusive.…”

Section: Continuum Emissionmentioning

confidence: 99%

Multiwavelength Observations of Flares on AD Leonis

Hawley

Allred

Johns–Krull

et al. 2003

ApJ

188

244

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We report results from a multiwavelength observing campaign conducted during 2000 March on the flare star AD Leo. Simultaneous data were obtained from several ground-and space-based observatories, including observations of eight sizable flares. We discuss the correlation of line and continuum emission in the optical and ultraviolet wavelength regimes, as well as the flare energy budget, and we find that the emission properties are remarkably similar even for flares of very different evolutionary morphology. This suggests a common heating mechanism and atmospheric structure that are independent of the detailed evolution of individual flares. We also discuss the Neupert effect, chromospheric line broadening, and velocity fields observed in several transition region emission lines. The latter show significant downflows during and shortly after the flare impulsive phase. Our observations are broadly consistent with the solar model of chromospheric evaporation and condensation following impulsive heating by a flux of nonthermal electrons. These data place strong constraints on the next generation of radiative hydrodynamic models of stellar flares.

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“…Besides the exploration of the radio emission from wellknown objects such as Jupiter, Sun, and pulsars, the receiver can also be used for detecting and analyzing other radio sources, previously unexplored with ground-based instruments. Those include, for example, Saturn's lightning (Griessmeier et al 2008), flaring stars (Abranin et al 1997;Konovalenko et al 2008), the elusive radio emission from exoplanets (Weber et al 2007;Ryabov et al 2004b).…”

Section: Resultsmentioning

confidence: 99%

A low-noise, high-dynamic-range, digital receiver for radio astronomy applications: an efficient solution for observing radio-bursts from Jupiter, the Sun, pulsars, and other astrophysical plasmas below 30 MHz

Ryabov¹,

Vavriv

Zarka

et al. 2010

A&A

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A new two-channel digital receiver that can be used for observing both stationary and sporadic radio sources in the decameter wave band is presented. Current implementation of the device operating at the sampling frequency of 66 MHz is described in detail, including the regimes of waveform capture, spectrogram analysis, and coherence analysis (cross covariance between the two inputs). Various issues pertaining to observational methods in the decameter waveband affected significantly by man-made interferences have been taken into account in the receiver design, as well as in the architecture of the interactive software that controls the receiver parameters in real time. Two examples of using the receiver with the UTR-2 array (Ukraine) are reported: S-bursts from Jupiter and low-frequency wide-band single pulses from the pulsar PSR0809+74

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Cited by 13 publications

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TIME-RESOLVED PROPERTIES AND GLOBAL TRENDS IN dMe FLARES FROM SIMULTANEOUS PHOTOMETRY AND SPECTRA

TIME-RESOLVED PROPERTIES AND GLOBAL TRENDS IN dMe FLARES FROM SIMULTANEOUS PHOTOMETRY AND SPECTRA

Multiwavelength Observations of Flares on AD Leonis

A low-noise, high-dynamic-range, digital receiver for radio astronomy applications: an efficient solution for observing radio-bursts from Jupiter, the Sun, pulsars, and other astrophysical plasmas below 30 MHz

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