Stratton, G. M.

Feldman, Richard S.; Sapio, Melissa; Kozmová, Miloslava; Taylor, Eugene; Fredman, Leah; Elhammoumi, Mohamed; Cautin, Robin L.; Rodkey, Elissa N.; Rich, Grant J.; Clark, David O.; Morris, Edward K.; Gergen, Kenneth J.; Jeshmaridian, Samvel; Lovie, Sandy; Lovie, Pat; Aloisio, Cara; Figuccio, Michael J.; Hogan, John D.; Lamiell, James T.; Doran, Jennifer; Winitz, Harris; Devonis, David C.; Evans, Rand B.; Seim, David L.; Thomas, Roger K.

doi:10.1007/978-1-4419-0463-8_119

Cited by 7 publications

(13 citation statements)

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“…The upper limit on the L X of α Cen A is estimated to be 2 × 10 28 ergs s −1 , based on the detection limit of 10 mCrab with MAXI/GSC. This is consistent with the X-ray luminosities observed in solar flares; L X is mostly lower than 10 27 -10 28 ergs s −1 (Feldman et al 1995). However, large X-ray flares with the respective L X of 10 29 ergs s −1 and 2 × 10 31 ergs s −1 have been observed from ordinary solar-type stars π 1 UMa (Landini et al 1986) and BD+10 • 2783 (Schaefer et al 2000).…”

Section: X-ray Activity On Solar-type Starssupporting

confidence: 87%

Large X-ray flares on stars detected with MAXI/GSC: A universal correlation between the duration of a flare and its X-ray luminosity

Tsuboi

Yamazaki

Sugawara

et al. 2016

Publications of the Astronomical Society of Japan

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23 giant flares from 13 active stars (eight RS CVn systems, one Algol system, three dMe stars and one YSO) were detected during the first two years of our all-sky X-ray monitoring with the gas propotional counters (GSC) of the Monitor of All-sky X-ray Image (MAXI). The observed parameters of all of these MAXI/GSC flares are found to be at the upper ends for stellar flares with the luminosity of 10 31−34 ergs s −1 in the 2-20 keV band, the emission measure of 10 54−57 cm −3 , the e-folding time of 1 hour to 1.5 days, and the total radiative energy released during the flare of 10 34−39 ergs. Notably, the peak X-ray luminosity of 5 +4 −2 × 10 33 ergs s −1 in the 2-20 keV band was detected in one of the flares on II Peg, which is one of the, or potentially the, largest ever observed in stellar flares. X-ray flares were detected from GT Mus, V841 Cen, SZ Psc, and TWA-7 for the first time in this survey. Whereas most of our detected sources are multiple-star systems, two of them are single stars (YZ CMi and TWA-7). Among the stellar sources within 100 pc distance, the MAXI/GSC sources have larger rotation velocities than the 2 other sources. This suggests that the rapid rotation velocity may play a key role in generating large flares. Combining the X-ray flare data of nearby stars and the sun, taken from literature and ou r own data, we discovered a universal correlation of τ ∝ L 0.2 X for the flare duration τ and the intrinsic X-ray luminosity L X in the 0.1-100 keV band, which holds for 5 and 12 orders of magnitude in τ and L X , respectively. The MAXI/GSC sample is located at the highest ends on the correlation.

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Section: X-ray Activity On Solar-type Starssupporting

confidence: 87%

Large X-ray flares on stars detected with MAXI/GSC: A universal correlation between the duration of a flare and its X-ray luminosity

Tsuboi

Yamazaki

Sugawara

et al. 2016

Publications of the Astronomical Society of Japan

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“…This appears to be supported by the SUMER observations showing that except for initial flow pulses no persistent background flow was found in hot loops (Wang et al 2005). The density deficit caused by the conduction suppression may be estimated based on the EM-T correlation for flare loops where T is the peak temperature and EM(≃ n 2 L 3 ) the volume emission measure (Feldman et al 1995;Shibata & Yokoyama 1999. Assuming a balance between conduction cooling and reconnection heating and the pressure balance of flare loops, Shibata & Yokoyama (1999) derived the scaling law EM ∝ B −5 T 17/2 , where B is the magnetic field strength.…”

Section: Wave Trigger Mechanismmentioning

confidence: 99%

Effect of Transport Coefficients on Excitation of Flare-induced Standing Slow-mode Waves in Coronal Loops

Wang

Ofman

Sun

et al. 2018

ApJ

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Standing slow-mode waves have been recently observed in flaring loops by the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO). By means of the coronal seismology technique transport coefficients in hot (∼10 MK) plasma were determined by Wang et al. (2015, Paper I), revealing that thermal conductivity is nearly suppressed and compressive viscosity is enhanced by more than an order of magnitude. In this study we use 1D nonlinear MHD simulations to validate the predicted results from the linear theory and investigate the standing slow-mode wave excitation mechanism. We first explore the wave trigger based on the magnetic field extrapolation and flare emission features. Using a flow pulse driven at one footpoint we simulate the wave excitation in two types of loop models: model 1 with the classical transport coefficients and model 2 with the seismology-determined transport coefficients. We find that model 2 can form the standing wave pattern (within about one period) from initial propagating disturbances much faster than model 1, in better agreement with the observations. Simulations of the harmonic waves and the Fourier decomposition analysis show that the scaling law between damping time (τ ) and wave period (P ) follows τ ∝ P 2 in model 2, while τ ∝ P in model 1. This indicates that the largely enhanced viscosity efficiently increases the dissipation of higher harmonic components, favoring the quick formation of the fundamental standing mode. Our study suggests that observational constraints on the transport coefficients are important in understanding both, the wave excitation and damping mechanisms.

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“…Flares are observed with various wavelength ranges (Kane 1974), and several aspects of the emissions can be explained by the above flare model. According to Feldman et al (1995), Shimizu (1995), and Yuda et al (1997), there is a universal correlation between the temperature (T ) and emission measure (EM) among not only solar flares but also stellar flares. Shibata & Yokoyama (1999, 2002 suggested a theoretical scaling law describing this correlation.…”

Section: Introductionmentioning

confidence: 99%

Validation of a scaling law for the coronal magnetic field strength and loop length of solar and stellar flares

Namekata

Sakaue

Watanabe

et al. 2016

Publications of the Astronomical Society of Japan

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Shibata & Yokoyama (1999, 2002 proposed a method of estimating the coronal magnetic field strengths (B) and magnetic loop lengths (L) of solar and stellar flares, on the basis of magnetohydrodynamic simulations of the magnetic reconnection model. Using the scaling law provided by Shibata & Yokoyama (1999, 2002, B and L are obtained as functions of the emission measure (EM = n 2 L 3 ) and temperature (T ) at the flare peak. Here, n is the coronal electron density of the flares. This scaling law enables the estimation of B and L for unresolved stellar flares from the observable physical quantities EM and T , which is helpful for studying stellar surface activities. To apply this scaling law to stellar flares, we discuss its validity for spatially resolved solar flares. EM and T were calculated from GOES soft X-ray flux data, and B and L are theoretically estimated using the scaling law. For the same flare events, B and L were also observationally estimated with images taken by Solar Dynamics Observatory (SDO)/ Helioseismic and Magnetic Imager (HMI) Magnetogram and Atmospheric Imaging Assembly (AIA) 94Å pass band. As expected, a positive correlation was found between the theoretically and observationally estimated values. We interpret this result as indirect evidence that flares are caused by magnetic reconnection. Moreover, this analysis makes us confident in the validity of applying this scaling law to stellar flares as well as solar flares.

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Stratton, G. M.

Cited by 7 publications

References 0 publications

Large X-ray flares on stars detected with MAXI/GSC: A universal correlation between the duration of a flare and its X-ray luminosity

Large X-ray flares on stars detected with MAXI/GSC: A universal correlation between the duration of a flare and its X-ray luminosity

Effect of Transport Coefficients on Excitation of Flare-induced Standing Slow-mode Waves in Coronal Loops

Validation of a scaling law for the coronal magnetic field strength and loop length of solar and stellar flares

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