Coronal and Transition Region Structure in the RS Canum Venaticorum Binaries V711 Tauri, AR Lacertae, and II Pegasi. I. Data Analysis and Emission Measure Distributions

Griffiths, N. W.; Jordan, C.

doi:10.1086/305502

Cited by 63 publications

(67 citation statements)

References 53 publications

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“…5 plots the DEM integrated over intervals of D log T ¼ 0:05). Griffiths & Jordan (1998) derived emission measures from UV, EUV, and X-ray data, and Rodonò et al (1999), who analyzed SAX data, found temperature components similar to our peak DEM temperatures and integrated emission measures of about half our value. Singh et al (1996) also derived similar temperature components and emission measures from ROSAT and ASCA spectra, with an integrated emission value more similar to ours.…”

Section: Discussionsupporting

confidence: 78%

“…At log T ¼ 6:2, there is a weak peak required by the EUV lines from lower ionization states of iron (ix-xvi), which provide a much better constraint than does the relatively low signalto-noise detection of N vii (24.8 Å ). The overlapping temperature distributions of N and the EUV Fe lines serve to better constrain the abundance of N. We note that the derived DEM is similar to that obtained for the RS CVn system HR 1099 by Drake et al (2001) based on Chandra HETG spectra, while the double-peaked structure at high temperatures is also reminiscent of the emission measure distributions for AR Lac, HR 1099, II Peg, and other stars derived from EUVE spectra by Griffiths & Jordan (1998) and Sanz-Forcada et al (2002); the cool bump is also seen in some of the emission measures derived by the latter authors. It is tempting to conclude that the detailed structure in the DEM derived in this study and others does indeed reflect the true source temperature structure.…”

Section: Temperature Distributionsupporting

confidence: 84%

“…Some extended chromospheric material was also detected by Montes et al (1997) and Frasca et al (2000). Analysis of high-resolution EUVE data (Griffiths & Jordan 1998;Brickhouse et al 1999;Sanz-Forcada, Brickhouse, & Dupree 2003) showed a corona dominated by material at T $ 10 6:9 K and a substantial amount of material at hotter temperatures of T $ 10 7:3 K.…”

Section: Introductionmentioning

confidence: 99%

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The Coronae of AR Lacertae

Huenemoerder

Canizares

Drake

et al. 2003

ApJ

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We observed the coronally active eclipsing binary AR Lac with the High Energy Transmission Grating on Chandra for a total of 97 ks, spaced over five orbits, at quadratures and conjunctions. Contemporaneous and simultaneous EUV spectra and photometry were also obtained with the Extreme Ultraviolet Explorer. Significant variability in both X-ray and EUV fluxes were observed, dominated by at least one X-ray flare and one EUV flare. We saw no evidence of primary or secondary eclipses, but exposures at these phases were short and intrinsic variability compromised detection of any geometric modulation. X-ray flux modulation was largest at high temperature, indicative of flare heating of coronal plasma rather than changes in emitting volume or global emission measure. Analysis of spectral line widths interpreted in terms of Doppler broadening suggests that both binary stellar components are active. On the basis of line fluxes obtained from total integrated spectra, we have modeled the emission measure and abundance distributions. The EUV spectral line fluxes were particularly useful for constraining the parameters of the '' cool '' ( 2 Â 10 6 K) plasma. A strong maximum was found in the differential emission measure, characterized by two apparent peaks at log T ¼ 6:9 and 7.4, together with a weak but significant cooler maximum near log T ¼ 6:2 and a moderately strong hot tail from log T ¼ 7:6 8:2. Coronal abundances have a broad distribution and show no simple correlation with first ionization potential. While the resulting model spectrum generally agrees very well with the observed spectrum, there are some significant discrepancies, especially among the many Fe L lines. Both the emission measure and abundance distributions are qualitatively similar to prior determinations from other X-ray and ultraviolet spectra, indicating some long-term stability in the overall coronal structure.

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Section: Discussionsupporting

confidence: 78%

Section: Temperature Distributionsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

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The Coronae of AR Lacertae

Huenemoerder

Canizares

Drake

et al. 2003

ApJ

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“…The temperatures of these components are close to the temperatures found in the X-ray emission from V390 Aurigae. There is also evidence that the emission measure distribution of very active stellar coronae, obtained from spectrally resolved XUV observations, is double-peaked with a peak often found above 10 7 K (Griffiths & Jordan 1998). Recently, Sanz-Forcada et al (2002) noticed that emission measure distribution are remarkably similar among a sample of RSCVn's binaries and single active stars including the low-rotation giant β Cet, showing a narrow enhancement or bump around log T e ≈ 6.9.…”

Section: Structure Of V390 Aurigae Coronamentioning

confidence: 97%

The corona of V390 Aurigae (HD 33798)

Gondoin

2003

A&A

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Abstract. V390 Aurigae (HD 33798) is a rapidly rotating, lithium rich, late-type giant whose distinctive characteristics include a high X-ray luminosity observed by the XMM-Newton space observatory. Series of lines of highly ionized Fe and several Lyman lines of hydrogen-like ions and triplet lines of helium-like ions are visible in the reflection grating spectra, most notably from O and Ne. X-ray emission from plasma at high temperature (T > 10 7 K) indicates intense flaring activity on this star. Analysis results suggest a scenario where the corona of V390 Aurigae is dominated by large magnetic structures similar in size to interconnecting loops between solar active regions but significantly hotter. The interaction of these structures could explain the permanent flaring activity on large scales that is responsible for heating plasma to high temperatures. The intense activity on V390 Aurigae is related to its evolutionary position at the bottom of the red giant branch. It is anticipated that the rotation of the star will spin-down in the future, thus decreasing the efficiency of its α − Ω dynamo with the suppressing of large scale magnetic structures in its corona.

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“…Multi-temperature models are now necessary to explain highresolution spectra of bright stellar coronae (Dupree et al 1993;Griffiths & Jordan 1998;Bowyer et al 2000). Recent analysis of XMM−Newton and Chandra X-ray spectra find that a continuous emission measure distribution fits the data better and is more realistic physically (Audard et al 2001a,b;Güdel et al 2001;Mewe et al 2001).…”

Section: Spectral Analysis Of Epic Datamentioning

confidence: 99%

X-ray spectroscopy of the W UMa-type binary 44 Bootis

Gondoin¹

2004

A&A

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Abstract. 44 Boo B, a W UMa-type binary system, was observed in June 2001 during one entire revolution period with the XMM−Newton observatory. The count rate in the 0.3 to 2 keV band is constant in average with 5 to 20% count rate increases reminiscent of flares. Spectral fitting of the EPIC spectra indicates a corona configuration with little contribution from quiet regions, similar to the Sun. On the contrary, the (2-9) × 10 6 K temperature range of the "cool" plasma suggests that the active corona around the two companions is densely filled with low-lying loops similar to those found in solar-type active regions. The 44 Boo O VII He-like triplet constrains the electron density to an upper limit n e < 8.6 × 10 10 cm −3 . We argue that this low-lying loop system may be overlaid by larger loops. Magnetic reconnection phenomena in this large loops system may explain the characteristic flare decay time in the light curve that implies loop lengths of about 16 × 10 9 cm. An extended corona around 44 Boo would explain the absence of eclipses in its X-ray light curve. The average element abundance in 44 Boo corona is found to be lower than the solar photospheric value. The spectral analysis indicates enhanced abundances of oxygen and neon relative to iron which suggest an inverse FIP effect. Compared with other active binary systems such as RSCVn or BY Dra, 44 Boo has relatively less material at temperatures higher than 10 7 K and the temperature of its hottest plasma component appears to be lower.

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Coronal and Transition Region Structure in the RS Canum Venaticorum Binaries V711 Tauri, AR Lacertae, and II Pegasi. I. Data Analysis and Emission Measure Distributions

Cited by 63 publications

References 53 publications

The Coronae of AR Lacertae

The Coronae of AR Lacertae

The corona of V390 Aurigae (HD 33798)

X-ray spectroscopy of the W UMa-type binary 44 Bootis

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