Untitled

Rodono, M.; Pagano, I.; Cutispoto, G.; Marino, G.; Messina, S.; Leto, G.

doi:10.1023/a:1001154800483

Cited by 25 publications

(61 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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: 77%

“…Both studies also obtained values systematically lower than ours for all other element fits (S, O, N, Ar, Ne). Global fits to low-resolution BeppoSAX spectra of AR Lac by Rodonò et al (1999) obtained an average metal abundance of 0.66, similar to our values for Fe, Si, S, Mg, and O.…”

Section: Abundancessupporting

confidence: 85%

“…In contrast, the ASCA light curve (Siarkowski et al 1996) was relatively smooth and showed broad and deep primary eclipse and broad, shallow secondary eclipse. Rodonò et al (1999) summarize and compare many of the X-ray observations. Some aspects of the data are quite confusing and challenging to explain.…”

Section: Discussionmentioning

confidence: 99%

“…Subsequent X-ray studies were undertaken by Ottmann, Schmitt, & Kuerster (1993;ROSAT), White et al (1990;EXOSAT), Rodonò et al (1999;BeppoSAX ), and White et al (1994;ASCA).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The Coronae of AR Lacertae

Huenemoerder

Canizares

Drake

et al. 2003

ApJ

View full text Add to dashboard Cite

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.

show abstract

Section: Discussionsupporting

confidence: 77%

Section: Abundancessupporting

confidence: 85%

Section: Discussionmentioning

confidence: 99%

“…Subsequent X-ray studies were undertaken by Ottmann, Schmitt, & Kuerster (1993;ROSAT), White et al (1990;EXOSAT), Rodonò et al (1999;BeppoSAX ), and White et al (1994;ASCA).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The Coronae of AR Lacertae

Huenemoerder

Canizares

Drake

et al. 2003

ApJ

View full text Add to dashboard Cite

show abstract

“…For our purposes, this ephemeris is essentially identical to that of Marino et al (1998), that was also adopted by Rodonò et al (1999). The relevant parameters are listed in Table 1.…”

mentioning

confidence: 96%

A 33 yr CONSTANCY OF THE X-RAY CORONAE OF AR Lac AND ECLIPSE DIAGNOSIS OF SCALE HEIGHT

Drake

Ratzlaff

Kashyap

et al. 2014

ApJ

View full text Add to dashboard Cite

Extensive X-ray and extreme ultraviolet (EUV) photometric observations of the eclipsing RS CVn system AR Lac were obtained over the years 1997 to 2013 with the Chandra X-ray Observatory Extreme Ultraviolet Explorer. During primary eclipse, HRC count rates decrease by ∼40%. A similar minimum is seen during one primary eclipse observed by EUVE but not in others owing to intrinsic source variability. Little evidence for secondary eclipses is present in either the X-ray or EUV data, reminiscent of earlier X-ray and EUV observations. Primary eclipses allow us to estimate the extent of a spherically symmetric corona on the primary G star of about 1.3R , or 0.86R , and indicate the G star is likely brighter than the K component by a factor of 2-5. Brightness changes not attributable to eclipses appear to be dominated by stochastic variability and are generally non-repeating. X-ray and EUV light curves cannot therefore be reliably used to reconstruct the spatial distribution of emission assuming only eclipses and rotational modulation are at work. Moderate flaring is observed, where count rates increase by up to a factor of three above quiescence. Combined with older ASCA, Einstein, EXOSAT, ROSAT and Beppo-SAX observations, the data show that the level of quiescent coronal emission at X-ray wavelengths has remained remarkably constant over 33 years, with no sign of variation due to magnetic cycles. Variations in base level X-ray emission seen by Chandra over 13 years are only ∼ 10%, while variations back to pioneering Einstein observations in 1980 amount to a maximum of 45% and more typically about 15%.

show abstract

Stellar activity cycles: observing the dynamo?

Strassmeier

2005

Astron Nachr

View full text Add to dashboard Cite

Abstract. The enormous complexity of the atmospheric structure observed on the Sun makes it very difficult to compare the Sun with "solar-type stars". Clearly, we need to identify parameters that can be observed on the Sun as well as on other stars which can be interpreted unambiguously. The most widely accepted dynamo signature is the presence of an activity cycle, well documented for the Sun and for main-sequence stars due to the Mount Wilson Ca II H&K project. Only recently have we detected spatial information, differential rotation and possibly meridional flows on other stars and thereby adding another constraint for its interpretation within a dynamo theory. Again, the picture is not complete yet, despite that there is just a single main ingredient that acts as the driving mechanism for activity in all atmospheric layers and the convective envelope of a solar-type star: the dynamo-related magnetic field. I stress the importance of mapping stellar surfaces as fingerprints of the underlying dynamo action over long periods of time.

show abstract

Untitled

Cited by 25 publications

References 0 publications

The Coronae of AR Lacertae

The Coronae of AR Lacertae

A 33 yr CONSTANCY OF THE X-RAY CORONAE OF AR Lac AND ECLIPSE DIAGNOSIS OF SCALE HEIGHT

Stellar activity cycles: observing the dynamo?

Contact Info

Product

Resources

About