A study of X-ray flares - II. RS CVn-type binaries

Pandey, J. C.; Singh, K. P.

doi:10.1111/j.1365-2966.2011.19776.x

Cited by 71 publications

(70 citation statements)

References 85 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Another approach is to look at flares, but the height of these is typically smaller than the scale height. In the case of EI Eri a flare was seen and measured to be about 0.23R * (Pandey & Singh 2012). These sizes and temperature scales are consistent with the model posited here.…”

Section: Discussionsupporting

confidence: 74%

“…This is similar to the results for systems with higher mass secondaries (eg. σ 2 Cor Bor, AR LAc, V711 Tau, Osten et al 2003;Pandey & Singh 2012;Drake et al 2014). The scale height of the corona of the G star in AR Lac is about 1.3 solar radii (Drake et al 2014).…”

Section: Discussionmentioning

confidence: 99%

“…One with a mid M secondary is EI Eri. Pandey & Singh (2012) fitted this system as a three component plasma with Plasma temperatures ranging from 5-30Mk. With the emission measure peaking around 10 MK.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Giant Coronal Loops Dominate the Quiescent X-Ray Emission in Rapidly Rotating M Stars

Cohen

Yadav

Garraffo

et al. 2016

ApJ

View full text Add to dashboard Cite

Observations indicate that magnetic fields in rapidly rotating stars are very strong, on both small and large scales. What is the nature of the resulting corona? Here we seek to shed some light on this question. We use the results of an anelastic dynamo simulation of a rapidly rotating fully-convective M-star to drive a physics-based model for the stellar corona. We find that due to the several kilo Gauss large-scale magnetic fields at high latitudes, the corona and its X-ray emission are dominated by star-size large hot loops, while the smaller, underlying colder loops are not visible much in the X-ray. Based on this result we propose that, in rapidly rotating stars, emission from such coronal structures dominates the quiescent, cooler but saturated X-ray emission.

show abstract

Section: Discussionsupporting

confidence: 74%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Giant Coronal Loops Dominate the Quiescent X-Ray Emission in Rapidly Rotating M Stars

Cohen

Yadav

Garraffo

et al. 2016

ApJ

View full text Add to dashboard Cite

show abstract

“…The XMM-Newton CCD spectra of a short flare on EI Eri on 2009-08-06 during the present campaign was analyzed by Pandey & Singh (2012), who suggested the flare originated from a loop the size of ∼R * (primary), which is about a tenth of the binary separation distance.…”

Section: Ei Erimentioning

confidence: 99%

Variability of a stellar corona on a time scale of days

Nordon

Behar

Drake

2013

A&A

View full text Add to dashboard Cite

Elemental abundance effects in active coronae have eluded our understanding for almost three decades, since the discovery of the first ionization potential (FIP) effect on the sun. The goal of this paper is to monitor the same coronal structures over a time interval of six days and resolve active regions on a stellar corona through rotational modulation. We report on four iso-phase X-ray spectroscopic observations of the RS CVn binary EI Eri with XMM-Newton, carried out approximately every two days, to match the rotation period of EI Eri. We present an analysis of the thermal and chemical structure of the EI Eri corona as it evolves over the six days. Although the corona is rather steady in its temperature distribution, the emission measure and FIP bias both vary and seem to be correlated. An active region, predating the beginning of the campaign, repeatedly enters into our view at the same phase as it rotates from beyond the stellar limb. As a result, the abundances tend slightly, but consistently, to increase for high FIP elements (an inverse FIP effect) with phase. We estimate the abundance increase of high FIP elements in the active region to be of about 75% over the coronal mean. This observed fractionation of elements in an active region on time scales of days provides circumstantial clues regarding the element enrichment mechanism of non-flaring stellar coronae.

show abstract

“…This rapid rotation is thought to engender strong dynamo action that makes them magnetically active and thus copious sources of chromospheric and coronal emission; they are among the very brightest stellar coronal sources observed at short wavelengths with X-ray luminosities up to ten thousand times that of the typical active Sun (e.g. Walter et al 1978;Pallavicini et al 1981;Drake et al 1992;Dempsey et al 1993;Singh et al 1996;Makarov 2003;Pandey & Singh 2012).…”

mentioning

confidence: 99%

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

A study of X-ray flares - II. RS CVn-type binaries

Cited by 71 publications

References 85 publications

Giant Coronal Loops Dominate the Quiescent X-Ray Emission in Rapidly Rotating M Stars

Giant Coronal Loops Dominate the Quiescent X-Ray Emission in Rapidly Rotating M Stars

Variability of a stellar corona on a time scale of days

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

Contact Info

Product

Resources

About