Diagnostics of stellar flares from X-ray observations:  from the decay to the rise phase

Reale, F.

doi:10.1051/0004-6361:20077223

Cited by 107 publications

(209 citation statements)

References 25 publications

(45 reference statements)

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“…Using Eq. (12)) in Reale (2007), we find a loop semi-length of ∼4 × 10 10 cm for both flares. It is unclear which star of the ρ Ophiuchi C system flared.…”

Section: A88 Page 8 Of 17mentioning

confidence: 67%

“…In this case, the third thermal component had a best fit value of kT 3 = 2.5±0.3 keV and normalization N 3 = (2, 3 ± 0.2) × 10 −4 cm −5 , that is, a factor of 2 to 2.8 higher than the thermal components of the post-flare spectrum. By using the scaling laws of Reale (2007) and Serio et al (1991) as in the case of ρ Ophiuchi C, we estimate a loop semilength of l ≥ 5.8 × 10 10 cm or 0.8 R . This is a lower limit given that we did not observe the rise and the peak of the flare.…”

Section: Other Variable Sourcesmentioning

confidence: 88%

“…Modeling of magnetically confined plasma in solar coronal loops has been extensively studied by Reale (2007) in order to develop diagnostics for stellar flares. We can apply this modeling to the flare light curve in order to derive a loop length, by taking into account the rise and decay times (1.8 ks and 10 ks, respectively) and the peak plasma temperature derived from the flaring intervals in Table 2.…”

Section: A88 Page 8 Of 17mentioning

confidence: 99%

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First stars of theρOphiuchi dark cloud

Pillitteri

Wolk

Chen

et al. 2016

A&A

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Star formation in molecular clouds can be triggered by the dynamical action of winds from massive stars. Furthermore, X-ray and UV fluxes from massive stars can influence the life time of surrounding circumstellar disks. We present the results of a 53 ks XMMNewton observation centered on the ρ Ophiuchi A+B binary system. ρ Ophiuchi lies in the center of a ring of dust, likely formed by the action of its winds. This region is different from the dense core of the cloud (L1688 Core F) where star formation is at work. X-rays are detected from ρ Ophiuchi as well as a group of surrounding X-ray sources. We detected 89 X-ray sources, 47 of them have at least one counterpart in 2MASS+All-WISE catalogs. Based on IR and X-ray properties, we can distinguish between young stellar objects (YSOs) belonging to the cloud and background objects. Among the cloud members, we detect three debris-disk objects and 22 disk-less − Class III young stars. We show that these stars have ages in 5−10 Myr, and are significantly older than the YSOs in L1688. We speculate that they are the result of an early burst of star formation in the cloud. An X-ray energy of ≥5 × 10 44 erg has been injected into the surrounding medium over the past 5 Myr, we discuss the effects of such energy budget in relation to the cloud properties and dynamics.

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“…Using Eq. (12)) in Reale (2007), we find a loop semi-length of ∼4 × 10 10 cm for both flares. It is unclear which star of the ρ Ophiuchi C system flared.…”

Section: A88 Page 8 Of 17mentioning

confidence: 67%

Section: Other Variable Sourcesmentioning

confidence: 88%

Section: A88 Page 8 Of 17mentioning

confidence: 99%

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First stars of theρOphiuchi dark cloud

Pillitteri

Wolk

Chen

et al. 2016

A&A

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“…Assuming a single, loop-like emitting structure, we can derive its size by adopting the formalism described in Reale et al (1997) and parameters applicable to XMM/EPIC as given in Reale (2007). By using the maximum plasma temperature and the flare decay time obtained from the light curve, one can determine the size of the flaring structure, that is treated as an instantaneously heated coronal loop.…”

Section: The Flare Under Scrutinymentioning

confidence: 99%

New X-ray observations of IQ Aurigae andα² Canum Venaticorum

Robrade

Schmitt

2011

A&A

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Aims. We re-examine the scenario of X-ray emission from magnetically confined/channeled wind shocks (MCWS) for Ap/Bp stars, a model originally developed to explain the ROSAT detection of the A0p star IQ Aur. Methods. We present new X-ray observations of the A0p stars α 2 CVn (Chandra) and IQ Aur (XMM-Newton) and discuss our findings in the context of X-ray generating mechanisms of magnetic, chemically peculiar intermediate mass stars. Results. The X-ray luminosities of IQ Aur with log L X = 29.6 erg s −1 and α 2 CVn with log L X 26.0 erg s −1 differ by at least three orders of magnitude, although both are A0p stars. By studying a sample of comparison stars, we find that X-ray emission is preferably generated by more massive objects such as IQ Aur. Besides a strong, cool plasma component, significant amounts of hot (>10 MK) plasma are present during the quasi-quiescent phase of IQ Aur; moreover, diagnostics of the UV sensitive f /i line ratio in He-like O vii triplet point to X-ray emitting regions well above the stellar surface of IQ Aur. In addition we detect a large flare from IQ Aur with temperatures up to ∼100 MK and a peak X-ray luminosity of log L X ≈ 31.5 erg s −1 . The flare, showing a fast rise and e-folding decay time of less than half an hour, originates in a fairly compact structure and is accompanied by a significant metallicity increase. The X-ray properties of IQ Aur cannot be described by wind shocks only and require the presence of magnetic reconnection. This is most evident in the, to our knowledge, first X-ray flare reported from an A0p star. Conclusions. Our study indicates that the occurrence the of X-ray emission in A0p stars generated by magnetically channeled wind shocks depends on stellar properties such as luminosity, which promote a high mass loss rate, whereas magnetic field configuration and transient phenomena refine their appearance. While we cannot rule out unknown close companions, the X-ray emission from IQ Aur can be described consistently in the MCWS scenario, in which the very strong magnetic confinement of the stellar wind has led to the build-up of a rigidly rotating disk around the star, where magnetic reconnection and centrifugal breakout events occur.

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“…Additionally, hydrodynamic loop modeling approaches allow to assess the loop length from the analysis of the decay of the flare in X-rays and to estimate the amount of additional heating (Serio et al 1991;Reale et al 1997). This approach has recently been extended to an analysis of the rise phase of the flare (Reale 2007). Individual flare events can thus be characterized with respect to to the physical properties of the flaring structure from observational quantities also available for stellar events.…”

Section: Introductionmentioning

confidence: 99%

Multiwavelength observations of a giant flare on CN Leonis

Liefke¹,

Fuhrmeister²,

Schmitt³

2010

A&A

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Context. Stellar flares affect all atmospheric layers from the photosphere over chromosphere and transition region up into the corona. Simultaneous observations in different spectral bands allow to obtain a comprehensive picture of the environmental conditions and the physical processes going on during different phases of the flare. Aims. We investigate the properties of the coronal plasma during a giant flare on the active M dwarf CN Leo observed simultaneously with the UVES spectrograph at the VLT and XMM-Newton. Methods. From the X-ray data, we analyze the temporal evolution of the coronal temperature and emission measure, and investigate variations in electron density and coronal abundances during the flare. Optical Fe xiii line emission traces the cooler quiescent corona.Results. Although of rather short duration (exponential decay time τ LC < 5 min), the X-ray flux at flare peak exceeds the quiescent level by a factor of ≈100. The electron density averaged over the whole flare is greater than 5 × 10 11 cm −3 . The flare plasma shows an enhancement of iron by a factor of ≈2 during the rise and peak phase of the flare. We derive a size of <9000 km for the flaring structure from the evolution of the the emitting plasma during flare rise, peak, and decay. Conclusions. The characteristics of the flare plasma suggest that the flare originates from a compact arcade instead of a single loop. The combined results from X-ray and optical data further confine the plasma properties and the geometry of the flaring structure in different atmospheric layers.

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Diagnostics of stellar flares from X-ray observations: from the decay to the rise phase

Cited by 107 publications

References 25 publications

First stars of theρOphiuchi dark cloud

First stars of theρOphiuchi dark cloud

New X-ray observations of IQ Aurigae andα² Canum Venaticorum

Multiwavelength observations of a giant flare on CN Leonis

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Diagnostics of stellar flares from X-ray observations: from the decay to the rise phase

Cited by 107 publications

References 25 publications

First stars of theρOphiuchi dark cloud

First stars of theρOphiuchi dark cloud

New X-ray observations of IQ Aurigae andα2 Canum Venaticorum

Multiwavelength observations of a giant flare on CN Leonis

Contact Info

Product

Resources

About

New X-ray observations of IQ Aurigae andα² Canum Venaticorum