X-ray properties of active M dwarfs as observed by XMM-Newton

Robrade, J.; Schmitt, J. H. M. M.

doi:10.1051/0004-6361:20041941

Cited by 84 publications

(107 citation statements)

References 40 publications

(63 reference statements)

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“…Early results of the XMM-Newton monitoring program of the α Cen stars were presented by Robrade & Schmitt (2005). Most strikingly an X-ray dimming of α Cen A by an order of magnitude within three years was observed in the bandpass of the EPIC detectors, caused by a strong decrease in emission measure at a few MK.…”

Section: α Centaurimentioning

confidence: 99%

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Coronal activity cycles in nearby G and K stars

Robrade

Schmitt

Favata

2012

A&A

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Context. While we have ample evidence of stellar analogues to the solar activity cycle for chromospheric activity, very little is known about stellar coronal cycles and their possible similarities to the solar behavior.Aims. An ongoing X-ray monitoring program of solar-like stars with XMM-Newton is performed to investigate coronal activity cycles. Methods. We used X-ray observations of the nearby binaries 61 Cyg A/B (K5V and K7V) and α Cen A/B (G2V and K1V) to study the long-term evolution of magnetic activity in weakly to moderately active G + K dwarfs over nearly a decade. Specifically we searched for X-ray activity cycles and related coronal changes and compared them to the solar behavior. Results. For 61 Cyg A we find a regular coronal activity cycle analog to its 7.3 yr chromospheric cycle. The X-ray brightness variations are with a factor of three significantly lower than on the Sun, yet the changes of coronal properties resemble the solar behavior, with stronger variations occurring in the respective hotter plasma components. 61 Cyg B does not show a clear cyclic coronal trend so far, but the X-ray data match the more irregular chromospheric cycle. The two α Cen stars exhibit significant long-term X-ray variability. α Cen A shows indications for cyclic variability of an order of magnitude with a period of about 12−15 years; the α Cen B data suggest an X-ray cycle with an amplitude of about six to eight and a period of 8−9 years. The sample stars exhibit X-ray luminosities ranging between L X < ∼ 1 × 10 26 −3 × 10 27 erg s −1 in the 0.2−2.0 keV band and have coronae dominated by cool plasma with variable average temperatures of around 1.0−2.5 MK. Conclusions. Coronal activity cycles are apparently a common phenomenon in older, slowly rotating G and K stars. The spectral changes of the coronal X-ray emission over the cycles are solar-like in all studied targets.

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Section: α Centaurimentioning

confidence: 99%

“…A flare of similar energy from α Cen B which was detected in 01/2004 at about activity maximum was discussed in Robrade & Schmitt (2005); likely these events are among the faintest stellar flares with a clearly observed rise and decay phase detected in X-rays. Several small and intermediate events are also detected from 61 Cyg A and 61 Cyg B.…”

Section: Flaresmentioning

confidence: 99%

Coronal activity cycles in nearby G and K stars

Robrade

Schmitt

Favata

2012

A&A

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“…Fe xiii is an indicator for cool coronal plasma (≈1.5 MK), while typical coronal emission measure distributions of earlier M dwarfs peak around 7-8 MK (e.g. Robrade & Schmitt 2005), i.e., temperatures where the ionization equilibrium is shifted towards Fe xvii. Fuhrmeister et al (2007) found significant amounts of cooler plasma in the corona of CN Leo from X-ray spectra obtained with XMM-Newton, consistent with the Fe xiii line fluxes from simultaneous optical spectroscopy.…”

Section: The Active M Dwarf Cn Leomentioning

confidence: 99%

Multiwavelength observations of a giant flare on CN Leonis

Liefke¹,

Fuhrmeister²,

Schmitt³

2010

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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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“…This value increases to 1.1 × 10 30 erg s −1 during the flare. The quiescence luminosity is very similar to the typical L X of other dMe stars (Mitra-Kraev et al 2005;Robrade & Schmitt 2005), and is lower than for PMS T Tauri stars or RS CVn interacting binaries. Moreover, the log(L X /L BOL ) ratio amounts to −3.3 in quiescence and −2.6 during the flare, which is the typical ratio observed at the saturation limit for coronally-active sources (Riaz et al 2006).…”

Section: Rxs J1715024−333344mentioning

confidence: 61%

“…First, the flare, since magnetically active M dwarves frequently present flares in their X-ray emission (e.g. Raassen et al 2003;Robrade & Schmitt 2005;Wargelin et al 2008). The hardening during the flare (associated with a higher emission measure of the hottest components) and the shifted maximum of the hard X-ray lightcurve are also indicative of a coronal source (Wargelin et al 2008).…”

Section: Rxs J1715024−333344mentioning

confidence: 99%

Hot and cool: two emission-line stars with constrasting behaviours in the same XMM-Newtonfield

Nazé

Rauw

ud‐Doula

2010

A&A

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High-energy emissions are good indicators of peculiar behaviours in stars. We have therefore obtained an XMM-Newton observation of HD 155806 and 1RXS J171502.4−333344, and derived their spectral properties for the first time. The X-ray spectrum of HD 155806 appears soft, even slightly softer than usual for O-type stars (as shown by a comparison with the O9 star HD 155889 in the same XMM-Newton field). It is well-fitted with a two-component thermal model with low temperatures (0.2 and 0.6 keV), and it shows no overluminosity (log[L X /L BOL ] = −6.75). The high-resolution spectrum, though noisy, reveals a few broad, symmetric X-ray lines (FWHM ∼ 2500 km s −1 ). The X-ray emission is compatible with the wind-shock model and therefore appears unaffected by the putative dense equatorial regions at the origin of the Oe classification. 1RXS J171502.4−333344 is a nearby flaring source of moderate X-ray luminosity (log[L X /L BOL ] = −3), with a soft thermal spectrum composed of narrow lines and presenting a larger abundance of elements (e.g. Ne) with a high first ionization potential (FIP) compared to lower-FIP elements. All the evidence indicates a coronal origin for the X-ray emission, in agreement with the dMe classification of this source.

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X-ray properties of active M dwarfs as observed by XMM-Newton

Cited by 84 publications

References 40 publications

Coronal activity cycles in nearby G and K stars

Coronal activity cycles in nearby G and K stars

Multiwavelength observations of a giant flare on CN Leonis

Hot and cool: two emission-line stars with constrasting behaviours in the same XMM-Newtonfield

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