Modeling the long duration rise phase of a flare detected on the M star TWA 11 B

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Abstract

We present preliminary results from the analysis of a long duration flare that was observed in a serendipitous XMM-Newton detection of the M star CD-39 7717 B (TWA 11 B), member of the young stellar association TW Hya. Only the rise phase (with a duration of ~35 ks) and possibly the flare peak are present in the light-curve. The decay phase was not monitored. The fluorescent iron emission line at 6.4 keV was observed during this event. As far as we are concerned, since TWA 11 B seems to have no disk, this is only the third detection of Fe photospheric fluorescence. During the flare, the X-ray flux increased a factor of ~4. Taking the light curve and the evolution of the hardness ratio into account, we interpret the rise phase as resulting from the ignition of a first group of loops (part 1) which triggered a subsequent two-ribbon flare (part 2). Part 1 is analysed using the Reale's (2007) model, since it has been assumed to be dominated by a single loop. For part 2, the diagnostic method for two-ribbon flares developed by Kopp & Poletto (1984) is applied. Loop semi-lengths of about 2.5-3.0 stellar radii are obtained. These large structures were previously detected only in very young objects, this is the first time that are detected in a more evolved (~8 Myr) star.
Lingua originaleEnglish
Stato di pubblicazionePublished - 2009

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M stars
flares
ribbons
light curve
XMM-Newton telescope
newton
ignition
hardness
iron
stars
fluorescence
radii
decay
x rays

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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@conference{b0bf3381b435447ab047296a92dc9a9e,
title = "Modeling the long duration rise phase of a flare detected on the M star TWA 11 B",
abstract = "We present preliminary results from the analysis of a long duration flare that was observed in a serendipitous XMM-Newton detection of the M star CD-39 7717 B (TWA 11 B), member of the young stellar association TW Hya. Only the rise phase (with a duration of ~35 ks) and possibly the flare peak are present in the light-curve. The decay phase was not monitored. The fluorescent iron emission line at 6.4 keV was observed during this event. As far as we are concerned, since TWA 11 B seems to have no disk, this is only the third detection of Fe photospheric fluorescence. During the flare, the X-ray flux increased a factor of ~4. Taking the light curve and the evolution of the hardness ratio into account, we interpret the rise phase as resulting from the ignition of a first group of loops (part 1) which triggered a subsequent two-ribbon flare (part 2). Part 1 is analysed using the Reale's (2007) model, since it has been assumed to be dominated by a single loop. For part 2, the diagnostic method for two-ribbon flares developed by Kopp & Poletto (1984) is applied. Loop semi-lengths of about 2.5-3.0 stellar radii are obtained. These large structures were previously detected only in very young objects, this is the first time that are detected in a more evolved (~8 Myr) star.",
keywords = "Stars: X-ray; Stars: flare",
author = "Fabio Reale",
year = "2009",
language = "English",

}

TY - CONF

T1 - Modeling the long duration rise phase of a flare detected on the M star TWA 11 B

AU - Reale, Fabio

PY - 2009

Y1 - 2009

N2 - We present preliminary results from the analysis of a long duration flare that was observed in a serendipitous XMM-Newton detection of the M star CD-39 7717 B (TWA 11 B), member of the young stellar association TW Hya. Only the rise phase (with a duration of ~35 ks) and possibly the flare peak are present in the light-curve. The decay phase was not monitored. The fluorescent iron emission line at 6.4 keV was observed during this event. As far as we are concerned, since TWA 11 B seems to have no disk, this is only the third detection of Fe photospheric fluorescence. During the flare, the X-ray flux increased a factor of ~4. Taking the light curve and the evolution of the hardness ratio into account, we interpret the rise phase as resulting from the ignition of a first group of loops (part 1) which triggered a subsequent two-ribbon flare (part 2). Part 1 is analysed using the Reale's (2007) model, since it has been assumed to be dominated by a single loop. For part 2, the diagnostic method for two-ribbon flares developed by Kopp & Poletto (1984) is applied. Loop semi-lengths of about 2.5-3.0 stellar radii are obtained. These large structures were previously detected only in very young objects, this is the first time that are detected in a more evolved (~8 Myr) star.

AB - We present preliminary results from the analysis of a long duration flare that was observed in a serendipitous XMM-Newton detection of the M star CD-39 7717 B (TWA 11 B), member of the young stellar association TW Hya. Only the rise phase (with a duration of ~35 ks) and possibly the flare peak are present in the light-curve. The decay phase was not monitored. The fluorescent iron emission line at 6.4 keV was observed during this event. As far as we are concerned, since TWA 11 B seems to have no disk, this is only the third detection of Fe photospheric fluorescence. During the flare, the X-ray flux increased a factor of ~4. Taking the light curve and the evolution of the hardness ratio into account, we interpret the rise phase as resulting from the ignition of a first group of loops (part 1) which triggered a subsequent two-ribbon flare (part 2). Part 1 is analysed using the Reale's (2007) model, since it has been assumed to be dominated by a single loop. For part 2, the diagnostic method for two-ribbon flares developed by Kopp & Poletto (1984) is applied. Loop semi-lengths of about 2.5-3.0 stellar radii are obtained. These large structures were previously detected only in very young objects, this is the first time that are detected in a more evolved (~8 Myr) star.

KW - Stars: X-ray; Stars: flare

UR - http://hdl.handle.net/10447/46237

M3 - Paper

ER -