EXTraS discovery of an X-ray superflare from an L dwarf
| العنوان: | EXTraS discovery of an X-ray superflare from an L dwarf |
|---|---|
| المؤلفون: | Beate Stelzer, D. Pizzocaro, Piero Ranalli, Paolo Esposito, S. Raetz, G. Novara, A. De Luca, M. Marelli, Adam J. Burgasser, Andrea Belfiore, M. Fumana, Cristian Vignali, Roberto Gilli, Ruben Salvaterra, P. Franzetti, Andrea Tiengo |
| المساهمون: | De Luca A., Stelzer B., Burgasser A.J., Pizzocaro D., Ranalli P., Raetz S., Marelli M., Novara G., Vignali C., Belfiore A., Esposito P., Franzetti P., Fumana M., Gilli R., Salvaterra R., Tiengo A. |
| سنة النشر: | 2020 |
| مصطلحات موضوعية: | Stars: activity, Stars: flare, FOS: Physical sciences, X-rays: stars, Astrophysics, Stars: late-type, Stellar classification, 01 natural sciences, Power law, Luminosity, law.invention, law, 0103 physical sciences, Stars: coronae, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Magnetic energy, 010308 nuclear & particles physics, Astronomy and Astrophysics, Magnetic reconnection, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, Erg, Superflare, Flare |
| الوصف: | We present the first detection of an X-ray flare from an ultracool dwarf of spectral class L. The event was identified in the EXTraS database of XMM-Newton variable sources, and its optical counterpart, J0331-27, was found through a cross-match with the Dark Energy Survey Year 3 release. Next to an earlier four-photon detection of Kelu-1, J0331-27 is only the second L dwarf detected in X-rays, and much more distant than other ultracool dwarfs with X-ray detections (photometric distance of 240 pc). From an optical spectrum with the VIMOS instrument at the VLT, we determine the spectral type of J0331-27 to be L1. The X-ray flare has an energy of E_X,F ~ 2x10^33 erg, placing it in the regime of superflares. No quiescent emission is detected, and from 2.5 Msec of XMM data we derive an upper limit of L_X,qui < 10^27 erg/s. The flare peak luminosity L_X,peak = 6.3x10^29 erg/s, flare duration tau_decay ~ 2400 s, and plasma temperature (~16 MK) are similar to values observed in X-ray flares of M dwarfs. This shows that strong magnetic reconnection events and the ensuing plasma heating are still present even in objects with photospheres as cool as ~2100 K. However, the absence of any other flares above the detection threshold of E_X,F ~2.5x10^32 erg in a total of ~2.5 Ms of X-ray data yields a flare energy number distribution inconsistent with the canonical power law dN/dE ~ E^-2, suggesting that magnetic energy release in J0331-27 -- and possibly in all L dwarfs -- takes place predominantly in the form of giant flares. 5 pages, 3 figures. Published as a Letter to A&A |
| وصف الملف: | STAMPA |
| اللغة: | English |
| URL الوصول: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::4de678a53c7e1af43777ad0f903580fc http://hdl.handle.net/11585/808929 |
| حقوق: | OPEN |
| رقم الأكسشن: | edsair.doi.dedup.....4de678a53c7e1af43777ad0f903580fc |
| قاعدة البيانات: | OpenAIRE |
| الوصف غير متاح. |