EXTraS discovery of a peculiar flaring X-ray source in the Galactic globular cluster NGC 6540
May 21, 20185 pages
Published in:
- Astron.Astrophys. 616 (2018) A36
- Published: Aug 1, 2018
e-Print:
- 1805.08057 [astro-ph.HE]
DOI:
- 10.1051/0004-6361/201833086 (publication)
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Abstract: (EDP Sciences)
We report the discovery of a flaring X-ray source 7″ from the center of the globular cluster NGC 6540 obtained during the EXTraS project devoted to a systematic search for variability in archival data of the XMM–Newton satellite. The source had a quiescent X-ray luminosity on the order of ~1032 erg s−1 in the 0.5–10 keV range (for a distance of NGC 6540 of 4 kpc) and showed a flare lasting about 300 s. During the flare, the X-ray luminosity increased by more than a factor 40, with a total emitted energy of ~1036 erg. These properties, as well as Hubble Space Telescope photometry of the possible optical counterparts, suggest the identification with a chromospherically active binary in the cluster. However, the flare luminosity is significantly higher than what is commonly observed in stellar flares of such a short duration, leaving open the possibility of other interpretations.Key words: globular clusters: individual: NGC 6540 / stars: flare / X-rays: binaries / X-rays: burstsNote:
- To appear in Astronomy and Astrophysics
- globular clusters: individual: NGC 6540
- stars: flare
- X-rays: binaries
- X-rays: bursts
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