The Return of the Bursts: Thermonuclear Flashes from Circinus X-1

We report the detection of 15 X-ray bursts with RXTE and Swift observations of the peculiar X-ray binary Circinus X-1 (Cir X-1) during its 2010 May X-ray re-brightening. These are the first X-ray bursts observed from the source after the initial discovery by Tennant and collaborators, 25 years ago....

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Bibliographic Details
Published in:Astrophysical journal. Letters 2010-08, Vol.719 (1), p.L84-L89
Main Authors: Linares, M, Watts, A, Altamirano, D, Soleri, P, Degenaar, N, Yang, Y, Wijnands, R, Casella, P, Homan, J, Chakrabarty, D, Rea, N, Armas-Padilla, M, Cavecchi, Y, Kalamkar, M, Kaur, R, Patruno, A, van der Klis, M
Format: Article
Language:English
Subjects:
ACCRETION DISKS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
EVOLUTION
MAGNETIC FIELDS
NEUTRON STARS
STAR EVOLUTION
STARS
SYMMETRY
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Summary:We report the detection of 15 X-ray bursts with RXTE and Swift observations of the peculiar X-ray binary Circinus X-1 (Cir X-1) during its 2010 May X-ray re-brightening. These are the first X-ray bursts observed from the source after the initial discovery by Tennant and collaborators, 25 years ago. By studying their spectral evolution, we firmly identify nine of the bursts as type I (thermonuclear) X-ray bursts. We obtain an arcsecond location of the bursts that confirms once and for all the identification of Cir X-1 as a type I X-ray burst source, and therefore as a low magnetic field accreting neutron star. The first five bursts observed by RXTE are weak and show approximately symmetric light curves, without detectable signs of cooling along the burst decay. We discuss their possible nature. Finally, we explore a scenario to explain why Cir X-1 shows thermonuclear bursts now but not in the past, when it was extensively observed and accreting at a similar rate.
ISSN:2041-8205
2041-8213
DOI:10.1088/2041-8205/719/1/L84