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Post Info TOPIC: Circinus X-1
Blobrana


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RE: Circinus X-1
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Title: kHz QPO pairs expose the neutron star of Circinus X-1
Authors: S. Boutloukos, M. van der Klis, D. Altamirano, M. Klein-Wolt, R. Wijnands
(revised v2)

We discovered kHz QPOs in 80 archived RXTE observations from the peculiar low-mass X-ray binary (LMXB) Circinus X-1. In 11 cases these appear in pairs in the frequency range of ~230 Hz to ~500 Hz for the upper kHz QPO and ~56 Hz to ~225 Hz for the lower kHz QPO. Their correlation with each other, which is similar to that of frequencies of kHz QPO pairs in other LMXBs containing a neutron star, and their variation by a factor two confirm that the central object is a neutron star. These are the lowest frequencies of kHz QPO pairs discovered so far and extend the above correlation over a frequency range of factor four. In this new frequency range the frequency difference of the two kHz QPOs increases monotonically by more than ~170 Hz with increasing kHz QPO frequency, challenging theoretical models.

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Blobrana


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Title: The large-scale jet-powered radio nebula of Circinus X-1
Authors: V. Tudose (1,2), R. P. Fender (3,1), C. R. Kaiser (3), A. K. Tzioumis (4), M. van der Klis (1), R. Spencer (5) ((1) Amsterdam, (2) Bucharest, (3) Southampton, (4) ATNF, (5) Manchester)

Researchers present multi-epoch observations of the radio nebula around the neutron star X-ray binary Circinus X-1 made at 1.4 and 2.5 GHz with the Australia Telescope Compact Array between October 2000 and September 2004.
The nebula can be seen as a result of the interaction between the jet from the system and the interstellar medium and it is likely that we are actually looking toward the central X-ray binary system through the jet-powered radio lobe. The study of the nebula thus offers a unique opportunity to estimate for the first time using calorimetry the energetics of a jet from an object clearly identified as a neutron star. An extensive discussion on the energetics of the complex is presented: a first approach is based on the minimum energy estimation, while a second one employs a self-similar model of the interaction between the jets and the surrounding medium. The results suggest an age for the nebula of ≤ 10^5 years and a corresponding time-averaged jet power ≥ 10^35 erg s^-1. During periodic flaring episodes, the instantaneous jet power may reach values of similar magnitude to the X-ray luminosity.

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