|Unraveling the Outburst and Quiescent Emission Properties of the Enigmatic Binary Cir X-1
|Cir X-1 is an unusual X-ray binary in that it has large scale outbursts every 16.58 d. The cause of these outbursts is believed to be due to episodic mass transfer events that occur when a non-degenerate companion, in a highly eccentric orbit around a compact object, passes through periastron. In the 1970.s, Cir X-1 was in a very luminous high state that resembled the outbursts of X-ray transients with black hole primaries. At this time, the maxima of the outbursts reached to K = 7.7, even though Cir X-1 is more than 5 kpc from the Sun! In the early 1980.s, Cir X-1 was observed to show Type I X-ray bursts that indicated the compact object was a neutron star. Unfortunately, these events stopped shortly after they began, only resuming recently. In the 1990.s, however, the X-ray behavior of Cir X-1 was finally confirmed to be due to accretion onto a neutron star primary. What makes Cir X-1 especially interesting is the presence of an ultra-relativistic jet. This jet is seen in both the X-ray and radio, and extends to parsec scales. There is also evidence that this jet is precessing. If true, then Cir X-1 is the neutron star counterpart to the unusual high mass X-ray binary system SS433 (where the compact primary is a black hole). We propose to obtain PACS + SPIRE photometry of Cir X-1 both in outburst, and during quiescence, to identify the dominant emission processes that occur during these phases. These observations will allow us to determine if the outbursts are due to a synchrotron jet that simply turns on during outburst or, alternatively, whether the jet is always present, but precesses across our line-of-sight once every 16 d. Precessing jets are seen in pre-main sequence stars, other X-ray binaries, and AGN. Given its extensive observational history, Cir X-1 is the ideal source for understanding the processes responsible for launching relativistic jets. Our program requests 2.5 hr of Herschel time.
|Herschel Observations of Circinus X-1 during Outburst and Quiescence . Harrison Thomas E. et al. . The Astronomical Journal, Volume 148, Issue 1, article id. 22, 19 pp. (2014). . 148 . 10.1088/0004-6256/148/1/22 . 2014AJ....148...22H ,
|Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
|Publisher And Registrant
|European Space Agency
|European Space Agency, 2013, OT2_tharriso_6, SPG v14.2.0. https://doi.org/10.5270/esa-30zenhb