The neutron star LMXB, Cen X-4, has been in quiescence since 1979. Its quiescentX-ray emission consists of both a thermal and power-law component, withvariability observed on timescales as short as hundreds of seconds and as longas years. Yet, this variability is not understood. We recently found Cen X- 4 ina historically low-state, over 5 times fainter than before. Such a differencerequires the thermal component to vary. This poses a big problem for usingthermal emission to measure neutron star radii and constrain the dense matterequation of state. To investigate the nature of this variability and theemission mechanisms from X-rays through to the optical, we propose four, 12 ksobservations of Cen X-4 to obtain good X-ray spectra and accurate photometry in 5 optical/UV filters.
Instrument
EMOS1, EMOS2, EPN, OM, RGS1, RGS2
Temporal Coverage
2010-08-25T07:49:02Z/2011-01-31T20:56:23Z
Version
17.56_20190403_1200
Mission Description
The European Space Agencys (ESA) X-ray Multi-Mirror Mission (XMM-Newton) was launched by an Ariane 504 on December 10th 1999. XMM-Newton is ESAs second cornerstone of the Horizon 2000 Science Programme. It carries 3 high throughput X-ray telescopes with an unprecedented effective area, and an optical monitor, the first flown on a X-ray observatory. The large collecting area and ability to make long uninterrupted exposures provide highly sensitive observations. Since Earths atmosphere blocks out all X-rays, only a telescope in space can detect and study celestial X-ray sources. The XMM-Newton mission is helping scientists to solve a number of cosmic mysteries, ranging from the enigmatic black holes to the origins of the Universe itself. Observing time on XMM-Newton is being made available to the scientific community, applying for observational periods on a competitive basis.
European Space Agency, Dr Edward Cackett, 2012, 'The nature of quiescent emission in the neutron star Cen X-4', 17.56_20190403_1200, European Space Agency, https://doi.org/10.5270/esa-2m8a4xo
