HMCnc is a system hosting two white dwarfs and has the shortest known orbital period (321s). The X-ray monitoring of this unique source over the last 16 years, made it possible to assess that the modulation is steadly decreasing at about 1ms/yr. Two competing scenarios have been suggested: the direct impact model, involving matter accretion, and the unipolar inductor, which considers the WDs as components of an electric circuit. In the former the orbital decay is expected to be ruled by GW emission only with a second period derivative of <-1E-7s/yr^2, while in the latter magnetic stresses produce a larger component. The additional pointing will allow us to achieve a sensitivity of -8E-8 s/yr^2, providing the way of undertanding the nature of HMCnc.
Instrument
EMOS1, EMOS2, EPN, OM, RGS1, RGS2
Temporal Coverage
2012-10-12T23:40:21Z/2012-10-13T08:55:39Z
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, Prof Gian Luca Israel, 2013, 'Detecting the orbital period decay of HMCnc: G.W. emission vs magnetic stresses', 17.56_20190403_1200, European Space Agency, https://doi.org/10.5270/esa-qyjzaur
