HMCnc is a two white dwarfs system with the shortest orbital period (321s). TheX-ray monitoring of this unique source over the last 20 years, made it possibleto assess that the modulation is decreasing at about 1ms/yr. Two competingscenarios have been suggested for HMCnc: the direct impact model, involvingmatter accretion, and the unipolar inductor, which considers the WDs ascomponents of an electric circuit. In the former the orbital decay is expectedto be ruled by GW emission only and a second period derivative <-1E-7s/yr/yr isexpected, while in the latter magnetic stresses are expected to produce a largercomponent. The new pointing we are requesting will allow us to detect a secondperiod derivative or to set a tight upper limit, thus discerning between the two competing models.
Instrument
EMOS1, EMOS2, EPN, OM, RGS1, RGS2
Temporal Coverage
2016-04-18T08:40:58Z/2016-04-18T17:34:19Z
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, 2017, '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-b84dp53
