XMM-Newton Status Report - May 2007
Operations and Archiving
A Mission Extended Operations Review (MEOR) is planned for early May. This has the objective of making recommendations on the mission operation concept and support, appropriate for the interval beyond the design lifetime of the mission. The MEOR will also examine proposed changes in the operational concept designed to reduce costs while maintaining an acceptable level of scientific return.
The selection of the successful AO-6 proposals has been made by the Observation Time Allocation Committee and the proposers have been informed on the outcomes. The next observing Announcement of Opportunity (AO-7) will open on 28 August 2007 with a deadline of 5 October 2007.
The next XMM-Newton Science Operations Centre organized workshop, "XMM-Newton: The Next Decade", will take place on 4-6 June 2007 at ESAC. As the title suggests, the focus of the workshop is to look forward to the science topics likely to be addressed by XMM-Newton observations in the future paying particular attention to any changes in operational concepts needed to accommodate them. The event page is linked in the right-hand navigation.
Science Highlights
XMM-Newton data have been published in 1428 refereed papers, of which 85 are from 2007.
XMM-Newton, together with NASA's Chandra X-ray observatory has found evidence for a new class of supernova. This strengthens the case for a population of very short lived stars that are rapidly destroyed by thermonuclear explosions. Thermonuclear, or Type Ia, supernova occur in binary systems when a white dwarf star becomes to massive as it accretes material from a companion star and it collapses forming an incredibly dense neutron star. These supernovea are often used as standard candles allowing for example, the nature of dark energy and dark matter to be investigated. However, observations of two supernova remnants (SNRs) in the Large Magellenic Cloud, DEM L238 and DEM L249, have cast doubt on the standard models of Type Ia explosions.
The observations revealed the presence of bright central emission surrounded by a faint shell. The central emissions show an overabundance of Iron - a characteristic of white dwarf collapse (Type Ia) - rather than the more common Type II SNR due to the explosion of a massive star. However, the gas in the remnants is much denser and brighter in X-rays than expected from Type Ia explosions. This implies that the white dwarves exploded into very dense environments which could only be produced by the winds of very massive stars since these expel more gas into their surroundings during their short lives.
Since such massive stars have very short lifetimes, this means that Type Ia supernovae could occur much earlier in the Universe's history than expected, allowing them to probe the expansion of the Universe at these early epochs. Another possibility is that these Type Ia explosions may also differ in other properties. If so, the assumption that Type Ia's are standard candles may have to be revised, complicating the study of dark energy and dark matter.