The accretion process in young stars produces intense X-rays. Very-low-massstars (VLMS) cannot have post-shock hotter than 2MK, preventing any X-rayemission. Nonetheless 2 accreting VLMS showed X-rays from accretion shocks. Toconfirm or reject this finding we propose to observe 3 other accreting VLMS withXMM/EPIC (10ks for each target) to measure the plasma temperature, and hencedistinguish between X-rays due to corona or to accretion. Accretion-drivenX-rays in VLMS would indicate post-shocks hotter than 2MK, possible only ifaccretion velocity is higher than free fall velocity. Checking the hypothesis ofaccretion-driven X-rays in VLMS is fundamental to test whether anothermechanism, other than gravity, accelerates accreting material.
Instrument
EMOS1, EMOS2, EPN, OM, RGS1, RGS2
Temporal Coverage
2012-10-13T18:33:50Z/2013-01-11T02:42:50Z
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 Costanza Argiroffi, 2014, 'Can accretion shocks of very-low-mass stars produce X-ray emissionquestionMark', 17.56_20190403_1200, European Space Agency, https://doi.org/10.5270/esa-z6u5ofg
