Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe first optical validation of an XLEO: a detection in the XMM-Newton observation of the CDFS
114
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present the first optical validation of an X-ray Line-Emitting Object (XLEO) discovered in the XMM-Newton observation of the Chandra Deep Field South. The object is an AGN at z_x ~ 0.66. An optical spectrum of the source indeed confirms and refines (z_o = 0.665) the redshift obtained from the X-ray line. The X-ray and optical properties of the source are presented and discussed.
rate research
Read More
We present the first results from a 40 ks Guaranteed Time XMM-Newton pointing in the Pleiades. We detect almost all early-mid dM members in the field and several very low mass (VLM) stars - including the brown dwarf (BD) candidate Roque 9 - and investigate the variation of X-ray activity levels, hardness ratios and flare frequency with spectral type down to the BD regime.
We report the analysis of an XMM-Newton observation of the close binary HD159176 (O7V + O7V). The observed L_X/L_bol ratio reveals an X-ray luminosity exceeding by a factor ~ 7 the expected value for X-ray emission from single O-stars, therefore suggesting a wind-wind interaction scenario. EPIC and RGS spectra are fitted consistently with a two temperature mekal optically thin thermal plasma model, with temperatures ranging from ~ 2 to 6 10^6 K. At first sight, these rather low temperatures are consistent with the expectations for a close binary system where the winds collide well before reaching their terminal velocities. We also investigate the variability of the X-ray light curve of HD159176 on various short time scales. No significant variability is found and we conclude that if hydrodynamical instabilities exist in the wind interaction region of HD159176, they are not sufficient to produce an observable signature in the X-ray emission. Hydrodynamic simulations using wind parameters from the literature reveal some puzzling discrepancies. The most striking one concerns the predicted X-ray luminosity which is one or more orders of magnitude larger than the observed one. A significant reduction of the mass loss rate of the components compared to the values quoted in the literature alleviates the discrepancy but is not sufficient to fully account for the observed luminosity. Because hydrodynamical models are best for the adiabatic case whereas the colliding winds in HD159176 are most likely highly radiative, a totally new approach has been envisaged... (see paper for complete abstract)
We present the first X-ray observation of Jupiter by XMM-Newton. Images taken with the EPIC cameras show prominent emission, essentially all confined to the 0.2-2.0 keV band, from the planets auroral spots; their spectra can be modelled with a combination of unresolved emission lines of highly ionised oxygen (OVII and OVIII), and a pseudo-continuum which may also be due to the superposition of many weak lines. A 2.8 sigma enhancement in the RGS spectrum at 21-22 A (~0.57 keV) is consistent with an OVII identification. Our spectral analysis supports the hypothesis that Jupiters auroral emissions originate from the capture and acceleration of solar wind ions in the planets magnetosphere, followed by X-ray production by charge exchange. The X-ray flux of the North spot is modulated at Jupiters rotation period. We do not detect evidence for the ~45 min X-ray oscillations observed by Chandra more than two years earlier. Emission from the equatorial regions of the planets disk is also observed. Its spectrum is consistent with that of scattered solar X-rays.
We present results from the XMM-Newton observation of the binary cluster A1750 at z = 0.086. We have performed a detailed study of the surface brightness, temperature and entropy distribution and confirm that the two main clusters of the system (A1750 N and A1750 C) have just started to interact. From the temperature distribution, we calculate that they are likely to merge sometime in the next 1 Gyr. The more massive cluster, A1750 C, displays a more complicated temperature structure than expected. We detect a hot region associated with a density jump ~450 kpc east of the cluster centre, which appears to be a shock wave. This shock is not connected with the binary merger, but it is intrinsic to A1750 C itself. From simple physical arguments and comparison with numerical simulations, we argue that this shock is related to a merging event that A1750 C has suffered in the past 1-2 Gyr. The larger scale structure around A1750 suggests that the system belongs to a rich supercluster, which would presumably increase the likelihood of merger events. These new XMM-Newton data thus show that A1750 is a complex system, where two clusters are starting to interact before having re-established equilibrium after a previous merger. This merger within a merger indicates that the present day morphology of clusters may depend not only on on-going interactions or the last major merging event, but also on the more ancient merger history, especially in dense environments.
We present the observation of the Tycho supernova remnant obtained with the EPIC and RGS instruments onboard the XMM-Newton satellite. We compare images and azimuthally averaged radial profiles in emission lines from different elements (silicon and iron) and different transition lines of iron (Fe L and Fe K). While the Fe XVII L line and Si XIII K line images are globally spatially coincident, the Fe K emission clearly peaks at a smaller radius, indicating a higher temperature toward the reverse shock. This is qualitatively the profile expected when the reverse shock, after travelling through the outer power-law density profile, has entered the central plateau of the ejecta. The high energy continuum map has an overall smooth distribution, with a similar extent to the radio emission. Its radial profile peaks further out than the lines emission. Brighter and harder continuum regions are observed with a rough bipolar symmetry in the eastern and western edges. The spectral analysis of the southeastern knots supports spatial variations of the relative abundance of silicon and iron, which implies an incomplete mixing of the silicon and iron layers.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
