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A large X-ray flare from the Herbig Ae star V892 Tau
Micela, G.; Favata, F.; Giardino, G. +1 more
We report the XMM-Newton observation of a large X-ray flare from the Herbig Ae star V892 Tau. The apparent low mass companion of V892 Tau, V892 Tau NE, is unresolved by XMM-Newton. Nevertheless there is compelling evidence from combined XMM-Newton and Chandra data that the origin of the flare is the Herbig Ae star V892 Tau. During the flare the X-…
X-ray spectroscopy of the Hertzsprung-gap giant star 31 Com, observed with XMM-Newton
Peres, G.; Maggio, A.; Scelsi, L. +1 more
We have analysed the XMM-Newton X-ray spectra of the yellow giant 31 Com with the aim of deriving information on the coronal structures of this archetypical Hertzsprung-gap star. To determine the emission measure distribution vs. temperature, EM(T), and the elemental abundances of the coronal plasma, with an accurate line-based approach, we have d…
The Continued Spectral Evolution of the Neutron Star RX J0720.4-3125
Verbunt, Frank; Vink, Jacco; de Vries, Cor P. +1 more
We observed the isolated neutron star RX J0720.4-3125 with Chandra's Low Energy Transmission Grating Spectrometer, following the XMM-Newton discovery of the long-term spectral evolution of this source. The new observation shows that the spectrum of RX J0720.4-3125 has continued to change in the course of 5 months. It has remained hard, similar to …
Microlensing Candidates in M87 and the Virgo Cluster with the Hubble Space Telescope
Zurek, David R.; Zepf, Stephen E.; Lauer, Tod R. +4 more
The position of the giant elliptical galaxy M87 at the center of the Virgo Cluster means that the inferred column density of dark matter associated with both the cluster halo and the galaxy halo is quite large. This system is thus an important laboratory for studying massive dark objects in elliptical galaxies and galaxy clusters by gravitational …
Why does the intermediate polar V405 Aurigae show a double-peaked spin pulse?
Hellier, Coel; Evans, P. A.
V405 Aurigae is an intermediate polar showing a double-peaked pulsation in soft X-rays and a single-peaked pulsation in harder X-rays. From XMM-Newton observations, we find that the soft band is dominated by blackbody emission from the heated white dwarf surface. Such emission is at a maximum when either magnetic pole points towards us, explaining…
The reprocessing features in the X-ray spectrum of the NELG MCG -5-23-16
Bianchi, S.; Balestra, I.; Matt, G.
We present results from the spectral analysis of the Seyfert 1.9 galaxy MCG -5-23-16, based on ASCA, BeppoSAX, Chandra and XMM-Newton observations. The spectrum of this object shows a complex iron Kα emission line, which is best modeled by a superposition of a narrow and a broad (possibly relativistic) iron line, together with a Compton reflection…
Iron Kα Emission from the Low-Luminosity Active Galaxies M81 and NGC 4579
Schurch, N. J.; Dewangan, G. C.; Griffiths, R. E. +1 more
We report on the XMM-Newton spectroscopy of the low-luminosity active galaxies (LLAGNs) M81 and NGC 4579, both of which have known black hole masses and well-sampled spectral energy distributions (SEDs). The iron Kα line profiles from both LLAGNs can be described in terms of two components: a narrow line at 6.4 keV, and a moderately broad line (FW…
The X-ray emission mechanism in the protostellar jet HH 154
Orlando, S.; Bonito, R.; Peres, G. +2 more
We study the mechanism causing the X-ray emission recently detected in protostellar jets, by performing a detailed modeling of the interaction between a supersonic jet originating from a young stellar object and the ambient medium, for various values of density contrast, ν, between the ambient density and the jet, and of Mach number, M; radiative …
Models for Solar Magnetic Loops. III. Dynamic Models and Coronal Diagnostic Spectrometer Observations
Landini, M.; Landi, E.
In the present work SOHO Coronal Diagnostic Spectrometer (CDS) observations of a quiescent active region loop are compared to a steady state, dynamic loop model. Three different heating functions are adopted: uniform, concentrated at the top, and concentrated at the footpoints. Predicted temperature and density profiles of the selected loop are co…
Chandra observations of five X-ray transient galactic nuclei
Vaughan, S.; Warwick, R. S.; Edelson, R.
We report on exploratory Chandra observations of five galactic nuclei that were found to be X-ray bright during the ROSAT All-Sky Survey (with LX>~ 1043 erg s-1) but subsequently exhibited a dramatic decline in X-ray luminosity. Very little is known about the post-outburst X-ray properties of these enigmatic sou…