Search Publications
Ni Abundance in the Core of the Perseus Cluster: An Answer to the Significance of Resonant Scattering
Gastaldello, Fabio; Molendi, Silvano
Using an XMM-Newton observation of the Perseus cluster we show that the excess in the flux of the 7-8 keV line complex previously detected by ASCA and BeppoSAX is due to an overabundance of nickel rather than to an anomalously high Fe Heβ/Fe Heα ratio. This observational fact leads to the main result that resonant scattering, which was assumed to …
On the Hipparcos parallaxes of O stars
Kaper, L.; Schröder, S. E.; Brown, A. G. A. +1 more
We compare the absolute visual magnitude of the majority of bright O stars in the sky as predicted from their spectral type with the absolute magnitude calculated from their apparent magnitude and the Hipparcos parallax. We find that many stars appear to be much fainter than expected, up to five magnitudes. We find no evidence for a correlation be…
Timing analysis of the isolated neutron star RX J0720.4-3125 revisited
Cropper, Mark; Zavlin, Vyacheslav E.; Haberl, Frank +1 more
We present a reanalysis of the X-ray data for RX J0720.4-3125 presented in our previous paper, Zane et al., using more data recently available from XMM-Newton and Chandra. This analysis also corrects the ROSAT data used in that paper to the barycentric dynamical time (TDB) system, incorporates the revised XMM-Newton barycentric correction availabl…
XMM-Newton Observations of an Intermediate X-Ray Object in NGC 2276
Mushotzky, Richard F.; Davis, David S.
We present the results from a ~53 ks XMM-Newton observation of NGC 2276. This galaxy has an unusual optical morphology with the disk of this spiral appearing to be truncated along the western edge. This XMM-Newton observation shows that the X-ray source at the western edge is a bright intermediate X-ray object (IXO). Its spectrum is well fitted by…
Resolving the Stellar Population of the Standard Elliptical Galaxy NGC 3379
Ferguson, Henry C.; Gregg, Michael D.; Minniti, Dante +2 more
Using the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on board the Hubble Space Telescope, we have obtained F110W (~J) and F160W (~H) images of three fields in NGC 3379, a nearby normal giant elliptical galaxy. These images resolve individual red giant stars, yielding the first accurate color-magnitude diagrams for a normal luminou…
Relationship between solar wind low-energy energetic ion enhancements and large geomagnetic storms
Smith, Z.; Murtagh, W.; Smithtro, C.
It is well established that energetic ion enhancements (an energetic ion enhancement will hereafter be referred to as an EIE) are partly due to acceleration by interplanetary shocks as the shocks propagate towards Earth and that arrivals of these shocks at Earth are well associated with geomagnetic storms. The observation of EIEs at satellites loc…
The Orbit and Albedo of Trans-Neptunian Binary (58534) 1997 CQ29
Noll, Keith S.; Stephens, Denise C.; Grundy, Will M. +2 more
We have measured the separations and position angles of the two components of the binary trans-Neptunian object (58534) 1997 CQ29 at eight epochs. From these data we are able to constrain the orbit and mass of this binary system. The best-fitting orbit has an orbital period of P=312+/-3 days. The orbital eccentricity is e=0.45+/-0.03 an…
Oscillations in the Umbral Atmosphere
Foley, C. R.; Fredvik, T.; Kjeldseth-Moe, O. +2 more
The results of simultaneous observations of oscillations in the chromosphere, transition region, and corona above nine sunspots are presented. The data are obtained through coordinated observing with the Solar and Heliospheric Observatory — SOHO and the Transition Region And Coronal Explorer — TRACE. Oscillations are detected above each umbra. The…
XMM-Newton EPIC and Optical Monitor observations of Her X-1 over the 35-d beat period
Hailey, Charles J.; Ramsay, Gavin; Zane, Silvia +2 more
We present the results of a series of XMM-Newton European Photon Imaging Camera (EPIC) and Optical Monitor observations of Her X-1, spread over a wide range of the 35-d precession period. We confirm that the spin modulation of the neutron star is weak or absent in the low state - in marked contrast to the main or short-on states. During the states…
Recent advances in the long-wavelength radio physics of the Sun
Gopalswamy, N.
Solar radio bursts at long wavelengths provide information on solar disturbances such as coronal mass ejections (CMEs) and shocks at the moment of their departure from the Sun. The radio bursts also provide information on the physical properties (density, temperature and magnetic field) of the medium that supports the propagation of the disturbanc…