Search Publications
The stellar content, metallicity and ionization structure of H II regions
Tielens, A. G. G. M.; Peeters, E.; van der Hulst, J. M. +2 more
Observations of infrared fine-structure lines provide direct information on the metallicity and ionization structure of H Ii regions and indirectly on the hardness of the radiation field ionizing these nebulae. We have analyzed a sample of Galactic and Magellanic Cloud H Ii regions observed by the Infrared Space Observatory (ISO) to examine the in…
A rapidly variable narrow X-ray iron line in Mkn 841
Maraschi, L.; Henri, G.; Matt, G. +8 more
We report on the detection of a rapidly variable narrow Fe Kalpha line in Mkn 841. The source has been observed two times by XMM-Newton and simultaneously with BeppoSAX. The two observations, of about 10 ks long each, were separated by ~ 15 hours. The line flux reaches a maximum during the first observation and is significantly reduced in the seco…
CO and H2O vibrational emission toward Orion Peak 1 and Peak 2
van Dishoeck, E. F.; Cernicharo, J.; González-Alfonso, E. +3 more
ISO/SWS observations of Orion Peak 1 and Peak 2 show strong emission in the ro-vibrational lines of CO v=1-0 at 4.45-4.95 µm and of H2O ν2=1-0 at 6.3-7.0 µm. Toward Peak 1 the total flux in both bands is, assuming isotropic emission, ≈2.4 and ≈0.53 Lsun, respectively. This corresponds to ≈14 and ≈3% of …
Iron abundance in hot hydrogen-deficient central stars and white dwarfs from FUSE, HST, and IUE spectroscopy
Rauch, T.; Werner, K.; Kruk, J. W. +3 more
We present a first systematic investigation of the iron abundance in very hot (Teff >= 50 000 K) hydrogen-deficient post-AGB stars. Our sample comprises 16 PG 1159 stars and four DO white dwarfs. We use recent FUSE observations as well as HST and IUE archival data to perform spectral analyses with line blanketed NLTE model atmosphere…
Diffuse X-ray emission from the planetary nebula NGC 7009
Gruendl, R. A.; Chu, Y. -H.; Guerrero, M. A.
XMM-Newton EPIC observations of the planetary nebula (PN) NGC 7009, the Saturn Nebula, have detected extended X-ray emission in its central cavity. The diffuse X-ray emission must originate in the shocked fast stellar wind. The spectra show that the temperature of the hot gas is 1.8x 106 K. The rms density derived from the volume emissi…
A new, cleaner colour-magnitude diagram for the metal-rich globular cluster NGC 6528. Velocity dispersion in the Bulge, age and proper motion of NGC 6528
Feltzing, S.; Johnson, R. A.
Using two epochs of HST/WFPC2 images of the metal-rich globular cluster NGC 6528 we derive the proper motions of the stars and use them to separate the stars belonging to NGC 6528 from those of the Galactic bulge. The stellar sequences in the resulting colour-magnitude diagram for the cluster are significantly better determined than in previously …
X-ray and optical monitoring of the peculiar source 4U 1700+24/V934 Her
Cusumano, G.; Palazzi, E.; Frontera, F. +10 more
We report on ASCA and BeppoSAX X-ray broad band observations of the galactic low-luminosity X-ray source 4U 1700+24 performed on 1995 and 1998, respectively, and on (quasi-)simultaneous ground observations of its optical counterpart, V934 Her, from the Loiano 1.5-meter telescope. In order to better understand the nature of the source we also analy…
A multi-wavelength investigation of the non-thermal radio emitting O-star 9 Sgr
Corcoran, M. F.; Blomme, R.; Rauw, G. +7 more
We report the results of a multi-wavelength investigation of the O4 V star 9 Sgr (= HD 164794). Our data include observations in the X-ray domain with XMM-Newton, in the radio domain with the VLA as well as optical spectroscopy. 9 Sgr is one of a few presumably single OB stars that display non-thermal radio emission. This phenomenon is attributed …
The X-ray afterglows of gamma-ray bursts GRB 001025A and GRB 010220 observed with XMM-Newton
Santos-Lleó, M.; Ehle, M.; Watson, D. +5 more
The X-ray afterglows of GRB 001025A and GRB 010220 were detected by XMM-Newton with an average 0.2-10.0 keV flux of 4.4 and 3.3*E-14 erg cm-2 s-1 respectively; the afterglow of GRB 001025A is observed to decay. Afterglows at other wavelengths were not detected for either burst. A set of broadened soft X-ray emissio…
Trajectories of microwave prominence eruptions
Culhane, J. L.; Hori, K.
On the basis of 17 GHz microwave images from the Nobeyama Radioheliograph near solar maximum (1999-2000), we examined trajectories of 50 prominence eruptions in order to address how prominence motions affect or reflect the surrounding coronal structures. We marked the heliocentric latitude of the top of the moving prominences on the white-light sy…