Search Publications
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…
XMM-Newton observations of the Seyfert 1 galaxy Mrk 335
Gondoin, P.; Santos-Lleo, M.; Orr, A. +1 more
We report on an XMM-Newton observation of the Seyfert 1 galaxy Mrk 335 performed in December 2000. The power law component of its spectrum above 2 keV has a photon index Gamma =2.3 much steeper than that of a ``normal'' Seyfert 1 galaxy. A broad spectral feature is observed around 6.0 keV (+/-1 keV) that can be fitted by a relativistic emission pr…
Analysis of colour-magnitude diagrams of rich LMC clusters: NGC 1831
Santiago, B. X.; Kerber, L. O.; Valls-Gabaud, D. +1 more
We present the analysis of a deep colour-magnitude diagram (CMD) of NGC 1831, a rich star cluster in the LMC. The data were obtained with HST/WFPC2 in the F555W ( ~ V) and F814W ( ~ I) filters, reaching m555 ~ 25. We discuss and apply a method of correcting the CMD for sampling incompleteness and field star contamination. Efficient use …
HST, VLT, and NTT imaging search for wide companions to bona-fide and candidate brown dwarfs in the Cha I dark cloud
Neuhäuser, R.; Comerón, F.; Brandner, W. +2 more
We present results from a deep imaging search for companions around the young bona-fide and candidate brown dwarfs Cha Hα 1 to 12 in the Cha I dark cloud, performed with HST WFPC2 (R, I, Hα ), VLT FORS1 (VRI), and NTT SofI (JHKs). We find 16 faint companion candidates around five primaries with separations between 1.5'' and 7…
The Phoenix galaxy: UGC 4203 re-birth from its ashes?
Perola, G. C.; Fiore, F.; Guainazzi, M. +1 more
We report on a dramatic transition between a Compton-thick, reflection-dominated state and a Compton-thin state in the Seyfert 2 galaxy UGC 4203, discovered by comparing a recent (May 2001) XMM-Newton observation with ASCA observations performed about six years earlier. This transition can be explained either as a change in the column density of t…