Search Publications
Inferences on the solar envelope with high-degree modes
Christensen-Dalsgaard, J.; Rabello-Soares, M. C.; Basu, S. +1 more
We investigate the structure of the Sun by helioseismic inversion of a set of p-mode frequencies which includes new precise observations of modes with high degree (l < 1000) obtained from the MDI instrument on the SOHO satellite (Rhodes et al. \cite{rh98}). Such data have the potential to improve the resolution of the solar structure in the nea…
A Comparison between Coronal Emission Lines from an Isothermal Spectrum Observed with the Coronal Diagnostic Spectrometer and CHIANTI Emissivities
Dere, K. P.; Landi, E.; Feldman, U.
The present paper compares off-disk spectral observations of the solar corona in the ranges 307-379 and 513-633 Å with theoretical emissivities calculated using the CHIANTI database. The observed spectra were recorded by the Coronal Diagnostic Spectrometer instrument on board the Solar and Heliospheric Observatory using the normal-incidence portio…
Calibration of the distance scale from galactic Cepheids. II. Use of the HIPPARCOS calibration
Musella, I.; Paturel, G.; Theureau, G. +3 more
New estimates of the distances of 36 nearby galaxies is presented. These are based on the calibration of the V- and I-band Period-Luminosity relations for galactic Cepheids measured by the HIPPARCOS mission. The distance moduli are obtained in a classical way. The statistical bias due to the incompleteness of the sample is corrected according to t…
XMM-Newton Observations of the Spiral Galaxy M74 (NGC 628)
Soria, Roberto; Kong, Albert K. H.
The face-on spiral galaxy M74 (NGC 628) was observed by XMM-Newton on 2002 February 2. In total, 21 sources are found in the inner 5' from the nucleus (after rejection of a few sources associated to foreground stars). Hardness ratios suggest that about half of them belong to the galaxy. The higher luminosity end of the luminosity function is fitte…
Intermediate- and High-Velocity Ionized Gas toward ζ Orionis
Jenkins, Edward B.; York, Donald G.; Raymond, John C. +2 more
We combine near-UV spectra obtained with the Hubble Space Telescope GHRS echelle with far-UV spectra obtained with the Interstellar Medium Absorption Profile Spectrograph and Copernicus to study the abundances and physical conditions in the predominantly ionized gas seen at high velocity (-105 km s-1<~vsolar<~-65 km s
The Galactic distribution of asymptotic giant branch stars
Knapp, G. R.; Ivezić, Željko; Jackson, Tom
We study the Galactic distribution of ~10000 candidate asymptotic giant branch (AGB) stars selected by IRAS colours and variability index. The distance to each star is estimated by assuming a narrow luminosity function and a model-derived bolometric correction. The characteristic AGB star luminosity, LAGB, is determined from the conditi…
The Star Formation History of the Blue Compact Dwarf Galaxy UGCA 290
Greggio, Laura; Hopp, Ulrich; Schulte-Ladbeck, Regina E. +1 more
We present the star formation history of UGCA 290, a galaxy with properties intermediate between blue compact dwarfs (BCDs) and dwarf irregulars. This galaxy is particularly interesting because its young stellar population is extremely similar to that of the well-studied type iE blue compact dwarf VII Zw 403, despite its different spatial morpholo…
A Probable Optical Counterpart to the Isolated Neutron Star RX J1308.6+2127
Kulkarni, S. R.; van Kerkwijk, M. H.; Kaplan, D. L.
Using a very deep observation from the Hubble Space Telescope Space Telescope Imaging Spectrometer, we have searched for an optical counterpart to the nearby radio-quiet isolated neutron star RX J1308.6+2127 (RBS 1223). We have identified a single object in the 90% Chandra error circle that we believe to be the optical counterpart. This object has…
The peculiar cooling flow cluster RX J0820.9+0752
Fabian, A. C.; Allen, S. W.; Edge, A. C. +2 more
We present observations of the cluster of galaxies associated with the X-ray source RX J0820.9+0752 and its dramatic central cluster galaxy in the optical and X-ray wavebands. Unlike other cooling flow central cluster galaxies studied in detail, this system does not contain a powerful radio source at its core, and so provides us with an important …
XMM-Newton and Very Large Array Observations of the Variable Wolf-Rayet Star EZ Canis Majoris: Evidence for a Close Companion?
Skinner, Stephen L.; Zhekov, Svetozar A.; Güdel, Manuel +1 more
We present new X-ray and radio observations of the Wolf-Rayet star EZ CMa (HD 50896) obtained with XMM-Newton and the Very Large Array (VLA). This WN4 star exhibits optical and UV variability at a period of 3.765 days whose cause is unknown. Binarity may be responsible, but the existence of a companion has not been proven. The radio spectral energ…