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Evolutionary status and age spread in the young LMC cluster NGC 1850A
Caloi, V.; Cassatella, A.
IUE spectra have been obtained for 15 members of the very young LMC cluster NGC 1850A. The extinction law toward the cluster is similar to the one generally accepted for the 30 Dor region. We derive the effective temperatures and bolometric luminosities to estimate the age and mass for each star. An age spread of 2 to 10 Myr is estimated, suggesti…
A Photometric and Spectrophotometric Study of MR Cygni
Hubeny, I.; Linnell, A. P.; Etzel, P. B. +1 more
A self-consistent, physically accurate program suite has been used in an accurate simulation of new spectroscopy and photometry of MR Cygni. Analysis of both the spectroscopic and photometric data used spectrum synthesis techniques and a synthetic photometry augmentation of a light synthesis program package. The theoretical light curves closely fi…
UVCS/SOHO: The First Two Years
Cranmer, S. R.; Noci, G.; Kohl, J. L.
The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) has observed the extended solar corona between 1 and 10 R· for more than two years. We review spectroscopic and polarimetric measurements made in coronal holes, equatorial streamers, and coronal mass ejections, as well as selected non-solar targets. UVCS/SOHO has provided a great amount of …
Compact HII regions in the Large Magellanic Cloud observed by ISO
Comeron, F.; Claes, P.
We present ISOCAM observations of five fields in the Large Magellanic Cloud centered on IRAS point sources with colors of ultracompact HII regions. Three bright sources of parsec or subparsec size, with luminosities consistent with being embedded O stars, are detected at 15 mu m in two fields belonging to the HII region N 159. Using published high…
ISO observations of the GRB 970402 error box
Altieri, B.; Palazzi, E.; Frontera, F. +12 more
Following the detection by BeppoSAX of GRB 970402, a Target-of-Opportunity Observation by ISO was scheduled for 5 April, about 55-hours after the event, i.e. simultaneous with a second BeppoSAX pointing. The CAM instrument was used in the 6('') /pixel mode, in the 8-15 mu m band (IRAS) for covering the entire BeppoSAX GRB error box. A further obse…
A Possible Companion to Proxima Centauri
Benedict, G. F.; Franz, O. G.; Bruhweiler, F. C. +10 more
We report Hubble Space Telescope observations that provide evidence for a companion to Proxima Centauri (Gl 551), the closest star to the Sun. Data acquired with the Faint Object Spectrograph (FOS), used as a coronagraphic camera, show excess light that can be interpreted as being from a substellar object within 0.5" of Proxima Cen. Two observatio…
Discovery of a 6.4 Micron Dust Feature in Hydrogen-Poor Planetary Nebulae
Borkowski, Kazimierz J.; Bregman, Jesse D.; Tsvetanov, Zlatan I. +2 more
Hydrogen-poor planetary nebulae (PNe) Abell 58, Abell 78, and IRAS 15154-5258 were observed with the ISOPHOT low-resolution spectrometer on board the Infrared Space Observatory. Polycyclic aromatic hydrocarbon (PAH) features, commonly seen in H II regions, PNe, and in the diffuse interstellar medium, are absent from their infrared (IR) spectra. A …
IUE high-resolution observations of the symbiotic star CHCygni: confirmation of the triple-star model
Bode, M. F.; Drechsel, H.; Skopal, A. +1 more
We present and analyse ultraviolet high-resolution spectra of CHCyg taken during the whole period of the International Ultraviolet Exploler (IUE) mission. Our analysis of the observed variation in the line spectrum confirms a triple-star model recently suggested for CHCyg. Radial velocities of emission lines, which are subject to eclipse in the sy…
The Close Magnetic/Nonmagnetic Double-degenerate Binary LB 11146
Liebert, James; Schmidt, Gary D.; Smith, Paul S.
Spacecraft imaging of the remarkable strongly magnetic/nonmagnetic white dwarf binary system LB 11146 establishes an upper limit to the component separation of 0.025", corresponding to a 90% likelihood that the orbital separation is a < 500 R_⊙. The large and nearly identical inferred masses for the two components make it very likely that some …
Simultaneous Hubble Space Telescope/Rossi X-Ray Timing Explorer Observations of Scorpius X-1
Kallman, T.; Boroson, B.; Vrtilek, S. D.
Scorpius X-1 is the brightest extrasolar point source of X-rays and may serve as a prototype for low-mass X-ray binaries as a class. It has been suggested that the UV and optical emission arise as a result of reprocessing of X-rays and that a likely site for such reprocessing is an accretion disk around the X-ray source. If UV and optical emission…