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Imaging the shell of nova Cygni 1992 with HST.
Paresce, Francesco
The Faint Object Camera (FOC) on the Hubble Space Telescope (HST) observed Nova Cyg 1992 on May 31, 1993 in the UV. The images reveal a bright, well defined, circular, inhomogeneous ring of emission of 0.13 sec radius centered on the star. The data indicate that the ring is most likely due to a thin, limb-brightened shell of emitting material of r…
On the modulated light in the intermediate polar FO Aquarii/H 2215-086.
Mukai, K.; de Martino, D.; Buckley, D. A. H. +1 more
The modulated light in the intermediate polar FO Aqr at the three periods Pspin = 20.9 min, Porb = 4.85 h and Pbeat = 22.5 min is studied in different spectral ranges to derive information on their nature. In this system the accretion geometry, with or without an accretion disc, is still a matter of debate (Hellier…
The distance to the Complex C of high-velocity halo clouds
Wakker, B. P.; Bomans, D. J.; de Boer, K. S. +5 more
High resolution IUE spectra of sdB and HBB stars in the direction of the concentration of neutral hydrogen gas at high-velocity named Complex C have been obtained. The interstellar absorption line profiles are compared with Effelsberg HI 21-cm emission profiles. Since the distances to the stars are known from spectroscopic investigations, firm low…
Modeling the X-ray spectrum of Kepler's supernova remnant.
Ballet, J.; Decourchelle, A.
We introduce realistic initial conditions for the ejecta density profile (power law) and propose to explain the silicon, sulphur and iron excess seen in Kepler's supernova remnant as associated with shocked enriched ejecta. We assume the composition of the interstellar medium to be solar. We describe the hydrodynamic interaction between the ejecta…
Abundance and origin of the CH_n_^+^ ions in the coma of comet P/Halley
Altwegg, K.; Balsiger, H.; Geiss, J.
We analyzed data in the mass/charge group 12-16 amu/e from the High Intensity Sensor (HIS) of the Ion Mass Spectrometer IMS on board the spacecraft Giotto during the comet Halley flyby. The most abundant ion in this mass/charge range is CH_3_^+^. Its parent molecules are either CH_2_, CH_3_ or CH_4_. Hereby, the methane abundance serves as an impo…
High-resolution spectroscopy of two young stars between the Magellanic Clouds
Howarth, I. D.; Dufton, P. L.; Hambly, N. C. +3 more
High-resolution echelle spectra of one main sequence B-type star and one B-type supergiant in the Bridge between the Magellanic Clouds have been obtained using the 3.9-m Anglo-Australian Telescope. These spectra have been analyzed in conjunction with IUE low-resolution observations by using ATLAS9 LTE model atmosphere techniques, to derive the ste…
Faint blue stars in the core of NGC 6397.
Paresce, F.; de Marchi, G.
The inner core of the globular cluster NGC 6397 within approximately 6 arcsecs of the geometrical centre has been investigated with high resolution deep images taken through several medium- and broad-band UV filters with the Faint Object Camera (FOC) on board the Hubble Space Telescope (HST). Approximately 110 stars down to instrumental magnitude …
A "cool" PG 1159 star discovered by the Hamburg Schmidt Survey: NLTE analysis of HS 0704+6153.
Werner, K.; Dreizler, S.; Jordan, S. +1 more
The discovery of a new PG 1159 star by follow-up spectroscopy of candidates selected from objective-prism plates of the Hamburg Schmidt Survey is presented. From a NLTE model atmosphere analysis an effective temperature of 65 000 K and a surface gravity of logg=7.0 is determined, which together with the extreme helium abundance (H/He<1 by numbe…
Ultraviolet and optical spectroscopy of a B supergiant star in M 31.
Massey, Philip; Hutchings, J. B.; Bianchi, Luciana +4 more
We present and discuss the UV spectrum of the supergiant star in NGC206-277 in M 31, obtained with the Faint Object Spectrograph (FOS) on Hubble Space Telescope. Customised extraction of the data was used to properly correct for the background light in the FOS. An optical blue spectrum taken at KPNO is also shown. From the optical and UV line spec…
G191-B2B: accurate abundances for nitrogen, silicon, and iron from GHRS observations.
Koester, D.; Vauclair, G.; Ferlet, R. +5 more
We present a new abundance analysis from high resolution GHRS spectra for 3 heavy elements showing spectral lines that are almost certainly of photospheric origin. The derived values (number abundances relative to hydrogen are 4+/-1.5x10^-6^ for N, 3+/-1.5x10^-7^ for Si, and 3+/-1.5x10^-6^ for Fe. These abundances are more accurate than previous v…