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Optical and ultraviolet observations of a strong flare in the young, single K2 dwarf LQ Hya
Montes, D.; Collier Cameron, A.; Saar, S. H. +1 more
We present high-resolution optical echelle spectra and IUE observations during a strong flare on 1993 December 22 in the very active, young, rapidly rotating, single K2 dwarf LQ Hya. The initial impulsive phase of the flare, which started sometime between 2:42 ut and 4:07 ut, was characterized by strong optical continuum enhancement and blueshifte…
The symbiotic binary system RX Puppis: a possible recurrent nova with a Mira companion
Whitelock, Patricia A.; Barba, Rodolfo; Hack, Warren +4 more
We present an analysis of photometric and spectroscopic observations of the symbiotic binary system RX Pup with the aim of developing a reliable binary model for the system and identifying mechanisms responsible for its spectacular activity. The binary is composed of a long-period Mira variable surrounded by a thick dust shell and a hot ~ 0.8 M_su…
The 1995-96 decline of R Coronae Borealis: high-resolution optical spectroscopy
Hatzes, Artie P.; Lambert, David L.; Pandey, Gajendra +10 more
A set of high-resolution optical spectra of R CrB acquired before, during and after its 1995-96 decline is discussed. All of the components reported from earlier declines are seen. This novel data set provides new information on these components including several aspects not previously seen in declines of R CrB and other R Coronae Borealis stars. …
Accretion shocks in T Tauri stars: diagnosis via semiforbidden ultraviolet line ratios
Lamzin, S. A.; Gomez de Castro, Ana I.
Numerical calculations of the structure of accretion shocks in T Tauri stars (TTSs) indicate that the C III]1909, O III]1661+1666 and Si III]1892 ultraviolet lines should have comparable intensities. We show how the density and the velocity of the accreted gas can be derived from these line ratios. We also indicate how these parameters can be used…
Evidence for the stratification of Fe in the photosphere of G191-B2B
Barstow, M. A.; Holberg, J. B.; Hubeny, I.
The presence of heavy elements in the atmospheres of the hottest H-rich DA white dwarfs has been the subject of considerable interest. While theoretical calculations can demonstrate that radiative forces, counteracting the effects of gravitational settling, can explain the detections of individual species, the predicted abundances do not accord we…
Emission lines of [O II] in the optical and ultraviolet spectra of planetary nebulae
Feibelman, W. A.; Keenan, F. P.; Hyung, S. +5 more
Recent R-matrix calculations of electron impact excitation rates in O II are used to calculate the emission-line ratio-ratio diagrams (R_1, R_2), (R_1, R_3) and (R_1, R_4), where R_1 = I(3729 A)/I(3726 A), R_2 = I(7320 A)/I(3726 + 3729 A), R_3 = I(7330 A)/I(3726 + 3729 A) and R_4 = I(2470 A)/I(3726 + 3729 A), for a range of electron temperatures (…
M4-18: the planetary nebula and its WC10 central star
De Marco, Orsola; Crowther, Paul A.
We present a detailed analysis of the planetary nebula M4-18 (G146.7+07.6) and its WC10-type Wolf-Rayet (WR) central star, based on high-quality optical spectroscopy (WHT/UES, INT/IDS, WIYN/DensPak) and imaging (HST/WFPC2). From a non-LTE model atmosphere analysis of the stellar spectrum, we derive T_eff=31kK, log(Msolar/M_solaryr^-1)=-6.05, v_∞=1…
Elemental abundances for Nova LMC 1990#1
Shore, Steven N.; Sonneborn, George; Starrfield, Sumner +1 more
We present our analysis of the UV spectra of the fast ONeMg Nova LMC 1990#1. Observations with the IUE began on 1990 January 18 and continued through to 1990 March 15. We have analysed these spectra, and determined line fluxes and physical parameters as a function of time. Using both Heii lines and the Balmer decrement, we find the reddening for t…
A non-local thermodynamic equilibrium spherical line-blanketed stellar atmosphere model of the early B giant beta CMa
Hauschildt, P. H.; Baron, E.; Aufdenberg, J. P.
The observed multiwavelength spectrum of the B1II--III star beta CMa is successfully reproduced, including the extreme ultraviolet (EUV) continuum observed by Extreme Ultraviolet Explorer (EUVE), with a non-local thermodynamic equilibrium fully line-blanketed spherical hydrostatic model atmosphere. The available spectrophotometry of beta CMa from …
Consistency of accretion discs with Seyfert 1 UV fluxes and Hβ emission-line profiles
Boisson, C.; Rokaki, E.
This paper presents accretion disc fits to the UV continuum and Hβ emission line in a complete sample of broad-emission-line AGN sources. Disc fits to the UV continuum emission leave an ambiguity between the central mass and the orientation of the disc in that more massive black holes mimic more edge-on discs. The opposite dependence between mass …