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IUE observations of the M dwarfs CM Draconis and Rossiter 137B : magnetic activity at saturated levels.
Linsky, J. L.; Vilhu, O.; Neff, J. E. +4 more
IUE observations of two active M dwarfs with known rotation rate or age and presumed to be almost totally convective are presented. The first of these stars, CM Draconis (Gl 630.1), is an old Population II binary with its components in tidally induced rapid rotation (P = 1.27 d, dM 4 + dM 4). The other one, Rossiter 137 B, forms with HD 36705 (AB …
The distance of the helium-variable B star HD 37479.
Heber, U.; Groote, D.; Hunger, K.
The gravity of HD 37479 (Sigma Ori E) is redetermined using eight high resolution and high S/N ratio spectrograms. The analysis is carried out differentially with respect to the main sequence stars Gamma Peg and Sigma Ori D. It is confirmed that the gravity of HD 37479 is log g = 3.95 + or - 0.15. Evidence is presented for a peculiar interstellar …
Constraints from the UV delay in dwarf nova outbursts.
Meyer, F.; Meyer-Hofmeister, E.
Observations of outbursts of the dwarf nova system VW Hydri show a delay of the rise of the UV flux with respect to that of the optical flux. The difficulties in modeling this feature in the context of the accretion disk instability are discussed and a modified limit cycle based on the same value of the frictional parameter alpha for the cool disk…
IUE observations of variability in the WN6 star HD 192163.
Willis, A. J.; Smith, L. J.; Conti, P. S. +3 more
Results are presented of a study of 77 high-resolution IUE spectra of the WN6 star HD 192163, for which new IUE observations obtained over 48 hrs in 1987 were combined with data drawn from the IUE archive, covering various epochs over the 1978-1987 period. The 1987 series of 48 spectra were found to exhibit significant variability over a period of…
Activity in late-type dwarfs. III. Chromospheric and transition region line fluxes for two dM stars.
Doyle, J. G.; Byrne, P. B.
Weak upper-chromospheric and transition-region emission from two dM stars (Gl 784 and Gl 825) has been observed using deep UV spectroscopy. Ly-alpha fluxes for the two stars were also determined for the first time. Using these results it is shown that the transition from weakly active dM to active dMe star is probably due to increasing surface cov…
A correlation between shape and (UV-V) color for early-type galaxies.
Bender, R.; Longo, G.; Capaccioli, M. +1 more
We present a correlation between the isophotal-shape parameter α_4_/α (Bender et al. 1989a) and the ultraviolet (UV) color index (1330 A-V) (Longo et al. 1989): boxy galaxies are found to be UV brighter than disky galaxies. The interpretation of the correlation between Mg_2_ and the UV color suggested by Burstein et al. (1988; hereafter BBBFL) is …
Revisited mass-loss rates for a sample of central stars of planetary nebulae.
Surdej, J.; Hutsemekers, D.
Using improved relations for the first order moment of a P Cygni line profile, mass-loss rates have been rederived for a sample of seventeen central stars of planetary nebulae observed with IUE in the low resolution mode. The average value of the mass-loss rates lies between 10 to the -7th and 10 to the -8th solar masses/yr. It is confirmed that t…
LMC X-2 : an extragalactic bulge-type source.
Parmar, A. N.; Motch, C.; Beuermann, K. +3 more
The X-ray source LMC X-2 was observed with EXOSAT for ~8 h on February 2, 1984 with simultaneous photometric and spectroscopic optical coverage. The source was seen at a luminosity of L_x_ ~1.5 10^38^ erg s^-1^ with a mean X-ray spectrum can be described equally well by either the superposition of thermal emission from an optically thin (T_th_ ~5 …
Carbon abundance in the primaries of six Algol-type stars.
Cugier, H.
The abundance analysis of carbon in six Algol-type stars was performed using IUE archival data. In order to interpret the observed spectra, both LTE and non-LTE line profiles are computed. A cosmic abundance of carbon is obtained, log N(C/H) = - 3.48, in the primary components of Delta Librae, U Sagittae, RS Vulpeculae and u Herculis. All these sy…
EXO 032957-2606.9 : a new long-period probable AM Herculis binary.
Tagliaferri, G.; Beuermann, K.; Giommi, P. +2 more
The identification of the serendipitous Exosat X-ray source EXO032957-2606.9 with a new probable long-period AM Herculis binary is reported. The orbital period is (228 + or - 1) min (1-sigma error). The classification as an AM Herculis binary is based on the very soft X-ray spectrum and the characteristics of the high-excitation optical spectrum. …