Search Publications
Variability and emission mechanism in Seyfert 1 galaxies : a near-infrared outburst in NGC 4051.
Hunt, L. K.; Del Zanna, G.; Wamsteker, W. +6 more
In the course of a 2.2 micron monitoring programme of nearby Seyfert 1 galaxies, we have detected an outburst in NGC 4051 in which the source flared and dimmed by more than a factor of 2 in 6 months. The UV flux, although sparsely sampled, is less variable than the near infrared. The available data suggest that dust reprocessing of the UV radiatio…
ROSAT-pointed observations of two gamma-ray burst error boxes.
Hurley, K.; Motch, C.; Kouveliotou, C. +3 more
We present ROSAT observations of two gamma-ray burst error boxes and of one possible optical transient source. No point sources were detected and a comparison is made with previous observations of the same objects (Boer et al. 1988, 1991). We interpret the data in the context of gamma-ray burst models that invoke galactic neutron stars. Although r…
Tracing the roots of interstellar mid-infrared emission.
Desert, F. -X.; Jenniskens, P.
An attempt is made to link components of the interstellar extinction curve to mid infrared emission of interstellar dust. The IRAS mid-infrared emission has been sought for in the direction to all early type stars for which IUE extinction curves have been published. In 44 lines of sight we were able to obtain well defined colours. By comparing the…
Ultraviolet observations of the circumstellar envelope of alpha1 HER in the line of sight of alpha2 Her.
Reimers, D.; Thiering, I.
We establish an empirical model of the circumstellar envelope of the red giant α1 Her, using spectroscopic UV and optical observations of its visual binary companion α2 Her. In particular, we obtained high-resolution IUE long wavelength spectra of α2 Her, in which for the first time α1 Her could be exclu…
Coordinated UV-optical observations of quasars : the evolution of the Lyman absorption.
Cristiani, S.; Giallongo, E.; Buson, L. M. +2 more
The average flux decrement shortward the Lyα emission, due to the well-known "forest" of absorptions, has been measured in the spectra of 8 quasars. Quasi-simultaneous optical and IUE observations of the two low redshift quasars PKS 0637-75 (z = 0.654) and MC 1104+16 (z = 0.632) have been carried out, obtaining relatively high S/N, spectrophotomet…
Rotational modulation and flares on the RS Canum Venaticorum binary II Pagasi in July/September 1990 : spots and flares on II Peg.
Doyle, J. G.; Mathioudakis, M.; Avgoloupis, S. +3 more
During ultraviolet spectroscopic observations of the RS CVn star II Peg in September 1990 a long duration (greater than or = 3 hrs.) flare was observed. During the early stage of the event, a feature at 1354 A was present, however, within the spectral resolution of the data it is not possible to identify this line. A contribution from the hot coro…
Radiative energy flux changes of PLEIONE in the far-UV through the Be-shell ---> Be transition.
Mauron, N.; Doazan, V.; Barylak, M. +2 more
We present far UV observations of Pleione made with the IUE satellite in the time-interval 1979-1991 which show, for the first time in the wavelength range 1250-3000 A, the dramatic changes of the FUV radiative energy flux between the Be-shell and the Be phases of a Be star. Between 1979, when Pleione exhibited a strong shell spectrum, and 1991, w…
Spectrophotometric behavior of 56 Arietis.
Stepien, K.; Czechowski, W.
Archival IUE and published visual spectrophotometric data on the magnetic CP star 56 Ari are combined in nearly 20 energy distributions for different phases of the rotational cycle. Comparison with spectral variations shows that the light variations in the shortest wavelength region are strongly influenced by the nonuniformity of the silicon distr…
The X Persei system in the ROSAT all-sky survey.
Mavromatakis, F.
We report the analysis of soft X-ray data from the X-ray pulsar 4U 0352+30, taken by the ROSAT satellite. The mean luminosity, in the ROSAT bandpass (0.1-2.4 keV), is 6 × 1O33 d2kpc erg s-1 and is consistent with that usually seen in the soft X-ray band. The energy spectrum can be described by a flat pow…
Activity in late-type stars. IX. The weakest chromosphere M dwarf yet discovered : GL 105B.
Byrne, P. B.
We present an estimate of chromospheric radiative losses from the dM(e) star, Gl 105B, based on a measurement of the MgII h&k emission line flux, which indicates that this star has the weakest chromospheric heating rate yet found in any M dwarf and that it lies well below the 'basal' heating rate of derived by Schrijver (1987).