Search Publications
The Prominence - Corona and the Filament - Corona Transition Region: is There any Difference?
Landi, E.; Chiuderi Drago, F.
The ratio between the Extreme Ultraviolet emission of the prominence-corona transition region and that of the quiet Sun (QS) transition region is measured using observations from the CDS and SUMER instruments on board the SOHO Satellite. These results are compared with those obtained in an earlier paper, analysing the same prominence as a filament…
A radio continuum study of the `Engraved Hourglass' nebula, MyCn 18
Bryce, M.; Bains, I.; Calabretta, M. +1 more
We present the first radio continuum images of the `Engraved Hourglass' planetary nebula (PN) MyCn 18 from multifrequency observations with the Australia Telescope. The radio emission is strongly core-dominated at all frequencies investigated. At the three higher observing frequencies, the radio emission is seen to trace the optically-visible hour…
The Shadow of Comet Hale-Bopp in Lyman-Alpha
Bertaux, Jean-Loup; Lallement, Rosine; Szegö, Karöly +1 more
For a few months around perihelion, the central part of the Hale-Bopp hydrogen cloud has been optically thick to the solar Lyα radiation, and has significantly reduced the solar flux available for the resonance glow of interstellar hydrogen beyond the comet. This shadowing effect on the interstellar gas is the first ever observed comet shadow. It …
Lasers without inversion (LWI) in Space: A possible explanation for intense, narrow-band, emissions that dominate the visible and/or far-UV (FUV) spectra of certain astronomical objects
Sorokin, P. P.; Glownia, J. H.
The optical or far-UV (FUV) spectra of certain objects in Space are completely dominated by one or two spectrally narrow emission lines, strongly suggesting that laser action of some kind occurs in these objects. However, the electronic level structures of the atoms/ions producing these emissions preclude the possibility of maintaining population …
Limb profiles of the Moon from grazing occultation observations collected at RGO
Soma, Mitsuru; Kato, Yuji
From lunar grazing occultation observations it is shown that the present lunar limb profile data have sometimes large errors, and therefore it is apparent that they need to be modified. For that purpose observations of grazing occultations collected at the Royal Greenwich Observatory until 1980 were analyzed and lunar limb profile data were obtain…
The Ultraviolet Light Curve of LMC X-4: X-Ray Heating of the O Star and Accretion Disk
Boroson, Bram; Vrtilek, Saeqa Dil; Preciado, Michael E.
We present an archival study of ultraviolet spectra of the X-ray binary LMC X-4 obtained with the IUE satellite. We fit these spectra with models that incorporate the X-ray heating of the O star and accretion disk. A systematic analysis of the UV continuum confirms the general picture of an O star that fills its Roche lobe and is heated by X-rays …
Solar activities associated with interplanetary magnetic flux ropes
Marubashi, K.; Watanabe, T.; Watari, S.
A smoothly rotating interplanetary magnetic field with duration on the order of a day has been detected in solar wind observations. This structure is called an "interplanetary magnetic flux rope." Here, we studied the relationship between interplanetary magnetic flux ropes observed by Ulysses when it was near the solar limb and coronal mass ejecti…
Effective Temperatures of Solar Type Stars
Shenavrin, V. I.; Glushneva, I. N.; Roshchina, I. A.
For 29 stars of G0-G5 spectral types with color indices 0.60 leq Bndash V le 0.68 and parallaxes obtained by Hipparcos satellite effective temperatures, angular diameters and radii are determined by means of the method of infrared fluxes (IRFM) on the basis of JHKLM photometry. Effective temperatures obtained by iterations in the process of combin…
Irradiation phenomena in young solar-type stars and the early solar system: X-ray observations and γ-ray constraints
Montmerle, Thierry
The high levels of X-ray flaring activity observed in young stars and protostars suggest correspondingly high levels of low-energy particle irradiation of their circumstellar disks, and hence of early solar system material like meteorites. We first briefly review the latest X-ray observational results obtained by Chandra and XMM-Newton on two 'typ…
Identification of RR Lyrae stars in the Tycho-2 catalogue
Mennessier, M. O.; Colomé, J.
The Tycho-2 catalogue provides astrometric and photometric data for the 2.5 million brightest stars in the sky. Therefore it can provide much larger samples than the Hipparcos samples used to date in statistical studies. The object of this paper is the cross-identification of Tycho-2 sources and known variable stars of RR Lyrae type. The Tycho-2 d…