Search Publications
Ca II activity and rotation in F-K evolved stars
Pasquini, L.; de Medeiros, J. R.; Girardi, L.
Ca II H and K high resolution observations for 60 evolved stars in the field and in 5 open clusters are presented. From these spectra chromospheric fluxes are derived, and a homogeneous sample of more than 100 giants is built adding data from the literature. In addition, for most stars, rotational velocities were derived from CORAVEL observations.…
Photometric Recovery of Crowded Stellar Fields Observed with HST/WFPC2 and the Effects of Confusion Noise on the Extragalactic Distance Scale
Freedman, Wendy L.; Stetson, Peter B.; Ferrarese, Laura +4 more
We explore the limits of photometric reductions of crowded stellar fields observed with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope. Two photometric procedures, based on the DoPHOT and DAOPHOT/ALLFRAME programs, are tested, and the effects of crowding, complex sky background, and cosmic-ray contamination are discussed…
The Globular Cluster Systems in the Coma Ellipticals. I. The Luminosity Function in NGC 4874 and Implications for Hubble's Constant
Kavelaars, J. J.; Harris, William E.; Hesser, James E. +2 more
We have used deep Hubble Space Telescope WFPC2 images in V (F606W) and I (F814W) to measure the luminosity distribution of the globular clusters in NGC 4874, the central cD galaxy of the Coma cluster. We find the ``turnover'' point of the globular cluster luminosity function (GCLF) to lie at V=27.88+/-0.12, while the overall GCLF shape matches the…
Observations of a Possible New Soft Gamma Repeater, SGR 1801-23
Cline, T.; Hurley, K.; Kouveliotou, C. +4 more
We report on two 1997 June observations of a soft bursting source whose time histories and energy spectra are consistent with those of the soft gamma repeaters. The source can be localized only to an ~3.8d long error box in the direction of the Galactic center, whose area is ~80 arcmin2. The location of the source, while not consistent …
A 500kms-1 outflow from the young bipolar planetary nebula Mz 3
Redman, M. P.; Meaburn, J.; Holloway, A. J. +2 more
We report the discovery of a pair of hypersonic (~=+/-500kms-1) velocity features located along the bipolar axis of the young planetary nebula Mz 3. The possible physical mechanisms that can produce such extreme outflows are briefly discussed and compared with mechanisms thought to operate in MyCn 18, He 2-111 and KjPn 8, all of which e…
Spectropolarimetric measurements of the mean longitudinal magnetic field of chemically peculiar stars. On the light, spectral and magnetic variability
Leone, F.; Catalano, S.; Catanzaro, G.
We have equipped the spectrograph of the Catania Astrophysical Observatory with a polarimetric module which gives simultaneous circularly right and left polarised radiation spectra. This facility has been used to perform time-resolved spectropolarimetric (Stokes V) measurements of the mean longitudinal (effective) magnetic field for seven chemical…
Near-infrared photometry of isolated spirals with and without an AGN --- II. Photometric properties of the host galaxies
Roth, M.; Durret, F.; González Delgado, R. M. +6 more
We present here the analysis of morphological and photometric properties of a sample of isolated spirals with (18) and without (11) an active nucleus, based on near-infrared imaging in the J and K' bands (Paper I). The aim of that comparative analysis is to find the differential properties that could be directly connected with the phenomenon of nu…
Diagnostics of the Jovian Aurora Deduced from Ultraviolet Spectroscopy: Model and HST/GHRS Observations
Clarke, J. T.; Grodent, D.; Dols, V. +2 more
A model coupling an electron energy degradation code with a detailed synthetic spectrum of the H 2 Lyman and Werner band system is used to calculate the emerging auroral ultraviolet spectra from Jupiter's atmosphere excited by electrons with different initial energy distributions. The atmospheric model is adapted from the vertical P-T p…
PMN J1838-3427: A New Gravitationally Lensed Quasar
Kochanek, C. S.; Rix, H. -W.; Dressler, Alan +11 more
We report the discovery of a new double-image quasar that was found during a search for gravitational lenses in the southern sky. Radio source PMN J1838-3427 is composed of two flat-spectrum components with separation 1.0", flux density ratio 14:1, and matching spectral indices in VLA and VLBA images. Ground-based BRI images show the optical count…
Radiance variations of the quiet Sun at far-ultraviolet wavelengths
Wilhelm, K.; Schühle, U.; Lemaire, P. +2 more
We have measured the radiance of quiet-Sun areas at the centre of the solar disk using the vacuum-ultraviolet telescope-spectrograph SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on the Solar and Heliospheric Observatory (SOHO). The radiances of selected emission lines have been measured from March 1996 to the present. The lines that…