Search Publications
The Continuing Slow Decline of AG Pegasi
Kenyon, Scott J.; Proga, Daniel; Keyes, Charles D.
We analyze optical and ultraviolet observations of the symbiotic binary AG Pegasi acquired during 1992-1997. The bolometric luminosity of the hot component declined by a factor of 2-3 from 1980-1985 to 1997. Since 1992, the effective temperature of the hot component may have declined by 10%-20%, but this decline is comparable to the measurement er…
Long period variable stars: galactic populations and infrared luminosity calibrations
Luri, X.; Mowlavi, N.; Mennessier, M. O. +1 more
In this paper HIPPARCOS astrometric and kinematic data are used to calibrate both infrared luminosities and kinematical parameters of Long Period Variable stars (LPVs). Individual absolute K and IRAS 12 and 25 luminosities of 800 LPVs are determined and made available in electronic form. The estimated mean kinematics is analyzed in terms of galact…
General relativistic satellite astrometry. II. Modeling parallax and proper motion
Lattanzi, M. G.; Bucciarelli, B.; Vecchiato, A. +1 more
The non-perturbative general relativistic approach to global astrometry introduced by de Felice et al. (\cite{defetal}) is here extended to account for the star motions on the Schwarzschild celestial sphere. A new expression of the observables, i.e. angular distances among stars, is provided, which takes into account the effects of parallax and pr…
A Shock-induced Photodissociation Region in the HH 80/81 Flow: Far-Infrared Spectroscopy
Molinari, Sergio; Noriega-Crespo, Alberto; Spinoglio, Luigi
The two spectrometers on board the Infrared Space Observatory were used to observe the Herbig-Haro objects HH 80, 81, and 80N, as well as their candidate exciting source IRAS 18162-2048. The fine structure lines of [O I] 63 µm, [O I] 145 µm, and [C II] 158 µm are detected everywhere, while [N II] 122 µm and [O III] 88.3 &mi…
Eruption of a Flux Rope on the Disk of the Sun: Evidence for the Coronal Mass Ejection Trigger?
Harra, Louise K.; Mason, Keith O.; Culhane, J. Leonard +1 more
The first evidence of acceleration of a flux rope from the disk of the Sun using the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO) is presented. A distinct blueshifted emission component (-480 km s-1) was observed by the EUV spectrometer on SOHO at the start of the impulsive phase of an X2.3 flar…
Cosmic shear from STIS pure parallels. I. Data
White, S. D. M.; Micol, A.; Fosbury, R. A. E. +9 more
Following the second HST servicing mission in 1997 when the STIS instrument was installed and the capability for parallel observations was enhanced, a substantial archive of non-proprietary parallel data has been accumulating. In this paper, we discuss the use of unfiltered STIS imaging data for a project that requires deep observations along as m…
Abundances in the Planetary Nebula IC 5217
Feibelman, Walter A.; Hyung, Siek; Aller, Lawrence H. +1 more
High-resolution optical wavelength spectroscopic data were secured in the optical wavelengths, 3700-10050 Å, for the planetary nebula IC 5217 with the Hamilton Echelle Spectrograph at Lick Observatory. These optical spectra have been analyzed along with the near-UV and UV archive data. Diagnostic analyses indicate a nebular physical condition with…
Kilometric Type III Radio Bursts, Electron Beams, and Interplanetary Density Structures
Reiner, Michael
We briefly review kilometric type III radio bursts and what their physical characteristics reveal about the propagation and characteristics of suprathermal electron beams and about density structures in interplanetary medium.
The New Two-Image Gravitational Lens System CLASS B2319+051
Pearson, T. J.; Blandford, R. D.; Koopmans, L. V. E. +10 more
We report the discovery of a new two-image gravitational lens system, CLASS B2319+051, from the Cosmic Lens All-Sky Survey. Radio imaging with the Very Large Array (VLA) and Multielement Radio-linked Interferometer Network (MERLIN) shows two compact components with a flux density ratio of ~=5:1, separated by 1.36". Observations with the Very Long …
WFPC2 observations of two dwarf spheroidal galaxies in the M 81 group
Sarajedini, A.; Dolphin, A. E.; Grebel, E. K. +7 more
We have obtained HST WFPC2 and ground-based images of two low surface brightness dwarf spheroidal galaxies in the M 81 group, FM1 and KKH57. Their colour-magnitude diagrams show red giant branches with tips at I = 23.77 +/- 0.14 and I = 23.97 +/-0.17, respectively. The derived true distance moduli, 27.66 +/- 0.16 and 27.96 +/- 0.19, agree well wit…