Search Publications
Physical Conditions in the Emission-Line Gas in the Extremely Low Luminosity Seyfert Nucleus of NGC 4395
Filippenko, Alexei V.; Ho, Luis C.; Shields, Joseph C. +2 more
We have combined Hubble Space Telescope/Faint Object Spectrograph, ground-based, and Infrared Space Observatory spectra of the nucleus of NGC 4395, the least luminous and nearest known type 1 Seyfert galaxy. The spectra show emission lines from a wide range of ionization states and critical densities. We have generated multicomponent photoionizati…
An Edge-brightened Bicone in the Nuclear Regions of Cygnus A
Tadhunter, C. N.; Packham, C.; Sparks, W. +5 more
Infrared-imaging observations that span the wavelength range of 0.8-2.35 µm have been obtained for the archetypal powerful radio galaxy Cygnus A using the Near-Infrared Camera and Multiobject Spectrograph on board the Hubble Space Telescope. At 2.25 µm, the images are dominated by the presence of a nuclear point source (FWHM < 0.21"…
Large atomic oxygen abundance towards the molecular cloud L1689N
Liseau, R.; White, G. J.; Ceccarelli, C. +6 more
We present spectroscopic ISO-LWS observations of the [OI] (63 mu m and 145 mu m), the [CII] (158 mu m) and the H_2O (179 mu m) lines towards the molecular cloud L1689N. From the observed ratio of the two [OI] lines, we deduce a mean gas temperature of (26 +/-0.5) K, an H2 density >= 3 x 10(4) cm(-3) and an [OI] column density >= 5…
Isotopic lithium abundances in five metal-poor disk stars
Lambert, D. L.; Nissen, P. E.; Primas, F. +1 more
High resolution (R =~ 110 000), very high S/N spectra centered on the 6707.8 Ä Li I line have been obtained with the ESO Coudé Echelle Spectrometer for five, metal-poor (-0.8 < [Fe/H] < -0.6) disk stars in the turnoff region of the HR-diagram. The instrumental and stellar atmospheric line broadening have been determined from two unblended ir…
Galaxy Structural Parameters: Star Formation Rate and Evolution with Redshift
Takamiya, M.
The evolution of the structure of galaxies as a function of redshift is investigated using two parameters: the metric radius of the galaxy (Rη) and the power at high spatial frequencies in the disk of the galaxy (χ). A direct comparison is made between nearby (z~0) and distant (0.2<~z<~1) galaxies by following a fixed range in res…
Inversion methods in helioseismology and solar tomography.
Kosovichev, A. G.
Basic methods by which the internal structure and dynamics of the Sun can be inferred from observed frequencies of solar oscillations and acoustic travel times are discussed. The methods for inverting the oscillation frequencies are based on a variational formulation of the adiabatic eigenvalue problem for a star. The inversion technique formulate…
Doppler imaging of stellar surface structure. XI. The super starspots on the K0 giant HD 12545: larger than the entire Sun
Strassmeier, K. G.
The active K0 giant HD 12545 is the star with the largest starspots ever observed. We report a record light-curve amplitude of 0\fm63 in V and 0\fm17 in V-I in January 1998. At the same time, HD 12545 was at its brightest magnitude since the discovery of its light variability in 1985. We present the first Doppler image of HD 12545 from observation…
High-resolution spectroscopy of ROSAT-discovered weak-line T Tauri stars near Lupus
Hauschildt, P. H.; Alcalá, J. M.; Covino, E. +3 more
We present high-resolution optical echelle spectroscopy for a large fraction of the Li-rich late-type stars recently discovered in the vicinity of the Lupus dark clouds. Our results confirm the high Liilambda6708 equivalent widths previously estimated from medium-resolution spectra, thus adding strength to the conclusion that the large majority of…
Properties of hot stars in the Wolf-Rayet galaxy NGC 5253 from ISO-SWS spectroscopy
Sutherland, Ralph S.; Conti, Peter S.; Morris, Patrick W. +3 more
ISO-SWS spectroscopy of the Wolf-Rayet galaxy NGC 5253 is presented, and analysed to provide estimates of its hot young star population. Our approach differs from previous investigations in that we are able to distinguish between the regions in which different infrared fine-structure lines form, using complementary ground-based observations. The h…
Unraveling the Structure of Aspherical Proto-Planetary Nebulae. I. Hubble Space Telescope Imaging and Hydroxyl Maser Line Observations of Roberts 22
Bujarrabal, V.; Sahai, Raghvendra; Zijlstra, A. +1 more
We have obtained high-resolution wide-band, narrowband, and polarimetric images of the bipolar proto-planetary nebula Roberts 22 with the Wide Field Planetary Camera 2 on the Hubble Space Telescope. OH maser-line emission has also been observed using the Australia Telescope Compact Array. The wide-band images at 0.6 µm show bright bipolar lo…