Search Publications
Optical-IUE observations of the gamma-ray loud BL Lacertae object S5 0716+714: data and interpretation.
Maraschi, L.; Ghisellini, G.; Pian, E. +14 more
We monitored the BL Lac object S5 0716+714 in the optical band during the period November 1994 - April 1995, which includes the time of a γ-ray observation by the Energetic Gamma Ray Experiment Telescope (EGRET) on February 14-28, 1995. The light curves in the R and B bands show fast fluctuations superimposed on longer timescale variations. The co…
Absolute Magnitude Calibration for the W UMa-Type Systems Based on HIPPARCOS Data
Rucinski, S. M.; Duerbeck, H. W.
Hipparcos parallax data for 40 contact binary stars of the W UMa-type (with epsilon M_V < 0.5) are used to derive a new, (B-V)-based absolute-magnitude calibration of the form M_V = M_V(log P,B-V). The calibration covers the ranges 0.26 < (B-V)_0 < 1.14, 0.24 < P < 1.15 day, and 1.4 < M_V < 6.1; it is based on a solution weigh…
Optical Rotation Curves of Distant Field Galaxies: Sub-L* Systems
Illingworth, Garth D.; Faber, S. M.; Gronwall, Caryl +6 more
Moderate-resolution spectroscopic observations from the Keck 10 m telescope are used to derive internal kinematics for eight faint disk galaxies in the fields flanking the Hubble Deep Field. The spectroscopic data are combined with high-resolution F814W Wide Field Planetary Camera 2 images from the Hubble Space Telescope that provide morphologies,…
Ellipticals with Kinematically Distinct Cores: V - I Color Images with WPFC2
Franx, Marijn; Illingworth, Garth D.; Forbes, Duncan A. +1 more
We have analyzed Hubble Space Telescope WFPC2 F555W and F814W (i.e., V and I) images for 15 elliptical galaxies with kinematically distinct cores. For each of them, we have derived surface brightness and isophotal parameter profiles in the two bands, color maps, and radial profiles in V - I. Most galaxies show patchy dust absorption close to their…
HST observations of blue Straggler stars in the core of the globular cluster M 3.
Burgarella, D.; Cacciari, C.; Buonanno, R. +7 more
The core of the Galactic Globular Cluster M 3 (NGC 5272) has been observed with the WFPC2 through the filters F255W, F336W, F555W, and F814W. Using these observations along with a thorough reanalysis of earlier catalogs, we have produced a catalog of blue straggler stars (BSS) spanning the cluster. Earlier studies and the fainter part of our sampl…
The optical counterpart to γ-ray burst GRB970228 observed using the Hubble Space Telescope
Livio, Mario; Kouveliotou, Chryssa; Sahu, Kailash C. +7 more
Although more than 2,000 astronomical γ-ray bursts (GRBs) have been detected, and numerous models proposed to explain their occurrence1, they have remained enigmatic owing to the lack of an obvious counterpart at other wavelengths2-5. The recent ground-based detection6,7 of a transient optical source in the vicinit…
An Empirical Study of the Electron Temperature and Heavy Ion Velocities in the South Polar Coronal Hole
Gloeckler, George; Geiss, Johannes; Fisk, Lennard A. +2 more
The solar wind ions flowing outward through the solar corona generally have their ionic fractions `freeze-in' within 5 solar radii. The altitude where the freeze-in occurs depends on the competition between two time scales: the time over which the wind flows through a density scale height, and the time over which the ions achieve ionization equili…
Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XI. Intensive Monitoring of the Ultraviolet Spectrum of NGC 7469
Shull, J. M.; Malkan, M. A.; Nandra, K. +54 more
From 1996 June 10 to July 29, the International Ultraviolet Explorer monitored the Seyfert 1 galaxy NGC 7469 continuously in an attempt to measure time delays between the continuum and emission-line fluxes. From the time delays, one can estimate the size of the region dominating the production of the UV emission lines in this source. We find the s…
Patchy intergalactic He II absorption in HE 2347-4342. II. The possible discovery of the epoch of He-reionization
Reimers, D.; Wamsteker, W.; Rodriguez-Pascual, P. +3 more
We report on observations of redshifted Heii303.8 Angstroms absorption in the high-redshift QSO HE2347-4342 (z=2.885, V=16.1) with the Goddard High Resolution Spectrograph on board HST in its low resolution mode (bigtriangleup lambda = 0.7 Angstroms). With f_λ=3.6\ 10(-15) ergcm(-2) s(-1) Angstroms(-1) at the expected position of Heii304 Angstroms…
The Ultraviolet Properties of the Narrow-Line Quasar I Zw 1
Laor, Ari; Green, Richard F.; Jannuzi, Buell T. +1 more
I Zwicky 1 (I Zw 1) is the prototype narrow-line quasar. Its narrow-line profiles minimize blending effects and thus allow a significantly more accurate study of individual quasar emission lines. We report here the results of our study of the 1150-3250 Å emission of I Zw 1 using a high signal-to-noise (50-120) spectrum obtained with the Faint Obje…