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Observations of GRB 970228 and GRB 970508 and the Neutron Star Merger Model
Livio, Mario; Bond, Howard E.; Kouveliotou, Chryssa +6 more
We present the discovery observations for the optical counterpart of the gamma -ray burster GRB 970508 and discuss its light curve in the context of the fireball model. We analyze the HST data for this object and conclude that any underlying galaxy must be fainter than R=25.5 . We also present a detailed analysis of the HST images of GRB 970228, f…
Time-Resolved Ultraviolet Observations of the Globular Cluster X-Ray Source in NGC 6624: The Shortest Known Period Binary System
Anderson, Scott F.; Margon, Bruce; Deutsch, Eric W. +2 more
Using the Faint Object Spectrograph (FOS) aboard the Hubble Space Telescope (HST), we have obtained the first time-resolved spectra of the King et al. (1993) ultraviolet-bright counterpart to the 11 minute binary X-ray source in the core of the globular cluster NGC 6624. This object cannot be readily observed in the visible, even from HST, because…
Evidence of a Thermonuclear Runaway and Proton-Capture Material on a White Dwarf in a Dwarf Nova
Szkody, Paula; Sion, Edward M.; Hubeny, Ivan +3 more
We present Hubble Space Telescope Goddard High-Resolution Spectrograph G160M spectra of the white dwarf in VW Hydri, exposed during quiescence, 1 month after the end of a normal dwarf nova outburst. Our spectra, covering the wavelength interval 1236-1272 Å, were obtained at orbital phase 0.06-1.60 they reveal strong photospheric Si II λλ1260, 1265…
Hubble Space Telescope Observations of the Middle-aged Pulsar 0656+14
Córdova, F. A.; Pavlov, G. G.; Welty, A. D.
Multiwavelength spectral observations of middle-aged (τ~104-106 yr) isolated pulsars enable one in principle to separate thermal radiation emitted from the neutron star surface and nonthermal radiation from its magnetosphere. We have previously detected the middle-aged radio and soft X-ray pulsar 0656+14 with the Hubble Space…
The Shock and Extended Remnant around the Crab Nebula
Hester, J. Jeff; Sankrit, Ravi
The [O III] ``skin'' around the Crab Nebula was shown by Hester et al. to be the Rayleigh-Taylor (R-T)-unstable interface between the synchrotron nebula and swept-up ejecta from the supernova explosion. Unlike the bright photoionized filaments, this skin is most easily understood as the cooling region behind a shock driven into an extended remnant…
The Abundance of Mg in the Interstellar Medium
Fitzpatrick, Edward L.
An empirical determination of the f-values of the far-UV Mg II λλ1239, 1240 lines is reported. The strong near-UV Mg II λλ2796, 2803 lines are generally highly saturated along most interstellar sight lines outside the local interstellar medium (ISM) and usually yield extremely uncertain estimates of Mg+ column densities in interstellar …
Pulsations and Accretion Geometry in YY Draconis: A Study Based on Hubble Space Telescope Observations
Thorstensen, John R.; Hellier, Coel; Haswell, Carole A. +2 more
We present 1 Å resolution fast ultraviolet spectroscopy of YY Dra, coordinated U, B, V, R, and I photometry, and Hα spectroscopy. The UV continuum is strongly pulsed: we found 16% semiamplitude pulses with period 264.7(1) s; there was no evidence for power at twice this period. The UBV pulses are in phase with the UV continuum pulsation. A color t…
The Hourglass Nebulae of Sher 25 and SN 1987A: Two of a Kind? 1
Grebel, Eva K.; Brandner, Wolfgang; Chu, You-Hua +2 more
We have performed a detailed study of the morphology and kinematics of the hourglass-shaped nebula around the blue supergiant Sher 25 in the galactic giant H II region NGC 3603. Near-infrared high-resolution adaptive optics images in the Br gamma line and HST/NICMOS images in the He I 1.08 mu m line were compared with isovelocity maps in the H alp…
Association of Extreme-Ultraviolet Imaging Telescope (EIT) Polar Plumes with Mixed-Polarity Magnetic Network
Michels, D. J.; Gurman, J. B.; Delaboudinière, J. -P. +18 more
SOHO EIT spectroheliograms showing the polar coronal holes during the present sunspot minimum are compared with National Solar Observatory (Kitt Peak) magnetograms taken in Fe I λ8688 and Ca II λ8542. The chromospheric λ8542 magnetograms, obtained on a routine, near-daily basis since 1996 June, reveal the Sun's strong polar fields with remarkable …
The Nuclear Region of NGC 1068: High-Accuracy Alignment of the Optical and Radio Emission
Macchetto, F. D.; Capetti, A.; Lattanzi, M. G.
We present the results of a campaign to obtain an accurate registration of Hubble Space Telescope (HST) and MERLIN images of NGC 1068, the prototypical Seyfert 2 galaxy. The final registration is accurate to 100 mas.
A strong anticorrelation between radio and optical emission is revealed; in particular, the radio jet lies on a region of relat…