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HST/STIS Ultraviolet Imaging of Polar Aurora on Ganymede
Wolven, Brian C.; Feldman, Paul D.; Strobel, Darrell F. +3 more
We report new observations of the spectrum of Ganymede in the spectral range 1160-1720 Å made with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) on 1998 October 30. The observations were undertaken to locate the regions of the atomic oxygen emissions at 1304 and 1356 Å, previously observed with the Goddard Hig…
Hubble Space Telescope Observations of Star Clusters in NGC 1023: Evidence for Three Cluster Populations?
Brodie, Jean P.; Larsen, Søren S.
Using Hubble Space Telescope images we have carried out a study of cluster populations in the nearby S0 galaxy NGC 1023. In two WFPC2 pointings we have identified 221 cluster candidates. The small distance (~9 Mpc) combined with deep F555W and F814W images allows us to reach about 2 mag below the expected turnover of the globular cluster luminosit…
From Stars to Superplanets: The Low-Mass Initial Mass Function in the Young Cluster IC 348
Najita, Joan R.; Tiede, Glenn P.; Carr, John S.
We investigate the low-mass population of the young cluster IC 348 down to the deuterium-burning limit, a fiducial boundary between brown dwarf and planetary mass objects, using a new and innovative method for the spectral classification of late-type objects. Using photometric indices, constructed from HST/NICMOS narrowband imaging, that measure t…
A high-resolution study of episodic mass loss from the carbon star TT Cygni
Eriksson, K.; Gustafsson, B.; Olofsson, H. +3 more
CO radio line observations with the IRAM Plateau de Bure interferometer show that the carbon star TT Cyg is surrounded by a large (radius ~ 35arcsec or 2.7x1017 cm), geometrically thin (average width ~ 2farcs 5 or 1.9x1016 cm) shell of gas, which has a remarkable overall spherical symmetry (e.g., its radius varies by less tha…
Resolving Gamma-Ray Burst 000301C with a Gravitational Microlens
Loeb, Abraham; Garnavich, Peter M.; Stanek, K. Z.
The afterglow of the gamma-ray burst (GRB) 000301C exhibited achromatic, short-timescale variability that is difficult to reconcile with the standard relativistic shock model. We interpret the observed light curves as a microlensing event superposed on power-law flux decays typical of afterglows. In general, a relativistic GRB shock appears on the…
The composition of the circumstellar dust around the Herbig Ae stars AB Aur and HD 163296
Waters, L. B. F. M.; de Koter, A.; van den Ancker, M. E. +1 more
We have analysed the 2-200 µm ISO spectra of two bright Herbig Ae stars, AB Aur and HD 163296, in order to derive the composition and mass over temperature distribution of the circumstellar dust. We find that the two stars have a similar composition of the dust, however also with some important differences. We address the onset of the strong…
Local galactic kinematics from Hipparcos proper motions
Mignard, F.
The stellar velocity field within two kiloparsecs of the solar system is investigated from the Hipparcos proper motions and parallaxes of about 20 000 single stars farther than 100 pc. The motion of the sun relative to the Local Standard of Rest and the relative systematic velocity field due to the galactic rotation are studied simultaneously for …
The X-Ray Remnant of SN 1987A
Petre, Robert; Chevalier, Roger A.; Garmire, Gordon P. +6 more
We present high-resolution Chandra observations of the remnant of SN 1987A in the Large Magellanic Cloud. The high angular resolution of the Chandra X-Ray Observatory permits us to resolve the X-ray remnant. We find that the remnant is shell-like in morphology, with X-ray peaks associated with some of the optical hot spots seen in Hubble Space Tel…
Three-dimensional Stereoscopic Analysis of Solar Active Region Loops. II. SOHO/EIT Observations at Temperatures of 1.5-2.5 MK
Klimchuk, J. A.; Alexander, David; Aschwanden, Markus J. +4 more
In this paper we study the three-dimensional structure of hot (Te~1.5-2.5 MK) loops in solar active region NOAA 7986, observed on 1996 August 30 with the Extreme-ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO). This complements a first study (Paper I) on cooler (Te~1.0-1.5 MK) loops …
A Strong Jet-Cloud Interaction in the Seyfert Galaxy IC 5063: VLBI Observations
Tsvetanov, Z.; Morganti, R.; Oosterloo, T. A. +4 more
We present 21 cm H I line and 13 cm continuum observations, obtained with the Australian Long Baseline Array, of the Seyfert 2 galaxy IC 5063. This object appears to be one of the best examples of Seyfert galaxies where shocks produced by the radio plasma jet influence both the radio and the near-infrared emission. The picture resulting from the n…