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The timing properties of Sco X-1 along its Z track with EXOSAT
van der Klis, Michiel; Dieters, Stefan W.
We present a systematic, homogeneous analysis of all the EXOSAT ME, high time resolution data on Sco X-1. We investigate, for the first time, all power spectral properties of the <100Hz quasi-periodic oscillations (QPO) and noise of Sco X-1 as a function of position on the Z-shaped track traced out in the X-ray colour-colour diagram. For this p…
LWS spectroscopy of the luminous blue compact galaxy Haro 11
Östlin, G.; Bergvall, N.; Cernicharo, J. +1 more
We present the results of far infrared (FIR) spectroscopy of the luminous blue compact galaxy (BCG)
The White Dwarf Cooling Age of the Open Cluster NGC 2420
Gilmore, Gerard; von Hippel, Ted
We have used deep HST WFPC2 observations of two fields in NGC 2420 to produce a cluster color-magnitude diagram down to V~27. After imposing morphological selection criteria we find eight candidate white dwarfs in NGC 2420. Our completeness estimates indicate that we have found the terminus of the WD cooling sequence. We argue that the cluster dis…
Stochastic Seismic Emission from Acoustic Glories and the Quiet Sun
Braun, D. C.; Lindsey, C.; Donea, A. -C.
Helioseismic images of multipolar active regions show enhanced seismic emission in 5-mHz oscillations in a halo surrounding the active region called the `acoustic glory'. The acoustic glories contain elements that sustain an average seismic emission 50% greater than similar elements in the quiet Sun. The most intense seismic emitters tend to form …
The Star Formation History of the Starburst Region NGC 2363 and its Surroundings
Drissen, Laurent; Robert, Carmelle; Doyon, René +2 more
We present Hubble Space Telescope optical images and UV spectra, as well as ground-based near-infrared images of the high surface-brightness giant H II region NGC 2363 (NGC 2366-I) and its surroundings. The massive star content of the southern end of the dwarf irregular galaxy NGC 2366 is investigated, with an emphasis on Wolf-Rayet and red superg…
The Galactic warp in OB stars from Hipparcos
Lattanzi, M. G.; Drimmel, R.; Smart, R. L.
The kinematics of distant OB stars perpendicular to the Galactic plane, inferred from proper motions in the Hipparcos catalogue, are analysed and compared to the kinematic signature that would be induced by a long-lived Galactic warp. Previously we reported that the kinematics of the OB stars toward the anticenter were inconsistent with the assump…
Large [O]/[CO] ratios in cold molecular clouds towards W 49N
Ceccarelli, C.; Caux, E.; Vastel, C. +3 more
We present ISO-LWS high spectral resolution (R ~ 104) observations of the [OI] 63 mu m and 145 mu m lines towards the high mass star formation region W49N. At 145 mu m the observed spectrum shows an emission component only, while at 63 mu m it shows both emission and absorption components. We performed an analysis of the observed spectr…
A Search for Faint Companions to Nearby Stars Using the Wide Field Planetary Camera 2
Krist, John E.; Golimowski, David A.; Schroeder, Daniel J. +9 more
We have completed a direct-imaging search for faint companions (FCs) to 23 stars within 13 pc of the Sun using the Hubble Space Telescope Planetary Camera. The strategy of this search changed considerably from that reported in 1996. To maximize the image contrast between potential FCs and a target star's point-spread function, we adopted the F1042…
Interplanetary and Interacting Protons Accelerated in a Parallel Shock Wave
Laitinen, T.; Vainio, R.; Kocharov, L.
We present a test-particle model of diffusive shock acceleration on open coronal field lines based on one-dimensional diffusion-convection equation with finite upstream and downstream diffusion regions. We calculate the energy spectrum of protons escaping into the interplanetary space and that of protons interacting with the subcoronal material pr…
The Hubble Space Telescope Survey of BL Lacertae Objects. IV. Infrared Imaging of Host Galaxies
Calzetti, Daniela; Urry, C. Megan; O'Dowd, Matthew +2 more
The Hubble Space Telescope NICMOS Camera 2 was used for H-band imaging of 12 BL Lacertae objects taken from the larger sample observed with the WFPC2 in the R band by Urry and coworkers and Scarpa and coworkers. Ten of the 12 BL Lacs are clearly resolved, and the detected host galaxies are large, bright ellipticals with average absolute magnitude …