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Solar-cycle variation of the sound-speed asphericity from GONG and MDI data 1995-2000
Howe, R.; Hill, F.; Schou, J. +3 more
We study the variation of the frequency splitting coefficients describing the solar asphericity in both GONG and MDI data, and use these data to investigate temporal sound-speed variations as a function of both depth and latitude during the period 1995-2000 and a little beyond. The temporal variations in even splitting coefficients are found to be…
Multiwavelength Monitoring of the Narrow-Line Seyfert 1 Galaxy Arakelian 564. II. Ultraviolet Continuum and Emission-Line Variability
Brandt, W. N.; Clavel, J.; Kriss, G. A. +15 more
We present results of an intensive 2 month campaign of approximately daily spectrophotometric monitoring of the narrow-line Seyfert 1 galaxy (NLS1) Ark 564 with the Hubble Space Telescope. The fractional variability amplitude of the continuum variations between 1365 and 3000 Å is ~6%, about a factor of 3 less than that found in typical Seyfert 1 g…
Chemical abundances and winds of massive stars in M31: a B-type supergiant and a WC star in OB 10
Smartt, S. J.; Crowther, P. A.; Dufton, P. L. +5 more
We present high quality spectroscopic data for two massive stars in the OB 10 association of M31, OB 10-64 (B0 Ia) and OB 10-WR1 (WC6). Medium resolution spectra of both stars were obtained using the ISIS spectrograph on the William Herschel Telescope. This is supplemented with Hubble Space Telescope STIS UV spectroscopy and Keck I HIRES data for …
Space Telescope Imaging Spectrograph Observations of Interstellar Oxygen and Krypton in Translucent Clouds
Meyer, David M.; Cartledge, Stefan I. B.; Lauroesch, J. T. +1 more
We have obtained high-resolution Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) observations of O I λ1356 and Kr I λ1236 absorption in 11 sight lines characterized by high extinction, large H I column densities, and/or long path lengths. Previous Goddard High Resolution Spectrograph (GHRS) measurements of these weak featu…
Theoretical Modeling of Infrared Emission from Neutral and Charged Polycyclic Aromatic Hydrocarbons. II.
Tielens, A. G. G. M.; Bakes, E. L. O.; Bauschlicher, Charles W., Jr. +2 more
The nature of the carriers of the interstellar infrared (IR) emission features between 3.3 and 12.7 µm is complex. We must consider emission from a family of polycyclic aromatic hydrocarbons (PAHs) in a multiplicity of cationic charge states (+1, +2, +3, and so on), along with neutral and anionic PAHs. The adopted intrinsic IR cross sections…
Optical Detection of a Variable Millisecond Pulsar Companion in 47 Tucanae
Heinke, Craig O.; Gilliland, Ronald L.; Edmonds, Peter D. +2 more
Using results from radio and X-ray observations of millisecond pulsars in 47 Tucanae, and extensive Hubble Space Telescope U, V, and I imaging of the globular cluster core, we have derived a common astrometric solution good to less than 0.1". A close positional coincidence is found for 47 Tuc U, a 4.3 ms pulsar in a 0.429 day orbit, detected in ra…
The complete ISO spectrum of NGC 6302
Waters, L. B. F. M.; Beintema, D. A.; Barlow, M. J. +6 more
We present the combined Infrared Space Observatory Short-Wavelength Spectrometer and Long-Wavelength Spectrometer 2.4-197 mu m spectrum of the Planetary Nebula NGC 6302 which contains in addition to strong atomic lines, a series of emission features due to solid state components. The broad wavelength coverage enables us to more accurately identify…
Helium White Dwarfs and BY Draconis Binaries in the Globular Cluster NGC 6397
Cool, A. M.; Grindlay, J. E.; Edmonds, P. D. +1 more
We examine 15 orbits of Hubble Space Telescope observations of the nearby post-core-collapsed globular cluster NGC 6397 using narrowband photometry in Hα with broadband photometry in V, R, and I. We recover the candidate helium white dwarfs (He WDs) recently discovered by Cool et al., of which one was examined spectroscopically by Edmonds et al., …
First simultaneous observations of flux transfer events at the high-latitude magnetopause by the Cluster spacecraft and pulsed radar signatures in the conjugate ionosphere by the CUTLASS and EISCAT radars
Balogh, A.; Davies, J. A.; Wild, J. A. +9 more
Cluster magnetic field data are studied during an outbound pass through the post-noon high-latitude magnetopause region on 14 February 2001. The onset of several minute perturbations in the magnetospheric field was observed in conjunction with a southward turn of the interplanetary magnetic field observed upstream by the ACE spacecraft and lagged …
Hubble Space Telescope NICMOS Detection of a Partially Embedded, Intermediate-Mass, Pre-Main-Sequence Population in the 30 Doradus Nebula
Walborn, Nolan R.; Grebel, Eva K.; Brandner, Wolfgang +2 more
We present the detection of an intermediate-mass, pre-main-sequence population embedded in the nebular filaments surrounding the 30 Doradus region in the Large Magellanic Cloud (LMC) using HST/NICMOS. In addition to four previously known luminous Class I infrared ``protostars,'' the NICMOS data reveal 20 new sources with intrinsic infrared excess …