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Empirical reconstruction and long-duration tracking of the magnetospheric boundary in single- and multi-spacecraft contexts
Owen, C. J.; Roth, M.; Dunlop, M. W. +3 more
The magnetospheric boundary is always moving, making it difficult to establish its structure. This paper presents a novel method for tracking the motion of the boundary, based on in-situ observations of the plasma velocity and of one or more additional observables. This method allows the moving boundary to be followed for extended periods of time …
Extragalactic globular clusters in the near-infrared. V. IC 4051 and NGC 3311
Hoard, D. W.; Geisler, D.; Hempel, M. +1 more
We present the results of combined optical and near-infrared photometry for the globular cluster systems of the giant ellipticals IC 4051 and NGC 3311. We use the reduced age-metallicity degeneracy in (V-I) vs. (V-H) color-color diagrams to derive the cumulative age distribution within the red sub-population of globular clusters and to search for …
Clearing up the clouds around NGC 4151: evidence of a highly ionized absorber
Piro, L.; de Rosa, A.; Perola, G. C. +1 more
The Seyfert 1 galaxy NGC 4151 is characterized by complex X-ray absorption, well described by a dual absorber, composed of a uniform mildly ionized gas and a cold system that partially covers the central source. However, in one of the 5 BeppoSAX observations, the spectrum shows two peculiar features. An absorption feature is detected around 8.5-9 …
Photometric Redshift of the GRB 981226 Host Galaxy
Christensen, L.; Gorosabel, J.; Hjorth, J.
No optical afterglow was found for the dark burst GRB 981226, and hence no absorption redshift has been obtained. We here use ground-based and space imaging observations to analyze the spectral energy distribution (SED) of the host galaxy. By comparison with synthetic template spectra, we determine the photometric redshift of the GRB 981226 host t…
The INTEGRAL spectrometer SPI: performance of point-source data analysis
Knödlseder, J.; von Kienlin, A.; Bouchet, L. +9 more
The performance of the SPI point-source data analysis system is assessed using a combination of simulations and of observations gathered during the first year of INTEGRAL operations. External error estimates are derived by comparing source positions and fluxes obtained from independent analyses. When the source detection significance provided by t…
Pulsation of the K 2.5 giant star GSC 09137-03505?
Zwintz, K.; Guenther, D. B.; Weiss, W. W. +2 more
In July, 1999, the Hubble Space Telescope (HST) pointed for more than 8 days continuously at the globular cluster 47 Tucanae. Two guide stars were used during this campaign by the Fine Guidance Sensors (FGS). Using more than 19 million photometric FGS data for the guide star GSC 09137-03505 we found brightness variability corresponding to three ap…
Star cluster detection with WFC/ACS in M 33. 33 new clusters and 51 candidates
Anderson, J.; Baume, G.; Momany, Y. +5 more
In this work we present the detection of 33 star clusters and 51 candidates in one field of the near by galaxy M 33. This study is based on WFC/ACS images available from the HST archive. Thanks to the high resolving power, we were able to confirm that two candidates previously indicated by Christian & Schommer (1982, ApJS, 49, 405) are indeed …
Discovery of an X-Ray Nova in M31
Williams, Benjamin F.; Kong, Albert K. H.; Murray, Stephen S. +2 more
We have obtained snapshot images of an X-ray nova in M31 from Chandra ACIS-I and the Hubble Space Telescope (HST) Advanced Camera for Surveys. The Chandra position of the X-ray nova was R.A.=00h44m06.68s 68+/-1.74s, decl.=+41deg12'20.0"+/-2.31" (J2000.0). A follow-up HST observation 24 days later reveale…
Identification of the Source Region of a ``Halo'' Coronal Mass Ejection Using Meter-Wavelength Radio Data
Ramesh, R.; Kathiravan, C.
We present meter-wavelength observations of the solar corona close to the onset of the ``halo'' coronal mass ejection (CME) of 1998 January 21 and estimate the change in electron density with time through a reproduction of the observed two-dimensional radio brightness distribution using a ray-tracing technique. Our calculations show that the avera…
The Planets and Titan Observed by ISO
Bézard, Bruno; Fouchet, Thierry; Encrenaz, Therese
Infrared spectroscopic observations of planets and Saturn's satellite Titan with the Infrared Space Observatory led to many significant discoveries that improved our understanding on the formation, physics and chemistry of these objects. The prime results achieved by ISO are: (1) a new and consistent determination of the D/H ratios on the giant pl…