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FORS spectroscopy of galaxies in the Hubble Deep Field-South
Berta, S.; Aussel, H.; Franceschini, A. +2 more
We present low resolution multi-object spectroscopy of an I-band magnitude limited (IAB ≃ 23-23.5) sample of galaxies located in an area centered on the Hubble Deep Field-South (HDFS). The observations were obtained using the Focal Reducer/low dispersion Spectrograph (FORS) on the ESO Very Large Telescope. Thirty-two primary spectroscop…
AGN variability time scales and the discrete-event model
Paltani, S.; Courvoisier, T. J. -L.; Favre, P.
We analyse the ultraviolet variability time scales in a sample of 15 type 1 Active Galactic Nuclei (AGN) observed by IUE. Using a structure function analysis, we demonstrate the existence in most objects of a maximum variability time scale of the order of 0.02-1.00 year. We do not find any significant dependence of these maximum variability time s…
Erupting Cataclysmic Variable Stars in the Nearest Globular Cluster, NGC 6397: Intermediate Polars?
Zurek, David R.; Knigge, C.; Hinkley, Sasha +2 more
NGC 6397 is the closest globular cluster and hence the ideal place to search for faint stellar populations such as cataclysmic variables (CVs). Hubble Space Telescope (HST) and Chandra observers have identified nine certain and likely CVs in this nearby cluster, including several magnetic CV candidates. We have combined our recent UV imagery with …
On the X-ray properties of OH megamaser sources: Chandra snapshot observations
Brandt, William N.; Comastri, Andrea; Vignali, Cristian +1 more
We present Chandra snapshot observations for a sample of seven sources selected from the Arecibo OH megamaser (OHM) survey at z~ 0.13-0.22 and with far-infrared (FIR) luminosities in excess of 1011Lsolar. In contrast with the known H2O megamasers, which are mostly associated with powerful active galactic nuclei (AG…
Statistical phase propagation and dispersion analysis of low frequency waves in the magnetosheath
Fränz, M.; Dandouras, I.; Glassmeier, K. -H. +3 more
We present the results of a statistical analysis of low-frequency fluctuations in the high latitude regions of the dayside magnetosheath using CLUSTER as a wave telescope. Magnetic field observations are used to determine wave propagation directions and wave numbers for selected frequencies. Using observations of the plasma flow velocity we correc…
Latitudinal Distribution of Solar Flares and Their Association with Coronal Mass Ejections
Shrivastava, Pankaj K.; Singh, Neelam
Major solar flare events have been utilised to study the latitudinal frequency distribution of solar flares in northern and southern hemispheres for the period of 1986 to 2003. A statistical analysis has been performed to obtain the correlation between Coronal Mass Ejections (CMEs) and Forbush decrease (Fds) of cosmic ray intensity. Almost the sam…
Evidence of transverse magnetospheric field line oscillations as observed from Cluster and ground magnetometers
Balogh, A.; Wild, J. A.; Yeoman, T. K. +3 more
The dynamic spectrum of ULF waves from magnetic field data obtained by the elliptically orbiting Cluster satellites (with an apogee of 119000km, perigee of 19000km and the orbital period of 57h) have been prepared in the frequency range 0 to 120mHz when the satellite was near its perigee. The existence of field line oscillations, with increasing f…
Relating near-Earth observations of an interplanetary coronal mass ejection to the conditions at its site of origin in the solar corona
Balogh, A.; van Driel-Gesztelyi, L.; Lucek, E. +7 more
A halo coronal mass ejection (CME) was detected on January 20, 2004. We use solar remote sensing data (SOHO, Culgoora) and near-Earth in situ data (Cluster) to identify the CME source event and show that it was a long duration flare in which a magnetic flux rope was ejected, carrying overlying coronal arcade material along with it. We demonstrate …
Neutral sheet normal direction determination
Balogh, A.; Zhang, T. L.; Glassmeier, K. -H. +5 more
One of the important parameters in magnetotail studies is the thickness of the current sheet. The determination of this thickness is subject to many assumptions of the geometry, such as the current sheet normal direction. The minimum variance analysis (MVA) has been widely used in studies of the current sheet in the tail or at the magnetopause wit…
ISO observations of 3-200 µm emission by three dust populations in an isolated local translucent cloud
Juvela, M.; Lemke, D.; Lehtinen, K. +2 more
We present ISOPHOT spectrophotometry of three positions within the isolated high-latitude cirrus cloud G 300.2-16.8, spanning from the near- to far-infrared (NIR to FIR). The positions exhibit contrasting emission spectrum contributions from the unidentified infrared bands (UIBs), very small grains (VSGs) and large classical grains, and both semi-…