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Magnetospherically reflected chorus waves revealed by ray tracing with CLUSTER data
Maksimovic, M.; Santolík, O.; Parrot, M. +2 more
This paper is related to the propagation characteristics of a chorus emission recorded simultaneously by the 4 satellites of the CLUSTER mission on 29 October 2001 between 01:00 and 05:00 UT. During this day, the spacecraft (SC) 1, 2, and 4 are relatively close to each other but SC3 has been delayed by half an hour. We use the data recorded aboard…
The central star of the planetary nebula N 66 in the Large Magellanic Cloud: A detailed analysis of its dramatic evolution 1983-2000
Hamann, W. -R.; Gräfener, G.; Ruiz, M. T. +1 more
The central star of the planetary nebula N 66 (alias WS 35, SMP 83 and HV 5967) in the Large Magellanic Cloud enhanced its brightness dramatically in 1993 and 1994. Within the subsequent four years it returned to the previous level. Its spectrum resembles that of a Wolf-Rayet star of the nitrogen sequence (WN4.5). We monitored the object intensive…
AD Leonis : Flares observed by XMM-Newton and Chandra
Raassen, A. J. J.; Mewe, R.; Audard, M. +3 more
The M-dwarf
Fast photospheric flows and magnetic fields in a flaring active region
Meunier, N.; Kosovichev, A.
We present new results from the coordinated observations between the THEMIS telescope (in the multi-line spectropolarimetric mode) and Michelson Doppler Imager (MDI) on SOHO obtained in November 2000 for active region NOAA 9236 which was the source of several X-class flares. The goal of these observations was twofold: to verify MDI measurements of…
The Remarkable Alternating Spectra of the Of?p Star HD 191612
Walborn, Nolan R.; Howarth, Ian D.; Herrero, Artemio +1 more
The spectrum of HD 191612 has been found to display large, recurrent variations between two highly reproducible, peculiar states; at least four transformations have occurred since 1950. In one state, the spectral type is O6-O7, with C III λ4650 emission comparable to N III λ4640 (the definition of the Of?p category) and P Cygni profiles at He II λ…
INTEGRAL and XMM-Newton Observations of the Weak Gamma-Ray Burst GRB 030227
Tiengo, A.; Götz, D.; Mereghetti, S. +16 more
We present International Gamma-Ray Astrophysical Laboratory (INTEGRAL) and XMM-Newton observations of the prompt γ-ray emission and the X-ray afterglow of GRB 030227, the first gamma-ray burst for which the quick localization obtained with the INTEGRAL Burst Alert System has led to the discovery of X-ray and optical afterglows. GRB 030227 had a du…
Magnetoacoustic Waves in Sunspots
Bellot Rubio, L. R.; Collados, M.; Khomenko, E. V.
Observed variations of the magnetic field strength in sunspot umbrae consist of intrinsic oscillations and ``false'' oscillations due to time-dependent opacity effects. Here we present an approach intended for the separation of these components. We develop a mathematical formalism based on the analytical solution of the MHD equations including gra…
The planetary nebula K 1-2 and its binary central star VW Pyx
Exter, K. M.; Pollacco, D. L.; Bell, S. A.
New data are presented of the post-common-envelope binary VW Pyx and its associated planetary nebula (PN), K 1-2. The central star is found to be a single-lined (and possibly double-lined) spectroscopic binary and is a good candidate for a system in which the main-sequence secondary star is more massive than the subdwarf primary star. The old PN h…
The XMM-Newton/2dF survey - I. X-ray properties of normal galaxies
Georgakakis, A.; Georgantopoulos, I.; Shanks, T. +2 more
This paper explores the X-ray properties of `normal' galaxies using a shallow (2-10 ks) XMM-Newton survey covering an area of ~1.5 deg2. The X-ray survey overlaps with the 2dF Galaxy Redshift Survey. Compared with previous studies this has the advantage that high-quality spectra and spectral classifications (early-, late-type) exist for…
The First Two Host Galaxies of X-Ray Flashes: XRF 011030 and XRF 020427
Berger, E.; Bloom, J. S.; Djorgovski, S. G. +4 more
Given the paucity of empirical constraints, the nature of the newly recognized phenomena called X-ray flashes (XRFs) has been an open question. However, with the recent detections of radio and X-ray afterglow it is finally possible to study the large- and small-scale environments of XRFs. We present Chandra, Hubble Space Telescope (HST), and Keck …