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Properties of the Lower Transition Region: The Widths of Optically Allowed and Intersystem Spectral Lines
Doschek, G. A.; Feldman, U.
The widths of spectral lines in the ultraviolet (UV) and extreme ultraviolet (EUV) spectral regions that are formed in the solar transition region and corona are usually greater than the optically thin widths due to thermal Doppler broadening calculated under the assumption of ionization equilibrium. Although opacity can explain the widths of some…
The XMM-Newton/2dF survey - IV. The X-ray spectral properties of the hard sources
Georgakakis, A.; Georgantopoulos, I.; Shanks, T. +4 more
We present an analysis of the X-ray spectral properties of 61 hard X-ray-selected (2-8 keV) sources from the bright (f2-8keV > 10-14 erg cm-2 s-1)XMM-Newton/2dF survey. This comprises nine XMM-Newton pointings in the North Galactic Pole region (~1.6 deg2) and overlaps with the SDSS, 2QZ and…
[O I] 63 Micron Emission from High- and Low-Luminosity Active Galactic Nucleus Galaxies
Beichman, Charles A.; Dale, Daniel A.; Malhotra, Sangeeta +3 more
The Infrared Space Observatory (ISO) was used to search for a tracer of the warm and dense neutral interstellar medium, the [O I] 63.18 µm line, in four ultraluminous IRAS sources lying at redshifts between 0.6 and 1.4. While these sources are quasars, their infrared continuum emission suggests a substantial interstellar medium. No [O I] flu…
Photospheric and stellar wind variability in ɛ Ori (B0 Ia)
Stahl, O.; Rivinius, Th.; Orlando, S. +4 more
We provide direct observational evidence for a link between photospheric activity and perturbations in the dense inner-most stellar wind regions of the B supergiant star ɛ Ori. The results, which are relevant to our understanding of the origin of wind structure, are based on a multi-spectral line analysis of optical time-series data secured in 199…
An active M8.5 dwarf wide companion to the M4/DA binary LHS 4039/LHS 4040
Schwope, A.; Lodieu, N.; Scholz, R. -D. +4 more
Low-mass and brown dwarfs have recently been found as wide companions to many nearby stars, formerly believed to be single. Wide binaries are usually found as common proper motion pairs. Sometimes, more than two objects share the same large proper motion, identifying them as nearby systems. We have found a third, low-mass component to a known wide…
Present-day scaling relations for submillimetre galaxies: the origin of spheroidal systems
Takagi, T.; Hanami, H.; Arimoto, N.
We analyse the spectral energy distributions (SEDs) of 23 submillimetre galaxies and three ISO-detected extremely red objects, all of which have the spectroscopic redshifts, using an evolutionary SED model of starbursts. This SED model allows us to investigate the intrinsic properties of starbursts, such as the starburst age and the mean stellar m…
Solar type II and type IV radio bursts observed during 1998-2000 with the ARTEMIS-IV radiospectrograph
Hillaris, A.; Preka-Papadema, P.; Moussas, X. +9 more
A catalogue of the type II and type IV solar radio bursts in the 110-687 MHz range, observed with the radio spectrograph ARTEMIS-IV operated by the University of Athens at Thermopylae, Greece from 1998-2000 is presented. These observations are compared with the LASCO archives of Coronal Mass Ejections and the Solar Geophysical Reports of solar fla…
Flare observation of the Sun as a star by SUMER/SOHO in the hydrogen Lyman continuum
Vial, J. -C.; Wilhelm, K.; Curdt, W. +3 more
During the execution of the programme ``Sun as a star'', while the SUMER (Solar Ultraviolet Emission of Emitted Radiation)/SOHO (SOlar and Heliospheric Observatory) slit was collecting the scattered radiation from the telescope mirror far away from the solar disk image, a class X5.3/3b flare erupted on the solar disk, on 25 August 2001. During the…
Identifying young gamma-ray burst fossils
Ramirez-Ruiz, Enrico
The recent reports of temporal and spectral peculiarities in the early stages of some afterglows suggest that we may be wrong in postulating a central engine that becomes dormant after the burst itself. A continually decreasing post-burst relativistic outflow, such as put out by a decaying magnetar, may continue to be emitted for periods of days o…
Theoretical Prediction of an Observed Solar g-Mode
Guzik, Joyce A.; Cox, Arthur N.
This Letter considers the weak but persistent radial velocity variations measured by the Global Oscillations at Low Frequencies instrument on the Solar and Heliospheric Observatory satellite at 75.55 minutes (220.6 µHz), which is very close to our new theoretical solar model period prediction of 75.15 minutes (221.8 µHz) for the angula…