Search Publications
Cyclotron Heating of the Solar Corona
Marsch, Eckart
A physical model of the solar transition region and corona is presented, in which plasma flows in rapidly-diverging coronal funnels and holes are described within the framework of a two-fluid model including wave-particle interactions. The ions are heated by wave dissipation and accelerated by the pressure gradient of high-frequency Alfvén waves, …
M84: A Warp Caused by Jet-induced Pressure Gradients?
Bower, Gary A.; Quillen, A. C.
In radio galaxies such as M84 dust features tend to be nearly perpendicular to radio jets yet are not aligned with the galaxy isophotes. The timescale for precession in the galaxy is short (~107 yr at 100 pc), suggesting that an alternative mechanism causes the gas disk to be misaligned with the galaxy. In M84 we estimate the pressure o…
The molecular cloud core M 17-North: New ISOCAM observations
Henning, Th.; Cesarsky, D.; Klein, R.
We present spectro-imaging data of the molecular cloud core M17-North. The data have been obtained with the ISOCAM camera on board of the Infrared Space Observatory (ISO) using the circular variable filters (CVF). The spectra have a spectral resolution of about 40. They are dominated by PAH emission bands. A band at 16.6{ mu m} is detected which i…
Solar oscillations: time analysis of the GOLF p-mode signal
Turck-Chièze, S.; Ulrich, R. K.; Boumier, P. +5 more
We determine the intrinsic phase lag of the GOLF data for the solar p-mode velocity deduced either from one of the narrow band photometers working alternatively on blue and red wing of the sodium lines. The timing of the ``blue wing'' velocity coming from the current GOLF data is given in respect to the ground-based observations. The phase lag for…
Statistical Analysis of EUV and UV Lines Inside and Outside of Solar Coronal Holes
Wilhelm, K.; Curdt, W.; Dammasch, I. E. +1 more
Two studies performed with SUMER (the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on SOHO) in September 1996 are presented. Spatial scans, a long exposure time and a broad spectral window provide reliable line profiles for various regions of the Sun (off-limb corona, coronal hole, quiet Sun, bright and dark regions on disk) an…
Opacities along the line of sight to and in the atmosphere of the white dwarf in the close detached DAO+dM binary RE J0720-318
Barstow, M. A.; Hubeny, I.; Burleigh, M. R. +1 more
We present the results from a multi-wavelength study of the mixed H+He composition DAO white dwarf
The absolute magnitude of K0V stars from BT HIPPARCOS parallaxes
Groenewegen, Martin A. T.; Schrijver, Hans; Oudmaijer, Renéd.
We investigate the properties of K0V stars with Hipparcos parallaxes and spectral types taken from the Michigan Spectral Survey. The sample of 200 objects allows the empirical investigation of the magnitude selection (Malmquist) bias, which appears clearly present. By selecting those objects that are not affected by bias, we find a mean absolute m…
ISO SWS/LWS observations of SN 1987A
Sollerman, J.; Lundqvist, P.; Spyromilio, J. +5 more
We report on observations of SN 1987A with ISO SWS/LWS made 9-11 years after the explosion. No emission from the supernova was seen. In particular, the upper limits on the fluxes of [Fe I] 24.05 µm and [Fe II] 25.99 µm on day 3 999 are ~ 1.1 Jy and ~ 1.4 Jy, respectively. Assuming a homogeneous distribution of (44) Ti inside 2 000 km s…
The Extended Narrow-Line Region of 3C 299
McCarthy, Patrick J.; Sparks, William B.; Macchetto, F. Duccio +2 more
We present results of Hubble Space Telescope (HST) observations of the radio galaxy 3C 299. The broadband F702W (R) and F555W (V) images (WFPC2/PC) show an elliptical galaxy with a comet-like structure extending to the northeast in the radio jet direction. The [O III] λ5007 emission-line map shows a biconical structure centered on the nucleus, whi…
A Possible Gravitational Lens in the Hubble Deep Field South
Hogg, David W.; Blandford, Roger; Barkana, Rennan
We model an apparent gravitational lens system HDFS 2232509-603243 in the Hubble Deep Field South. The system consists of a blue V=25 mag arc separated by 0.9" from a red V=22 mag elliptical galaxy. A mass distribution that follows the observed light distribution with a constant mass-to-light ratio can fit the arc component positions if external s…