Search Publications
A Search for Helium in Ultramassive White Dwarfs
Vennes, Stéphane; Chayer, Pierre; Dupuis, Jean
We have obtained extreme ultraviolet (EUV) spectra of eight hot, ultramassive white dwarfs (M=0.9-1.3Msolar) with the Extreme Ultraviolet Explorer. The stars are, on average, twice as massive as normal white dwarfs. The relatively high turnout of ultramassive white dwarfs in EUV surveys is difficult to explain in the context of single-s…
Microwave Detection of Shock and Associated Electron Beam Formation
Reiner, M.; Shibasaki, K.; Karlický, M. +1 more
We use complementary European and Japanese solar radio ground-based observations, together with Yohkoh soft X-ray and SOHO extreme-UV images, to search for the signature of flare-related waves at different heights above the Sun. The key data set for event selection is 40-800 MHz dynamic radio spectra from the Potsdam Astrophysical Institute, whose…
Kinematics of Hipparcos Visual Binaries. II. Stars with Ground-Based Orbital Solutions
Bartkevičius, A.; Gudas, A.
This paper continues kinematical investigations of the Hipparcos visual binaries with known orbits. A sample, consisting of 804 binary systems with orbital elements determined from ground-based observations, is selected. The mean relative error of their parallaxes is about 12% and the mean relative error of proper motions is about 4%. However, eve…
Spectroscopy of SN 1987A at 0.9-2.4µm: days 1348-3158
Spyromilio, J.; Meikle, W. P. S.; Fassia, A.
We present near-infrared spectroscopic observations of SN 1987A covering the period 1358 to 3158 d post explosion. This is the first time that IR spectra of a supernova have been obtained to such late epochs. The spectra comprise emission from both the ejecta and the bright, ring-shaped circumstellar medium (CSM). The most prominent CSM emission l…
Metallicity and radial velocity of the second parameter globular cluster Terzan 1 in the galactic bulge
Bica, E.; Barbuy, B.; Ortolani, S. +3 more
Terzan 1 is the globular cluster with closest projection relative to the Galactic center. We report radial velocities and metallicities of 17 stars in order to investigate their membership in the cluster. From the 11 probable members of Terzan 1, a radial velocity of vr = 114 +/- 14 km s-1 is obtained. For this sample an inte…
Three-dimensional energetic ion sounding of the magnetopause using Cluster/RAPID
Zong, Q. -G.; Fritz, T. A.; Wilken, B. +2 more
We present new results using energetic particles to remotely sound the high-latitude magnetopause in three-dimensions. Less than two gyro radii from an absorbing boundary a trapped particle distribution appears non-gyrotropic, as particles start to cross the boundary. Knowing the magnetic field and the particle mass and energy, it is possible to d…
Time series photometric spot modelling V. Phase coherence of spots on UZ Librae
Strassmeier, K. G.; Granzer, T.; Oláh, K.
We present spot models for nine years of continuous VI_C photometry of UZ Lib from 1993-2001. The relatively stable double-humped light curve shape suggests extreme phase coherence. From the spot-modelling analysis, we found that the major spots or spot groups are always located on the hemisphere facing the secondary star and exactly in the opposi…
HST NICMOS imaging of z∼2-3 radio-quiet quasars
Calzetti, D.; Lehnert, M.; Ridgway, S. +1 more
We will present the results of a NICMOS H-band imaging survey of a small sample of z∼2-3 radio-quiet quasars. We have resolved extension in at least four of five objects and find evidence for a wide range in the morphologies and magnitudes of these hosts. The host galaxy luminosities range from sub- L ∗ to about 4 L ∗, with m…
Bipolar and Multipolar Jets in Protoplanetary and Planetary Nebulae
Sahai, R.
One of the most exciting challenges facing theories of post-main sequence evolution today is to understand how Asymptotic Giant Branch (AGB) stars and their round circumstellar envelopes (CSEs) transform themselves into planetary nebulae (PNe) with their dazzling variety of aspherical morphologies. The most succesful model for shaping PNe--the ``g…
Ultraviolet Imaging Polarimetry of the Peculiar Seyfert 2 Galaxy Markarian 477
Cohen, Ross D.; Antonucci, Robert; Kishimoto, Makoto +3 more
We present the results of UV imaging polarimetry of the Seyfert 2 galaxy Mrk 477 taken by the Faint Object Camera on board the Hubble Space Telescope (HST). From a previous HST UV image (λ~2180 Å), Mrk 477 has been known to have a pointlike bright UV hot spot in the central region, peculiar among nearby Seyfert 2 galaxies. There are also claims of…